AC1C. Stay Current—Cosmic Cataclysms

A Changing Cosmos Cover

Staying current for Chapter 1

{ A Changing Cosmos Contents }

SEE ALSO: 
Life & Climate Chapter 9, What Happened to the Dinosaurs?
and General Astronomy Resources

Articles from 2002 – present

2022-09-12. NASA’s unprecedented asteroid-deflection mission is more than ‘billiards in space,’ scientists say. [https://www.science.org/content/article/nasa-s-unprecedented-asteroid-deflection-mission-more-billiards-space-scientists-say] By Zack Savitsky, Science Magazine. Excerpt: On 26 September, an act of targeted violence will unfold 11 million kilometers from Earth, as a spacecraft about the size of a vending machine smashes into a small asteroid at 6 kilometers per second. Unlike some asteroids that stray worrisomely close to Earth’s orbit, Dimorphos—the 160-meter moon of a larger body—is an innocent bystander, posing no threat to our world. But the looming assault represents humanity’s first-ever field test of a planetary defense mission: NASA’s Double Asteroid Redirection Test, or DART. The hope is that the collision will nudge Dimorphos into a closer orbit around its 780-meter partner, Didymos, shortening its nearly 12-hour orbital period by a few minutes. A successful strike would support the idea that, in the future, similar efforts could deflect threatening asteroids onto safer courses. But new simulations and lab experiments show the fate of the mission depends heavily on a crucial question: Are such small asteroids solid boulders or—as astronomers increasingly believe—loose heaps of rubble? The answer, which should be revealed from the crater and ejecta produced by DART’s collision, could determine just how hard to hit an asteroid when the exercise is not a test. …Dimorphos-size asteroids are thousands of times more likely to strike Earth than the larger ones that have triggered mass extinction events in the geologic past, and they are still capable of devastating a state or small country, making these smaller bodies the top priority for planetary defense efforts.…

2022-05-09. Discoveries shed new light on the day the dinosaurs died. By Dave Kindy, The Washington Post. Excerpt: …Thescelosaurus panicked and looked to flee — but it was too late. Everything changed in a heartbeat as a 30-foot-high wave of mud and debris came racing up the seaway from the south, sweeping away life and limb in the process. The dinosaur was caught in the destructive deluge, its leg ripped off at the hip by the devastating surge. That moment — 66 million years ago at the end of the Cretaceous period, when an earth-shattering asteroid ended the reign of the dinosaurs — is frozen in time today through a stunning fossil found last year at the Tanis dig site in North Dakota. This perfectly preserved leg clearly shows the skin, muscle and bones of the three-toed Thescelosaurus. …“We’re never going to say with 100 percent certainty that this leg came from an animal that died on that day,” the scientist said. “The thing we can do is determine the likelihood that it died the day the meteor struck. When we look at the preservation of the leg and the skin around the articulated bones, we’re talking on the day of impact or right before. There was no advanced decay.” DePalma and the dinosaur leg will be featured in two episodes of “Nova” on PBS airing back-to-back on Wednesday: “Dinosaur Apocalypse: The New Evidence” and “Dinosaur Apocalypse: The Last Day.” Biologist and natural historian Sir David Attenborough will host the programs, which were produced in conjunction with the BBC. The leg and several other relics discovered at the North Dakota site are the first actual fossils found showing the death and destruction that took place when a 10-mile-long space rock struck the Yucatán Peninsula in the Gulf of Mexico.… [https://www.washingtonpost.com/history/2022/05/09/how-dinosaurs-died-tanis/]

2022-05-01. Catch a failing star: the tense wait for a supernova. By Robin McKie, The Guardian. Excerpt: …When a supernova erupts, it sprays the cosmos with heavy elements – so observing one nearby would provide precious information about the creation of matter in our galaxy. …Scientists estimate that on average about 20 supernovae occur in a galaxy such as ours every thousand years. Yet only five have been observed in the last millennium. East Asian and Arabic records indicate there were supernovae in 1006, 1054 and 1181, while European documents recall ones that occurred in 1572 and 1604. …if supernovae are so brilliant, why have we only detected five in the past 1,000 years? Why have we not seen a number that is nearer the 20 suggested by observations of other galaxies? The answer is straightforward, says Sullivan. “Our galaxy is like a flat plate and our solar system is about two-thirds of the way towards its edge. A supernova that occurs on the other side of the plate will simply be obscured by all the dust and stars that lie at the centre of the galaxy.”… [https://www.theguardian.com/science/2022/may/01/catch-a-failing-star-the-tense-wait-for-a-supernova]

2022-02-16. Evidence of giant asteroid strike may be buried under Wyoming. By Paul Voosen, Science Magazine. Excerpt: Some 280 million years ago, before the rise of the Rocky Mountains—or even the dinosaurs—a 2.5-kilometer-wide asteroid smashed into the supercontinent of Pangaea, near the eastern border of present-day Wyoming. The impact’s heat and shock wave would have killed anything within 400 kilometers, making it one of the largest asteroid strikes in North American history. …And there the crater may sit, kilometers down, even to this day. That’s the scenario painted in new work. Researchers haven’t found the crater itself, but they have identified a series of 31 smaller craters, each no wider than a U.S. football field. These “secondary” craters would have been formed by boulders ejected by the impact, landing up to 200 kilometers away. It is the first time a secondary crater field—commonly seen on other planetary bodies, including the Moon—has been discovered on Earth. …The craters’ pattern was similar to the rays and streaks of small craters that surround large craters on the Moon, like Tycho. They provide clear evidence that such formations are possible on Earth, the researchers conclude this month in the Geological Society of America Bulletin.… [https://www.science.org/content/article/evidence-giant-asteroid-strike-may-be-buried-under-wyoming]

2022-02-02. A Giant Impact Triggered Earthquakes for Thousands of Years. By Katherine Kornei, Eos/AGU. Excerpt: When an asteroid struck South Africa during the Precambrian, earthquakes rocked the region for millennia as Earth’s crust reequilibrated, new research reveals.… [https://eos.org/articles/a-giant-impact-triggered-earthquakes-for-thousands-of-years]

2022-01-02. Did a Meteor Explode Over Pittsburgh? By Azi Paybarah, The New York Times. Excerpt: For Heather Lin Ishler, the first morning of 2022 in Dormont, a neighborhood just south of downtown Pittsburgh, began like most days had in 2021. …Then, the bed shook. “The sensation,” Ms. Ishler, 34, later said, “reminded me of fireworks” and how, if you stand too close, you can feel “a rumbling in your chest.” …“It was just the feeling of the shock wave,” Ms. Ishler recalled, “but no sound or flash or anything like that.” …Diane Turnshek, an astronomer who lectures at Carnegie Mellon University, felt something powerful on Saturday morning, too. She was in her home atop a Pittsburgh hill, 1,120 feet above sea level. Her initial thought was that her dryer had fallen off the washing machine in the room next door. Calls started coming into the Pittsburgh office of the National Weather Service from people who had heard “a really loud sound but didn’t see anything,” said Jenna Lake, a Weather Service meteorologist. Soon, it seemed as if everyone was looking for answers. …No earthquakes were detected by the seismograph at the nearby Allegheny Observatory, Ms. Turnshek said. …Ms. Lake at the Weather Service said the air over Pittsburgh on Saturday was “too benign” for storms or lightning, so those were ruled out, too. …For now, a meteor explosion is the best theory about what happened over Pittsburgh on Saturday, Ms. Lake said, though it will remain just that — a theory — “unless someone finds some rocks in their backyard,” she said.… [https://www.nytimes.com/2022/01/02/us/meteor-explosion-pittsburgh.html]

2021-11-18. NASA’s first planetary defense mission will nudge an asteroid. By Adam Mann, Science Magazine. Excerpt: Intentional crash of robotic probe will test way to avert asteroid impacts on Earth. In the name of planetary defense, NASA is set to launch a robotic probe next week that in late 2022 will hurtle into a sizable space rock in the hopes of nudging its orbit. Although the celestial target of the Double Asteroid Redirection Test (DART) poses no danger to our planet, the mission will assess the feasibility of deflecting potentially hazardous objects away from Earth.… [DART successfully launched last night (Tuesday, Nov. 23, at 10:21 p.m. PST)] [https://www.science.org/content/article/nasa-s-first-planetary-defense-mission-will-nudge-asteroid] See also New York Times article.

