Spotting extra-solar impacts


3 Nov 05 Comment by Michael Paine: The November issue Scientific American has an article about transpermia by David Warmflash and Benjamin Weiss http://www.sciam.com/issue.cfm?issuedate=Nov-05
There is no charge to view the online copy. See also my notes and links on this topic at;
http://users.tpg.com.au/horsts/swaprock.html
and an estimate of the flux of rocks between Mars and Earth at:
http://users.tpg.com.au/horsts/transpermia.html

It made me wonder about the possibility of detecting extra-solar impacts through new telescopes such as the Large Synoptic Survey Telescope (LSST) and Panoramic Survey Telescope and Rapid Response System (Pan-STARRS).

There are several issues that would need to be resolved to check the feasibility of this idea, including:
1. Whether the impact flash would be bright enough the detect, and not be swamped by the nearby star
2. The number of stars that the systems are able to scan, the sky coverage and the response time.

Assuming these are OK, then applying the characteristics of our solar system can give a very rough idea of the frequency of impact events. Say a very large impact every 100 million years (eg Chicxulub) for each of 4 rocky planets (OK the Moon and Mercury count as one) = one impact every 25 million years. Half will occur on the "wrong" hemisphere >> one impact every 50 million years. So the system would need to "continuously" scan 50 million solar systems in order to detect, on average, one impact every 12 months. Daunting but possible!

Of course, if typical solar systems are dissimilar to ours (number of rocky planets and number of asteroids/comets) then the stats will vary. This may be a way a checking whether we are "typical". It may also tell us the balance between gas-giant (eg SL-9 type impacts) and rocky planets.