<p>I shall answer this old question with new information! I'd like to keep this question relevant for future readers.</p>
<p>On January 17th 2022, NASA released the following <a href="https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars" rel="nofollow noreferrer">statement:</a></p>
<p>&quot;Scientists today announced that several of the samples are rich in a type of carbon that on Earth is associated with biological processes.&quot;</p>
<p>So yeah, chances are something was alive there at one point or another. Gale crater (the massive hole-in-the-ground that <a href="https://en.wikipedia.org/wiki/Curiosity_(rover)" rel="nofollow noreferrer">Curiosity</a> calls home) is in a favorable location for life.</p>
<p>As James K has brought up, the fact that Curiosity found carbon doesn't change anything. If there is or ever was anything in that soil would require close observation with a microscope to prove it, which the MSL (Curiosity) rover is not equipped with. The NASA source states that since there is carbon, carbon that is usually associated with biologic processes, the likelihood of life on Mars may be higher than what is stated in the other answer, there just hasn't been enough science power of this particular spacecraft to prove such a thing, and therefore this may be partially based on theory. However, life on Mars period is just a theory. Because this question is more about just on other planets in general, I should address those, but Mars is the most famous example of this. If I had to guess, I'd say there's about a 50% chance that there was something in Gale crater at some point, but I think the chances of life on Europa (A moon of Jupiter) are around 60-70%.</p>
<p>As for my favorite mars rover of all time, <a href="https://en.wikipedia.org/wiki/Perseverance_(rover)" rel="nofollow noreferrer">Perseverance</a>, no word yet on any carbon, bacteria, or anything living whatsoever. But I believe that Perseverance will find something of this nature sometime during its mission since it is equipped with a microscope. And, let's face it, Perseverance is just so much better than Curiosity (No offence, my robot friend Curiosity, but you're just no longer the new shiny thing).</p>

CC BY-SA 4.0
2023-01-20T22:49:44.857Z
"While the finding is intriguing, it doesn’t necessarily point to ancient life on Mars" - (your source)  So your conclusion "something was alive there at one point of another" is not found in your source.  Instead you should say "While this is consistent with ancient life, there are several other, plausible, non-biological explanations, so the probability that life was once on Mars can still only be estimated as 'between 0 and 1'"
James K
CC BY-SA 4.0
2023-01-20T22:47:06.263Z
2023-01-21T21:45:33.990Z
2023-01-21T21:45:33.990Z
Deko Revinio
<p>The probabilites are unknown at the moment (March 2014), since there is only one known planet (Earth) harboring life. This doesn't allow any meaningful probability estimates for the occurence of life, based on empirical data.</p>

<p>The overall formation of life is too complex to allow simulations based on current technology.
Although some intermediate steps can be <a href="http://en.wikipedia.org/wiki/Evolutionary_algorithm">simulated</a> or performed by experiment, e.g. by the <a href="http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment">Miller-Urey experiment</a>.</p>

<p>The <a href="http://en.wikipedia.org/wiki/Drake_equation">Drake equation</a> is a simplified attempt to decompose the probability into factors. Some of the factors aren't known yet. But there has been much progress in estimating the <a href="http://www.nasa.gov/ames/kepler/nasas-kepler-mission-announces-a-planet-bonanza/#.Uyl8TKh5Oqi">frequency of exoplanets</a>, and the <a href="http://arxiv.org/ftp/arxiv/papers/1212/1212.0113.pdf">probability of planets to be habitable</a>. From <a href="http://planetquest.jpl.nasa.gov/news/139">this news release</a> one could estimate (order of magnitude), that there is one habitable planet around a Sun-like star per about 1,700 (about 12³) cubic light years in our region of the Milky Way ("... the nearest sun-like star with an Earth-size planet in its habitable zone is probably only 12 light years away...").</p>

<p>We don't know the probability for habitable planets to develop life, nor to be <a href="http://en.wikipedia.org/wiki/Panspermia">colonized</a>. Probabilities of complex life forms are even more difficult to estimate (yet). <a href="http://en.wikipedia.org/wiki/Planetary_habitability">More discussion about habitability of exoplanets on Wikipedia</a>.</p>

CC BY-SA 3.0
2014-03-19T16:11:52.077Z
Thanks Gerald I have greatly enjoyed reading on the Milley-Ulrey experiment and the Drake equation.  While the former experiment proves that a habitable planet will mostly likely develop life the odds of that life becoming intelligent enough to colonize seem quite low as is evidenced by our planet. But then there are uncountable galaxies in the observable universe so a low non zero probability of planets with intelligent life could still translate to many intelligent life forms out there.
nemesis22
CC BY-SA 3.0
2014-03-19T18:07:18.990Z
@nemesis22 That's plausible; may be there are billions of intelligent life forms in the observable universe, but it's hard to prove.
Gerald
CC BY-SA 3.0
2014-03-20T09:34:34.823Z
One observation, yes, and that one is statistically invalid since we are the observer observing ourselves. Our existance is exactly as likely in a universe where we are alone as in a universe where we have company: 100%.
LocalFluff
CC BY-SA 3.0
2014-09-01T18:52:28.733Z
Drakes equation should take relativity into account... It'll significantly reduce the chances for life existing elsewhere; as seen by us.
frodeborli
CC BY-SA 3.0
2014-03-19T12:09:16.570Z
2014-03-19T12:09:16.570Z
Gerald
<p>From a mathematical point of view,  what is the probability that </p>

<p>1) There is organic life on other planets </p>

<p>2) There are advanced species like us or even greater than us on other planets?</p>

<p>Is there a formula or equation or a way we can calculate this probability?</p>

CC BY-SA 3.0
2017-11-06T23:01:51.103Z
Somewhere between 0 and 1.
ProfRob
CC BY-SA 4.0
2023-01-23T13:31:49.883Z
In my personal opinion, there is even an extra distinction to take care of: there might be life, elsewhere in our galaxy, based on the same structure as ours (proteins, forming DNA), based on the "panspermal" theory, and their might be life which looks entirely different.
Dominique
<galaxy><life><mathematics>
What is the probability that there is life on other planets?
nemesis22
# What is the probability that there is life on other planets?

