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View Full Version : Could Rogue Interstellar Planets Support Life



FriedPhoton
2008-Feb-10, 10:58 PM
I find the concept of interstellar planets interesting. They'd make convenient way-stations if we ever were able to travel beyond the solar system, assuming any just happened to be along the way.

I've read that it's possible life could exist on such worlds, that dense atmospheres and/or volcanoes could provide the heat required to support it. Of course this would be life that required no sunlight whatsoever.

It is said that planets like this would lack weather due to the lack of a sun. Which leaves me wondering how much longer it might take life to evolve in such a place without the dynamic chaotic environment that weather provides. It seems more likely that if life was ever found in such a place it might have started first while the planet was in orbit in a solar system and hung on tight while whatever catastrophe occurred that flung it out to wander aimlessly among the stars.

I'm curious to know if anyone knows of any processes that would occur on such a world that would provide a chaotic enough environment that life could spontaneously form. It seems that waiting on geologic processes might take a very long time.

Ronald Brak
2008-Feb-10, 11:07 PM
As far as we know, life doesn't need a dynamic, chaotic environment provided by wheather to develop or evolve. We don't know if stability or change is most helpful in the development of self replicators. It is quite possible that life tends to first form underground, which makes wheather rather irrelevant.

FriedPhoton
2008-Feb-10, 11:29 PM
I have no way of proving this because despite all attempts with kitchen chemicals I have yet to create life, but it seems to me that some degree of chaos would be involved to sort through the myriad chemical combinations required to create self-replicating molecules. And then once that occurred, some level of additional chaos would be required to create conditions conducive to evolutionary processes.

For instance, if a self-replicating molecule formed in some primordial soup that did no harm to the self-replicator then there would be no selection process. So it seems there would have to be a range of conditions to which the molecules were subjected that would alternately support then not support the molecule's ability to replicate and then the changes would occur that would allow random molecular mutations to be selected for fitness.

It just seems to make sense to me that some chaotic processes must occur to continuously shuffle through the possibilities. However, I am open to hearing alternative ideas.

Ronald Brak
2008-Feb-10, 11:39 PM
The chaos to which you are referring doesn't require wheather.

And how would you know if you've managed to create life or not in your experiments with kitchen stuff? It can be what we scientists call very very small.

Ronald Brak
2008-Feb-10, 11:40 PM
Much too small to make off with say, a whole leg.

WaxRubiks
2008-Feb-11, 12:02 AM
the magic ingredient to making life is, Barry White. RNA spontaneously forms to his hits.

FriedPhoton
2008-Feb-11, 12:16 AM
The chaos to which you are referring doesn't require wheather.

If not weather, then what is required and how can that occur on a interstellar planet?

Ronald Brak
2008-Feb-11, 12:28 AM
If not weather, then what is required and how can that occur on a interstellar planet?

We don't know what's required. But plenty of people have made suggestions, and there is no particular reason at the moment to believe that there is only one path that leads to self replicating molecules.

This Wikipedia article lists several posibilities:

http://en.wikipedia.org/wiki/Origin_of_life

Tim Thompson
2008-Feb-11, 12:36 AM
I've read that it's possible life could exist on such worlds, that dense atmospheres and/or volcanoes could provide the heat required to support it. Of course this would be life that required no sunlight whatsoever.
If life on such a planet is not impossible, it's mighty close to impossible. Pluto is hardly "interstellar", and it has a surface temperature about 50 Kelvins (-223 C, -369 F). A larger planet, like Earth, would surely retain internal heat a lot longer, and even after a few billion years, still probably not be quite that cold, at Pluto's distance from the sun. Still, the globally averaged heat flow of Earth is miniscule compared to solar input.

An interstellar planet must have started out near a star, but except perhaps near a thermal vent, its surface would be frozen solid, and so would any atmosphere it once had. If life had a chance to start while the planet was still "stellar", it might cling at such places, but I doubt it. Certainly, if life had not already started, it would never start under such unfavorable conditions.

grant hutchison
2008-Feb-11, 12:48 AM
David J Stevenson's paper Possibility of life-sustaining planets in interstellar space (http://www.gps.caltech.edu/uploads/File/People/djs/interstellar_planets.pdf) (pdf) describes one possibility: the retention of a dense hydrogen atmosphere with a high infra-red opacity, which maintains the planet's surface temperature above the freezing point of water, from internal radioactive heating alone.

