Larger planet supporting life?

[Deathsoul097]

Would it be possible for a slightly larger planet than earth (Say 1.5 G, and 1.1xEq radius) to support life? Theories, anyone? And could it have a water covered habitable moon? (I am writing a story, so I want to see what the general community consensus is)

[Ralathon]

Sure, 1.5G's isn't that much more than earth. I could easily imagine something evolving there if the conditions are favorable.

It would affect their physiology though. In general lifeforms would be smaller and build bulkier (Thanks to the cube-square law). Don't expect tall trees to evolve and flying would be limited to small buglike creatures (Assuming normal atmospheric pressure).

As for a moon with water, that mostly depends on the mass of that moon. To have liquid water on the surface you need an atmosphere and to have an atmosphere you need a certain minimum mass. I don't know what that mass limit is for a planet in the Goldilocks zone, but I suspect it is rather high. So I think it would be classified as a binary system instead of a planet - moon system (Just like Pluto and Charon). Then again, that's just a classification thing. It is perfectly possible for such a system to be stable. This will cause massive tides on both bodies if they aren't tidally locked, so stay away from the shores.

Do note however that it is practically impossible to actually get to that moon from the main planet's surface using current day technology. Even today escaping earth orbit is only barely possible, if the earth was a few % heavier we wouldn't be able to get out. So if you want to have travel within the system the species that inhabit it need to be a lot more technologically advanced than we are.

[Scotius]

I'm sure such planet would have no problems with supporting life, as long as it would have proper atmosphere and water. Organisms evolved in such environment would adapt to increased surface gravity by being massively built, squat and with sturdy skeletons.

[lajoswinkler]

1.5 G is not much and there should be no problems with advanced lifeforms. They'd have increased density of structural elements that hold weight, and mildly bulkier construction if they're on dry land. Lifeforms in liquid medium would need higher bouyancy and the ones flying through gas would need more advanced wings.

If conditions for the evolution of collosal trees would exist, their whole water transport apparatus would have to be more robust.

All in all, that's just 1.5 G. It would be much more interesting to see the evolution of life at 5 or 10 G.

[diomedea]

I believe it is impossible in reality to have two bodies of comparable size, so to be both able to sustain life, to create a binary system. Given the size, only one such body may orbit a principal body (star or gas giant planet).

As to why, it has to do with one of the most credited theories about planet formation, the planetesimal theory. I remember to have read (sorry I can't find where, probably an article on Scientific American) of a number of simulations being conducted, always to demonstrate that every time a body large enough forms, it eats all other planetesimals in the same or close to its orbit, given enough time. Therefore it would be impossible that two similar bodies form in the same area.

A different scenario may involve planet migration, where a close encounter with a larger body alters the orbit of a planet. And it is possible that a deviated planet gets very close to another of similar size, but then it would require magic to stabilize both of them in a same orbit. While interacting in a yet unstable orbital configuration, it is most probable that one gets more energy (at the expense of the other) so to pull out, or the lighter one loses energy and falls.

[Nuke]

i read an article awhile back that said super earths were probibly more likely to support life than sub earths. idk where i read it though.

[Ralathon]

I believe it is impossible in reality to have two bodies of comparable size, so to be both able to sustain life, to create a binary system. Given the size, only one such body may orbit a principal body (star or gas giant planet).

As to why, it has to do with one of the most credited theories about planet formation, the planetesimal theory. I remember to have read (sorry I can't find where, probably an article on Scientific American) of a number of simulations being conducted, always to demonstrate that every time a body large enough forms, it eats all other planetesimals in the same or close to its orbit, given enough time. Therefore it would be impossible that two similar bodies form in the same area.

A different scenario may involve planet migration, where a close encounter with a larger body alters the orbit of a planet. And it is possible that a deviated planet gets very close to another of similar size, but then it would require magic to stabilize both of them in a same orbit. While interacting in a yet unstable orbital configuration, it is most probable that one gets more energy (at the expense of the other) so to pull out, or the lighter one loses energy and falls.

You are correct that planets clean up their local orbit when forming. But this does not exclude binary planets from existing, we have 2 in our very own solar system: Earth-Moon and Pluto-Charon and we can show that these systems are stable over very long time spans.

If our moon was a few times heavier it could very well have supported an atmosphere and therefore a biosphere. I'll immediately admit that very heavy moons like that are difficult to form, but it is by no means impossible.

[AngelLestat]

Would it be possible for a slightly larger planet than earth (Say 1.5 G, and 1.1xEq radius) to support life?

Sorry, but you need to be more specific with your question.

What we are talking about?

-Life as we know it on earth?

-How earth mammals will adapt?

-any kind of life? (to answer this question you must find a definition of "life" first.)

If we take life like any kind of replicant that evolves, then is difficult to imagine a place where life cant exist.

[ZetaX]

You seem to have missed the memo on pluto not being a planet anymore, and even if it would be, it is simply too small anyway.

