Checking for Life Beyond Earth

[Persefone]

How can we check if there is life in outter space?
Thankyou
--persefone--

 

[SGT]

About any form of life, probes sent to the Moon and to Mars have shown nothing. There is still hope to find some forms of life in the moons of the giant gas planets, like Titan and Europa.
As for intelligent life, the project SETI (Search for Extraterrestrial Intelligence) has nothing to report after decades of scanning the sky. This does not mean such life does not exist, only that we are unable to detect it.

 

[Persefone]

I think that is just what people believe, I mean "there should be life in outter space".
But do you know what changes in the atmosphere can help us draw some conclusions on the existence of life ?

 

[SGT]

I think that is just what people believe, I mean "there should be life in outter space".
But do you know what changes in the atmosphere can help us draw some conclusions on the existence of life ?

The atmospheres of the great moons are not so different of what is believed was the atmosphere of primordial Earth, so it is possible the existence of anaerobical life on those moons.
If there was vegetal life there would be free oxygen in the atmosphere. Superior animal life needs oxygen and consequently plants or green algae to develop.

 

[Chronos]

Let's not forget mars. While no smoking gun has been found, there are still tantalizing clues.

 

[DaveC426913]

If there was vegetal life there would be free oxygen in the atmosphere.

If it were Earthlike vegetation, yes. We cannot assume that.

Superior animal life needs oxygen and consequently plants or green algae to develop.

If it is Earthlike animal life, yes. We cannot assume that.



P.S. Be carfeul throwing around that word 'superior'. There is a pretty strong argument that simpler life forms which have done quite nicely unchanged for a billion years, are 'superior' to more complex forms that have only been around for millions our even thousands of years.

 

[SGT]

If it were Earthlike vegetation, yes. We cannot assume that.

If it is Earthlike animal life, yes. We cannot assume that.



P.S. Be carfeul throwing around that word 'superior'. There is a pretty strong argument that simpler life forms which have done quite nicely unchanged for a billion years, are 'superior' to more complex forms that have only been around for millions our even thousands of years.

The only lifeforms we know are Earthlike. If we are to detect non intelligent life at a distance, as the OP asked, we are limited to what lifeforms we know.
I think you are being PC with my use of the word superior. What I mean by superior is complex life. Simpler forms of life can extract energy from fermentation, but this is not very efficient. To provide energy to complex forms of life we need oxidation. Even if there are other possible oxidizers, like chlorine, they are not as abundant as oxygen, so I think there must be free oxygen in the atmosphere to allow complex life.

 

[Phobos]

How can we check if there is life in outter space?
Thankyou
--persefone--

(1) Missions to other planets to check first-hand (e.g., what we've been doing on Mars)
(2) Inference from tell-tale signs as observed through telescopes (e.g., out-of-equilibrium chemistry in the atmosphere not explained by geologic processes such as all the methane in Earth's atmosphere).
(3) Listening for signals (e.g., SETI).
(4) Examining meteorites on Earth that may contain signs of life from their place of origin.
(5) Checking that the folks on the ISS still have air.

 

[Phobos]

As for intelligent life, the project SETI (Search for Extraterrestrial Intelligence) has nothing to report after decades of scanning the sky.

Well, they do have a few "wow" signals that would be excellent possibilities if it weren't for one critical failing...the signals were never repeated so they can't be confirmed.

 

[Ivan Seeking]

As for intelligent life, the project SETI (Search for Extraterrestrial Intelligence) has nothing to report after decades of scanning the sky. This does not mean such life does not exist, only that we are unable to detect it.

It is much too early to draw any conclusion from SETI. We have hardly even begun to look. In fact, due to some new systems coming online, I think it was Seth Shostak who just commented that he expects success within ten years.

 

[Arctic Fox]

SETI is listening on the wrong frequencies...

 

[whozum]

Whose to say that life out there would need the same premises to live as we did/would? If its a completely separate development of life happening completely independantly of ours, why would it be required to follow the same design that life on Earth followed from?

This is a very evolutionary-sounding post.

 

[SGT]

Whose to say that life out there would need the same premises to live as we did/would? If its a completely separate development of life happening completely independantly of ours, why would it be required to follow the same design that life on Earth followed from?

This is a very evolutionary-sounding post.

Life on Earth is very successful. Since we believe that the laws of chemistry are the same in all Universe, there is no reason for life to be entirely different elsewhere. If it is we will be in great difficulty to detect it.

 

[Phobos]

SETI is listening on the wrong frequencies...

or at the wrong times...or at too blunt a detection capability

 

[Phobos]

Whose to say that life out there would need the same premises to live as we did/would? If its a completely separate development of life happening completely independantly of ours, why would it be required to follow the same design that life on Earth followed from?

As noted above, it appears that the laws of physics are the same throughout the universe. Even if an alien lifeform is very different, if it is a technological one, then it should know about radio waves. And it should realize that radio waves provide one of the most effective means for interstellar communication (cheap, easy, fast, long-range, commonplace).

 

[Nereid]

As noted above, it appears that the laws of physics are the same throughout the universe. Even if an alien lifeform is very different, if it is a technological one, then it should know about radio waves. And it should realize that radio waves provide one of the most effective means for interstellar communication (cheap, easy, fast, long-range, commonplace).

Except, of course, that we Homo sap. only 'learned' about radio a century or so ago; maybe in another century, Phobos III will write: Even if an alien lifeform is very different, if it is a technological one, then it should know about neutrinos. And it should realize that neutrinos provide one of the most effective means for interstellar communication (cheap, easy, fast, long-range, commonplace).

Maybe we just haven't 'got' it yet?

 

[Phobos]

Sure, why not.
Of course, I'd have to disown Phobos III for such insolence. ;)

 

[Nereid]

Sure, why not.
Of course, I'd have to disown Phobos III for such insolence. ;)

Nah, you'll be the proudest grandparent on the planet - such insight! such originality! :!)

 

[Boogeyman]

just throwing this out there, but what if there are elements not known to man present on other planets that other life are able to sustain themselves on. Or did we discover all elements already?

 

[arildno]

just throwing this out there, but what if there are elements not known to man present on other planets that other life are able to sustain themselves on. Or did we discover all elements already?

The periodic table is not a fantasy. What are you getting at?

Besides, don't be a paleontologist.

 

[Boogeyman]

whoa, dude i am sorry.

okay, another question. say these aliens are from other galaxies. the nearest stars are light years away, right? so that would mean that aliens travel for years to get here, or they travel faster than the speed of light, and we know nothing travels faster than the speed of light.

just something to ponder on.

 

[Ivan Seeking]

whoa, dude i am sorry.

Don't worry about it.

The periodic table predicts the elements based on the number of protons that are present in an atom. So we can easily predict element 1, 2, 3, etc and see if they exist, and what properties they have. The last time that I checked, there were only a few predicted elements - very heavy elements that do not occur naturally - that have not been detected.

The periodic chart also allows us, to an extent, to anticipate the properties of elements based on their position in the chart.

okay, another question. say these aliens are from other galaxies. the nearest stars are light years away, right? so that would mean that aliens travel for years to get here, or they travel faster than the speed of light, and we know nothing travels faster than the speed of light.

just something to ponder on.

We have a long discussion about the possibilities in the following thread.
https://www.physicsforums.com/showthread.php?t=154990