Grant Hutchison

Ronald Brak
2008-Feb-11, 01:38 AM
If the earth were somehow flung deep into interstellar space, bacteria in the crust would continue to go on living for billions of years, so life is not in such a precarious position on such a world, and for all we know, life started underground. As Grant has mentioned, a strong greenhouse atmosphere could keep the surface of a rouge planet warm as well.

FriedPhoton
2008-Feb-11, 01:52 AM
It is interesting you turned up Stevenson's paper. That is what led me to think about this stuff in the first place.

I will grant the probability of life forming on an interstellar planet is minuscule but it seems it may not be impossible under certain conditions. I just think that perhaps the chances aren't quite as good as Stevenson so optimistically states.

It seems unlikely such a planet would have a moon, but if it did it could go a long way toward helping produce and sustaining life. It would help by generating heat through tidal forces, helping stir the oceans, and possibly creating more weather variations. I imagine a planet with no sun as having stagnant oceans, very little weather, and slow dynamic processes that might not stir things up enough to create life.

At least with a moon the core may not cool as quickly as it would without one, and that extra time may make a difference.

Ronald Brak
2008-Feb-11, 02:01 AM
Gas giants and be flung out of solar systems and it's possible for their moons to survive this process. They could be tidally heated with an interior ocean like Europa, or could have surface liquid water.

FriedPhoton
2008-Feb-11, 02:09 AM
Gas giants and be flung out of solar systems and it's possible for their moons to survive this process. They could be tidally heated with an interior ocean like Europa, or could have surface liquid water.

I'm not really sure what you mean. I'm supposing English isn't your first language so I'm just looking for clarification.

While the theory states rogue planets could occur by being flung from a solar system by a gas giant, it also states that it could grow in interstellar gas as well, and I would imagine that a moon might be more probable in that situation than in one where the planet was sling-shotted by a playful Jupiter.

Ronald Brak
2008-Feb-11, 02:38 AM
It is possible for a gas giant to be ejected from a solar system (most likely due to interaction with another gas giant) without losing all its moons. Gas giants plus moons could also form without a star.

FriedPhoton
2008-Feb-11, 02:44 AM
Do you suppose that under similar circumstances a planet could swipe a moon from a gas giant that is flinging it?

Romanus
2008-Feb-11, 02:44 AM
I think it's possible, especially for planets slightly greater than Earth-mass. However, without any "free" energy from sunlight, limiting life's options to anaerobic and/or chemosynthetic reactions, I'm guessing the biosphere would be very sluggish and energy-poor.

Ronald Brak
2008-Feb-11, 02:58 AM
Do you suppose that under similar circumstances a planet could swipe a moon from a gas giant that is flinging it?

I think so.

FriedPhoton
2008-Feb-11, 03:40 AM
I think it's possible, especially for planets slightly greater than Earth-mass. However, without any "free" energy from sunlight, limiting life's options to anaerobic and/or chemosynthetic reactions, I'm guessing the biosphere would be very sluggish and energy-poor.

Are the lifeforms near ocean vents using anaerobic respiration or chemosynthetic reactions or are they benefiting from a planet bathed in sunlight in an indirect fashion such as fallen detritus and oxygen derived from photosynthesis across the globe? Are they really on some kind of independent system down there or does that system rely upon normal life cycles elsewhere?

Romanus
2008-Feb-11, 02:02 PM
^
A little of both, IIRC.

Noclevername
2008-Feb-11, 04:53 PM
I find the concept of interstellar planets interesting. They'd make convenient way-stations if we ever were able to travel beyond the solar system, assuming any just happened to be along the way.


Actually, they would probably not, as you'd have to slow down and match their trajectory to reach them, and then accelerate again to reach a star system, so the stop would ultimately be a loss rather than a gain.

kzb
2008-Feb-11, 06:35 PM
Wind speeds INCREASE as you go further from the sun. The fastest wind speeds in the solar system are on Neptune. (We don't get supersonic weather here on Earth.) I don't know if the energy for these winds come from the sun or internal heat?

kzb
2008-Feb-11, 06:37 PM
How many of these orphan planets (planemos ?) could there be?

Romanus
2008-Feb-11, 09:48 PM
^
If planets are as common as some theories suggest, and if many of them are ejected before a given planetary system "settles down" into a stable configuration, lots and lots and lots.

Re wind speed:
The winds on the outer planets are probably internally generated, though competing theories still abound.