And the problem is not just the rarety of such a binary planet, but also the effects comming along. One of the two planets being tidally locked to the other is really not good for life, but is bound to happen over time. And if their sizes are rather similiar, the distance they have to be apart to not rip each other into pieces is also problematic.

[magnemoe]

You are correct that planets clean up their local orbit when forming. But this does not exclude binary planets from existing, we have 2 in our very own solar system: Earth-Moon and Pluto-Charon and we can show that these systems are stable over very long time spans.

If our moon was a few times heavier it could very well have supported an atmosphere and therefore a biosphere. I'll immediately admit that very heavy moons like that are difficult to form, but it is by no means impossible.

True, no problem giving earth an larger moon, just make the planet who grazed earth larger.

Take the solar system, make mars as large as earth but probably no moons, it would keep the atmosphere. Pull Venus a bit out and give it an large moon to get rid of a lot of atmosphere. Give earth an moon larger than mars and you could have had four planets with life.

You can not have two planets in the same orbit probably that you think off.

[diomedea]

You are correct that planets clean up their local orbit when forming. But this does not exclude binary planets from existing, we have 2 in our very own solar system: Earth-Moon and Pluto-Charon and we can show that these systems are stable over very long time spans.

If our moon was a few times heavier it could very well have supported an atmosphere and therefore a biosphere. I'll immediately admit that very heavy moons like that are difficult to form, but it is by no means impossible.

If our moon would have been heavier, it would not have entered a stable orbit with Earth. The Earth-Moon configuration cannot be called binary, one body is clearly much bigger thus it made the lesser one stabilize its orbit around.

Pluto-Charon, as somebody else already pointed out, cannot be considered as Pluto itself is no more to be considered a planet. Being so smaller and unable to support life itself, Pluto is more similar to one of the remnants from the protoplanets. Due to the extreme size of its orbit, it just needs more time to complete the process, and then Charon will be no more...

BTW, Charon's mass is just 11,6% of Pluto's: not really big enough to be considered of similar size. I would not consider the two as forming a binary system. The IAU classifies Charon as a moon of Pluto, having so far rejected to define the two as a binary system.

Edited December 1, 2013 by diomedea

[Ralathon]

If our moon would have been heavier, it would not have entered a stable orbit with Earth. The Earth-Moon configuration cannot be called binary, one body is clearly much bigger thus it made the lesser one stabilize its orbit around.

Pluto-Charon, as somebody else already pointed out, cannot be considered as Pluto itself is no more to be considered a planet. Being so smaller and unable to support life itself, Pluto is more similar to one of the remnants from the protoplanets. Due to the extreme size of its orbit, it just needs more time to complete the process, and then Charon will be no more...

BTW, Charon's mass is just 11,6% of Pluto's: not really big enough to be considered of similar size. I would not consider the two as forming a binary system. The IAU classifies Charon as a moon of Pluto, having so far rejected to define the two as a binary system.

You're arguing semantics here. Pluto, Ceres and Vesta aren't considered planets, but that doesn't change the fact that they're large spheres of ice and rock. One could imagine an asteroid belt in the Goldilocks zone that contains one or several objects with enough mass to retain an atmosphere and life. They wouldn't be considered planets according to the current definition but that doesn't impede their ability to sustain their biosphere.

I see no reason why a double planet where both bodies are heavy enough to hold an atmosphere couldn't exist. The main losses in terms of orbital energy would be tidal drag (Which would be negated when the planets tidally lock to each other) and perturbations by the rest of the system which should be negligible provided that the 2 bodies orbit closely enough. The tidal drag would actually make the system self stabilizing.

I'm not saying this is a very common configuration. The capture mechanics for such a system would be very rare indeed. But once it exists I doubt it would destabilize quickly.

[magnemoe]

You're arguing semantics here. Pluto, Ceres and Vesta aren't considered planets, but that doesn't change the fact that they're large spheres of ice and rock. One could imagine an asteroid belt in the Goldilocks zone that contains one or several objects with enough mass to retain an atmosphere and life. They wouldn't be considered planets according to the current definition but that doesn't impede their ability to sustain their biosphere.

I see no reason why a double planet where both bodies are heavy enough to hold an atmosphere couldn't exist. The main losses in terms of orbital energy would be tidal drag (Which would be negated when the planets tidally lock to each other) and perturbations by the rest of the system which should be negligible provided that the 2 bodies orbit closely enough. The tidal drag would actually make the system self stabilizing.

I'm not saying this is a very common configuration. The capture mechanics for such a system would be very rare indeed. But once it exists I doubt it would destabilize quickly.

If an body has to small mass it gravity becomes to low to clear its orbit, the body would have to be far smaller than mars probably far smaller than the moon, they can not have atmosphere more than the moon.

However I neither see any reason why we could not have an double planet with life on both. Yes this is less likely than something like Earth-moon as the masses is larger.