2021-10-22. Dinosaurs thrived until the moment asteroid hit, excavators of controversial site claim. By Michael Price, Science Magazine. Excerpt: …Two years ago, a paleontologist claimed to have found evidence at a fossil-rich North Dakotan site called Tanis that dinosaurs were alive until moments after the impact, when floodwaters surged over them. But many paleontologists were skeptical, especially because the dinosaur data were first discussed in a magazine story rather than a peer-reviewed journal. Last week, at the annual meeting of the Geological Society of America (GSA) in Portland, Oregon, paleontologist Robert DePalma and colleagues added detail to their claims. They presented evidence of fossils from Tanis—including stunningly well-preserved bones, skin, and footprints from what’s probably a Triceratops—that suggest dinosaurs were indeed witnesses to the asteroid that ushered them out of existence.… [https://www.science.org/content/article/dinosaurs-thrived-until-moment-asteroid-hit-excavators-controversial-site-claim]

2021-08-25. Deflecting an Asteroid Before It Hits Earth May Take Multiple Bumps. Source: By Katherine Kornei, The New York Times. Excerpt: There’s probably a large space rock out there, somewhere, that has Earth in its cross hairs. Scientists have in fact spotted one candidate — Bennu, which has a small chance of banging into our planet in the year 2182. But whether it’s Bennu or another asteroid, the question will be how to avoid a very unwelcome cosmic rendezvous. For almost 20 years, a team of researchers has been preparing for such a scenario. Using a specially designed gun, they’ve repeatedly fired projectiles at meteorites and measured how the space rocks recoiled and, in some cases, shattered. These observations shed light on how an asteroid might respond to a high-velocity impact intended to deflect it away from Earth. At the 84th annual meeting of the Meteoritical Society held in Chicago this month, researchers presented findings from all of that high-powered marksmanship. Their results suggest that whether we’re able to knock an asteroid away from our planet could depend on what kind of space rock we’re faced with, and how many times we hit it.… [https://www.nytimes.com/2021/08/25/science/asteroid-deflection-collision.html]

2021-08-12. Ancient supernovae might have upended Earth’s evolution. By Claire Hogan, Science Magazine. Excerpt: When stars run out of fuel, they can collapse under their own gravity, exploding as supernovae that blast debris and radioactive nuclei far into space. Most of these events are too far from Earth to affect our planet. But if one happened nearby, the effects could be dramatic. By studying radioactive isotopes on Earth, scientists have uncovered evidence suggesting two near-Earth supernovae occurred in the past few million years. Some researchers now hypothesize that supernova-generated particles known as cosmic rays might have depleted the ozone layer, increased cancer rates in ancient organisms, sparked wildfires, and even started an ice age…. [https://www.sciencemag.org/news/2021/08/ancient-supernovae-might-have-upended-earth-s-evolution]

2021-07-15. [https://www.sciencemag.org/news/2021/07/exploding-stars-may-have-assaulted-ancient-earth] – Exploding stars may have assaulted ancient Earth. Source: By Daniel Clery, Since Magazine. Excerpt: …Over the past 2 decades, researchers have found hundreds of radioactive atoms, trapped in seafloor minerals, that came from an ancient explosion marking the death of a nearby star. Its fusion fuel exhausted, the star had collapsed, generating a shock wave that blasted away its outer layers in an expanding ball of gas and dust so hot that it briefly glowed as bright as a galaxy—and ultimately showered Earth with those telltale atoms. Erupting from hundreds of light-years away, the flash of x-rays and gamma rays probably did no harm on Earth. But the expanding fireball also accelerated cosmic rays—mostly nuclei of hydrogen and helium—to close to the speed of light. These projectiles arrived stealthily, decades later, ramping up into an invisible fusillade that could have lasted for thousands of years and might have affected the atmosphere—and life. …A cosmic ray barrage might have boosted mutation rates by eroding Earth’s protective ozone layer and generating showers of secondary, tissue-penetrating particles. Tearing through the atmosphere, the particles would have also created pathways for lightning, perhaps kindling a spate of wildfires. At the same time, atmospheric reactions triggered by the radiation could have led to a rain of nitrogen compounds, which would have fertilized plants, drawing down carbon dioxide. In that way, the celestial event could have cooled the climate and helped initiate the ice ages 2.5 million years ago, at the start of the Pleistocene epoch. … Adrian Melott, an astronomer at the University of Kansas, Lawrence, who explores how nearby cosmic cataclysms might affect Earth, says it’s time to more carefully probe Earth’s history for ancient supernova strikes. …a few supernovae go off in the Milky Way every century. By the law of averages, a handful must have exploded very close to Earth—within 30 light-years—during its 4.5-billion-year lifetime, with potentially catastrophic effects…. 

2021-01-27. An Asteroid “Double Disaster” Struck Germany in the Miocene. By Katherine Kornei, Eos/AGU. Excerpt: A Gothic church rises high above the medieval town of Nördlingen, Germany. But unlike most churches, St. George’s is composed of a very special type of rock: suevite, a coarse-grained breccia that’s formed only in powerful impacts. That discovery and other lines of evidence have helped researchers determine that Nördlingen lies within an impact crater. Now, scientists have unearthed evidence that this crater and another one just 40 kilometers away were formed by a “double disaster” of two independent asteroid impacts. …Our planet is dotted with nearly 200 confirmed impact structures, and a handful of them appear in close pairs. Some researchers have proposed that these apparent double craters are scars created by binary asteroids slamming into Earth at the same time. …However, scientists have theoretically determined that the binary asteroid scenario is unlikely. That’s because most binary asteroids are orbiting one another too closely to produce two distinct craters…. …Now, Elmar Buchner, a geologist at the Neu-Ulm University of Applied Sciences in Nue-Ulm, Germany, and his colleagues have investigated the provenance of two impact craters near Stuttgart using observational data. They focused on the 24-kilometer-diameter Ries crater—which encompasses the town of Nördlingen—and the 4-kilometer-diameter Steinheim Basin, which are located roughly 40 kilometers from one another. …The impact that created the Ries crater must have formed first, the scientists surmised, because blocks of limestone—ejecta from the Ries impact—cap the lower seismite horizon. That’s consistent with previous research suggesting that fossils within the Ries crater are a few hundred thousand years older than fossils found within the Steinheim Basin. This region “witnessed a double disaster in the Middle Miocene,” the team concluded in their paper, which was published last month in Scientific Reports…. [https://eos.org/articles/an-asteroid-double-disaster-struck-germany-in-the-miocene

2019-03-29. 66 million-year-old deathbed linked to dinosaur-killing meteor. [https://news.berkeley.edu/2019/03/29/66-million-year-old-deathbed-linked-to-dinosaur-killing-meteor/] For A Changing Cosmos chapter 1 and Life and Climate chapter 9. Excerpt: The beginning of the end started with violent shaking that raised giant waves in the waters of an inland sea in what is now North Dakota. Then, tiny glass beads began to fall like birdshot from the heavens. The rain of glass was so heavy it may have set fire to much of the vegetation on land. In the water, fish struggled to breathe as the beads clogged their gills. The heaving sea turned into a 30-foot wall of water when it reached the mouth of a river, tossing hundreds, if not thousands, of fresh-water fish — sturgeon and paddlefish — onto a sand bar and temporarily reversing the flow of the river. Stranded by the receding water, the fish were pelted by glass beads up to 5 millimeters in diameter, some burying themselves inches deep in the mud. The torrent of rocks, like fine sand, and small glass beads continued for another 10 to 20 minutes before a second large wave inundated the shore and covered the fish with gravel, sand and fine sediment, sealing them from the world for 66 million years. This unique, fossilized graveyard — fish stacked one atop another and mixed in with burned tree trunks, conifer branches, dead mammals, mosasaur bones, insects, the partial carcass of a Triceratops, marine microorganisms called dinoflagellates and snail-like marine cephalopods called ammonites — was unearthed by paleontologist Robert DePalma over the past six years in the Hell Creek Formation, not far from Bowman, North Dakota. The evidence confirms a suspicion that nagged at DePalma in his first digging season during the summer of 2013 — that this was a killing field laid down soon after the asteroid impact that eventually led to the extinction of all ground-dwelling dinosaurs. The impact at the end of the Cretaceous Period, the so-called K-T boundary, exterminated 75 percent of life on Earth…. 

2019-03-29. Fossil Site Reveals Day That Meteor Hit Earth and, Maybe, Wiped Out Dinosaurs. [https://www.nytimes.com/2019/03/29/science/dinosaurs-extinction-asteroid.html] For GSS Life and Climate chapter 9 and a Changing Cosmos chapter 1. Excerpt: Sixty-six million years ago, a giant meteor slammed into Earth off the coast of modern-day Mexico. Firestorms incinerated the landscape for miles around. Even creatures thousands of miles away were doomed on that fateful day, if not by fire and brimstone, then by mega-earthquakes and waves of unimaginable size. Now, scientists have unearthed a remarkable trove of fossils that appear to date from the very day of the impact. The burial site consists of more than four feet of sediments and organic remains that were dumped in North Dakota almost instantly and transformed into rock over the eons. It evidently captures, in unparalleled detail, the repercussions of the giant doomsday rock…. …When the meteor smashed into waters near what is now Mexico’s Yucatán Peninsula, it left a giant crater known as Chicxulub and prompted upheavals thousands of miles away, including what is now North Dakota. Within hours and perhaps minutes of the titanic collision, sea creatures were swept inland by tsunamis and earthquakes, tossed together and deposited with a diverse array of landlocked life, including trees, flowers and vanished types of freshwater fish. …The jumble was swiftly entombed, and exquisitely preserved. Permeating the deposit were tiny spheres of clay and glass, known as tektites, which formed as molten rock, ejected by the impact, showered from the sky…. See also Science Magazine article Astonishment, skepticism greet fossils claimed to record dinosaur-killing asteroid impact, 4/1/2019 by Colin Barras. [https://www.sciencemag.org/news/2019/04/astonishment-skepticism-greet-fossils-claimed-record-dinosaur-killing-asteroid-impact

