[danmaz74]

"In the absence of a mechanism by which large particles like these can be transported to the stratosphere, we can only conclude that the biological entities originated from space" so, just because we don't KNOW of any mechanism by which large particles could be transported to the stratosphere, we conclude that the particles originated from space - even if we obviously don't KNOW of any mechanism by which life could originate from space and fall on Earth? This looks like very very weak reasoning.

[bayesianhorse]

The mechanism to get these particles there would both have to be very powerful and very not obvious.

The scientists don't say that these particles must be from space, it's just possible, or even very likely.

[danmaz74]

Possible, yes. Very likely... from your handle, you should know about Bayesan reasoning. Considering that we know for sure that there is life on Earth (p=1), while having free-floating life in outer space is a very remote hypothesis (0<p<<1), what of the following three are more likely using Bayesian inference?

a) the sample was contaminated, or there was some other error in the experiement

b) those life forms originated from Earth

c) those life forms originated from outer space

[bayesianhorse]

Setting p=1 is sort of frowned upon in the bayesian methodology. Bayesian inference has nothing to do with this discussion, because the results can only be explained by speculation, and have not been externally verified etc.

Constructing priors from the knowledge of what has not been seen before seems to me like an abuse of the methodology. You might as well say "It's impossible because it's impossible."

I do tend towards a terrestrial origin, but it's certainly a good thing to investigate further how these organisms got there, what are they doing and what sequences do they have...

[danmaz74]

Actually, to me, this seems like a perfect situation to apply Bayesian inference: we need to update the probability estimate of a hypothesis (there is life in outer space) based on new evidence (they found those particles through their experiment).

Anyway, I completely agree with your last sentence: It's certainly a good thing to investigate, I'm not saying they're charlatans. It's the "very likely" that I didn't agree with :)