Interesting. If we do not find any indicators that life once existed on Mars given that it could have, and given how quickly it seems to have originated on Earth, it would pain a much more dim picture of finding it elsewhere outside our solar system.

given how quickly it seems to have originated on Earth, it would pain a much more dim picture of finding it elsewhere outside our solar system.


I don't know why you would say that. While finding life did or does exist on Mars would greatly increase the possibility that life exists in great abundance in places besides earth, the lack of it being there has pretty well no impact on our chances of finding life elsewhere. It's a big universe out there!

Interesting. If we do not find any indicators that life once existed on Mars given that it could have, and given how quickly it seems to have originated on Earth, it would paint a much more dim picture of finding it elsewhere outside our solar system


Maybe, maybe not. That depends on why Mars didn't get life, if that turns out to be the case. If the reason is because of X and X is common on other planets, then that's bad. On the other hand, if X isn't common on other planets, then it doesn't tell us much.

Unfortunately, this is a case where the null hypothesis must be disproven rather than the other way around. Until we actually prove that life formed somewhere else independently from Earth, we can't assume that there's life anywhere else.

Even if we find signs of life on Mars, it doesn't mean much in terms of life elsewhere unless we can show that it was seperate from life on Earth as opposed to coming from a common source.

A reliance upon Impact Events as the source of heat to create these minerals on any large enough scale to give rise to life is probably mistaken, as heat produced in such fashion would be both intermittent and (relatively)short-lived.

Such events may very well be responsible for at least some of the alteration-product minerals found in this Martian meteoritic material, as well as on the Martian surface --but, geothermal heating and atmospheric/surface heating would be the most likely source to produce the conditions required for the beginning of any Life on Mars.

A reliance upon Impact Events as the source of heat to create these minerals on any large enough scale to give rise to life is probably mistaken


Yeah, I was thinking the same thing. We know that Mars was once volcanically active (olympus mons is hard to miss).

Maybe the guy who wrote the press release just didn't quote all of what the scientist said. That does happen quite a bit in these short stories.

The clays and the organics created by impacts in wet environments are raising habitability, so raising prospects for life.

@ GSwift 7: "Unfortunately, this is a case where the null hypothesis must be disproven rather than the other way around. Until we actually prove that life formed somewhere else independently from Earth, we can't assume that there's life anywhere else."

Now you equivocate between the two senses of null hypothesis, statistical (the one you want to test) and physical (the base scenario you want to test against). The null hypothesis is that life is an easy process, because we observe that it happens so fast.

You want to test that of course, but it is the null hypothesis what the constraint gives us. (Science doesn't do "assumptions", it does constraints.) You are arguing that it isn't the null from a position of ignorance.

The null hypothesis is that life is an easy process, because we observe that it happens so fast


No. We observe that life only started in one instance. No other bodies we can observe show any signs of life. Even a small variation away from conditions here on Earth, such as the difference between here and Mars, may have prevented it. Until proven otherwise, you must assume that life starting is rare. We only know of one instance, since all life here seems to have a common origin. If life is so easy to get started, wouldn't there be many different origins here on Earth? Wouldn't we still see new forms arising?

Furthermore, since we have yet to observe any planet that is likely to have characteristics truely similar to Earth, we have no grounds to assume how common such a planet is likely to be.

You are arguing that it isn't the null from a position of ignorance


That's just observation. We only know of one place where life has formed. There is no way to place any further constraint on that until we find at least one other instance where life formed.

Saying that the null hypothesis is that life formes anywhere the conditions are right is absurd. That's like saying that anywhere we find life, there will be fish. After all, we observe fish, right? Therefore, they must evolve anywhere life is allowed enough time to evolve them.

You cannot place a constraint on anything from just a single observation. Therefore you are left with only two choices: As Arthur C Clark put it, there are two choices: Either we are alone in the Universe, or we are not. Either is terrifying.

Based on current observations, knowledge and assumptions my guess is that simple life is exceedingly common, multicellular life is fairly common, complex multicellular life is rare, complex multicellular intelligent life is exceedingly rare, and complex life with technological civilization might not exist outside our solar system.

That somewhat pessimistic view would be made far more pessimistic if we could not find evidence for simple life developing on Mars at some point when it had good conditions and plenty of time to do so.

Based on current observations, knowledge and assumptions my guess is that simple life is exceedingly common, multicellular life is fairly common, complex multicellular life is rare, complex multicellular intelligent life is exceedingly rare, and complex life with technological civilization might not exist outside our solar system


I'm going to throw in the factor of time to further reduce your estimates. In 14 billion years, we know of only one instance where life formed, and it only started 3 billion years ago? Intelligent life is just a hundred thousand years, maybe a couple hundred thousand? Civilization less than ten thousand?

What are the odds of finding life, complex life, or civilization at any given place AND time?

What is the average life span of an average star?

How frequent are sterilizing events like planetesimal collisions or gamma ray bursts?

What percentage of planets eventually get ejected from their star?

How many planets are able to retain H?