There and Back Again

I've been telling people for a while that we're bound to discover the remains of life, at least microbial life, on Mars, simply because so much of this planet has been dumped on that planet over that last few billion years. Some of this has been due to the solar wind picking up microbial life in Earth's upper atmosphere and blowing it outwards, but a lot has been because of meteor impacts ejecting Earth material off the earth with more than escape velocity. Of course, I also knew that some would make it further out, to the moons of Jupiter and Saturn and further, which are considered to be possible life sites by some, but that seemed like a much smaller possibility to me.

However a new study shows that the Jovian moons would receive a lot of Earth ejecta because Jupiter is an enormous gravity well, and the moons then sweep up the orbiting rocks. In particular, Europa would receive about as many meteorites from Earth as Earth's Moon. Which is absolutely incredible. They would take longer to make the journey of course which would dramatically lower the possibility of survival, even of microbial life that can survive for extended periods in a vacuum (not to mention the fact that it was ejected from the earth by a huge impact and then would settle on another body by another huge impact, neither of which would be conducive towards survival). But still. The same would hold to a lesser extent for Saturn, since it is also an enormous gravity well, but not nearly as large as Jupiter.

The article also points out that most Earth meteorites, many of which would have life in them, would not have been captured by any gravity well in the solar system and would have been ejected into interstellar space. So in a million years or so, they would have reached other solar systems. They say, "Of course, nobody knows if microbes can survive that kind of journey..." Well, that's ridiculous. We know that they can't. The issue is whether a) the biological material could spark new life forms, b) if there are other nearby sites hospitable to life in our galaxy. These are still very controversial, but to the best of my knowledge, the answer to a) is no and the answer to b) is no as well, if we understand them naturalistically (that is, without intervention).