The world will have to live with surprise asteroid attacks on the scale of Friday's Russian fireball, at least for a while.

The meteor that exploded over the Russian city of Chelyabinsk without warning Friday (Feb. 15), damaging hundreds of buildings and wounding more than 1,000 people, was caused by a space rock about 50 feet (15 meters) wide, researchers said.

Asteroids of this size are both difficult to detect and incredibly numerous, so it will take a long time for astronomers to find and map out the orbits of all the potentially dangerous ones. Besides, researchers have bigger fish to fry.

"Defending the Earth against tiny asteroids such as the one that passed over Siberia and impacted there is a challenging issue that is something that is not currently our goal," Paul Chodas, a scientist with the Near Earth Object Program Office at NASA's Jet Propulsion Laboratory in Pasadena, Calif., told reporters Friday (Feb. 15). [Meteor Blast Over Russia Feb. 15: Complete Coverage]

"We are focusing on the larger asteroids first," Chodas added. "They are the ones that are the most hazardous."


Millions of asteroids

In 1998, Congress directed NASA to find all of the near-Earth asteroids at least 0.6 miles (1 kilometer) wide that could pose an impact risk to Earth. Such large space rocks have the potential to end human civilization if they hit us.

NASA met that challenge several years ago, and its scientists have now identified 95 percent of the 980 such mountain-size asteroids thought to be cruising through Earth's neighborhood. Happily, none of the known behemoths pose any threat to our planet for the foreseeable future.

But the outlook isn't so rosy for smaller asteroids.

Observations by NASA's WISE space telescope, for example, suggest that about 4,700 asteroids at least 330 feet (100 m) wide come uncomfortably close to our planet at some point in their orbits. To date, astronomers have detected less than 30 percent of these objects, which could destroy an area the size of a state if they slammed into Earth.

And researchers have spotted less than 1 percent of asteroids at least 130 feet (40 m) wide, according to officials with the B612 Foundation, a nonprofit organization dedicated to predicting and preventing catastrophic asteroid strikes.

Space rocks of this size can cause severe damage on a local scale, as the 1908 "Tunguska Event" shows. That year, a 130-foot-wide object exploded over Siberia's Podkamennaya Tunguska River, flattening roughly 825 square miles (2,137 square km) of forest.

A space rock in this size class gave Earth a close shave Friday. The 150-foot-wide (45 m) asteroid 2012 DA14 — which was just discovered in February 2012 — cruised within 17,200 miles (27,000 km) of our planet, marking the closest approach of such a big space rock that was ever predicted in advance.

Overall, scientists think 1 million or more near-Earth asteroids are lurking out there, and just 9,600 have been identified to date.


Improving the search

Searching near-Earth space in infrared wavelengths is a good way to find potentially hazardous asteroids, Chodas said, and many other scientists agree.

The B612 Foundation, in fact, plans to launch an infrared space telescope called Sentinel to a Venus-like orbit in 2018. From there, the instrument would peer out toward Earth's neighborhood without having to contend with the sun's overwhelming glare.

In less than six years of operation, Sentinel should spot 500,000 near-Earth asteroids, including the few remaining undetected mountain-size space rocks and more than 50 percent of the 130-footers, B612 officials have said. The goal is to find big, dangerous objects several decades before they may hit us, giving humanity enough lead time to mount a deflection mission.

But even if Sentinel lives up to its billing, many thousands of 130-foot asteroids would remain undetected, as would even more objects the size of the Russian fireball's parent body. So we're likely to be caught off guard again, as the people of Chelyabinsk were Friday.

"NASA has recognized that asteroids and meteoroids and orbital debris pose a bigger problem than anybody anticipated decades ago," said Bill Cooke, head of NASA's Meteoroid Environment Office at Marshall Space Flight Center in Huntsville, Ala.

