Thread: Could life evolve without a star to orbit?

Hi all,

First of all, I'd like to apologise if this thread would be more suitable in the Astronomy and Cosmology section. After some deliberation, I deemed this the more appropriate location for my thoughts.

My question is whether it is feasible that life could arise on a planet that does not orbit a star. First of all, I assume that it is possible for a planet to even exist without a star. Yes, an explosion of a star would be required for it to be there in the first place, but I can imagine a couple of events that would produce such a lonely planet, including it either being flung out of it's system by some collision or maybe survive the death of it's star without being engulfed in the process. Also, I think it would be extremely hard (or impossible?) for us to detect such a planet given our modern ways of finding exoplanets.

How important was the sun for our first steps into life? I think I am right in saying that there are organisms on the planet that rely on hot jets deep in the ocean. These organisms have never experienced the sun directly. Is it ridiculous to suppose that life like this could arise without "sunlight"? I suppose that on our planet these organisms have some common ancestor with us that did rely on light from the sun, and have (relatively) recently adapted to life without it.

I've been having a think about this for a while and would love some input and speculation from others.

(Also, please enjoy my use of a light bulb as the threads image, I thought it was very appropriate.)

Is it ridiculous to suppose that life like this could arise without "sunlight"?

It not only isn't ridiculous, but a good number of biologist think that's most likely how it happened--life originating in the deep oceans near hot jets of chemical saturated waters. But given our sample size of only one planet where life originated, I simply don't know, and are unlikely to know in our lifetimes.

Interesting question

My thoughts are:
The Sun is not a major contributor to the Earth's temperature, so although the surface temperature might drop to zero very quickly, there would be heat underground for millions of years.
Photosynthesis is only one of the suggested ways that water formed on the Earth, so there could be water available.
The Sun is also not the source of our atmosphere - so an atmosphere could exist.

In summary, I would say yes, life could form on a sunless planet - but I am not an expert. These are just some thoughts I had.

Dear talking on life is my favourite. Somewhere i had read that our life is Carbon based (search for term Catenation) but there may be silicon based life somewhere in this universe.
And thinking that light , water, air (O2 ) are important for a life to pop up may be wrong. But yet we have to advance in our technology to find if life exists on any exoplanet.
What about meteorite? Sometime before I had read an article that scientists had found a meteorite on which they found the imprints of Bacteria like life. But it was not proved. (Sorry I have no link for this)
What about life on a star itself?
Thanks for giving me chance to explain this to you.

Originally Posted by sir ir r aj

Sometime before I had read an article that scientists had found a meteorite on which they found the imprints of Bacteria like life. But it was not proved. (Sorry I have no link for this)

I think the technical term that covers this is Panspermia - Wikipedia, the free encyclopedia.

Hi Gritty,
there are certainly planets wandering around without stars and some of these have already been discovered. (Indeed there is one candidate, found by gravitational lensing, that is almost certainly accompanied by a moon.) These planets have likely been ejected from new planetary system during their early stages of formation. Jupiter ejected a lot of material from the solar system and this may have included terrestrial size planets.

As others have noted we are not sure of the conditions that are necessary for life to evolve. If all it needs is heat, then solitary exoplanets would retain enough heat for a sufficient time for live to arise and evolve. It is difficult to imagine advanced life evolving in a subterranean environment, but that may be a limitation of our imaginations. I have not seen, or made calculations on how long a liquid ocean could be sustained in deep space. If - and what a big if this is - intelligent life takes as long to develop as it did on Earth, then I have reservations about it being feasible.

Anyone who has done heat loss from a spherical body recently may want to run the calculations and let us know the results.

Originally Posted by John Galt

I have not seen, or made calculations on how long a liquid ocean could be sustained in deep space.

The problem I encountered when reading about this, was that we can currently only explain where ~50% of the Earth's heat originates (e.g. radioactive decay, energy from its original formation).
It seems to be accepted that the heat originates inside the Earth, but without knowing how, I am not sure we can know exactly what effect removing the Sun would have, or how long the heat will last.

Originally Posted by John Galt

Anyone who has done heat loss from a spherical body recently may want to run the calculations and let us know the results.

Another problem I found is how complicated the maths for this is; it is not simply a matter of a cooling sphere.