2019-01-17. Moon’s craters reveal recent spike in outer space impacts on Earth. By Paul Voosen, Science Magazine. [https://www.sciencemag.org/news/2019/01/moon-s-craters-reveal-recent-spike-outer-space-impacts-earth] Excerpt: It has long been thought that as the solar system grows older and stodgier, the number of asteroids and comets colliding with Earth and other planets has steadily gone down. But a new study reveals what appears to be a dramatic 2.5 times increase in the number of impacts striking Earth in the past 300 million years. …Scientists used a thermal camera on NASA’s Lunar Reconnaissance Orbiter to examine the number of large, heat-retaining rocks in the moon’s craters; those rocks are eventually ground to dust by minute meteorite impacts. By looking at previously dated craters, these rocks have been established as a reliable dating technique—the more intact the rocks, the younger the crater. In the new study, the team found a surprising abundance of young craters, seemingly matching the number on Earth. That means, they write today in Science, that in its modern geological history, Earth is much better at retaining the features of impact craters than once thought, and that the recent proliferation coincides with an actual increase in the number of bombarding asteroids or comets. But scientists still don’t know what caused the uptick. Perhaps several large asteroids collided or otherwise broke up some 300 million years ago, their chunks slowly migrating out from the asteroid belt to bombard Earth, the researchers say. And that could have included the giant impact, 66 million years ago, that wiped out most of the dinosaurs….  See also New York Times article, What Happened to Earth’s Ancient Craters? Scientists Seek Clues on the Moon’s Pocked Surface. [https://www.nytimes.com/2019/01/17/science/craters-meteors-moon.html]


2018-12-20. Huge Global Tsunami Followed Dinosaur-Killing Asteroid Impact. By Katherine Kornei, Eos/AGU. [https://eos.org/articles/huge-global-tsunami-followed-dinosaur-killing-asteroid-impact] Excerpt: The devastating tsunamis that struck the coastlines of Chile, Haiti, Indonesia, and Japan in recent decades produced waves tens of meters high, unimaginable to most people accustomed to gentle seas. But millions of years ago, a truly inconceivable set of waves—the tallest roughly 1,500 meters high—rammed through the Gulf of Mexico and spread throughout the ancient ocean, producing wave heights of several meters in distant waters, new simulations show. The enormous waves were triggered by a large asteroid slamming into the shallow waters of the modern-day Yucatán Peninsula. That asteroid impact, which occurred about 66 million years ago and created the Chicxulub crater, contributed to the demise of the dinosaurs….  


2018-11-14. International Team, NASA Make Unexpected Discovery Under Greenland Ice. NASA RELEASE 18-099. [https://eos.org/articles/huge-global-tsunami-followed-dinosaur-killing-asteroid-impact] Excerpt: The devastating tsunamis that struck the coastlines of Chile, Haiti, Indonesia, and Japan in recent decades produced waves tens of meters high, unimaginable to most people accustomed to gentle seas. But millions of years ago, a truly inconceivable set of waves—the tallest roughly 1,500 meters high—rammed through the Gulf of Mexico and spread throughout the ancient ocean, producing wave heights of several meters in distant waters, new simulations show. The enormous waves were triggered by a large asteroid slamming into the shallow waters of the modern-day Yucatán Peninsula. That asteroid impact, which occurred about 66 million years ago and created the Chicxulub crater, contributed to the demise of the dinosaurs….  


2018-08-08. Dinosaur-Killing Asteroid Impact Made Huge Dead Zones in Oceans. By Lucas Joel, Eos/AGU.  Excerpt: About 66 million years ago, an asteroid roughly 10 kilometers wide hit Earth in what is today the Gulf of Mexico. It brought annihilation: All the dinosaurs except for the birds went extinct; forests around the planet vanished temporarily, killing off all bird species that lived in trees; dust and other aerosols blocked the Sun, and global temperatures took a nosedive. The world plunged into a state analogous to nuclear winter. Another fallout effect of the impact, according to new work, was a depletion of oxygen in the oceans triggered by rapid global warming following the impact and nuclear winter. Such anoxia, the researchers behind the work report, devastated marine life. What’s more, this episode of anoxia may have parallels to the rapid global warming and resulting ocean anoxia being wrought by human-driven climate change today. “The global warming following the impact is one of the most rapid warmings in Earth’s history,” said Johan Vellekoop, a geologist at KU Leuven in Belgium who led the new research. “It’s on a human timescale.” He described that the postimpact warming happened over the course of only a few hundred to a few thousand years….https://eos.org/articles/dinosaur-killing-asteroid-impact-made-huge-dead-zones-in-oceans

2017-08-31. Big Space Rock to Pass near Earth on Friday. By Katherine Kornei, Eos/AGU. Excerpt: An asteroid named for Florence Nightingale will make its closest approach to our planet since 1890 but will remain a safe distance away. In the roughly 2 decades that scientists have systematically tracked asteroids speeding past Earth, never before has one so large come so close. On Friday, an asteroid called Florence will zip by our planet just 7 million kilometers away, or about 18 times the Earth–Moon distance, according to NASA. Many other asteroids have come closer, but none was as big as Florence, which measures about 4 kilometers in diameter. …Researchers will also be using NASA’s Goldstone Solar System Radar facility in California’s Mojave Desert to determine whether Florence has a natural satellite of its own, a moon. Fifteen percent of asteroids have moons, Mainzer noted, and finding a moon orbiting Florence would make it possible to calculate the asteroid’s mass…. https://eos.org/articles/big-space-rock-to-pass-near-earth-on-friday

2017-06-25. Could Asteroids Bombard the Earth to Cause a Mass Extinction in 10 Million Years? By Sanna Alwmark, Matthias Meier, Scientific American. Excerpt: Given the evidence that an asteroid triggered the dinosaur extinction, it makes sense to ask whether showers of asteroids could be to blame for regular extinction events….  https://www.scientificamerican.com/article/could-asteroids-bombard-the-earth-to-cause-a-mass-extinction-in-10-million-years/

2017-04-06. Asteroid to Fly Safely Past Earth on April 19. By Jet Propulsion Laboratory News. Excerpt:  A relatively large near-Earth asteroid discovered nearly three years ago will fly safely past Earth on April 19 at a distance of about 1.1 million miles (1.8 million kilometers), or about 4.6 times the distance from Earth to the moon. Although there is no possibility for the asteroid to collide with our planet, this will be a very close approach for an asteroid of this size. The asteroid, known as 2014 JO25, was discovered in May 2014 by astronomers at the Catalina Sky Survey near Tucson, Arizona — a project of NASA’s NEO Observations Program in collaboration with the University of Arizona. (An NEO is a near-Earth object). Contemporary measurements by NASA’s NEOWISE mission indicate that the asteroid is roughly 2,000 feet (650 meters) in size, and that its surface is about twice as reflective as that of the moon. …Small asteroids pass within this distance of Earth several times each week, but this upcoming close approach is the closest by any known asteroid of this size, or larger, since asteroid Toutatis , a 3.1-mile (five-kilometer) asteroid, which approached within about four lunar distances in September 2004. The next known encounter of an asteroid of comparable size will occur in 2027 when the half-mile-wide (800-meter-wide) asteroid 1999 AN10 will fly by at one lunar distance, about 236,000 miles (380,000 kilometers). …The encounter on April 19 is the closest this asteroid has come to Earth for at least the last 400 years and will be its closest approach for at least the next 500 years….  https://www.jpl.nasa.gov/news/news.php?feature=6807  See also https://echo.jpl.nasa.gov/asteroids/2014JO25/2014JO25_planning.html and http://www.skyandtelescope.com/observing/see-a-potentially-hazardous-asteroid-from-your-backyard/

2016-11-17. Updated: Drilling of dinosaur-killing impact crater explains buried circular hills. By Eric Hand, Science.  Excerpt: Today, scientists published their first results from a drilling expedition into Chicxulub crater, the buried remnants of an asteroid impact off the Yucatán Peninsula in Mexico that killed off the dinosaurs 66 million years ago. Their discovery of shocked, granite rocks from deep in the crust placed “out of order” on top of sedimentary rocks validates the dynamic collapse theory of formation for Chicxulub’s peak ring, the scientists says. Chicxulub is the only well-preserved crater on Earth with a peak ring, but they abound elsewhere in the inner solar system. Last month, scientists using instruments on a NASA lunar mission showed that the peak rings within the Orientale impact basin were likely to have formed in a similar way as at Chicxulub….  http://www.sciencemag.org/news/2016/11/update-drilling-dinosaur-killing-impact-crater-explains-buried-circular-hills

2016-07-14. Here’s how the world could end—and what we can do about it. By Julia Rosen, Science.  A treatment of 3 different threats: Solar storms; Cosmic collisions; Supervolcanoes.  http://www.sciencemag.org/news/2016/07/here-s-how-world-could-end-and-what-we-can-do-about-it