Ronald Brak
2008-Feb-11, 10:07 PM
In addition, many planets could form outside of star systems.

FriedPhoton
2008-Feb-12, 02:19 AM
Actually, they would probably not, as you'd have to slow down and match their trajectory to reach them, and then accelerate again to reach a star system, so the stop would ultimately be a loss rather than a gain.

You know, you're right, I always drive from Chicago to Las Vegas after completely filling my car with gas. I fill the tank, the trunk, the back seat, and the front passenger seat. I even make my kids sit on the roof with the promise of extra gambling cash if they don't whine too much and I make them fill their pocket's with gasoline too. Stopping is just so impractical, especially since I have so much room for fuel on-board. You know, you just toss the kid's a twinky every couple hundred miles to shut them up and it's clear sailing all the way to Vegas baby.


On a serious note, any of you mathmagicians out there know how to calculate whether one hop with a fuel tank of size X would be more practical than two hops with the same amount of fuel? You'd have longer acceleration burn time , which of course would require equivalent deceleration, but you could travel faster while coasting. It would be interesting to know if that extra speed would buy you more time than would be lost by decelerating and accelerating again at a half-way point to refuel.

Not that you'd want a half-way point to use as a base or anything...

Noclevername
2008-Feb-12, 04:33 AM
On a serious note, any of you mathmagicians out there know how to calculate whether one hop with a fuel tank of size X would be more practical than two hops with the same amount of fuel? You'd have longer acceleration burn time , which of course would require equivalent deceleration, but you could travel faster while coasting. It would be interesting to know if that extra speed would buy you more time than would be lost by decelerating and accelerating again at a half-way point to refuel.

Not that you'd want a half-way point to use as a base or anything...

..That sounds very wrong. Coasting requires no fuel.

Let's see...
Launch accelerate coast coast coast slow stop, or
Launch accelerate coast slow stop relaunch accelerate again coast slow again, stop again.

Which is faster?

JohnBStone
2008-Feb-12, 02:08 PM
On a serious note, any of you mathmagicians out there know how to calculate whether one hop with a fuel tank of size X would be more practical than two hops with the same amount of fuel? You'd have longer acceleration burn time , which of course would require equivalent deceleration, but you could travel faster while coasting. It would be interesting to know if that extra speed would buy you more time than would be lost by decelerating and accelerating again at a half-way point to refuel.
Decelerating and Accelerating cost exactly the same in fuel in space. So you gain nothing and lose an extra load of fuel and the time you spent slowing down and stopped getting it. Actually you would probably lose even more by stopping as planets "help" you into orbit as their orbital capture speeds are above zero so you don't have to decelerate as much.

grant hutchison
2008-Feb-12, 09:31 PM
The hypothetical planets from Stevenson's paper might at least provide a reason to stop: hundred-bar hydrogen atmospheres. Gas station, anyone?

Grant Hutchison

Noclevername
2008-Feb-13, 02:31 AM
The hypothetical planets from Stevenson's paper might at least provide a reason to stop: hundred-bar hydrogen atmospheres. Gas station, anyone?

Grant Hutchison

See above. Stopping can't get you more fuel than you spend stopping and starting again.

FriedPhoton
2008-Feb-13, 05:58 AM
Ok, so let me see if I have this right. If I have 1 gallon of gas in my flying saucer and I want to go one light year, I know I can burn a 1/2 gallon accelerating because I need 1/2 gallon to decelerate. So the acceleration I get from half a gallon of gas allows me to coast from completing my initial burn at speed X.

So, let's say my destination 1 light year distant.

If I burn the whole gallon of gas I would accelerate long... hmm... ok... I get it now. :doh:

My flaw was in thinking I would be able to burn twice as much fuel accelerating because I was going half the distance. But I can't do that because I'd use it all and wouldn't be able to decelerate and I'd have to settle in for a nice long journey. So, no matter how far I'm going, it'll take half my fuel to accelerate and half my fuel to decelerate, so I can only travel speed X because my gas tank only holds a gallon of unleaded.

However! If I put a refueling ship in orbit around the rogue planet that will come out, match speeds with me, refuel as I blow past, I can burn all my fuel on my acceleration and refuel for my deceleration along the way. I can't think of why that might be more practical than just having a big extra tank I'd use to accelerate and lose it once I hit cruising speed.

Ok, so using the planet as a half-way point to refuel is probably dumb for a one shot trip out and back. But if I want to explore, I'd be better off using the rogue planet as a base for refueling so I wouldn't have to come all the way back.

