http://arxiv.org/abs/2005.09360
Impactors have hit the Earth ever since its formation and have continued to be infrequent guests throughout the Earth’s history. Although the early part of the Earth’s history was marked by these violent events, it is known that life was present early, possibly existing already in the Hadean Eon. It is possible that life can be, and still is, transported between the worlds of the solar system due to impacts leading material away from the impact region. In addition to this lithopanspermia theory, it has been suggested that ejected material can also return to its home planet and ‘reseed’ life after the world has recovered after a global impactor, thus restarting evolution, the so-called refugium hypothesis. Next to such impactors more frequent impacts from smaller non-sterilizing impactors existed during the Heavy Bombardment epoch, feeding material potentially harboring viable organisms into near Earth space. During the three stages of planetary reseeding the encapsulated bacterial population will experience abiotic stressors, specifically they will experience pressure and heat shock twice, in stage 1 and after a recovery phase in stage 2, again in stage 3.While many circumstances have played a role in lifes endurance in the early history of the Earth, a particular biological effect could potentially be conferred on a bacterial population in this scenario. Thus, the surviving population will not only experience an increase in the frequency of robust genotypes, but it can also be expected that their stress tolerance is enhanced compared to non-stressed organisms of the same species. Hence, the trampoline effect means that the mean robustness of the bacterial population towards these stressors is higher in stage 3, than at stage 1.In principle, the time between the impactor and the reimpactor need not be long before this trampoline effect appears.
I. Hegner
Wed, 20 May 20
2/66
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