This is question is similar to this, but that question has already been voted to be closed. I will add though that I joined this website today, so I am still learning how to write a good question here. And I was guided by @uhoh (thank you) to modify my question and repost it.

When scientists explore other planets such as Mars, it seems that

  1. they generally look for life derived from water, oxygen and carbon, and
  2. that they do this with a purpose to see whether that planet is habitable for humans or not.

Please correct me if I am wrong on either of these.

But here I would like to ask something different and that is, have there been any searches for extraterrestrial life which doesn't require water, oxygen and carbon? If not, does that mean that with today's science and technology we would not be able to detect such life forms?

I did find the following two questions, but they and their answers focus on why carbon and water are essential for life.

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    $\begingroup$ I've made an edit and adjusted the question a bit, you can ask follow-up questions once this has been answered if you'd like to go deeper. Different but related: What if we are looking for the wrong signs of life on other planets? $\endgroup$
    – uhoh
    Jul 19 at 23:47
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    $\begingroup$ This would presumeably require knowing the chemical signatures you're looking for in advance. Seems unlikely to get funding for an explicit search at present and I'm not sure such knowledge exists anyway. $\endgroup$ Jul 20 at 1:01
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    $\begingroup$ @StephenG-HelpUkraine These days that might be true but in the past there may have been less "carbon water bias". And I also wonder if there have been searches for life that don't require "chemical signatures" at all? Or would those be considered searches for intelligence without there necessarily being life? $\endgroup$
    – uhoh
    Jul 20 at 1:30
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    $\begingroup$ As a chemist, I see the carbon-based chemistry and liquid water conditions for life as the best bet, by far, for extrapolation out into the universe. It works here, so maybe a variant works out there. Given that we still do not have a universally agreed upon definition of life, what are the practical guidelines for searching for life not based on organic chemistry and liquid water? $\endgroup$
    – Ed V
    Jul 20 at 12:31

1 Answer 1


Some of the projects carried out by The Search for Extraterrestrial Intelligence (SETI) would appear to make no carbon/water-based assumptions - for example Laser Seti, which looks for optical beacons across the whole sky. Although some of SETI's targeted searches, e.g. looking for radio emission from "habitable" exoplanets do.

Ditto I suppose for searches for alien megastructures (Dyson spheres and the like). They too would seem to be agnostic to the chemistry of their constructors.


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