By Larry Klaes Tau Zero journalist Larry Klaes now looks at recent activity in near-Earth space, where a variety of objects have turned up just this year to remind us of the potential danger of impacts on our planet. With good connections at Cornell University, Larry is our point man for Arecibo information, the more of which the better as we assess the near-Earth asteroid issue and what can be done if one of these rogue objects is found to be on a collision course. The last two months have seen a fair number of objects from space making rather close encounters with the terrestrial worlds of our Solar System. In late January, a small planetoid designated 2007 WD5 made a relatively close pass of the planet Mars. Astronomers had earlier projected the planetoid might actually strike the Red Planet and hoped that one of the robotic spacecraft currently in Mars orbit would be able to record the 164-foot wide rock's impact on the planet's surface. However, as the scientists made...

The 70-meter Goldstone antenna in the Mojave Desert has begun observations of 2007 TU24, the asteroid that will pass 538,000 kilometers from the Earth on January 27-28. Early indications are that the object is asymmetrical, with a diameter of approximately 250 meters. Close pass by the Earth is to occur on January 29 at 0833 UTC, with no chance of a strike. Says JPL's Steve Ostro: "With these first radar observations finished, we can guarantee that next week's 1.4-lunar-distance approach is the closest until at least the end of the next century. It is also the asteroid's closest Earth approach for more than 2,000 years." Image: These low-resolution radar images of asteroid 2007 TU24 were taken over a few hours by the Goldstone Solar System Radar Telescope in California's Mojave Desert. Image resolution is approximately 20-meters per pixel. Next week, the plan is to have a combination of several telescopes provide higher resolution images. Credit: NASA/JPL-Caltech. Now we can...

With the news that an asteroid called 2007 TU24 will pass 538,000 kilometers from Earth on January 29, attention turns to the Catalina Sky Survey, which discovered this near-Earth object last October. The asteroid is thought to be between 150 and 600 meters in diameter, and should become visible to amateur astronomers in late January. The sky map below shows its track near Earth close approach as seen from Philadelphia, but you can generate personalized ephemeris tables here. The Near Earth Object Program is quick to point out that 2007 TU24 poses no threat to Earth during the upcoming encounter, and also notes that objects of this size are thought to pass this close to our planet every five years or so. With an estimated 7000 discovered and undiscovered asteroids in near-Earth orbits, let's keep the Catalina Sky Survey and other programs well funded. The next known close approach by an asteroid of this size will be in 2027, all of which should remind us of the need to get an...

Centauri Dreams has always advocated a robust asteroid detection program to help us get an accurate census of objects that might endanger Earth. Thus I'm happy to report on promising events at the UK's sole observatory dedicated to Earth-crossing asteroids. The Spaceguard Center in Wales has been offered a new telescope by the Institute of Astronomy (Cambridge), the light pollution in the latter location having reached the point where observations are seriously compromised. Fortunately, there are parts of Wales with dark skies indeed. Thus the Schmidt instrument, useful for identifying objects moving against the stellar background, should be useful not only for searching but also tracking comets and asteroids. Absent funding sources in Wales or the UK government itself, the observatory turns to private sponsorship as the potential solution. We'll keep an eye on how that effort goes -- an estimated £54,000 ought to do the trick, and as this BBC report notes, the site's possibilities...

The 36th Carnival of Space is up at Steinn Sigurðsson's Dynamics of Cats site. Standing out this week are the items flowing in from the American Astronomical Society meeting in Austin, which ran until Friday. The best place to get the overview is Universe Today, but both Random thoughts of an astro major and Bad Astronomy have tracked events closely. Also noteworthy this time around is the news that the asteroid strike on Mars is now effectively ruled out, the odds falling to one in 10,000. Image: 2007 WD5 from the University of Hawaii 2.2-meter telescope on Mauna Kea, Hawaii. The circled dot is the asteroid (click to enlarge; it's at dead center, in a green circle). Other dots are artifacts from cosmic rays. The stars are trailed because the telescope is tracking the asteroid as it moves among the stars. Credit: Tholen, Bernardi, Micheli with support from the National Science Foundation. Too bad, as the opportunities for close observation of such a hit would have taught us much...

