Caleb A. Scharf offers an interesting argument against interstellar panspermia: You and I, or fluffy bunnies and daffodils are all unlikely candidates for interplanetary or interstellar transferral. The sequence of events involved in panspermia will weed out all but the toughest or most serendipitously suited organisms. So, let’s suppose that galactic panspermia has really been going on for the past ten billion years or so – what do we end up with? …
Isn't life quite dominated by spore forming, radiation resistant, et cetera lifeforms anyway? How is his view affected by this?
Furthermore, no matter how adapted, as long as we aren't speaking of something silicon based straight out of science fiction, if there's no nutrients and no water and temperature is outside of certain range, life can't reproduce. We can't expect water based, carbon based life to thrive in space environment, panspermia or not, adapted to space or not.
If finding extra-terrestrial life in harsh environments is evidence for panspermia, it's absence has to be evidence against panspermia. Can't have it both ways.
Where did we look for life? I know we're preparing to look for it on mars, but the only place I know that we've already looked is Earth, and it's everywhere that there's water.
I don't buy Sharf's argument, by this logic there should be human babies everywhere because sperm manages to escape humans in one way or another, it generally doesn't reach a location with a human egg.
The lack of life everywhere isn't evidence against panspermia, it's evidence that that the interstellar sperm being sent out need a specific environment to create life, which is how sperm works for many animals.
I don't get why people take interstellar panspermia seriously. Intuitively, its much more parsimonious to hypothesize that life just appeared on earth than that it appeared somewhere else, then got jettisoned in space, survived for decades at least in an exceptionally harsh environment (with temperatures violently alternating between freezing cold and boiling hot, no atmosphere, no liquid water, UV solar radiation, cosmic rays) and then fell on this planet, survived atmospheric entry, and happened to find a compatible chemical environment.
It's already implausible inside the solar system, and much more at interstellar level, as stars are needles in the galactic haystack, solar radiation pressure deflects away small incoming objects and larger meteorites would reach the earth so fast that they will almost always burn during atmospheric entry.
Isn't life quite dominated by spore forming, radiation resistant, et cetera lifeforms anyway? How is his view affected by this?
Furthermore, no matter how adapted, as long as we aren't speaking of something silicon based straight out of science fiction, if there's no nutrients and no water and temperature is outside of certain range, life can't reproduce. We can't expect water based, carbon based life to thrive in space environment, panspermia or not, adapted to space or not.
If finding extra-terrestrial life in harsh environments is evidence for panspermia, it's absence has to be evidence against panspermia. Can't have it both ways.
Where did we look for life? I know we're preparing to look for it on mars, but the only place I know that we've already looked is Earth, and it's everywhere that there's water.
I don't buy Sharf's argument, by this logic there should be human babies everywhere because sperm manages to escape humans in one way or another, it generally doesn't reach a location with a human egg.
The lack of life everywhere isn't evidence against panspermia, it's evidence that that the interstellar sperm being sent out need a specific environment to create life, which is how sperm works for many animals.
Robin
I don't get why people take interstellar panspermia seriously. Intuitively, its much more parsimonious to hypothesize that life just appeared on earth than that it appeared somewhere else, then got jettisoned in space, survived for decades at least in an exceptionally harsh environment (with temperatures violently alternating between freezing cold and boiling hot, no atmosphere, no liquid water, UV solar radiation, cosmic rays) and then fell on this planet, survived atmospheric entry, and happened to find a compatible chemical environment.
It's already implausible inside the solar system, and much more at interstellar level, as stars are needles in the galactic haystack, solar radiation pressure deflects away small incoming objects and larger meteorites would reach the earth so fast that they will almost always burn during atmospheric entry.
(A quick googling turns up this: http://adsabs.harvard.edu/a...