Science & Technology
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).
"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.
Source: Space.com
Reader Comments
I'm not sure if humans even have the technology to predict where incoming space rocks are going to hit. I'm not even sure if they can even see them all anyway... just the big ones?
As for which ones they see or not, it's a game of chance. They saw 2012 DA14 coming a whole year in advance and it was estimated to be 45 metres in diameter. Last year, they didn't see 2012 BX34 (estimated to be 20 meters in diameter) until it was passing us by at 60,000 km.
The bottom line is that there is no comprehensive space monitoring program for Near Earth Objects below 1 km in diameter.
@ rbateman
Thank you for sharing, although you miss-stated how deterministic it all is.
Some gravitation resonances are the pragmatic solutions of complex equations, where over time asteroids take up residence exactly along that "cleared orbit path", where perturbations are effectively zeroed out.
"As discussed at Lagrange Points and Trojan Asteroids, there are certain orbital positions where asteroids can be "captured" by planets, in a gravitational tug of war with the Sun. The bodies found near these points are orbiting the Sun, but the way they do so is subtly altered by the gravity of the planets which share their orbits, so that instead of having completely independent orbits of their own, the asteroids follow nearly the same orbital path around the Sun as the planet that controls their orbit.
By far the most noticeable and numerous of these asteroids are the ones which orbit the Sun 60 degrees ahead of and behind Jupiter, … In fact, it was recently discovered that the Earth has a "Trojan" asteroid, orbiting the Sun 60 degrees ahead of us."
see [Link]
BTW, what is referred to as "cleared orbits" and "timing lock," are generally idealized ones, and constant perturbations are always occurring, so that the ephemeris ( en.wikipedia.org/wiki/Ephemeris ) of everything is perennially being re-calcuated and re-estimated ( from observables ).
You assert that things are stable, "Unless the Solar System encounters something," but every interaction of every orbit with every other orbit, is a minuscule but still significant "encounter." Comets come and go far beyond the nominal orbits of planets, but do slightly perturb them, while of themselves being perturbed by even more distant stars and Oort cloud objects ( etc … )
There is no closed form solution to these perturbations, as each set reflects upon and then impacts the next set, ad infinitum. This is a way of saying that there is no single equation that calculates it all.
In addition, Einstein's relativistic corrections are mandatory for Mercury's orbit, as it travels fastest of the planets -- and that is one way that science provided evidence of Einstein's theory.
The solar system model which considered to run like a huge clockworks, is flawed for an uncountable number of reasons. Only a broken clock is exactly right twice a day.
I completely agree when you mention "they are going to try it. Just because they can do it, like the A-bomb," and Robert Heinlein knew so as well, as he wrote about this using the moon's gravity well ( and rail guns built by Loonies ) to attack Earth ( in "The Moon is a Harsh Mistress" ). Why build A-bombs anymore, when throwing cheap iron wrapped rocks can work far better for less money ( and minimal radioactivity ) ?
Media conditioned us all along that big rocks are danger. small one's not a big issue despite tunguska warnings. Now they say Oops! we missed it. Still they may say No Money for it now, unless minimum wage is reduced and unions destroyed.
There is much of noisy discussions in the media at the moment
about the "Asteroid That _Flew_By_", but... did it really ?
Where is it _NOW_ ?
Where are the proofs ?
WHY it is so difficult to provide us with the present coordinates
of the 'flying away' 2012DA14 ?! Again: coordinates, not pictures!
There are many astro-amateurs well equipped with state-of-the art
instrumentation, ready/willing/able to successfully spot that object;
it shouldn't be very far away!:)
A 'cleared' orbit is one that has pre-collision collected most of the debris that was in it's path. After that, there is orbital resonance, such as Pluto and it's twin have with Neptune...they are currently in a timing lock where they never actually meet.
Unless the Solar System encounters something that alters those cleared orbits.
Now. What happens when an orbit is deliberately altered? Are there unintended consequences from a billiard-ball gravitational cascade effect? You know they are going to try it. Just because they can do it, like the A-bomb.