Noclevername
2008-Feb-13, 06:35 AM
Ok, so using the planet as a half-way point to refuel is probably dumb for a one shot trip out and back. But if I want to explore, I'd be better off using the rogue planet as a base for refueling so I wouldn't have to come all the way back.

Unless you have immortality, near-C drive, or both, almost any trip to another star will be one-way. Neither are likely near-term developments. (unless you believe this guy. (http://www.bautforum.com/space-exploration/68456-ray-kurzweil-immortality-within-15-years.html))

tony873004
2008-Feb-13, 10:36 AM
Frank Drake says yes.

He was a guest lecturer last year in an Astrobiology class I took. He said "habital zone" needs to be completely redefined as even interstellar planets might support life. He pointed out that the majority of Earth's biomass exists below the surface (I think by orders of magnitude greater than us surface dwellers). I asked the dumb question "do you means worms and gophers?" He meant microbial life. And he pointed out that interstellar planets can remain warm below the surface for billions of years.

Thinking about it, you don't need to go very deep on Earth before the crust is hotter that you would expect from the Sun alone. I think even deep mine shafts can be uncomfortably warm, and I doubt the Sun has anything to do with it.

marsbug
2008-Feb-13, 12:23 PM
[QUOTE=FriedPhoton;1170694]I find the concept of interstellar planets interesting. They'd make convenient way-stations if we ever were able to travel beyond the solar system, assuming any just happened to be along the way.QUOTE]

I think visiting a rouge interstellar planet could be an interesting precursor to visiting another star, instead of a way station. If there was one at say, twice the distance of the heliopause then an unmanned flyby could be launched with existing technology, although it would be fearsomely long-term (40 to 50 years at a guess). If we're lucky enough to find one so close by then we could launch a mission to a truly extra solar planet within my life time. A giant planet with its own system of moons could be even more exciting, as the moons might have some liquid water and chance for life. Anyone know how hard it would be to spot something jupiter-saturn sized at 100 to 200 AU distance?

tony873004
2008-Feb-13, 06:22 PM
I would guess the odds of one being that close are very slim to none.

kzb
2008-Feb-14, 01:06 PM
There should be an upper limit to the density of these free-floater planets from the MACHO studies?

Noclevername
2008-Feb-14, 06:21 PM
I would guess the odds of one being that close are very slim to none.

The odds are unknown.

RalofTyr
2008-Feb-15, 07:50 AM
Yes, if it were something like Europa. A world with a geologic active core that could keep liquid water protected against a insulating layer of ice.

Noclevername
2008-Feb-15, 05:58 PM
Yes, if it were something like Europa. A world with a geologic active core that could keep liquid water protected against a insulating layer of ice.

It could be a moon like Europa, getting energy from tidal stress from its primary, or perhaps a large planet with an active core generating its own heat.

A thick atmosphere makes better insulation than ice, BTW.

kzb
2008-Feb-18, 06:48 PM
Interesting article discussing modelling the ejection from proto stellar systems of earth-sized planets with moons. Estimated to be 70 billion in the galaxy, density 9E-04 per cubic parsec. However this is just a minority of free floating planets, as it is specifically those planets that retain their moon during ejection:

http://arxiv.org/PS_cache/arxiv/pdf/0709/0709.0945v1.pdf

kzb
2008-Feb-18, 06:49 PM
Correction, sorry that would be 70 MILLION....

grant hutchison
2008-Feb-18, 10:07 PM
The hypothetical planets from Stevenson's paper might at least provide a reason to stop: hundred-bar hydrogen atmospheres. Gas station, anyone?

Grant HutchisonSee above. Stopping can't get you more fuel than you spend stopping and starting again.Sorry about the slow reply; I seem to have lost contact with this thread.
I think you're right for any sort of "realistic" mission involving a prolonged period of low-velocity coasting.
But a refuelling stop is energy-efficient for a relativistic constant-boost journey, though it inevitably prolongs the journey time. You save on the big mass ratios required for constant boost over long distances.

As an example, a ten-light-year journey using a photon rocket to boost at 1g throughout, with a midcourse turnover, takes a mass ratio of 150 and an onboard time of 4.85 years.
Making the same journey with a refueling stop midway gives you a mass ratio of 49 for each of the two halves of the journey, so you use about 2/3 of the fuel; total on-board travel time is 7.55 years, but we need to add refuelling time.

Grant Hutchison