2016-03-29. Jupiter Got Whacked by Yet Another Asteroid/Comet! By Phil Plait, Bad Astronomy. Excerpt: On March 17, Gerrit Kernbauer, an amateur astronomer in Mödling, Austria, was taking video of Jupiter using a 20 cm telescope. …he got more than he expected. At 00:18:33 UTC he captured what looks very much like the impact of a small comet or asteroid into Jupiter! [see video] …On average …an object will hit Jupiter with roughly five times the velocity it hits Earth, so the impact energy is 25 times as high. The asteroid that burned up over Chelyabinsk, Russia, in 2013 was 19 meters across, and it exploded with the energy of 500,000 tons of TNT. Now multiply that by 25, and you can see how it doesn’t take all that big a rock to hit Jupiter for us to be able to see it from Earth. Incidentally, at these huge speeds, hitting the atmosphere is like slamming into a wall. A lot of people get understandably confused how an asteroid can explode due to air, but the pressures involved …are ridiculously huge. The air and rock heat up, the rock starts to fall apart, and each chunk then gets hot, and so on, creating a very rapid cascade that releases the energy of motion in just a second or two. Bang. Very, very big bang. Jupiter gets hit a lot. …The most famous is the string of impacts from the comet Shoemaker-Levy 9 in 1994, which hammered the planet over and again as the comet, broken into a dozen separate pieces by Jupiter’s gravity, slammed into the planet and exploded. In 2009 something relatively big hit the planet (and Hubble caught the aftermath). It was hit again in June 2010 (with a cool color photo this time), and then again in August 2010. A repeat performance was held in September 2012. …Looking over these observations, it seems that on average Jupiter gets hit by something big enough to see from Earth about once per year. Mind you, we miss ones that happen on the far side of the planet, or when Jupiter is too close to the Sun to be observed….  http://www.slate.com/blogs/bad_astronomy/2016/03/29/jupiter_hit_by_asteroid_or_comet_in_march_2016.html

[Here are observed impacts over the past couple decades on Jupiter:]

16-22 July 1994  [P/SL-9 20+ fragments]

19 July 2009 [Anthony Wesley]

3 June 2010 [Anthony Wesley & Christopher Go]

20 Aug 2010 [Masayuki Tachikawa]

10 Sept 2012 [Dan Petersen]

17 Mar 2016

2016-01-07. NASA Office to Coordinate Asteroid Detection, Hazard Mitigation. NASA Feature. Excerpt: NASA has formalized its ongoing program for detecting and tracking near-Earth objects (NEOs) as the Planetary Defense Coordination Office (PDCO). The office remains within NASA’s Planetary Science Division, in the agency’s Science Mission Directorate in Washington. The office will be responsible for supervision of all NASA-funded projects to find and characterize asteroids and comets that pass near Earth’s orbit around the sun. It will also take a leading role in coordinating interagency and intergovernmental efforts in response to any potential impact threats. More than 13,500 near-Earth objects of all sizes have been discovered to date—more than 95 percent of them since NASA-funded surveys began in 1998. About 1,500 NEOs are now detected each year….  http://www.nasa.gov/feature/nasa-office-to-coordinate-asteroid-detection-hazard-mitigation

2015-10-22. NASA Calls for American Industry Ideas on ARM Spacecraft Development. NASA Release 15-213. Excerpt: …NASA’s ARRM [Asteroid Redirect Robotic Mission] spacecraft will need to be able to demonstrate support of high power solar electric propulsion, with initial solar array power of approximately 50 kilowatts. The robotics capture system planned aboard the pioneering vehicle will be capable of acquiring a 20 ton (or larger) boulder of up to about 19 feet (six meters) in width from an asteroid’s surface and then returning it to an astronaut-accessible orbit near our moon. …The spacecraft will need to be ready for launch by the end of 2020. …While at a large asteroid, the spacecraft will demonstrate a “slow-push” planetary defense asteroid deflection technique during the mission. This uses the spacecraft and boulder’s combined gravitational pull to attempt to change the course of an asteroid….  http://www.nasa.gov/press-release/nasa-calls-for-american-industry-ideas-on-arm-spacecraft-development

2015-10-01. Volcano-asteroid combo may have done in the dinosaurs. By Sid Perkins, Science. Excerpt: Scientists have for decades hotly debated what killed the dinosaurs. One long-held hypothesis blames immense and long-lasting volcanic eruptions that drastically altered Earth’s climate. Another more recent hypothesis suggests that the dino die-offs occurred after a massive asteroid hit the planet near the Yucatán Peninsula. Now, research finds that the extraterrestrial impact may have led to increased volcanism in the Indian subcontinent, providing a double whammy that took out Tyrannosaurus rex and his kin. …The new study finally provides dates for those eruptions. Using an argon-argon radioactive dating technique, a team led by geochronologist Paul Renne of the University of California, Berkeley, sampled materials from ancient lava layers at sites in the Deccan Plateau of central and western India. They found that the Deccan eruptions started at least 173,000 years before the asteroid hit and continued for at least 500,000 years after the impact. What’s more, the researchers were able to determine the size and strength of each major eruption, based on lava flow estimates. Before the impact, the eruptions produced about 71,000 cubic kilometers of lava—an average rate of about 400 million cubic meters each year. But starting about 50,000 years after the asteroid impact, Deccan volcanoes and fissures began spewing lava at an average rate of about 900 million cubic meters per year, the researchers report online today in Science. …How the asteroid impact half a world away from India bumped up lava production is a mystery, Renne says. He speculates that its effects rippled along the boundaries of nearby tectonic plates until they reached the volcanoes, expanding the size of subterranean magma chambers and thus increasing the volume of magma they could spew during any given eruption. Not all scientists are convinced.  …Ironically, by more closely linking the date of the impact with the increase in Deccan volcanism, Renne and his team may have made it more difficult to tease out the relative contribution of each phenomenon to the die-offs, Melosh says. “These findings will add greatly to the controversy of volcanism versus impact.”  http://news.sciencemag.org/climate/2015/10/volcanoes-and-asteroid-strike-may-have-done-dinosaurs?utm_campaign=email-news-weekly  See also http://news.berkeley.edu/2015/10/01/asteroid-impact-volcanism-were-one-two-punch-for-dinosaurs/

2015-01-13. Asteroid to Fly By Earth Safely on January 26. NASA Jet Propulsion Laboratory. Excerpt:  An asteroid, designated 2004 BL86, will safely pass about three times the distance of Earth to the moon on January 26. …astronomers estimate that the asteroid is about a third of a mile (0.5 kilometers) in size. The flyby of 2004 BL86 will be the closest by any known space rock this large until asteroid 1999 AN10 flies past Earth in 2027. At the time of its closest approach on January 26, the asteroid will be approximately 745,000 miles (1.2 million kilometers) from Earth. “Monday, January 26 will be the closest asteroid 2004 BL86 will get to Earth for at least the next 200 years,” said Don Yeomans, who is retiring as manager of NASA’s Near Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, after 16 years in the position. “And while it poses no threat to Earth for the foreseeable future, it’s a relatively close approach by a relatively large asteroid, so it provides us a unique opportunity to observe and learn more.” …NASA’s Deep Space Network antenna at Goldstone, California, and the Arecibo Observatory in Puerto Rico will attempt to acquire science data and radar-generated images of the asteroid during the days surrounding its closest approach to Earth….  http://www.jpl.nasa.gov/news/news.php?feature=4441.

2014-11-15. New NASA map shows Earth bombarded by asteroids. By Shelby Lin Erdman, CNN. Excerpt: Fiery asteroids smash into Earth’s atmosphere at such a stunning rate, …. A new NASA map [http://www.nasa.gov/jpl/bolide-events-1994-2013/#.VGjvfoeRl7o] from the … Near-Earth Object Program [http://neo.jpl.nasa.gov/faq/], reveals that more than 556 space rocks smashed into the atmosphere over a 20-year period between 1994 and 2013. …The good news is most are small and harmless fireballs that disintegrate when they hit the atmosphere, …. An obvious exception occurred on February 15, 2013, when an asteroid as large as 55 feet in diameter with a mass of up to 10,000 tons crashed to earth in the Urals region in Russia, streaking through the morning sky in Chelyabinsk [http://www.youtube.com/watch?v=ZMT7rIhETJM] before landing in a fiery explosion that injured more than a thousand people and caused an estimated $33 million in damage. …NASA said the Chelyabinsk asteroid was the largest to hit the Earth during the agency’s mapping period. [see also Meteor blast at local school – https://www.youtube.com/watch?v=jn92CMmTd9o] …The NEO Program helps detect and track space rocks that could cause a potential danger to Earth. “The new data could help scientists better refine estimates of the distribution of the sizes of NEOs,” NASA explained. “Finding and characterizing hazardous asteroids to protect our home planet is a high priority.” …NASA is also developing an Asteroid Redirect Mission called ARM. In a plan that sounds a lot like science fiction, NASA wants to redirect a space rock into orbit around the moon by the 2020s so astronauts can study it more closely. The mission could also help develop ways to deflect an asteroid should one be found on a collision course for Earth. See also NASA’s All Sky Fireball Network [http://fireballs.ndc.nasa.gov/]…. Source: http://www.cnn.com/2014/11/15/us/nasa-asteroid-map/index.html.

2014 Feb. Video & animations of asteroid/meteroid impacts.  Produced by Jose Maria Madiedo, University of Huelva, and José Luis Ortiz, Andalusian Astrophysics Institute, on the occasion of the publication in Monthly Notices of the Royal Astronomical Society (MNRAS) of the paper entitled “A large lunar impact blast on 2013 September 11”. http://www.youtube.com/watch?v=perqv4qByaI&feature=youtu.be

2013-02-15. Impact event over the Southern Ural Mountains at 3:20:26 UTC (9:20 AM local time in Chelyabinsk, Russia). Dome-L Planetarians’ listserv. The meteor moved from East to West. It was also observed from Tyumen, Ekaterinaburg, and Northern Kazakhstan. Reports that a few fragments have been recovered ~80 km west of Chelyabinsk (near a village called Satka). Based on infrasound reports (9 stations reporting, one as far away as Alaska), the event lasted 32.5 seconds, corresponding to an equivalent yield of 470 kilotons TNT (which, in turn, equates to a size of ~17 meters; which, in turn, equates to a mass of ~10,000 metric tons). Velocity of impact: ~18 km/s (~40,000 mph). Largest reported fireball since Tunguska impact (1908 Jun 30). 1200+ people injured [no reported deaths] mostly from shattered glass. Blast wave damaged 3000+ structures (shallow graze, probably ~20 deg elevation; airburst and subsequent shockwaves from explosion). Why didn’t we see it coming? (1) It came at us from ‘out of the Sun’.  (2) Small objects like this (just under 20 meters) would likely be fainter than 25th mag–below our capability to detect right now. Compilation of videos: http://zyalt.livejournal.com/722930.html  There is no relation to the close approach of asteroid 2012 DA14 (same day, 15 Feb) as DA14 was on a South-to-North path over the Earth. [To see photos and videos of Asteroid 2012 DA14, visit Universe Today.]

