Impact Delivery of Organics to Mars: Oblique

Introduction and Motivation: Apart from Earth, Mars and Europa are the most likely worlds in our solar system on which evidence of present or past life may be found. In the case of Earth, we concluded that impact delivery of organics, in particular amino acids, could have played an important role in the organic inventory of the early Earth [1]. This was a result more optimistic with respect to organic impact survival that was found in much, though not all, previous work. In the case of Europa, we have found that intact organic delivery is unlikely to be important, although cometary delivery of biogenic elements appears significant [2]. A preliminary study for impact delivery on Mars indicated results for Mars similar to those for Earth, that is a substantial survival for some amino acids in comet impacts on Mars with little or no survival in asteroidal impacts, even though the mean impact velocity (9.3 km/s) is lower than that on the Earth [3]. However, in the case of Mars the lower gravitational field results in a much lower escape velocity, increasing the probability of projectile escaping after the impact. The earlier study using 2D impact simulations [3] indeed showed that in vertical impacts significant escape of cometary material occurs even at the lowest impact velocity modeled, 12.5 km/s. As found by Pierazzo and Melosh [4] this effect becomes more important for oblique impacts, when a larger fraction of the initial impact energy is partitioned to the projectile.