Things move around in the story queue here, but occasionally a particular item almost gets past me before I remember to cover it. Such is the recent work on the possible impact event some 12,900 years ago, which Richard Firestone (Lawrence Berkeley Laboratory) and colleagues have argued would have contributed to the extinction of such large mammals as woolly mammoths and mastodons, not to mention causing continent-wide wildfires that could have brought about the end of the Clovis culture in North America. The period in question comes at the beginning of the Younger Dryas, a 1300-year cold spell whose termination saw the temperature of Greenland warm by over 5°C in just a few decades (see comments below). We've speculated about the possibility of an asteroid or comet impact on Centauri Dreams (the most recent story is here), but new analysis casts doubt on the theory. Sandy Harrison (University of Bristol) has gone to work on charcoal and pollen evidence to study how wildfires...

A small asteroid hitting the Earth's atmosphere is a spectacular phenomenon, but one likely to go unseen if the object has not been previously tracked. But that may be changing as we continue to install automated cameras across the planet. Take a look at this video of the object that exploded over Scandinavia on January 17. A Swedish camera recorded the event, which now goes worldwide over the Net thanks to the camera's owner, one Roger Svensson, and spaceweather.com. The January 17 incident was little more than a lightshow, startling for local wildlife but unnoticed by the sleeping nation beneath the brief glare. It does, however, remind us of the 1017 potentially hazardous asteroids (PHAs) now known to scientists. A PHA is an asteroid larger than 100 meters that may come closer than 0.05 AU to Earth. Prowling around the spaceweather.com site, I find twelve Earth-asteroid encounters this January alone, the closest being the 1.8 lunar distance passage of 2009 BD on January 25. Only...

By Larry Klaes It was while I was working on our recent story on Near Earth Objects that Larry Klaes' obituary for Steve Ostro arrived, a serendipitous event given Ostro's landmark work in identifying planetoids and especially those that come perilously close to us. Ostro's death last December came at a time of increasing public understanding of the threat posed by these objects. Yet the JPL radar astronomer, who used Arecibo's facilities to such good effect, worked with tools that are now in danger of losing their funding, a commentary on how flexible our priorities can be even on issues of planetary survival. Ostro's voice in Arecibo's defense will be deeply missed. Steven J. Ostro, a major player in radar astronomy who was both an alumnus and teacher at Cornell University, passed away on December 15 from pneumonia brought on by a long bout with cancer. He was 62 years old. Ostro received his Master's Degree in engineering physics from Cornell in 1974. Ostro then went to the...

The Spaceguard program, originally mandated by Congress in the 1990s, is in the business of detecting, tracking and cataloging near-Earth objects (NEOs). Spaceguard's goal has always been as ambitious as it is crucial: To locate ninety percent or more of the objects that approach the Earth and are more than one kilometer in diameter. So how is Spaceguard doing? According to Stephen M. Larson (University of Arizona), who manages the Catalina Sky Survey, "We're about 85 percent there." But even when we reach 100 percent, the story is far from over. An object just a third of a kilometer in diameter would explode with an energy more than twenty times that of the largest thermonuclear bomb. NASA received another mandate in 2005 to identify near-Earth asteroids and comets down to 140 meters in diameter, still large enough to destroy a city. And even though impacts like these seem to occur only once every several thousand years, no one can say when the next potential strike could happen....

The 1300-year cold spell known as the Younger Dryas is back in the news. The sudden climate change, occurring between twelve and thirteen thousand years ago, may be related to the extinction of large species like the saber-tooth tiger and could have something to do with the disappearance of the Clovis culture, a people whose arrival in the Americas can be traced through their distinctive artifacts. Last year a team from sixteen institutions proposed that the climate change was the result of an impact event possibly involving multiple airbursts of cosmic debris. That theory has been regarded with skepticism, but Douglas Kennett (University of Oregon), who worked with the original team, now says that its research has uncovered billions of nanometer-sized diamonds concentrated in sediments in six locations, ranging from Arizona to Oklahoma, Michigan, South Carolina, Manitoba and Alberta. Such nano-diamonds are produced under the kind of high temperatures and pressures associated with...