2012-06-25. ‘Nature’s Masons’ Do Double Duty as Storytellers.  By Sean B. Carroll, New York Times.  Excerpt: GUBBIO, Italy — Excerpt: GUBBIO, Italy — …Limestone is composed largely of crystallized calcium carbonate. Some of it comes from the skeletal remains of well-known creatures like corals, but much of the rest comes from less appreciated but truly remarkable organisms called foraminifera, or forams for short. Forams have been called “nature’s masons,” … these single-celled protists construct surprisingly complex, ornate and beautiful shells to protect their bodies. After forams die, their shells settle in ocean sediments…. While tiny relative to ourselves …, forams are extremely large for single-celled organisms, … largest forams can reach a few centimeters. … forams are particularly valuable to geologists and paleontologists in telling us about Earth’s history. The forams in the limestone just outside Gubbio provided the first clues to … an asteroid that struck earth at the end of the Cretaceous period, 65 million years ago…about the size of Mount Everest and traveling at about 50,000 miles an hour when it hit the earth, drilling a 120-mile-wide crater and ejecting so much material into (and even out of) the atmosphere that food chains on land and in the oceans were disrupted for thousands of years. The impact caused one of the greatest mass extinctions in history, from the largest animals to tiny forams. …. Read the full article: http://www.nytimes.com/2012/06/26/science/natures-masons-do-double-duty-as-earths-storytellers.html?_r=1&emc=eta1

2012-05-16. NASA Survey Counts Potentially Hazardous Asteroid | NASA News Release 12-157. Excerpt: Observations from NASA’s Wide-field Infrared Survey Explorer (WISE) have led to the best assessment yet of our solar system’s population of potentially hazardous asteroids. The results reveal new information about their total numbers, origins and the possible dangers they may pose. …The project sampled 107 PHAs [potentially hazardous asteroids] to make predictions about the entire population as a whole. Findings indicate there are roughly 4,700 PHAs, plus or minus 1,500, with diameters larger than 330 feet (about 100 meters). So far, an estimated 20 to 30 percent of these objects have been found. While previous estimates of PHAs predicted similar numbers, they were rough approximations. …The new analysis also suggests that about twice as many PHAs as previously thought are likely to reside in “lower-inclination” orbits, which are more aligned with the plane of Earth’s orbit. In addition, these lower-inclination objects appear to be somewhat brighter and smaller than the other near-Earth asteroids that spend more time far away from Earth. A possible explanation is that many of the PHAs may have originated from a collision between two asteroids in the main belt lying between Mars and Jupiter. A larger body with a low-inclination orbit may have broken up in the main belt, causing some of the fragments to drift into orbits closer to Earth and eventually become PHAs. For more information about WISE, visit: http://www.nasa.gov/wise  

2012-05-07. Asteroid’s Impact Still Central to Dinosaurs’ Extinction | by JOHN NOBLE WILFORD, The NY Times. Excerpt: For some 30 years, scientists have debated what sealed the fate of the dinosaurs. Was an asteroid impact more or less solely responsible for the catastrophic mass extinction at the end of the Cretaceous geological period, 65 million years ago? Or were the dinosaurs already undergoing a long-term decline, and the asteroid was merely the coup de grâce? So three young researchers, led by Stephen L. Brusatte, a graduate student at Columbia University who is affiliated with the American Museum of Natural History, decided to test this hypothesis with a close examination of the fossil record over the 12 million years leading up to the mass extinction. For the study, the researchers departed from the practice of focusing almost exclusively on raw counts of the number of species over time. Instead, they analyzed changes in the anatomies and body plans of seven large groups of late Cretaceous dinosaurs for insights into their evolutionary trajectory….

2012-04-25. NASA Scientists Find History of Asteroid Impacts in Earth Rocks | by NASA, RELEASE : 12-135. Excerpt: … Research by NASA and international scientists concludes giant asteroids, similar or larger than the one believed to have killed the dinosaurs, hit Earth billions of years ago with more frequency than previously thought. To cause the dinosaur extinction, the killer asteroid that impacted Earth 65 million years ago would have been almost 6 miles (10 kilometers) in diameter. By studying ancient rocks in Australia and using computer models, researchers estimate that approximately 70 asteroids the same size or larger impacted Earth 1.8 to 3.8 billion years ago. During the same period, approximately four similarly-sized objects hit the moon….At least 12 mega-impacts produced spherule beds during the so-called Archean period 2.5 to 3.7 billion years ago, a formative time for life on Earth. Ancient spherule beds are rare finds, rarer than rocks of any other age. Most of the beds have been preserved amid mud deposited on the sea floor below the reach of waves. The impact believed to have killed the dinosaurs was the only known collision over the past half-billion years that made a spherule layer as deep as those of the Archean period. The relative abundance of the beds supports the hypothesis for many giant asteroid impacts during Earth’s early history. …To learn about the NLSI, visit: http://lunarscience.arc.nasa.gov 

2012 Jan 23. Death of a Star.  By C. Claiborne Ray, New York Times. Excerpt: Q. As our Sun dies, what will happen to the planets, especially our own? A. In about five billion years, scientists estimate, the Earth will be engulfed and burned up in the expanding radius of the Sun as it evolves. This event will be about a million years after Venus and Mercury “have suffered the same fate,” according to updated calculations published in 2008 in the journal Monthly Notices of the Royal Astronomical Society. …As the Sun ages into a red giant, it will expand, losing mass and cooling somewhat, but remaining very hot. “While solar-mass loss alone would allow the orbital radius of planet Earth to grow sufficiently to avoid this ‘doomsday’ scenario,” the authors of the study conclude, the tidal interaction of the Sun and the closely orbiting planet “will lead to a fatal decrease” in the size of Earth’s orbit….

2011 July 1. Last Dinosaur Before Mass Extinction Discovered. EarthSky. Excerpt: A team of scientists has discovered the newest dinosaur preserved in the fossil record before the catastrophic meteor impact 65 million years ago, which many scientists believe caused their extinction. The finding indicates that dinosaurs did not go extinct prior to the impact and provides further evidence of the impact as cause of extinction. Results of the study appear online July 13, 2011 in the journal Biology Letters….

2011 Feb 2. NASA RELEASE 11-029: NASA’s Neowise Completes Scan For Asteroids And Comets. Excerpt: WASHINGTON — NASA’s NEOWISE mission has completed its survey of small bodies, asteroids and comets, in our solar system. The mission’s discoveries of previously unknown objects include 20 comets, more than 33,000 asteroids in the main belt between Mars and Jupiter, and 134 near-Earth objects (NEOs)…asteroids and comets with orbits that come within 28 million miles of Earth’s path around the sun. NEOWISE is an enhancement of the Wide-field Infrared Survey Explorer, or WISE, mission that launched in December 2009. WISE scanned the entire celestial sky in infrared light about 1.5 times. It captured more than 2.7 million images of objects in space, ranging from faraway galaxies to asteroids and comets close to Earth. In early October 2010, after completing its prime science mission, the spacecraft ran out of frozen coolant that keeps its instrumentation cold. However, two of its four infrared cameras remained operational. These two channels were still useful for asteroid hunting, so NASA extended the NEOWISE portion of the WISE mission by four months, with the primary purpose of hunting for more asteroids and comets, and to finish one complete scan of the main asteroid belt.
 …In addition to discovering new asteroids and comets, NEOWISE also confirmed the presence of objects in the main belt that already had been detected. In just one year, it observed about 153,000 rocky bodies out of approximately 500,000 known objects. Those include the 33,000 that NEOWISE discovered. …The first batch of observations from the WISE mission will be available to the public and astronomical community in April…. For more information about WISE, visit: http://www.nasa.gov/wise [Mission website – http://wise.ssl.berkeley.edu/]

2010 September. Stars on Radio. By Kathleen M. Wong, Science Matters @ Berkeley. Excerpt: The radio sky to modern astronomers is much like the West was to Lewis and Clark. “It’s all very sparsely explored at this point,” says Geoffrey Bower. A Berkeley professor of astronomy, Bower is conducting systematic radio wavelength surveys of the heavens. Such comprehensive viewing goals, made possible by modern increases in data storage and processing abilities, were identified this August as among the highest priorities in astronomy by the National Academy of Sciences.
During his surveys, Bower expects to uncover not only new phenomena, but invent better ways to decipher the physics and structure of the universe.
…Bower has found one such tool by analyzing neutron stars. These ultra-dense collapsed stars can emit brief but astoundingly powerful bursts of radio wavelength energy…. Bower hopes to use these fleeting flashes to illuminate the spaces between galaxies.
…Bower’s radio surveys have already turned up another promising space exploration technique: astrometric planet hunting. …Radio measurements, they realized, yield measurements of a star’s position so precise that they could reveal the back-and-forth wobble caused by the orbit of a large planet. Bower is now using this method to search for extrasolar planets.

