<p>As far as I know, and aside from direct communication, there's only one way to "find life" on another planet. That method is to look for molecular oxygen in the atmosphere. Molecular oxygen hates existing by itself and loves to combine with other atoms and molecules through oxidation. The Earth's atmosphere is currently ~30% $\mathrm{O_2}$, but that's only because we have a huge amount of plant life (primarily algae) constantly producing it. If you removed all life from the Earth, the oxygen in the atmosphere would quickly oxidize out and you'd be left with an atmosphere primarily of nitrogen and a few smaller constituents.</p>

<p>What this means is that if we do see a substantial amount of oxygen on a planet, the best bet is that that oxygen was artificially produced by life. It's not ironclad evidence, but its a very strong indicator. We can search for oxygen through a few techniques that already exist. They're still being developed, but the technology is very quickly coming to fruition. Ultimately, you'd need to look at the spectrum of the planet's atmosphere. This can be achieved by either looking at the star's light as it passes through the planet's atmosphere, or else observing at numerous wavelengths and seeing how the transiting planet's radius changes (due to changing atmospheric opacity at different wavelengths).</p>

CC BY-SA 3.0
2017-02-23T17:15:10.913Z
You know that abiotic oxygen is a thing, right?
AtmosphericPrisonEscape
CC BY-SA 3.0
2017-02-23T17:19:52.970Z
@AtmosphericPrisonEscape Yes, that's why I said its not ironclad evidence. Oxygen can exist without life so seeing oxygen is not 100% an indicator life produced it, it is just highly suggestive.
zephyr
CC BY-SA 3.0
2017-02-23T17:21:50.097Z
Well, I would debate the 'highly suggestive'. In fact I always am. We don't know if it is highly suggestive. Low number statistics.
AtmosphericPrisonEscape
CC BY-SA 3.0
2017-02-23T16:59:05.380Z
2017-02-23T16:59:05.380Z
zephyr
<p>It is possible to search for life from here, how?
What methods could be used?
It is possible to look for organic matter?
Could we know if there is life according to the components of the planets atmosphere?</p>

<observational-astronomy><astrobiology><trappist-1>
How could we search for life in TRAPPIST-1
Martin De Simone
# How could we search for life in TRAPPIST-1

(Asked by: username_0 on 2017-02-23)

It is possible to search for life from here, how?
What methods could be used?
It is possible to look for organic matter?
Could we know if there is life according to the components of the planets atmosphere?

**Tags:** observational-astronomy, astrobiology, trappist-1


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## 1 answers

### Answer by username_1 on 2017-02-23. Score: 3 | Accepted answer

As far as I know, and aside from direct communication, there's only one way to "find life" on another planet. That method is to look for molecular oxygen in the atmosphere. Molecular oxygen hates existing by itself and loves to combine with other atoms and molecules through oxidation. The Earth's atmosphere is currently ~30% $\mathrm{O\_2}$, but that's only because we have a huge amount of plant life (primarily algae) constantly producing it. If you removed all life from the Earth, the oxygen in the atmosphere would quickly oxidize out and you'd be left with an atmosphere primarily of nitrogen and a few smaller constituents.

What this means is that if we do see a substantial amount of oxygen on a planet, the best bet is that that oxygen was artificially produced by life. It's not ironclad evidence, but its a very strong indicator. We can search for oxygen through a few techniques that already exist. They're still being developed, but the technology is very quickly coming to fruition. Ultimately, you'd need to look at the spectrum of the planet's atmosphere. This can be achieved by either looking at the star's light as it passes through the planet's atmosphere, or else observing at numerous wavelengths and seeing how the transiting planet's radius changes (due to changing atmospheric opacity at different wavelengths).

> **Comments:**
> **username_2**: You know that abiotic oxygen is a thing, right?  
> **username_1**: @username_2 Yes, that's why I said its not ironclad evidence. Oxygen can exist without life so seeing oxygen is not 100% an indicator life produced it, it is just highly suggestive.  
> **username_2**: Well, I would debate the 'highly suggestive'. In fact I always am. We don't know if it is highly suggestive. Low number statistics.  

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