[meteorite-list] Asteroid Pinpointed As Likely Source of Chelyabinsk Meteor

[Ron Baalke]

http://www.newscientist.com/article/dn23976-asteroid-pinpointed-as-likely-source-of-russian-meteor.html

Asteroid pinpointed as likely source of Russian meteor
by Jacob Aron
New Scientist
01 August 2013
	 
Who's been taking potshots at Earth? A new study shows how a 200-metre-wide 
cluster of rocks, first spotted by scientists in 2011, could have spawned 
the Chelyabinsk meteor which exploded over Russia earlier this year.

If correct, that means we may need to watch out for further impacts from 
other fragments of the cluster, which are still at large, in orbit around 
the sun.

The meteor that exploded over Russia on 15 February, scattering debris 
across the Chelyabinsk region and injuring hundreds , came as a complete 
surprise. Since then researchers have traced it to the Apollo asteroid 
family, but no one had matched it to a particular member of the group.

Now Carlos de la Fuente Marcos and his brother Raul, both of the Complutense 
University of Madrid, Spain, are pointing the finger at asteroid 2011 
EO40. Roughly 200 metres wide, it is a rock – or cluster of rocks - previously 
listed as potentially hazardous by the International Astronomical Union's 
Minor Planet Center in Cambridge, Massachusetts.

Rubble pile

First the pair used a computer simulation to create hypothetical orbital 
paths around the sun that would have intersected with Earth at the time 
that the meteor hit. Then they searched a database of known asteroids 
for ones that could have produced rocks that follow those orbits . The 
closest match was with 2011 EO40.

Most asteroids aren't solid rocks but rather rock clusters that have been 
gradually fragmenting for eons. "Most asteroids are rubble piles, very 
fragile," says Carlos. So the brothers also simulated the disintegration 
of an object the size of 2011 EO40 and showed that it could fragment to 
produce a Chelyabinsk-size object that would impact with Earth at the 
correct time.

Future observations of 2011 EO40 could help confirm it as the Chelyabinsk 
parent. Analysing the light bouncing off it would let us match its composition 
to fragments of the meteorite collected in Russia. Sending a probe to 
bring back samples of the asteroid is the only way to be sure, but that 
is a hugely expensive mission that is unlikely to happen. "The cheap but 
not fully conclusive approach will have to suffice for the time being," 
says Carlos.

Asteroid census

If 2011 EO40 really is Chelyabinsk's parent, future observations should 
also help us predict if Chelyabinsk has any siblings still in orbit that 
might also pose a threat to Earth, says Carlos. "Having a precise census 
of this population can help us predict similar impacts in the future."

Jorge Zuluaga of the University of Antioquia in Colombia, who traced the 
Chelyabinsk meteor to the Apollo asteroid family, cautions that EO40 2011 
has yet to be confirmed as the parent. And even it is, he is not too worried 
about it spawning further impacts.

"I don't think this particular asteroid is more hazardous than others 
in the MPC list," he says. He also points out that the asteroid itself 
isn't on a direct collision course with Earth, in any case.

Meanwhile, other researchers are working to piece together the orbit of 
the Chelyabinsk meteor by different methods. One recent study by Simon 
Proud of the University of Copenhagen, Denmark, unearthed satellite pictures 
that show what the meteor looked like from space as it streaked through 
our atmosphere.