2010 August 23. Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies. By Committee to Review Near-Earth Object Surveys and Hazard Mitigation Strategies; National Research Council. Excerpt: The United States spends approximately $4 million each year searching for near-Earth objects (NEOs). The objective is to detect those that may collide with Earth. The majority of this funding supports the operation of several observatories that scan the sky searching for NEOs. This, however, is insufficient in detecting the majority of NEOs that may present a tangible threat to humanity….
…Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies identifies the need for detection of objects as small as 30 to 50 meters as these can be highly destructive…
…Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies is a useful guide for scientists, astronomers, policy makers and engineers.

2010 August 20. New Worlds, New Horizons in Astronomy and Astrophysics. By Committee for a Decadal Survey of Astronomy and Astrophysics; National Research Council Excerpt: The field of astronomy and astrophysics is making new connections to physics, chemistry, biology, and computer science….
…New Worlds, New Horizons in Astronomy and Astrophysics outlines a plan for ground- and space- based astronomy and astrophysics for the decade of the 2010’s…
…The book recommends beginning construction on survey telescopes in space and on the ground to investigate the nature of dark energy, as well as the next generation of large ground-based giant optical telescopes and a new class of space-based gravitational observatory to observe the merging of distant black holes and precisely test theories of gravity. New Worlds, New Horizons in Astronomy and Astrophysics recommends a balanced and executable program that will support research surrounding the most profound questions about the cosmos…
…The discoveries ahead will facilitate the search for habitable planets, shed light on dark energy and dark matter, and aid our understanding of the history of the universe and how the earliest stars and galaxies formed.

2010 March 9. Alvarez Theory on Dinosaur Die-Out Upheld: Experts Find Asteroid Guilty of Killing the Dinosaurs. By Lynn Yarris, Lawrence Berkeley National Laboratory. Excerpt: In the March 5, 2010 edition of the journal Science, an international panel of 41 experts in geology, paleontology and other related fields, after an exhaustive review of the data, declared an end to a 30 year controversy over what triggered the extinction of the dinosaurs – an asteroid or volcanoes. The panel ruled in favor of the asteroid, a theory first put forth in 1980 by one of Berkeley Lab’s greatest scientists, the late Nobel laureate Luis Alvarez, and his son Walter, a geologist with UC Berkeley….

2009 October 26. Asteroid blast reveals holes in Earth’s defences. By David Shiga, NewScientist. Excerpt: As the US government ponders a strategy to deal with threatening asteroids, a dramatic explosion over Indonesia has underscored how blind we still are to hurtling space rocks.
On 8 October an asteroid detonated high in the atmosphere above South Sulawesi, Indonesia, releasing about as much energy as 50,000 tons of TNT, according to a NASA estimate released on Friday. That’s about three times more powerful than the atomic bomb that levelled Hiroshima, making it one of the largest asteroid explosions ever observed.
However, the blast caused no damage on the ground because of the high altitude, 15 to 20 kilometres above Earth’s surface, says astronomer Peter Brown of the University of Western Ontario (UWO), Canada.
…The amount of energy released suggests the object was about 10 metres across, the researchers say. Such objects are thought to hit Earth about once per decade.
No telescope spotted the asteroid ahead of its impact. That is not surprising, given that only a tiny fraction of asteroids smaller than 100 metres across have been catalogued, says Tim Spahr, director of the Minor Planet Center in Cambridge, Massachusetts. Yet objects as small as 20 or 30 metres across may be capable of doing damage on the ground, he says….

2009 Oct 7. NASA RELEASE: 09-232, NASA REFINES ASTEROID APOPHIS’ PATH TOWARD EARTH. Excerpt: PASADENA, Calif. — Using updated information, NASA scientists have recalculated the path of a large asteroid. The refined path indicates a significantly reduced likelihood of a hazardous encounter with Earth in 2036.
The Apophis asteroid is approximately the size of two-and-a-half football fields. The new data were documented by near-Earth object scientists Steve Chesley and Paul Chodas at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
“Apophis has been one of those celestial bodies that has captured the public’s interest since it was discovered in 2004,” said Chesley. “Updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036, for Apophis has dropped from one-in-45,000 to about four-in-a million.”
…Initially, Apophis was thought to have a 2.7 percent chance of impacting Earth in 2029. Additional observations of the asteriod ruled out any possibility of an impact in 2029. However, the asteroid is expected to make a record-setting — but harmless — close approach to Earth on Friday, April 13, 2029, when it comes no closer than 18,300 miles above Earth’s surface.
…NASA detects and tracks asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near Earth-Object Observations Program, commonly called “Spaceguard,” discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet. For more information about asteroids and near-Earth objects, visit:http://www.jpl.nasa.gov/asteroidwatch

2009 October 2. After Asteroid Strike, a Fast Rebound for Some. By Henry Fountain, The NY Times. Excerpt: The asteroid that struck the planet 65 million years ago was very bad for the dinosaurs, as everyone knows, but it wasn’t too good for smaller things, either. Even algae and other primary producers in the ocean were affected, probably because atmospheric debris from the impact reduced the sunlight available for photosynthesis.
But there is new evidence, reported in Science, that primary productivity in the oceans was not down for long. An analysis of sediments along a bluff in Denmark suggests that algae recovered in less than a century.
Julio Sepúlveda, a geochemist at the Massachusetts Institute of Technology and formerly at the University of Bremen in Germany, and colleagues studied a 15-inch layer of clay at Kulstirenden on the island of Zealand.
…Dr. Sepúlveda said the findings showed that “the most dramatic disruption in primary production was for a rather short period of time.” But the overall recovery of the oceans, particularly deep environments, took much longer….

2009 September 23. Space Scientists Weigh Technology, Diplomacy Challenges of Global Asteroid Threat. By Edward W. Lempinen, AAAS News. Excerpt: SAN FRANCISCO—Imagine this scenario: Astronomers discover a previously unknown asteroid. Though it is millions of miles away, initial calculations suggest that it will, in about 15 years, pass dangerously close to Earth. And though its size is modest—about 100 meters at its widest—it is more than big enough to destroy a major city.
If this were a conventional Hollywood thriller, the plot might focus on how nuclear weapons would be deployed and launched to destroy the menacing asteroid. But for former U.S. astronauts Rusty Schweickart and Edward Lu, any such mission to save the Earth would be far more complex. To create the greatest chance of success, they say, it should begin with ambitious science diplomacy and technology research and development long before the asteroid is discovered.
In a symposium at the annual meeting of the AAAS Pacific Division, Schweickart and Lu suggested that novel technology is available that would allow humans to closely track such an asteroid and to redirect its orbit. What’s lacking, they said, is political recognition that asteroids will periodically threaten Earth in the future—and that the time to plan and prepare is now.
…They have proposed ambitious efforts to track and respond to threatening “Near-Earth Objects,” or NEOs. The centerpiece of their strategy: A relatively simple, unmanned spacecraft that would fly to a suspect NEO and position itself close enough to exert a small pull of gravity; over a period of time, it would “tow” the object into a non-threatening orbit. NASA’s Jet Propulsion Laboratory last fall concluded that the plan is viable….

2009 August 15. Report: NASA can’t keep up with killer asteroids. By SETH BORENSTEIN, AP Science Writer. Excerpt: NASA is charged with spotting most of the asteroids that pose a threat to Earth but doesn’t have the money to complete the job, a federal report says.
That’s because even though Congress assigned the space agency that mission four years ago, it never gave NASA the money to build the necessary telescopes, according to the report released Wednesday by the National Academy of Sciences.
Specifically, the mission calls for NASA, by the year 2020, to locate 90 percent of the potentially deadly rocks hurtling through space. The agency says it’s been able to complete about one-third of its assignment with the current telescope system.
NASA estimates that there are about 20,000 asteroids and comets in our solar system that are potential threats. They are larger than 460 feet in diameter — slightly smaller than the Superdome in New Orleans. So far, scientists know where about 6,000 of these objects are.
Rocks between 460 feet and 3,280 feet in diameter can devastate an entire region, said Lindley Johnson, NASA’s manager of the near-Earth objects program. Objects bigger than that are even more threatening, of course.
Just last month astronomers were surprised when an object of unknown size and origin bashed into Jupiter and created an Earth-sized bruise that is still spreading. Jupiter does get slammed more often than Earth because of its immense gravity, enormous size and location.
…At the moment, NASA has identified about five near-Earth objects that pose better than a 1-in-a-million risk of hitting Earth and being big enough to cause serious damage, Johnson said….

