Harvard Origins Forum <br>September 19, at 4:00 PM<br>Biological Laboratories Lecture Hall (Room 1068), 16 Divinity Avenue.<br><br>Dr. Herbert Frey<br>Goddard Space Flight Center<br><br>A Late Heavy Bombardment on Mars:<br>
How counting craters on Mars may provide insight into the question of 'impact frustration of life' on Earth (and maybe Mars).<br><br>Abstract:<br>Dating the largest (> 1000 km diameter) impact basins on Mars suggests
<br>they all formed in a relatively short period of time, in what may have<br>been a martian analog of the Late Heavy Bombardment (LHB) on the Moon.<br>Crater retention ages for the large basins are derived from superimposed
<br>smaller visible and buried impact basins which have signatures in Mars<br>Orbiting Laser Altimeter (MOLA) topography or in model crustal thickness<br>data derived from MOLA topography and Mars Global Surveyor gravity<br>
models. If relative ages are converted to Hartmann-Neukum model<br>"absolute" ages, the time period for large basin formation on Mars may<br>have been <200 million years, consistent with the NICE model for a Late
<br>Heavy Bombardment of the inner solar system about 3.9 billion years ago<br>(BYA). It has been suggested that such a bombardment may have frustrated<br>the origin of life on Earth until about 3.8 BYA. An alternative is that
<br>life on Earth (and maybe Mars?) began earlier but was wiped out by large<br>impacts until the LHB ended. Our preliminary Mars data suggests the LHB<br>may have been a relatively brief impact "spike", which could permit an
<br>early habitable period prior to the LHB.<br><br>************************************************************************<br><br>