One night about ten years ago I was walking down a quiet road on Emerald Isle, NC, the spring air spangled with stars, when a meteor flamed across the sky with such vehemence that I fully expected to hear the sound of an impact. I didn't, of course, and on the normal scale of things, I wouldn't be likely to. Chances are that even if the meteor did survive the fall to Earth, to become one or more of the meteorites sought by scientists as interesting chunks of the early Solar System, it landed far away and was much smaller in size than its trail seemed to imply. Then I looked at Alan Dyer's post on the recent meteor in Alberta, one that Dyer has illustrated with videos of the event. Taken from this week's Carnival of Space, Dyer's account points out that Alberta is a fine hunting ground for meteorites, but even the flat prairie can be tricky to search when you're dealing with a momentarily visible event, a large search area and no reports of an object falling nearby. I also wondered if...

Now here's an interesting question. What would happen if a small asteroid like 2008 TC3, the three-meter object that exploded in the atmosphere late Monday, were headed for a large city? We were able to judge with a high degree of confidence that 2008 TC3 would pose no threat to the surface, and indeed, early reports suggest that its energies -- 1.1 to 2.1 kilotons of TNT -- were expended in the atmosphere. But even the most confident scientists might be hard put to sell the case for calm if the public started imagining worse case outcomes. David Morrison (NASA Ames) has written about the public response to a small impact scenario, a fact I'm drawing from the recent update of NEO News sent to me by Larry Klaes. Also available is a report from spaceweather.com of a visual sighting of the event, sent along by Jacob Kuiper, general aviation meteorologist at the National Weather Service in the Netherlands:: "Half an hour before the predicted impact of asteroid 2008 TC3, I informed an...

Are we going to detect 500,000 near-Earth objects in the next fifteen years as technologies improve? The Association of Space Explorers thinks so, and lays out its view of the danger we face from asteroids and other near-Earth objects in a new report. I'm looking through an executive summary of Asteroid Threats: A Call for Global Response right now, not long after the release of the report's results late last week. The ASE hopes to involve the United Nations in a global information network that would improve our existing capabilities at finding and tracking dangerous objects. It would also set up an oversight group to advise the Security Council about the risks and the best ways to deflect potential impactors. Why the UN? Because it's a global problem. The report points out that trying to deflect an incoming asteroid would create questions of authorization, liability and financial action that inevitably involve the international community. Citing its belief that existing technology...

We could do with as much information as possible about near-Earth asteroids. A manned mission is a natural step, both for investigating a class of object that could one day hit our planet, and also for continuing to develop technologies in directions that will be useful for our future infrastructure in space. You would think we would know much of what we needed from examining meteorites, which generally are chunks of asteroid material, but that assumption turns out to be erroneous. A recent paper in Nature has the story. Richard Binzel (MIT) and colleagues have been considering the properties of asteroids for a long time, looking at the spectral signatures of near-Earth asteroids and comparing them to spectra obtained from meteorites. And it turns out that most of the meteorites that fall to Earth represent types of asteroid that are different from the great bulk of near-Earth asteroids. In fact, the varied types of meteorites we find here generally resemble the mix of asteroids...

Photons streaming outward from the Sun can impart momentum, which is how a solar sail works. But even more subtle effects produced by the warming of irregular objects may have visible results. A new study of asteroid moons and how they form invokes the tongue-twister known as the Yarkovsky, O'Keefe, Radzievskii, Paddack effect, mercifully shortened to 'YORP effect' by those who study it. A body warmed by the Sun gives off infrared radiation, which carries momentum as well as heat. An asteroid's spin can thus be speeded or slowed by sunlight. Add plenty of time and things get interesting. Start with the kind of asteroid that is little more than a pile of rocky rubble held together by gravity, then spin that rubble pile up slowly over a period of millions of years and eventually material will be slung off from the asteroid's equator. Colliding materials of this nature can eventually coalesce into the satellite we see orbiting its parent, says Patrick Michel (Cote d'Azur Observatory,...