2009 June 11. Planets will collide in 5 billion years. David Perlman, SF Chronicle Science Editor. Excerpt: From chaos we all began, and to chaos we’ll all return, but not for a very, very long time – 5 billion years or so, more or less. In the journal Nature today, two French scientists, using arcane mathematical models, predict that in the distant future, the Earth and planet after planet will collide with each other as an inevitable part of the solar system’s long-term evolution. For many millennia, the scientists say, the orbits of the solar system’s eight planets will remain stable, just as they are today, but eventually small eccentricities in their flight paths around the sun could cause Mercury, Mars, Venus and Earth to smash into each other, either one at a time or all at once – the ultimate chaotic disaster. … the prophets of eventual doom – astronomer Jacques Laskar and computer engineer Mickael Gastineau of France’s Paris Observatory – calculate that the odds are 99-to-1 that the orbits of the four inner planets – Mercury, Venus, Earth and Mars – will remain stable for the full 5 billion years.
The time frame coincides with accepted theory that by the end of that same 5 billion years the sun will have burned up its hydrogen and in a cooler state will inflate itself into what’s called a red giant star, engulfing the entire inner solar system while the planets are still colliding. So, either way, the planets of the inner solar system are safe for another 5 billion years, according to Laughlin….

2009 April 28. New Blow Against Dinosaur-killing Asteroid Theory, Geologists Find. NSF Press Release. The enduringly popular theory that the Chicxulub crater holds the clue to the demise of the dinosaurs, along with some 65 percent of all species 65 million years ago, is challenged in a paper to be published in the Journal of the Geological Society on April 27, 2009.

Neil DeGrasse Tyson: Death by Black Hole. Video of astrophysicist Neil DeGrasse Tyson discussing asteroid collision.

2009 January 1. Diamonds Linked to Quick Cooling Eons Ago. By Kenneth Chang, The New York Times. Excerpt: At least once in Earth’s history, global warming ended quickly, and scientists have long wondered why.
Now researchers are reporting that the abrupt cooling — which took place about 12,900 years ago, just as the planet was emerging from an ice age — may have been caused by one or more meteors that slammed into North America.
That could explain the extinction of mammoths, saber-tooth tigers and maybe even the first human inhabitants of the Americas, the scientists report in Friday’s issue of the journal Science.
The hypothesis has been regarded skeptically, but its advocates now report perhaps more convincing residue of impact: a thin layer of microscopic diamonds found in rocks across America and in Europe.
…At each site the scientists looked at, the diamond layer in the rocks correlates to the date of the hypothesized impact. Within the layer, the scientists report finding a multitude of diamond particles, all encased within carbon spheres. “We’ve yet to find a single diamond above it,” Dr. West said. “We’ve yet to find a single diamond below it.”
Perhaps more telling, the scientists reported last month at a meeting of the American Geophysical Union in San Francisco, the carbon atoms inside some of the diamonds are lined up in a hexagonal crystal pattern instead of the usual cubic structure. The hexagonal diamonds, formed by extraordinary heat and pressure, have been found only at impact craters and within meteorites and cannot be formed in forest fires or volcanic eruptions, Dr. West said….

2008 December. Meteorites from the Lone Rock, SK Strewn Field. Web page set up by Bruce McCurdy of the Edmonton Space & Science Foundation showing pictures of the recovery efforts of the meteor impact of 2008 November 20 at 5:26.43 MST.

2008 November 3. Astronomers hunt for Earth-bound killer rocks. By Charles Burress, San Francisco Chronicle. Excerpt: …Giant rocks from space are hurtling toward us, on track to clobber our planet. But don’t panic. Scientists say the next killer asteroid – unlike those that pummeled us in the past – can be deflected if we know about it far enough in advance.
So while many of us sleep, two Bay Area astronomers have recently begun standing sentinel against the cosmic cannonballs that could smash into Earth. Their big eye is “Nellie,” the 36-inch reflecting telescope at the Chabot Space & Science Center in the Oakland hills.
“We’ve not discovered anything,” said asteroid-tracker Gerald McKeegan, a member of the Eastbay Astronomical Society, which is affiliated with Chabot. “A lot of what we do is follow-up work.”
…”You’ve got a rock, and now we have to figure out where that rock is going,” said Chabot staff astronomer Conrad Jung. “We play a small but important role in trying to figure it out.”
The Chabot center recently became the only Bay Area facility on active duty in the Earth-threatening asteroid search when it was selected to join an official worldwide network of observatories tracking potentially catastrophic “NEOs,” – space talk for near Earth objects.
…Chances are small that Earth will be hit by an asteroid soon, but the consequences would be so enormous that the U.S. government and many experts around the world say we must begin to prepare. NASA’s goal is to locate 90 percent of asteroids that could cause global disasters – those that come close to Earth’s orbit and are larger than 1 kilometer in diameter – by the end of this year….

2008 Apr 15. Gauging a Collider’s Odds of Creating a Black Hole. By DENNIS OVERBYE, NY Times. Excerpt: … the Large Hadron Collider… starts smashing protons together this summer at the European Center for Nuclear Research, or Cern, outside Geneva, in hopes of grabbing a piece of the primordial fire, forces and particles that may have existed a trillionth of a second after the Big Bang.
Critics have contended that the machine could produce a black hole that could eat the Earth or something equally catastrophic.
To most physicists, this fear is more science fiction than science fact. …In a paper published in 2000 with the title “Might a Laboratory Experiment Destroy Planet Earth?” Francesco Calogero, a nuclear physicist at the University of Rome and co-winner of the 1995 Nobel Peace Prize for his work with the Pugwash conferences on arms control, deplored a tendency among his colleagues to promulgate a “leave it to the experts” attitude. …society has never agreed on a standard of what is safe in these surreal realms when the odds of disaster might be tiny but the stakes are cosmically high. In such situations, probability estimates are often no more than “informed betting odds,” said Martin Rees, a Cambridge University cosmologist, the astronomer royal and the author of “Our Final Hour.” …the random nature of quantum physics means that there is always a minuscule, but nonzero, chance of anything occurring, including that the new collider could spit out man-eating dragons.
…Next year will see the release of the film version of “Angels and Demons,” …in which the bad guys use a Cern accelerator to gather antimatter for a bomb to blow up the Vatican, and it includes scenes at Cern.
…Neither Dr. Calogero nor Dr. Rees say they are losing sleep over the collider. Some risk is acceptable, even inevitable, in the pursuit of knowledge, they say, and they trust the physicists who have built it….

2007 September 20. Meteorite likely caused crater in Peru. By MONTE HAYES Associated Press Writer. The Associated PressExcerpt: Peruvian astronomers said Thursday that evidence shows a meteorite crashed near Lake Titicaca over the weekend, leaving an elliptical crater and magnetic rock fragments in an impact powerful enough to register on seismic charts….
The Earth is constantly bombarded with objects from outer space, but most burn up in the atmosphere and never reach the planet’s surface. Only one in a thousand rocks that that people claim are meteorites turn out to be real, according to Jay Melosh, an expert on impact craters and professor of planetary science at the University of Arizona….
Such impacts are rare, and astronomists still want to do other tests to confirm the strike…. Meteorites are actually cold when they hit Earth, astronomists say, since their outer layers burn up and fall away before impact…..
More details emerged when astrophysicist Jose Ishitsuka of Peru’s Geophysics Institute reached the site about 6 miles from Lake Titicaca. He confirmed that a meteorite caused a crater 42 feet wide and 15 feet deep, the institute’s president, Ronald Woodman, told The Associated Press on Thursday.
Ishitsuka recovered a 3-inch magnetic fragment and said it contained iron, a mineral found in all rocks from space. The impact also registered a magnitude-1.5 tremor on the institute’s seismic equipment – that’s as much as an explosion of 4.9 tons of dynamite, Woodman said….
Peasants living near the crater said they had smelled a sulfurous odor for at least an hour after the meteorite struck and that it had provoked upset stomachs and headaches….
Meteor expert Ursula Marvin said that if people were sickened, “it wouldn’t be the meteorite itself, but the dust it raises….”

2007 March 16. The Sky Is Falling. Really. By RUSSELL L. SCHWEICKART (a former Apollo astronaut, is the chairman of the B612 Foundation, which promotes efforts to alter the orbits of asteroids). Tiburon, Calif. Americans who read the papers or watch Jay Leno have been aware for some time now that there is a slim but real possibility – about 1 in 45,000 – that an 850-foot-long asteroid called Apophis could strike Earth with catastrophic consequences on April 13, 2036. What few probably realize is that there are thousands of other space objects that could hit us in the next century that could cause severe damage, if not total destruction.

2007 January 6. What Landed in New Jersey? It Came From Outer Space. By KAREEM FAHIM. Excerpt: The object that tore through the roof of a house in the New Jersey suburbs this week was an iron meteorite, perhaps billions of years old and maybe ripped from the belly of an asteroid, experts who examined it said yesterday. …it landed – and ruined a second-floor bathroom – the meteorite is only the second found in New Jersey, said Jeremy S. Delaney, a Rutgers University expert who examined it. …from looking at it, Dr. Delaney and other experts were able to tell that the object it had been part of – perhaps an asteroid – cooled relatively fast. It is magnetic, and reasonably dense, they determined. The leading edge – the one that faced forward as it traveled through the earth’s atmosphere – was much smoother, while the so-called trailing edge seemed to have caught pieces of molten metal. …”The worth of a meteorite like this is almost completely determined by where it fell,” said Eric Twelker, a geologist and a dealer in meteorites, who buys and sells perhaps a hundred of them a month on http://meteoritemarket.com, his Web site. He was speaking of the premium placed on meteorites with a compelling back story, like the football-size rock that crashed into a parked Chevrolet in Peekskill, N.Y., in 1992.

