<p>Some of the projects carried out by The Search for Extraterrestrial Intelligence (SETI) would appear to make no carbon/water-based assumptions - for example <a href="https://www.seti.org/laserseti" rel="nofollow noreferrer">Laser Seti</a>, which looks for optical beacons across the whole sky. Although some of SETI's targeted searches, e.g. looking for radio emission from &quot;habitable&quot; exoplanets do.</p>
<p>Ditto I suppose for searches for <a href="https://www.newscientist.com/article/mg24933190-800-dyson-spheres-how-to-spot-an-alien-megastructure/" rel="nofollow noreferrer">alien megastructures</a> (Dyson spheres and the like). They too would seem to be agnostic to the chemistry of their constructors.</p>

CC BY-SA 4.0
2022-07-20T12:44:19.127Z
Cheers, btw is this related to this article [Astronomers detect a radio “heartbeat” billions of light-years from Earth](https://news.mit.edu/2022/astronomers-detect-radio-heartbeat-billions-light-years-earth-0713)?
Ed_Gravy
CC BY-SA 4.0
2022-07-20T21:03:17.923Z
*Great answer!* These might be better classified as searches for *intelligence* than actual life, but that's probably a discussion for a different question and possible a different SE site.
uhoh
CC BY-SA 4.0
2022-07-20T05:27:53.860Z
2022-07-20T08:45:10.623Z
2022-07-20T08:45:10.623Z
ProfRob
<p>This is question is similar to <a href="https://astronomy.stackexchange.com/questions/49947/life-forms-on-planets-not-requiring-water-and-oxygen-as-basic-building-blocks?noredirect=1#comment110498_49947">this</a>, 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.</p>
<p>When scientists explore other planets such as Mars, it seems that</p>
<ol>
<li>they generally look for life derived from water, oxygen and carbon, and</li>
<li>that they do this with a purpose to see whether that planet is habitable for humans or not.</li>
</ol>
<p>Please correct me if I am wrong on either of these.</p>
<p>But here I would like to ask something different and that is, <em>have there been any searches for extraterrestrial life which doesn't require water, oxygen and carbon?</em> If not, does that mean that with today's science and technology we would not be able to detect such life forms?</p>
<p>I did find the following two questions, but they and their answers focus on why carbon and water <em>are essential</em> for life.</p>
<ul>
<li><a href="https://astronomy.stackexchange.com/questions/20858/why-do-aliens-have-to-be-carbon-based-lifeforms">Why do aliens have to be carbon based lifeforms?</a></li>
<li><a href="https://astronomy.stackexchange.com/questions/1611/why-is-liquid-water-considered-a-requirement-for-life">Why is liquid water considered a requirement for life?</a></li>
</ul>

CC BY-SA 4.0
2022-07-19T23:47:57.920Z
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?](https://astronomy.stackexchange.com/q/23370/7982)
uhoh
CC BY-SA 4.0
2022-07-20T01:01:56.797Z
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.
StephenG - Help Ukraine
CC BY-SA 4.0
2022-07-20T01:30:34.417Z
@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?
uhoh
CC BY-SA 4.0
2022-07-20T12:31:08.657Z
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?
Ed V
<planet><universe><life><astrobiology><origin-of-life>
Have there been any searches for extraterrestrial life which doesn't require water, oxygen and carbon?
Ed_Gravy
# Have there been any searches for extraterrestrial life which doesn't require water, oxygen and carbon?

(Asked by: username_0 on 2022-07-19)

This is question is similar to [this](https://astronomy.stackexchange.com/questions/49947/life-forms-on-planets-not-requiring-water-and-oxygen-as-basic-building-blocks?noredirect=1#comment110498_49947), 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 @username_1 (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.

* [Why do aliens have to be carbon based lifeforms?](https://astronomy.stackexchange.com/questions/20858/why-do-aliens-have-to-be-carbon-based-lifeforms)
* [Why is liquid water considered a requirement for life?](https://astronomy.stackexchange.com/questions/1611/why-is-liquid-water-considered-a-requirement-for-life)

**Tags:** planet, universe, life, astrobiology, origin-of-life

> **Comments:**
> **username_1**: 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?](https://astronomy.stackexchange.com/q/23370/7982)  
> **username_2**: 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.  
> **username_1**: @username_2 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?  
> **username_3**: 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?  

---

## 1 answers

### Answer by username_4 on 2022-07-20. Score: 5 | Accepted answer

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](https://www.seti.org/laserseti), 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](https://www.newscientist.com/article/mg24933190-800-dyson-spheres-how-to-spot-an-alien-megastructure/) (Dyson spheres and the like). They too would seem to be agnostic to the chemistry of their constructors.

> **Comments:**
> **username_0**: Cheers, btw is this related to this article [Astronomers detect a radio “heartbeat” billions of light-years from Earth](https://news.mit.edu/2022/astronomers-detect-radio-heartbeat-billions-light-years-earth-0713)?  
> **username_1**: *Great answer!* These might be better classified as searches for *intelligence* than actual life, but that's probably a discussion for a different question and possible a different SE site.  

---