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Replies to This Discussion

I agree Grinning Cat - good graphic

The Earth supports life so rare in the universe that it may be the only place so endowed with the elements necessary for human flourishing. If there are other life sustaining planets, we have not found them yet. Looking at the moon and Mars, it is easy to see they have been plummeted over and over again; the reason we know is because they don't have water and vegetation to conceal impacts. Earth surely has as many scars as moon and Mars; as many explosions with the capacity to change life as we know it. 

Not only does Earth have life, it has life so abundant and so diverse, we only begin to understand time and space dimensions and life forms. We begin to learn of other dimensions we can't even imagine. The pure joy of seeing those lovely birds with colors too beautiful to describe and behaviors too complex to imitate, and we take it all for granted. 

Sun or clouds, warm or cold, exciting or ordinary, each moment counts. Each breath offers a gift far beyond our ability to create. Every sight gives evidence of wonders far greater than anything we can produce. All sounds of hummingbirds and birds provide affirmation of forces in nature that bring pleasure. Awaken all senses to the miracle of being and the capacity to participate in community with others to use these gifts for the flourishing of all. May we use our power to bring justice and peace to the planet. 

The question of just how common life is in the universe is one of the most interesting ones science hasn't answered yet.

We know only that we haven't picked up signals from an extraterrestrial intelligence BUT that really doesn't say much; we could detect such signals only from "nearby" in our galaxy (which means most of our own galaxy could be teeming with intelligent life and we'd never know it), and of course our galaxy is one of ten billion or so (an estimate that seems to keep going up) in the observable universe.

With numbers like that I'd find it hard to believe we are unique.  I'd find it even harder to believe that life in general--not just intelligent life--is unique.

But we might be effectively unique (as an intelligence) if the other intelligence is far enough away that we can't contact it.

How common is life in general?  Even single celled organisms?  The answer to that will no doubt hinge on how the life we know about began; if it's a ridiculously easy process (given time), then it's common--if not, then it isn't.  Right now we don't know how it happened (except that goddidn'tdoit), and some of the scientists looking into it are deliberately NOT ruling out unlikely chains of events... figuring that an unlikely chain would just mean life is rare in the universe.

But as yet they don't have even one of those.

I hope I live long enough to see answers!

Goddidn'tdoit! That is for sure. With all of evolutionary evidence to examine, we have no reason to be bored with life. Curiosity and inquisitiveness keeps our minds rolling on, even as my body is weary. With quantum physics coming onto the scene, I am grateful to be in on that new adventure.

Right Joan - god didn't do it - but watch the preachers come out and say god is punishing someone for something ... you know the drill. After every disaster the religious folk come out and say that god is punishing someone.

very good questions SteveInCO

"Amen," Joan.  Beautiful.


There's an orange dwarf star called Gliese 710 that will pass close to the Sun in about a million years.  Not that it would hit anything itself, but it's likely to pass through the Oort Cloud and stir it up, causing comets to collide with the earth and maybe do a lot of damage.

The Russians are already accusing "warmongers" in the U.S. of being the real cause of the damage, by the way.  They have their own conspiracy theorists ...

Luara, I wonder how many people believe USA caused the meteor damage? I hope people are joining the "reasoning" club and getting all the benefits of sorting out fact from fiction.

I don't know, that's apparently some of the talk on the street, from an article I read about it.

I wonder how we and the Russian govt do know what it was?  I suppose satellites watch the atmosphere? 

Kind of scary to think that a meteor strike might make people mad(der) at the U.S.!

I have an emailpal who's a physics grad student in Siberia, I mentioned once we have alot of conspiracy-theory stuff in the U.S. and it makes me wonder how our democracy can work with so many people thinking things like that ... He said there's a lot of 9/11 conspiracy stuff etc. etc. there too.  I'm not sure what the main focus is, if it's the govt there or the U.S. govt or what.

Clearly they have readymade demons over there, too.

Good points Luara - I never even thought about conspiracy theories about the meteor.


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