As America celebrates its Independence Day, I'm thinking not only of the fireworks in store for tonight but also those that may have lit up northern Canada almost 13,000 years ago. The case for an asteroid or comet impact there has been strengthened by work in Ohio and Indiana that examines an unusual fact: Gold, diamonds and silver found in the region owe their origins to the diamond fields of Canada. Did glaciers bring these deposits, which evidently arrived in the same period as the supposed impact, much further south? Or is geophysicist Allen West correct in flagging them as the signs of an ancient catastrophe? Ken Tankersley, an anthropologist at the University of Cincinnati, doubted West's notion and opted for the glacier theory until his recent work on the deposits. Says Tankersley: "My smoking gun to disprove (West) was going to be the gold, silver and diamonds. But what I didn't know at that point was a conclusion he had reached that he had not yet made public -- that the...

By Larry Klaes "Suddenly in the north sky… the sky was split in two, and high above the forest the whole northern part of the sky appeared covered with fire… At that moment there was a bang in the sky and a mighty crash… The crash was followed by a noise like stones falling from the sky, or of guns firing. The earth trembled." So wrote a witness -- fully forty miles away from the event -- of the Tunguska impact of 1908, whose 100th anniversary is today. As Larry Klaes notes, small bodies still undetected by astronomers could pose the threat of another Tunguska, making the hunt for Earth-crossing objects a matter of high importance not just for science but planetary security. Across the many billions of miles of space that our Solar System occupies in its small piece of the vaster Milky Way galaxy, the most numerous members of our celestial neighborhood by far are the comets, planetoids, and meteoroids. Although much smaller than the Sun, the major planets, and...

With the 100th anniversary of the Tunguska impact in Siberia coming up on Monday (and we'll look at it closely then), several items seem germane to the topic of asteroid deflection. Yesterday, a technical briefing at the University of Calgary outlined the Canadian NEOSSat (Near Earth Orbit Surveillance Satellite) mission, a space telescope designed to track small objects near Earth, some of which may pose a collision threat. The suitcase-sized NEOSSat (launch date 2010) capitalizes on technology developed for Canada's MOST (Microvariability and Oscillation of STars) satellite, which was designed to measure stellar ages in our galaxy. While NEOSSat's asteroid-hunting capabilities draw most media attention, the satellite is also going to act as a monitor on other satellites orbiting the Earth, contributing to the worldwide Space Surveillance Network. Satellite-tracking tests using the MOST instrument have proven that a microsatellite can track other satellites, but tuning the...

Asteroid and comet impacts seem to be obvious culprits in mass extinctions on Earth. The heavily cratered Moon reminds us how severe earlier bombardments have been, and it's an easy segue to note that 23 extinction events are now thought to have occurred since the beginnings of life on our planet. In the past 540 million years (the period during which abundant animal life has existed), we can identify five mass extinctions, with huge losses in particular to marine plants and animals. The Chicxulub crater in the Yucatan is a striking piece of evidence for this scenario, but massive volcanic activity may well have played a role, and perhaps a major one. And what of the other extinctions? A new theory published in Nature seems to put a damper on the easy correlation of extinctions with impacts. Indeed, Shanan Peters (University of Wisconsin-Madison) argues that the largest factor may have been changes in ocean environments related to sea level. Says Rich Lane (National Science...

David S.F. Portree hosts the 54th Carnival of Space at his Altair VI site this week. I love Altair VI -- the stories are consistently interesting and the artwork well chosen as well as frequently unusual. Besides, a collector of old pulp magazines like myself can't help but be drawn to a site with an early 30's era Science Wonder Stories cover at the top. From this week's carnival, I'll send you to Starts with a Bang!, which looks at what we could do to nudge an asteroid away from a potential collision with Earth. Noting that 433 Eros, which came near Earth recently, sports a mass of 6 x 1015 kg, Ethan Siegel flags the thermonuclear option as the best bet for moving such a massive object, assuming we get two months' warning. Of course, two months' warning depends upon how well we've mapped Earth-crossing objects, an inventory still being built. Let's hope this century will see us create the infrastructure to nudge these things out of harm's way via missiles from launching sites at...