For example: any surface water would freeze - but that ice would, in turn, insulate the planet.
Also, the planet (if it was like Earth) would continue to generate heat from the radioactive decay in its core.
Add to that an atmosphere and the whole thing gets very complex.

Originally Posted by sir ir r aj

Dear talking on life is my favourite. Somewhere i had read that our life is Carbon based (search for term Catenation) but there may be silicon based life somewhere in this universe.

That is possible, but I find it very unlikely. Silicon has lower bond energies and forms thus weaker covalent bonds.
Not only that, but Si is actually scarce in terrestrial organisms, whilst it is the second most abundant element in the Earth's crust (25.7%).

What about meteorite? Sometime before I had read an article that scientists had found a meteorite on which they found the imprints of Bacteria like life. But it was not proved. (Sorry I have no link for this)

If you are referring to ALH84001, it was not confirmed that it had microscopic fossilized remains in it.
This was already explained by member John Galt and I in this thread (cf. post #26).

Thanks for the responses. I am pleased to have sparked some discussion and thought, that is of course why we come here

Originally Posted by Lynx_Fox

It not only isn't ridiculous, but a good number of biologist think that's most likely how it happened--life originating in the deep oceans near hot jets of chemical saturated waters.

Imagine the excitement of this early form of life upon discovering that above them was another energy-supplying factor to their world that they could exploit to dominate what would become a beautiful and thriving planet. It certainly beats huddling around a murky vent. Do not remind me that evolution by natural selection does not think, let alone become excited. Let me dream.

Originally Posted by John Galt

there are certainly planets wandering around without stars and some of these have already been discovered. (Indeed there is one candidate, found by gravitational lensing, that is almost certainly accompanied by a moon.) These planets have likely been ejected from new planetary system during their early stages of formation. Jupiter ejected a lot of material from the solar system and this may have included terrestrial size planets.

Thanks for this letting me know about this. I wasn't aware that it was possible to detect planets without a star as I had mistakenly assumed that a planetary eclipse of a star or a slight "wobble" was required to show the presence of a planet orbiting it.

Originally Posted by RedPanda

Interesting question

My thoughts are:
The Sun is not a major contributor to the Earth's temperature, so although the surface temperature might drop to zero very quickly, there would be heat underground for millions of years.
Photosynthesis is only one of the suggested ways that water formed on the Earth, so there could be water available.
The Sun is also not the source of our atmosphere - so an atmosphere could exist.

In summary, I would say yes, life could form on a sunless planet - but I am not an expert. These are just some thoughts I had.

You may not be an expect, but these are certainly thoughts worth sharing! Of course I may be wrong but I imagine that there was water before photosynthesis arose. Was this pre-life soup of sorts that contained the organic molecules water based?

Originally Posted by Gritty

Of course I may be wrong but I imagine that there was water before photosynthesis arose. Was this pre-life soup of sorts that contained the organic molecules water based?

Well, I know that the Miller–Urey experiment used water, but I don't think anyone's figured out if it is essential for abiogenesis.

The direction I was coming at this from was: What things do our planet's micro-organisms need and is the Sun the only source. My first thoughts were of air/water/heat.

The question as stated cannot be answered.

First : we do not know how life rose on Earth, though there are plenty of speculations. So we cannot say whether something similar could happen away from a star.

And of course, abiogenesis only results in the most basic of pre-bacterial living cells. For life to develop requires evolution, and that requires variation and lots of time. Would your habitat survive long enough?

there are all sorts of life forms. why would it be outrageous to believe that life elsewhere (maybe even without a star) would be impossible? also even us humans don't fully know how to define life

So the answer must be yes.

(mainly because if you can not be absolutely certain of no in an seemingly infinite pool of possibilities, the answer must be yes)

Life can evolve, because we can not simply define life, nor can we define evolution properly. At least not to a point where we can define stuff we don't even know that can exist. Also, there must be dark "stars" (supergasgiants) out there where planets orbit, and get heated by the gravity friction, and that formed some kind of biochemical pool of matter under the crust. That can convert heat plus molecules to a higher energy compound.

No Zwolver.
The answer is that we do not know.
There is never any shame in admitting this. Rather, shame comes from professing knowledge when it does not exist.