2006 November 14 Ancient Crash, Epic Wave. By SANDRA BLAKESLEE, NY Times. Excerpt: Did catastrophe fall from above in 2807 B.C.? Mega-tsunamis following meteor impacts left their mark, researchers say. At the southern end of Madagascar lie four enormous wedge-shaped sediment deposits, called chevrons, that are composed of material from the ocean floor. Each covers twice the area of Manhattan with sediment as deep as the Chrysler Building is high. On close inspection, the chevron deposits contain deep ocean microfossils that are fused with a medley of metals typically formed by cosmic impacts. And all of them point in the same direction – toward the middle of the Indian Ocean where a newly discovered crater, 18 miles in diameter, lies 12,500 feet below the surface. The explanation is obvious to some scientists. A large asteroid or comet, the kind that could kill a quarter of the world’s population, smashed into the Indian Ocean 4,800 years ago, producing a tsunami at least 600 feet high, about 13 times as big as the one that inundated Indonesia nearly two years ago. The wave carried the huge deposits of sediment to land. Most astronomers doubt that any large comets or asteroids have crashed into the Earth in the last 10,000 years. But the self-described “band of misfits” that make up the two-year-old Holocene Impact Working Group say that astronomers simply have not known how or where to look for evidence of such impacts along the world’s shorelines and in the deep ocean. …Peter Bobrowski, a senior research scientist in natural hazards at the Geological Survey of Canada, said “chevrons are fantastic features” but do not prove that megatsunamis are real. There are other interpretations for how chevrons are formed, including erosion and glaciation… It is up to the working group to prove its claims, he said. …Bruce Masse, an environmental archaeologist at the Los Alamos National Laboratory in New Mexico …thinks he can say precisely when the comet fell: on the morning of May 10, 2807 B.C. Dr. Masse analyzed 175 flood myths from around the world, and tried to relate them to known and accurately dated natural events like solar eclipses and volcanic eruptions. …14 flood myths specifically mention a full solar eclipse, which could have been the one that occurred in May 2807 B.C. Half the myths talk of a torrential downpour, Dr. Masse said. A third talk of a tsunami. Worldwide they describe hurricane force winds and darkness during the storm. All of these could come from a mega-tsunami. Of course, extraordinary claims require extraordinary proof, Dr. Masse said, “and we’re not there yet.”

Weather Photography has images of many types of weather/atmospheric phenomena.

2005

22 November 2005. Asteroid Poses Tiny Danger, but It May Be Lured Away. By HENRY FOUNTAIN, NY Times. Excerpt: From a human perspective, Earth-crossing asteroids can have good timing or bad timing. Good timing is when the asteroid and the Earth don’t meet. Bad timing is when they do. Astronomers say that a 1,000-foot diameter asteroid discovered last year may have bad timing. There is a slight possibility that the rock, 99942 Apophis, will hit Earth in 2036 after coming within about 20,000 miles in 2029. A collision could cause regional devastation on a scale far worse than last year’s tsunami. “The most likely thing is that it is not going to be a threat,” said Rusty Schweikart, the former Apollo astronaut and chairman of the B612 Foundation, which is concerned about protecting Earth from asteroids. “There’s 5,499 chances out of 5,500 that it’s going to miss us.” The trouble with Apophis, Mr. Schweikart said, is that that one chance cannot yet be ruled out. Better optical and radar observations are needed to determine the asteroid’s orbit, but the best measurements cannot be made until 2013.
That creates a different timing problem. If the threat from Apophis cannot be ruled out by then, will there be time to deflect it? Mr. Schweikart’s group is not sure and has urged NASA to plan a robotic mission to put a radio transponder on the asteroid so that its orbit can be precisely determined. If such a mission takes 10 years to design and execute, it will still give plenty of time to plan and carry out a deflection mission. NASA has said that planning for a transponder mission can wait till after the more precise measurements are made in 2013. “I have a very high confidence that we can pinpoint exactly the track it’s going to follow,” said Andy Dantzler, director of NASA’s solar system division. In the unlikely event that in 2013 a transponder mission would still be necessary, there would be enough time for that and a deflection mission, if needed, as well, he added. Mr. Schweikart said that NASA’s response was “probably fine.” But he added that it made “aggressive assumptions about how good things are going to be, and how much we’re going to know.” Edward T. Lu, a current astronaut and a board member of B612, … and another astronaut, Stanley G. Love, have a proposal for how to go about deflecting the asteroid: by using a spacecraft to tow it, but without a tow line. In a brief paper in Nature, the two describe how such a gravitational tractor, hovering near an asteroid with its engines canted to avoid the exhaust’s hitting the surface, can slowly pull it into a different orbit. The pulling force would only be about one newton, or roughly the amount of force used to hold a full cup of coffee. “But the point is, if you hang out long enough, it can add up to a substantial oomph,” Mr. Lu said.

10 May 2005. NASA RELEASE: 05-120. NASA’S Chandra Observatory Catches X-ray Super-flares. New results from NASA’s Chandra X-ray Observatory about the Orion Nebula imply super-flares torched our young solar system. Such X-ray flares likely affected the planet-forming disk around the early sun, and may have enhanced the survival chances of Earth. …”We don’t have a time machine to see how the young sun behaved, but the next best thing is to observe sun-like stars in Orion,” said Scott Wolk of Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “We are getting a unique look at stars between one and 10 million years old – a time when planets form.” A key finding is the more violent stars produce flares one hundred times as energetic as the more docile ones. This difference may specifically affect the fate of planets that are relatively small and rocky, like the Earth. “Big X-ray flares could lead to planetary systems like ours, where Earth is a safe distance from the sun,” said Eric Feigelson of Penn State University in University Park. He is the principal investigator for the international Chandra Orion Ultradeep Project. “Stars with smaller flares, on the other hand, might end up with Earth-like planets plummeting into the star.” According to recent theoretical work, X-ray flares can create turbulence when they strike planet-forming disks, and this affects the position of rocky planets as they form. Specifically, this turbulence can help prevent planets from rapidly migrating towards the young star. “Although these flares may be creating havoc in the disks, they ultimately could do more good than harm,” said Feigelson. “These flares may be acting like a planetary protection program.” Additional info at: http://chandra.harvard.edu & http://chandra.nasa.gov

6 April 2005. NASA Release 05-094. Explosions in Space May Have Initiated Ancient Extinction on Earth. Scientists at NASA and the University of Kansas say that a mass extinction on Earth hundreds of millions of years ago could have been triggered by a star explosion called a gamma-ray burst. The scientists do not have direct evidence that such a burst activated the ancient extinction. The strength of their work is their atmospheric modeling — essentially a “what if” scenario. The scientists calculated that gamma-ray radiation from a relatively nearby star explosion, hitting the Earth for only ten seconds, could deplete up to half of the atmosphere’s protective ozone layer. Recovery could take at least five years. With the ozone layer damaged, ultraviolet radiation from the Sun could kill much of the life on land and near the surface of oceans and lakes, and disrupt the food chain. Gamma-ray bursts in our Milky Way galaxy are indeed rare, but the scientists estimate that at least one nearby likely hit the Earth in the past billion years. Life on Earth is thought to have appeared at least 3.5 billion years ago. 

18 February 2005. Cosmic Explosion Among the Brightest in Recorded History. NASA Feature. Scientists have detected a flash of light from across the Galaxy so powerful that it bounced off the Moon and lit up the Earth’s upper atmosphere. The flash was brighter than anything ever detected from beyond our Solar System and lasted over a tenth of a second…. The scientists said the light came from a “giant flare” on the surface of an exotic neutron star, called a magnetar. …. The light was brightest in the gamma-ray energy range, far more energetic than visible light or X-rays and invisible to our eyes. Such a close and powerful eruption raises the question of whether an even larger influx of gamma rays, disturbing the atmosphere, was responsible for one of the mass extinctions known to have occurred on Earth hundreds of millions of years ago. Also, if giant flares can be this powerful, then some gamma-ray bursts (thought to be very distant black-hole-forming star explosions) could actually be from neutron star eruptions in nearby galaxies.

2004

26 December 2004. About tsunami from asteroidal impacts: Deep-sea waves generated at contact by asteroids varying in diameter from 1-100km (unaffected by interaction with sea floor) could reach heights of about 1 km, according asteroidal impact modeling studies (e.g. Gisler, Weaver, et al. 2002). This would translate into multi-km wave heights upon arrival in shallow/shore waters. Thankfully, these are rather rare events, even by geological standards.

2004 Sound of the Big Bang http://faculty.washington.edu/jcramer/BBSound.html

2002

4 September 2002. NASA SCIENTISTS DETERMINED TO UNEARTH ORIGIN OF THE ITURRALDE CRATER. Excerpt: NASA scientists will venture into an isolated part of the Bolivian Amazon to try and uncover the origin of a 5 mile (8 kilometer) diameter crater there known as the Iturralde Crater. Traveling to this inhospitable forest setting, the Iturralde Crater Expedition 2002 will seek to determine if the unusual circular crater was created by a meteor or comet.

Our Home: Earth from Space —video — (available fall 2002) Two student moderators engage the audience with satellite imagery, computer graphics, and historical footage to make the point that the Earth is an interconnected system of air, land, water, and life. The video includes segments on: An introduction to Earth system science; Using satellites to look at Earth from space; El Niño; Global Warming; Drought; Hurricanes (2:03), and An epilogue. Length: 22:00. The video can also be downloaded as QuickTime movies from: http://education.gsfc.nasa.gov/video/.