By Larry Klaes Any good news from Arecibo is welcome, and Larry Klaes here delivers it. The observatory, threatened with closure despite its key role in the hunt for Earth-crossing asteroids, may have found at least temporary deliverance. Politics seems to have played a role, as Larry notes, but for once with results that benefit science rather than compromising it. Meanwhile, a new study of the Chixculub impact 65 million years ago tells us that a hail of carbon cenospheres -- tiny carbon beads -- may have fallen planet-wide following the strike. The more we learn about past impacts, the more we realize how important a role our planetary radars play in forestalling future catastrophe. What exists on the island of Puerto Rico that is over 1,000 feet across, could hold ten billion bowls of cereal, pick up a cell phone call from the planet Venus, once sent a message to any potential inhabitants of a distant globular star cluster, discovered the first planets around another star, has...

One of the world's largest impact craters (see below) lies under Mexico's Yucatan peninsula, evidently a major player in the demise of the dinosaurs. Chicxulub is 180 kilometers in diameter, the subject of continuing research by the man who identified it, Alan Hildebrand (University of Calgary). So you could say Hildebrand has an idea what massive impacts from asteroids can do to the Earth's surface, having studied the environmental effects caused by this one and mapping the crater's structure to identify mineral, oil and gas resources. That interest has led Hildebrand into an ongoing asteroid hunt, and explains his current plans to build and launch a space-based observatory designed to look for near-Earth objects. The scientist currently uses use a retrofitted satellite tracking telescope in NEO work here on Earth. The instrument, based at the University of Calgary's Rothney Astrophysical Observatory (some 75 kilometers southwest of the city) is an extensive re-build, a Cold War era...

Do we have a good idea how many impact events have affected life on Earth? New work on ocean sediments offers the chance to expand our knowledge, helping to flag the distinctive signature of an impact and even to tell us how large the incoming object was. We may find more historical impacts than have previously been identified, reminding us yet again that our habitable zone is an active and sometimes dangerous place to be. True, the issues involved in mass extinctions are complicated, but major impacts clearly played a role in some, including the death of the dinosaurs. François Paquay and team estimate the impactor that struck 65 million years ago at the Cretaceous-Tertiary (K-T) boundary was between four and six kilometers in diameter. While other factors, including volcanism, can't be ruled out, the meteorite certainly didn't help matters. Paquay (University of Hawaii at Manoa) analyzed samples of ocean sediments to study osmium levels therein. The element is useful because, as...

Impacts from space debris are much in the news again. The death of Arthur C. Clarke plays a role in at least some of the interest, the New York Times reprinting an op-ed piece the writer did for that paper back in 1994. This was not long after Shoemaker-Levy demonstrated what a cometary impact might do even to a massive gas giant, getting people thinking about the options if we discovered an asteroid or comet heading our way. They might also have been reminded of Rendezvous with Rama. Clarke had discussed asteroid impacts in the early pages of the 1973 novel, setting up Project Spaceguard as a defense mechanism -- a 1992 NASA workshop report on near-Earth object detection honored Clarke by being named the Spaceguard Survey. In the op-ed, Clarke made it clear what he thought the stakes were: In view of the number of collisions that have taken place in this century alone -- most notably, a comet or asteroid that exploded in 1908 in Siberia with the force of 20 hydrogen bombs -- there...

The ever reliable Dennis Overbye gives us a look at the Earth's fate in his most recent story for the New York Times. Citing the work of Klaus-Peter Schroeder (University of Guanajuato, Mexico) and Robert Connon Smith (University of Sussex), Overbye describes our planet's eventual engulfment by a red giant Sun. Earlier studies had questioned whether the Earth might survive this phase, but Smith and Schroeder say no. Their calculations show a red giant Sun 256 times as wide as today's star, and fully 2730 times more luminous. And it will swallow the Earth. I was interested to see Overbye's reference to a 2001 paper that, in the spirit of speculative jeu d'esprit familiar in good science fiction, looks at a way to save the planet. But first, let's run through where our star is heading. Burning through its hydrogen on the main sequence, the Sun should keep getting hotter and larger. Figure 1.1 billion years until you reach the point where it is 11 percent brighter than today, creating a...