Tuesday, 30 August 2011

Asteroid impacts likely seeded Mars, icy moons and exo-systems

Impacts likely to have sent Earth-seeds to icy moons and exo-planet systems

The idea that Chixculub-sized impacts would eject life-bearing debris from Earth to the outer planets and beyond is being increasingly validated by computer orbit simulations. 
Mars is quite accessible via direct ejection or after sling-shot acceleration by the Moon.  The timescale to reach Jupiter and its moons via further sling-shots is ~1Myr.  Seeding planets beyond our Solar System as in our 2004 paper on interstellar panspermia had been dismissed, but the new calculations of longer-time orbits are supportive.  Gladman et al in 2006 considered seeding of Titan and Europa, now in 2011 Pennsylvania State Uni and NAU Mexico teams confirm it with the former running simulations as long as 10 Myr.  These calculations show greater transfer to the outer solar system because of higher ejection speeds assumed.  Their limitation is that they do not model the atmosphere’s strong effects on ejection, both the friction that throttles most ejecta and the impact vapour plume that blows out especially the smaller ejecta to higher speeds.
Delivery to icy satellites depends on survival in unbraked impact, whereas for delivery to embryonic exo-planets, Cardiff groups found impact fragmentation followed by gas friction slowing the seed-bearing fragments to be the most effective scenario.


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