alt Hacker NewsLife cannot appear in any of the small bodies that become meteors, because there is no source of energy for it.
Life can appear only on big planets or on big satellites, like the big satellites of Jupiter and Saturn, if they have a hot interior and volcanism.
Volcanism brings at the surface substances that are in chemical equilibrium at the high temperatures of the interior, but which are no longer at chemical equilibrium at the low temperatures of the surface, providing chemical energy that can be used to synthesize macromolecules.
Solar energy cannot be used for the appearance of life. Capturing light requires very complex structures that can be developed only after a very long evolution and which cannot form spontaneously in the absence of already existing living beings.
The only theory of panspermia that is somewhat plausible is that life could have appeared on Mars, which had habitable conditions earlier than Earth. Then, some impacts on Mars have ejected fragments that have fallen as meteorites on Earth and some remote ancestors of bacteria have survived this interplanetary trip.
There are many meteorites on Earth that have their origin in impacts from Mars, so at least this part is known as being possible.
Replies
> no source of energy
Asteroids early in the solar system would be very radioactive due to short lived isotopes formed during the formation of the solar system. The existence of these isotopes is known from the patterns of decay products found in asteroids. The current guess is the early protoplanetary disk was bombarded by intense GeV-scale protons accelerated in the shock of a nearby supernova, causing large scale transmutation in the disk.
> because there is no source of energy for it.
Couldn't it have started in the accretion disk?
>Solar energy cannot be used for the appearance of life. Capturing light requires very complex structures that can be developed only after a very long evolution and which cannot form spontaneously in the absence of already existing living beings.
I think that is putting the cart well before the horse. Earliest "life" I would say looks something like a short sequence of random RNA, in some structure (as in secondary), in some solution, among some nucleotides, where brownian motion lead to collision with nucleotides in the chain that grow the chain and/or template off the chain and make a copy. The energy requirements for this sort of pre cell life are far less than cell based life which has to spend energy on cell membrane or wall building. Energy could be quite low, it would just reduce the number of interactions over time. Likely also that this pre cell "life" would not die either so long as it is protected somewhat by cosmic radiation bombarding the chain (although to an extent this is also a ripe source of mutagenic potential).