The latest on the asteroid approaching Mars, with potentially Tunguska-like dangers, is that it will likely pass a safe 48,000 kilometers from the surface at about 1100 UTC on January 30. This news release describes the possibility of an impact as 'unlikely,' but goes on to say that if it does occur, the best view of the event will come from the Mars Reconnaissance Orbiter, whose High Resolution Imaging Experiment (HiRISE) would provide an unprecedented look at the crater. While the size of asteroid 2007 WD5 approximates the object whose impact formed Meteor Crater (northern Arizona) some 50,000 years ago, the latter is thought to have been a metallic asteroid, while the one approaching Mars is probably stony. Current estimates of 2007 WD5 make it out to be 50 meters wide, traveling at some 13 kilometers per second. That's enough to carry quite a punch, as the Tunguska impact proved in 1908, and as we may conceivably see at the end of January. As we watch for updates, ponder the...

Perhaps it's fortuitous that an object similar to the asteroid that caused the Tunguska event in Siberia may put on a display for us on Mars. It's only a one in 75 chance that 2007 WD5 will strike the surface, and those odds may change again as further data are analyzed, but if it does hit, the object could strike with much the same force as the Siberian explosion. This news story reports Tunguska as a 15-megaton explosion, though as we saw on Wednesday, new work at Sandia National Laboratories has re-considered that figure and now opts for the 3-5 megaton range. The potential impact site is near the Martian equator. If we were to witness such a spectacle, it would bring back memories of the 1994 strike of comet Shoemaker/Levy 9, the famous 'string of pearls', on Jupiter. The devastation of that event was stunning, far greater than 2007 WD5 would produce, but the latter might deliver enough fireworks to produce a crater the size of Meteor Crater in Arizona. Is the Solar System trying...

Fifteen megatons of TNT would set off a blast a thousand times more powerful than the weapon used on Hiroshima. 2000 square kilometers of flattened pine forest near the Podkamennaya Tunguska River in central Siberia bear witness to what such a blast can do. That explosion occurred on June 30, 1908 [original typo said '2008,' an obvious mistake!], and we're learning more about it. The Tunguska event seems to have been an air blast occurring at an altitude between five and ten kilometers. The presumed cause: A small asteroid slamming into our atmosphere at speeds in the range of 15-30 kilometers per second. But just how big was the asteroid? I've seen estimates in the range of 50-100 meters in diameter, but we know surprisingly little about the object. No fragments exist. The effects of the fireball and blast wave are apparent (and there are eyewitness accounts of hot winds and shaking buildings), but there is no crater at the epicenter of the blast. We're left to calculate the...

One of the things I like about Norway is that the government there requires at least one percent of public building budgets be devoted to artwork. Thus the plan for the Svalbard Global Seed Vault, which is designed as a hedge against planetary catastrophe. At the Spitsbergen site near the town of Longyearbyen, highly polished metal sheets installed on the roof and front of the entrance portal will create a sparkling sculpture visible for miles around, lit by the Sun or by fiber-optics during the long Arctic winters. I would imagine Norwegian artist Dyveke Sanne took the commission as quite a challenge. How do you capture the spirit of what is essentially a fail-safe backup of the world's vital food crops? Assume for a moment that we do get a massive blow one day from an Earth-crossing asteroid and our survivors, provided there are some, will want to re-start agriculture with the basic crops -- wheat, barley, peas, corn. And not just the basics, for it may be necessary to start over...

Universe Today offers up the latest edition of the Carnival of Space while announcing it will become the new venue for this gathering of Web links on space-related subjects. Among the posts garnered this time, it's Universe Today's own take on the Tunguska event that should most resonate with Centauri Dreams readers. Tadeusz J. Jopek (Astronomical Observatory UAM in Poland) and team have run simulations of the 1908 explosion to estimate the velocity and impact angle of the Tunguska meteorite. "We believe that TCB originated as the result of a breakup of a single body: a comet or an asteroid. In our study we concluded that it is more probable that it was an asteroid. We cannot point to which one; instead we have found several candidates for the Tunguska parent, and the asteroid 2000 WK63 is an example of it," Dr. Tadeusz said. Interesting! The relevant question, of course, is just how often we can expect such impacts to occur. Tunguska was, happily, a largely unsettled place at the...

