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Always puzzles me when looking for evidence of extraterrestrial life on exoplanets we always try to look for oxygen - life existed for a long time without it

svachalek 3y ago
Detecting that a planet might barely support life is impossible to do remotely for our next door neighbor Mars, and we have rovers and orbiters sending high resolution images every day. For exoplanets, we're working with 1 pixel images. Not 1 megapixel, 1 pixel. So for now we can only look for things that would make scientists say whoa, how can that possibly happen?
- passwordoops 3y ago
  I wouldn't say the planet "barely" supported life before the oxygenation event. Otherwise we wouldn't have as much fossil evidence as we have. I'd rephrase what you wrote with our current technical limitations make it more feasible to detect life by finding something that would make astrobiologists say woah, how can that possibly happen?
  - breischl 3y ago
    > I wouldn't say the planet "barely" supported life before the oxygenation event. Otherwise we wouldn't have as much fossil evidence as we have. I believe you're talking about Earth, and the person you're responding to was talking about Mars. At least I don't think Mars had an oxygenation event or fossils?
    - passwordoops 3y ago
      Ah yes, sorry. Every now and then I need a reminder to refrain from written communications before I finish my first coffee
ordu 3y ago
A policeman sees a drunk man searching for something under a streetlight and asks what the drunk has lost. He says he lost his keys and they both look under the streetlight together. After a few minutes the policeman asks if he is sure he lost them here, and the drunk replies, no, and that he lost them in the park. The policeman asks why he is searching here, and the drunk replies, "this is where the light is".[1] Science very thoroughly follows the drunkard principle, because there is no sense in looking at places were you unable to find anything. Science is looking for what it can possible see. It cannot see a bacteria under ice of Enceladus, so it doesn't even try. But it can see sometimes gases around Enceladus, so it looks for them. https://en.wikipedia.org/wiki/Streetlight_effect https://en.wikipedia.org/wiki/Streetlight_effect
gizmo686 3y ago
We don't just look for oxygen. For instance, there was some excitement a few years back when there was a tentative observation of phosphine in Venus's atmosphere. To have a good biosignature, you want a signal that cannot be explained by anything other than life. Of course, that means that there might be planets with life that we do not notice, because all of the observables we have access to have an abiotic explanation. Not much you can do about that other than a bunch of science.
renewiltord 3y ago
Becomes easier to understand when you design a different search and estimate cost. Try it.

svachalek 3y ago

Detecting that a planet might barely support life is impossible to do remotely for our next door neighbor Mars, and we have rovers and orbiters sending high resolution images every day. For exoplanets, we're working with 1 pixel images. Not 1 megapixel, 1 pixel. So for now we can only look for things that would make scientists say whoa, how can that possibly happen?

passwordoops 3y ago
I wouldn't say the planet "barely" supported life before the oxygenation event. Otherwise we wouldn't have as much fossil evidence as we have. I'd rephrase what you wrote with our current technical limitations make it more feasible to detect life by finding something that would make astrobiologists say woah, how can that possibly happen?
- breischl 3y ago
  > I wouldn't say the planet "barely" supported life before the oxygenation event. Otherwise we wouldn't have as much fossil evidence as we have. I believe you're talking about Earth, and the person you're responding to was talking about Mars. At least I don't think Mars had an oxygenation event or fossils?
  - passwordoops 3y ago
    Ah yes, sorry. Every now and then I need a reminder to refrain from written communications before I finish my first coffee

ordu 3y ago

A policeman sees a drunk man searching for something under a streetlight and asks what the drunk has lost. He says he lost his keys and they both look under the streetlight together. After a few minutes the policeman asks if he is sure he lost them here, and the drunk replies, no, and that he lost them in the park. The policeman asks why he is searching here, and the drunk replies, "this is where the light is".[1] Science very thoroughly follows the drunkard principle, because there is no sense in looking at places were you unable to find anything. Science is looking for what it can possible see. It cannot see a bacteria under ice of Enceladus, so it doesn't even try. But it can see sometimes gases around Enceladus, so it looks for them. https://en.wikipedia.org/wiki/Streetlight_effect https://en.wikipedia.org/wiki/Streetlight_effect

gizmo686 3y ago

We don't just look for oxygen. For instance, there was some excitement a few years back when there was a tentative observation of phosphine in Venus's atmosphere. To have a good biosignature, you want a signal that cannot be explained by anything other than life. Of course, that means that there might be planets with life that we do not notice, because all of the observables we have access to have an abiotic explanation. Not much you can do about that other than a bunch of science.

renewiltord 3y ago

Becomes easier to understand when you design a different search and estimate cost. Try it.