(Asked by: username_0 on 2014-03-18)

From a mathematical point of view, what is the probability that

1) There is organic life on other planets

2) There are advanced species like us or even greater than us on other planets?

Is there a formula or equation or a way we can calculate this probability?

**Tags:** galaxy, life, mathematics

> **Comments:**
> **username_1**: Somewhere between 0 and 1.  
> **username_2**: In my personal opinion, there is even an extra distinction to take care of: there might be life, elsewhere in our galaxy, based on the same structure as ours (proteins, forming DNA), based on the "panspermal" theory, and their might be life which looks entirely different.  

---

## 2 answers

### Answer by username_5 on 2014-03-19. Score: 9 | Accepted answer

The probabilites are unknown at the moment (March 2014), since there is only one known planet (Earth) harboring life. This doesn't allow any meaningful probability estimates for the occurence of life, based on empirical data.

The overall formation of life is too complex to allow simulations based on current technology.
Although some intermediate steps can be [simulated](http://en.wikipedia.org/wiki/Evolutionary_algorithm) or performed by experiment, e.g. by the [Miller-Urey experiment](http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment).

The [Drake equation](http://en.wikipedia.org/wiki/Drake_equation) is a simplified attempt to decompose the probability into factors. Some of the factors aren't known yet. But there has been much progress in estimating the [frequency of exoplanets](http://www.nasa.gov/ames/kepler/nasas-kepler-mission-announces-a-planet-bonanza/#.Uyl8TKh5Oqi), and the [probability of planets to be habitable](http://arxiv.org/ftp/arxiv/papers/1212/1212.0113.pdf). From [this news release](http://planetquest.jpl.nasa.gov/news/139) one could estimate (order of magnitude), that there is one habitable planet around a Sun-like star per about 1,700 (about 12³) cubic light years in our region of the Milky Way ("... the nearest sun-like star with an Earth-size planet in its habitable zone is probably only 12 light years away...").

We don't know the probability for habitable planets to develop life, nor to be [colonized](http://en.wikipedia.org/wiki/Panspermia). Probabilities of complex life forms are even more difficult to estimate (yet). [More discussion about habitability of exoplanets on Wikipedia](http://en.wikipedia.org/wiki/Planetary_habitability).

> **Comments:**
> **username_0**: Thanks username_5 I have greatly enjoyed reading on the Milley-Ulrey experiment and the Drake equation.  While the former experiment proves that a habitable planet will mostly likely develop life the odds of that life becoming intelligent enough to colonize seem quite low as is evidenced by our planet. But then there are uncountable galaxies in the observable universe so a low non zero probability of planets with intelligent life could still translate to many intelligent life forms out there.  
> **username_5**: @username_0 That's plausible; may be there are billions of intelligent life forms in the observable universe, but it's hard to prove.  
> **username_6**: One observation, yes, and that one is statistically invalid since we are the observer observing ourselves. Our existance is exactly as likely in a universe where we are alone as in a universe where we have company: 100%.  
> **username_7**: Drakes equation should take relativity into account... It'll significantly reduce the chances for life existing elsewhere; as seen by us.  

---

### Answer by username_3 on 2023-01-20. Score: 0

I shall answer this old question with new information! I'd like to keep this question relevant for future readers.

On January 17th 2022, NASA released the following [statement:](https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars)

"Scientists today announced that several of the samples are rich in a type of carbon that on Earth is associated with biological processes."

So yeah, chances are something was alive there at one point or another. Gale crater (the massive hole-in-the-ground that [Curiosity](https://en.wikipedia.org/wiki/Curiosity_(rover)) calls home) is in a favorable location for life.

As username_4 has brought up, the fact that Curiosity found carbon doesn't change anything. If there is or ever was anything in that soil would require close observation with a microscope to prove it, which the MSL (Curiosity) rover is not equipped with. The NASA source states that since there is carbon, carbon that is usually associated with biologic processes, the likelihood of life on Mars may be higher than what is stated in the other answer, there just hasn't been enough science power of this particular spacecraft to prove such a thing, and therefore this may be partially based on theory. However, life on Mars period is just a theory. Because this question is more about just on other planets in general, I should address those, but Mars is the most famous example of this. If I had to guess, I'd say there's about a 50% chance that there was something in Gale crater at some point, but I think the chances of life on Europa (A moon of Jupiter) are around 60-70%.

As for my favorite mars rover of all time, [Perseverance](https://en.wikipedia.org/wiki/Perseverance_(rover)), no word yet on any carbon, bacteria, or anything living whatsoever. But I believe that Perseverance will find something of this nature sometime during its mission since it is equipped with a microscope. And, let's face it, Perseverance is just so much better than Curiosity (No offence, my robot friend Curiosity, but you're just no longer the new shiny thing).

> **Comments:**
> **username_4**: "While the finding is intriguing, it doesn’t necessarily point to ancient life on Mars" - (your source)  So your conclusion "something was alive there at one point of another" is not found in your source.  Instead you should say "While this is consistent with ancient life, there are several other, plausible, non-biological explanations, so the probability that life was once on Mars can still only be estimated as 'between 0 and 1'"  

---