Originally Posted by skeptic

No Zwolver.
The answer is that we do not know.
There is never any shame in admitting this. Rather, shame comes from professing knowledge when it does not exist.

wrong

the answer to op's question is yes, it is possible
just because we haven't personally seen life on other planets doesn't mean it doesn't exist. in theory it is possible for there to be life on other planets

Originally Posted by skeptic

No Zwolver.
The answer is that we do not know.
There is never any shame in admitting this. Rather, shame comes from professing knowledge when it does not exist.

On the other hand, dithering is not always preferable to making even a random choice. I think Zwolver meant "If we had to choose". There is no shame in going forward with incomplete knowledge.

I say it is possible but...unlikely, or atleast. It would be much easier with a star.

Ways I see it working, If you include brown dwarfs these might put out enough heat for life, possibly even liquid water although orbit would have to be very close.

Another is with gravitational tidal forces. Europa for example is thought to have liquid water under the crust, due to pull from jupiter & sister moons causing its water to heat enough to liquify.

Another with our own core where it generates its own heat. However, i am unsure if our core would be molten without a sun or how long it would stay molten without the sun.

another possibility is a black dwarf, where a star has burned all its energy & is nothing but a smoldering ball of star ash. It might still give off enough heat for life but wouldn't really be a star anymore

Sometimes what we think are simple questions, really have presumptions attached that render them unanswerable. For example I could ask "Would fish evolve legs if the land was sandy" and we'd then debate the merits of slithering, tunneling, etc. Until someone point out that legs began evolving before animals left the water.

I'd be pretty confident a planet could orbit a black hole and gravity (as in Europa and Jupiter) could produce heat.

Or, I could say a Jupiter size planet could orbit a black instead of a Sun and have a moon like Europa.



Sorry if this is concise. I just noticed this thread.

Keep in mind europa is tugged from several diffrent directions at once. Its not just one like our moon. Its beening streched and pulled like modeling clay.

Originally Posted by bio

the answer to op's question is yes, it is possible

But we do not know if it is possible. So the statement that it is possible is incorrect. We simply do not know.

Originally Posted by skeptic

Originally Posted by bio

the answer to op's question is yes, it is possible

But we do not know if it is possible. So the statement that it is possible is incorrect. We simply do not know.

agreed. we also do not know if life exists anywhere else in the universe except earth. we do not know if it is possible.

Indeterminate.

But I love to flirt with the idea.

another fun question, on the same trend since we are here

Could life evolve without liquid water?

Liquid methane if heat isn't a needed factor?

I forget myself.

Originally Posted by RedPanda

The Sun is not a major contributor to the Earth's temperature, so although the surface temperature might drop to zero very quickly, there would be heat underground for millions of years.

True!

Photosynthesis is only one of the suggested ways that water formed on the Earth, so there could be water available.

Photosynthesis doesn't do much in terms of water creation.

The Sun is also not the source of our atmosphere - so an atmosphere could exist.

Well, not as a gas. The atmosphere would quickly condense out if we lost the Sun.

Originally Posted by billvon

Originally Posted by RedPanda

The Sun is also not the source of our atmosphere - so an atmosphere could exist.

Well, not as a gas. The atmosphere would quickly condense out if we lost the Sun.

Couldn't the earth's surface be warm enough to prevent the atmosphere condensing completely?

Originally Posted by GoldenRatio

Originally Posted by skeptic

Originally Posted by bio

the answer to op's question is yes, it is possible

But we do not know if it is possible. So the statement that it is possible is incorrect. We simply do not know.

agreed. we also do not know if life exists anywhere else in the universe except earth. we do not know if it is possible.

yes, however we roughly know how vast the universe. would it truly be illogical to assume that life exists somewhere else just because we haven't seen it?

Bio

That is a slightly different statement to the OP. You suggest that, because the universe is so large there should be life elsewhere other than Earth. I agree, with the proviso that it is still speculation, and we are talking probabilities, not certainties.

However, the OP was about life developing on a planet that did not orbit a star. While there are, no doubt, astronomically large numbers of such planets, the overall probability is less than the entire universe. Also we do not know of any mechanism by which life could originate, and then evolve under those conditions. In other words : we do not know.