The Chicxulub crater in the Yucatan gets plenty of press whenever the subject of asteroid deflection comes up, it being the supposed evidence of the 'dinosaur killer' that changed life on Earth forever some 65 million years ago. But other factors may have played a role in the dinosaur extinctions, among them geological events in India, now studied in the form of the so-called 'Deccan Traps,' immense lava beds that show the ancient flow of lava from the same era over an area of hundreds of miles. If current work is correct, the main phase of these eruptions released ten times the amount of climate-altering gases into the atmosphere as Chicxulub itself, which would have occurred more or less at the same point in geological history. And if iridium deposits were an early clue to what happened in the Yucatan, marine sediments and microscopic marine fossils point to the power of the volcanoes. The life forms that created these fossils are known to have evolved just after the extinction...

By Larry Klaes Tau Zero journalist Larry Klaes now returns with a look at the impact that evidently killed the dinosaurs, and the unusual family of planetoids now thought responsible. Is Chicxulub an event that could only have happened in the distant past, or a warning of possible danger ahead? About 65 million years ago, a large planetoid at least six miles in diameter struck our planet at what is now the Yucatan Peninsula in Mexico, leaving a crater over 100 miles across. The force of the impact, which was two million times more powerful than the greatest nuclear bomb ever detonated, instantly killed every living thing within a one thousand mile radius. Many other creatures suffered similar fates when debris from the planetoid impact flung high into the air came plunging back to the ground, setting off firestorms that spread across the globe. The clouds of smoke and dust from this event hung in our atmosphere for several years, blocking out the Sun and terminating many plants that...

A possible impact in the Laurentide ice sheet in northeastern North America some 13,000 years ago is the subject of a new National Geographic special. Called "Mammoth Mystery," the show ran yesterday and will replay multiple times this week. A clip from the show is available online. This is the impact (discussed in these pages in late May) that is implicated, some believe, in the extinction of the mammoth and mastodon, with presumably devastating effects on local human populations. A press conference on this event is now available on YouTube, while National Public Radio's Science Friday show offers its coverage here. The paper is Firestone et al., "Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas," Proceedings of the National Academy of Sciences 10.1073/pnas.0706977104 (27 September, 2007). Abstract online.

The return of 6344 P-L won't light up network switchboards over the weekend, but it's something to ponder, particularly in light of recent Arecibo happenings. 6344 P-L was first found in 1960 on photographic plates made with the 48-inch Schmidt instrument at Palomar Observatory. The discovery team, working at Leiden Observatory in the Netherlands, had found several thousand asteroids, but this one, recognized as a potential danger to Earth, had not been re-identified until now. Under its new name of 2007 RR9, the object remains curious. It is one of almost 900 asteroids bigger than 150 meters in diameter that close within 0.05 AU of Earth's orbit, and observations now indicate it may not be an asteroid at all. SETI Institute astronomer Peter Jenniskens, whose re-discovery of the object was recently confirmed, thinks we're dealing with something else, a dormant comet. Says Jenniskens: "This is a now-dormant comet nucleus, a fragment of a bigger object that, after breaking up in the...

Although I see no sign of it yet on the company's Web page, British aerospace firm EADS Astrium is designing a spacecraft to be called APEX for a potential mission to an asteroid. APEX is short for Apophis Explorer, naming the target of this interesting payload, which would rendezvous with the tiny asteroid in 2014 and spend three years sending back data on the object's size, shape, and composition. Apophis is of more than a little concern, of course, because observations in 2004 suggested a faint possibility that it would hit the Earth in 2029. That scenario has been largely ruled out in favor of a close pass, at 22,400 just slightly nearer than some of our communications satellites. A second flurry of concern has arisen over the possibility of a 2036 strike, but the truly troubling thing about any asteroid this close to us is that its orbit is uncertain. Blame it on the mouth-filling Yarkovsky-O'Keefe-Radzievskii-Paddack effect. As Centauri Dreams has done in previous stories,...

