It is about a billion times more likely that life was blasted off earth and colonized mars.
Considering that life has bloomed here non-stop for about 3.5 billion years and mars looks like it has been dead for at least a billion years (if not always.)
I always find it wierd that some people are more willing to believe life on earth must have come from somewhere else considering how hard it is to get started in the first place. Well it would have been just as hard (or more likely a billion times harder) for life to start somewhere else in the first place just as well.
There is however a strain of bacteria (the smallest known forms) that have adapted to survive extremely high radiation levels (levels that would have never existed on earth even in a highest radiation zones of a uranium mine). It would make no sense for a bacteria to develop a biologically- expensive process to withstand extreme radiation levels if those levels never existed on the planet. But those radiation levels just happen to exist in space.
Astronomers say they have spotted a cloud of alcohol in deep space that measures 463 billion kilometres across, a finding that could shed light on how giant stars are formed from primordial gas.
[snip]Around 130 organic molecules have also been identified so far in outer space, fuelling speculation that these complex molecules may have helped to sow the seeds for life on the fledgling Earth.