Originally Posted by bio

Originally Posted by GoldenRatio

Originally Posted by skeptic

Originally Posted by bio

the answer to op's question is yes, it is possible

But we do not know if it is possible. So the statement that it is possible is incorrect. We simply do not know.

agreed. we also do not know if life exists anywhere else in the universe except earth. we do not know if it is possible.

yes, however we roughly know how vast the universe. would it truly be illogical to assume that life exists somewhere else just because we haven't seen it?

oh, i agree with you completly. I was simply pointing out the fact that the only life we know of is confined to earth.

This is not to say its impossible that life doesnt exist off world, when its highly likely that it does. Its just saying we do not know of it. we have no proof of it.

I like you. You think positive. As if there wasn't anyone who could convince us of no, it could be yes. Too bad religion used this tactic for millennium.

On the question where one asked if life could evolve without liquid water, the answer is yes. Gaseous water, can support plant life. Given that an atmosphere is dense enough, and warm enough to keep the water a liquid. and bright enough for the photosynthesis. Problem with this is, that the gaseous water will at some point become liquid. To keep it a gas, it would have to boil, and that doesn't seem good for proteins.

But there could be other ways for the water to keep gaseous. Like a hyper-sonic planet. Sound waves can keep water gaseous indefinitely, without radically increasing the temperature.

Just playing with the idea though. I wouldn't like to walk the surface, but i would love to see a robot walk it..

@zwolver
Wouldnt that require a star, even with a hyper-sonic planet to remain gaseous? & with a star, would we also be looking at a venus type world due to the much denser atmosphere trapping heat?

Yes, a bigger planet, denser atmosphere, but yes, it would require a star. I was painting a planet without liquid water now.. Answering a question you asked earlier. (well.. kinda answered, haha)

Zwolver

You are a bit too ready to make definitive statements. When you suggest plants can use gaseous water, I suspect you are thinking of aeroponics. Hate to disillusion you, but that uses liquid water. If you tried gaseous water, also called steam, you would kill those plants post haste. Aeroponics uses water vapour, which is droplets of liquid water suspended as an aerosol in the air.

Life without liquid water has the same answer as the OP. We do not know.

Originally Posted by Zwolver

To keep it a gas, it would have to boil, and that doesn't seem good for proteins.

Boiling temperature depends on atmospheric pressure (i.e. the weight of atmosphere). You can certainly have conditions on planets or smaller bodies where boiling water doesn't cook. Like, it won't even make noodles or wilt spinach.

you guys are assuming that life on other planets is carbon based and that water etc is required. what if our definition of life is wrong (highly possible), and there are other lifeforms that are composed of different 'stuff'?

"It has been widely suggested that life based around carbon, hydrogen, oxygen, and nitrogen is the only plausible biochemistry, and specifically that terrestrial biochemistry of nucleic acids, proteins, and sugars is likely to be "universal." This is not an inevitable conclusion from our knowledge of chemistry. I argue that it is the nature of the liquid in which life evolves that defines the most appropriate chemistry. Fluids other than water could be abundant on a cosmic scale and could therefore be an environment in which non-terrestrial biochemistry could evolve. The chemical nature of these liquids could lead to quite different biochemistries, a hypothesis discussed in the context of the proposed "ammonochemistry" of the internal oceans of the Galilean satellites and a more speculative "silicon biochemistry" in liquid nitrogen. These different chemistries satisfy the thermodynamic drive for life through different mechanisms, and so will have different chemical signatures than terrestrial biochemistry."

To bio
Again the answer is that we do not know. We can speculate about alternative chemistries for life. But if we are honest, we will admit that we do not know if it is possible.

Originally Posted by skeptic

Zwolver

You are a bit too ready to make definitive statements. When you suggest plants can use gaseous water, I suspect you are thinking of aeroponics. Hate to disillusion you, but that uses liquid water. If you tried gaseous water, also called steam, you would kill those plants post haste. Aeroponics uses water vapour, which is droplets of liquid water suspended as an aerosol in the air.

Life without liquid water has the same answer as the OP. We do not know.

I give you this one.. But if the only liquid water is inside the cell of the organism, does that still count as no liquid water?