It's a disaster scenario that Hollywood has picked up on (think Deep Impact). An incoming object menaces the Earth. Scientists try to destroy it with nuclear weapons, but the horrified populace soon discovers that the blast has simply broken the object into pieces, each with the potential to wreak havoc planet-wide. Now we learn that an impact between two asteroids causing a similar crack-up may have resulted in the cataclysmic event some 65 million years ago that destroyed the dinosaurs. Researchers from Southwest Research Institute and Charles University (Prague) have been studying the asteroid (298) Baptistina, combining their observations with numerical simulations to model the impact event. As the theory goes, Baptistina's parent body, some 170 kilometers in diameter, was hit by another asteroid approximately 60 kilometers wide. The result: The Baptistina asteroid family, a cluster of fragments in similar orbits that once included 300 bodies larger than 10 kilometers and 140,000...

If we used nuclear weapons to deflect an asteroid, how would we go about it? One thing we don't want to do is explode a nuclear device that fails to move the target, thus scattering radioactive materials into Earth's atmosphere in addition to the damage the incoming object would cause. But Marshall Space Flight Center (Huntsville, AL) has been working up alternative scenarios in a study that looks at objects like Apophis, which will pass within the orbit of the Moon in 2029. Let's take a look at what MSFC is doing, and then ask whether there are better options. Flight International's story on this study reports that a nuclear interceptor could deflect a Near Earth Object (NEO) in the range of 100 to 500 meters if launched two years before impact. Larger NEOs might be deflected with a five year lead time. The idea here isn't to blast the asteroid into rubble, much of which would doubtless fall to Earth in any case, but to deflect it by a 'stand-off' detonation near the object. This...

In a world where climate change is everywhere under discussion, its causes pondered and its effects debated as political fodder, I suppose it makes sense that The Economist would look at the danger posed by Earth-crossing asteroids in the same context. Thus the sub-title of its recent story on the subject: "The ultimate environmental catastrophe." Which, of course, an asteroid impact could well be, particularly if large enough or placed in a highly populated area. I've subscribed to The Economist off and on for decades, always admiring its clarity and style. The magazine handles this subject with skill, noting how quickly the living ecology of Earth scrubs away the tell-tale signs of impact craters, citing the Moon as a counter-example, and going on to note that the Earth Impact Database in Canada can nonetheless identify more than 170 such craters. And it reminds us of NASA's scientist David Morrison's statement that a large meteorite strike is the only known natural disaster that...

"Let's hope that we find all the dangerous asteroids in the next few months," says Cornell astronomer Joseph Burns. He's talking about the Arecibo Observatory in Puerto Rico, which Cornell manages for the National Science Foundation. Word is that Arecibo's radar system may lose its NSF funding as early as 2008, leaving us without our premier tool for tracking asteroids of the Earth-crossing variety. Strictly speaking, Cornell's Arecibo effort runs through the university's National Astronomy and Ionosphere Center (NAIC), which will need to find outside partners to pick up as much as half of the observatory's operating costs or face the threat of total shutdown of the Arecibo telescope by 2011. Image: Aerial view of the Arecibo Telescope, equipped with a 12.6cm, 1.0MW radar transmitter. Credit: NAIC/Cornell University. It's hard to understand why, in its deliberations on the matter, the NSF all but ignored the contribution of Arecibo's radar. In fact, as this Cornell news release makes...

We often talk about the need to find and track Earth-crossing objects, but what do we do if we find one that's likely to hit us? We're far from demonstrating our ability to deflect an incoming asteroid, making a precursor mission of some kind a necessity. The European Space Agency has been carrying out design studies with three industrial consortia -- led by Alcatel Alenia Space, EADS Astrium and QinetiQ -- for a precursor mission called Don Quijote that would involve two separate spacecraft. What the ESA has in mind is to drive an impactor into an asteroid to assess the resulting deflection. The impactor vehicle, called Hidalgo, would hit the target asteroid at a relative speed in the area of ten kilometers per second. The orbiter, called Sancho, would measure the deflection with a high degree of precision and act as a data relay for the approaching impactor. It would also deploy instruments in the form of what ESA calls an 'autonomous surface package' to to study the asteroid's...