18 December 2009

AGU Public Lecture: Finding Near-Earth Objects and Asteroids Before They Find Us

Posted by Michael McFadden

Yeomans the big one.jpgIt may have been a mix of fascination and panic that attracted a full-house yesterday to Don Yeoman’s AGU Public Lecture, titled Near-Earth Objects and Asteroids: Finding Them Before They Find Us.

Don began his talk by talking about his brother-in-law who demands to know why Don spends tax-payer dollars on bits of old rock. The audience at the Exploratorium got a thorough preview of what Don will tell his family member.

Reason #1: By studying comets and asteroids, Don and his fellow researchers can find out a great deal about how our solar system formed, as comets and asteroids are the left-over chunks from that event. For me, Don’s first reason is sufficient; but in case understanding how our space environment won’t sway the doubtful…

Reason #2 The bombardment of Earth by comets and asteroids contributed to the conditions out of which life evolved. They brought water and material necessary for the veneer of carbon-based life.  Again, a pretty compelling justification for Don’s brother-in-law.

Reason #3 Humans owe their position at the top of the food chain in part to an enormous asteroid impact 65 million years ago that extinguished the supremacy of the dinosaurs. Fair enough, Don; but that’s just ancient history. Got anything relevant to today?

Reason #4 We have to search for all of the near-Earth objects bigger than 140 meters which are on course to collide with the Earth. If we find 90% of them, then we would reduce the risk of extinction or obliteration of kilometers of the Earth’s surface by 99%. I think that’s the clincher!
Don then explained that it’s not enough just to find these objects. We have to work out what they’re made of, as how we’ll prevent them hitting us depends on whether they’re ex-cometary fluff balls or spheres of solid iron. Some objects are 70% porous and could absorb the detonation from a missile. Some objects could be tractored out of Earth-trajectory by backing up a spacecraft close to the object and using the gravity between them to escort the asteroid out of our way. This gravity tractor solution would take many years to move the asteroid, so it’s urgent that we find near-Earth objects early.

Don gave an example of a lucky escape: Asteroid 2008 TC3 which burst in the air above railway Station 6 in Sudan. Scientists discovered the SUV-sized TC3 just 19 hours before it exploded 37 kilometers up in the Earth’s atmosphere with the force of 1 kiloton of TNT. Following NASA’s predictions for the debris, a team from the University of Khartoum found some remains of 2008 TC3.

We got lucky with asteroid 2008 TC3; unless we find the next one early, we may not be around to lament our fate.  During the question and answer period, Don explained that the chance of a huge impact is minuscule. The only reason we’re certain of that is because of the work of Don and scientists like him. We should all be immensely grateful; they’re protecting the planet. The packed auditorium at the Exploratorium heartily expressed their appreciation for Don’s lecture and his research. Surely Don’s brother-in-law will think his tax dollars are being spent very well.

–Paul Cooper, AGU Education & Career Services Coordinator