This happens during the process who clear the orbits, or perhaps later as the orbits adjusts, its estimated that the inner solar system held 50 objects who either collided or was sent out to Jupiter.

[Skyler4856]

sorry, but you need to be more specific with your question.

What we are talking about?

-life as we know it on earth?

-how earth mammals will adapt?

-any kind of life? (to answer this question you must find a definition of "life" first.)

if we take life like any kind of replicant that evolves, then is difficult to imagine a place where life cant exist.

the center of a star

[diomedea]

You're arguing semantics here. Pluto, Ceres and Vesta aren't considered planets, but that doesn't change the fact that they're large spheres of ice and rock. One could imagine an asteroid belt in the Goldilocks zone that contains one or several objects with enough mass to retain an atmosphere and life. They wouldn't be considered planets according to the current definition but that doesn't impede their ability to sustain their biosphere.

I see no reason why a double planet where both bodies are heavy enough to hold an atmosphere couldn't exist. The main losses in terms of orbital energy would be tidal drag (Which would be negated when the planets tidally lock to each other) and perturbations by the rest of the system which should be negligible provided that the 2 bodies orbit closely enough. The tidal drag would actually make the system self stabilizing.

I'm not saying this is a very common configuration. The capture mechanics for such a system would be very rare indeed. But once it exists I doubt it would destabilize quickly.

No, you really don't know what I'm talking about. However I said. Simulations have been conducted to see, extensively, hoe planetesimals grow and clear their orbit. There is no doubt left that no chance exists for any other body of the same size to remain in the same orbit. It would simply not be stable. We are talking billions of years, but that is the end result. And it takes billions of years to develop an environment able to support life. So the answer is no, it can't do. And please, don't even try to consider binary those that IAU negates to be.

[FenrirWolf]

Do note however that it is practically impossible to actually get to that moon from the main planet's surface using current day technology. Even today escaping earth orbit is only barely possible, if the earth was a few % heavier we wouldn't be able to get out. So if you want to have travel within the system the species that inhabit it need to be a lot more technologically advanced than we are.

Yup, we're pretty fortunate in that regard. I suppose if a species on a heavier planet were desperate enough to get into space they could use an Orion design. boost a ship up as far as it could go on chemical rockets, then let the bombs do the rest...

Hopefully they would come up with a less fallout-inducing method though!

[AngelLestat]

the center of a star

Haha, yeah, that seems challenging. But.. who knows..

[DonLorenzo]

There's quite a few varieties of life that don't really care what the gravity is. Microbes and anything on that scale have virtually nothing to do with it. Small multicellular life lives in a world where conditions are dictated more by surface tension than anything else. Anything in the oceans is hardly affected by gravity (they are neutrally buoyant, gravity provides an up and a down direction, not much else). Gravity would affect the weight of the water, meaning life taken from earth would thrive at different depths (equivalent pressure). That pressure difference coupled with light penetration (only dependent on depth not gravity) could cause some variations in oceanic life, but that's about it for that environment.

Just something extra to think about.

[DonLorenzo]

Haha, yeah, that seems challenging. But.. who knows..

There's a lot of cyclic activity going on in stars, and on many different timescales. If some of those events could carry information and... replicate. Perhaps that could go in the direction of something we call life. We started out with a weird molecule that replicated and passed on information

[lajoswinkler]

Haha, yeah, that seems challenging. But.. who knows..

No. Not possible. Life requires pretty low entropy and any part of any star is highly disordered. There is zero (0) chance life could exist there.

[kiwi1960]

Life can exist anywhere, even on our Jupiter.... the gravity there just means WE cannot survive there, but any life that started on that planet, could, in theory survive, because it would have evolved *IN* those harsh conditions.

Same with atmosphere... we cannot breathe in arsenic gas... but life that evolved on that planet could breathe it....

What I am saying is, in Sci Fi, it doesn't matter it life can or cannot exist, write your story, people will either love it or hate it. the "Fi" in that statement means FICTION, ie, not real... this is why people write stories like Star Wars even though none of the tech exists for us... but so what.... most of the science is also bogus, but so what....

Sci Fi writers have never been to other worlds, they make the science FIT their story. Who is going to argue with them? The Aliens of BORRUS IV?

[ZetaX]

You seem not to understand the difference between SciFi and Future Fantasy.

[AngelLestat]

First I want to mention that my post was only to ask to Deathsoul097 what kind of life he was talking about...

Becouse all were responding according to their own interpretation of the question. And depending the kind of life the answer may be totally different.

There's a lot of cyclic activity going on in stars, and on many different timescales. If some of those events could carry information and... replicate. Perhaps that could go in the direction of something we call life. We started out with a weird molecule that replicated and passed on information

Yeah, the problem that in my definition I mention the ability to evolve. So that reduce a lot the chances. But I like your point of view from the information.

No. Not possible. Life requires pretty low entropy and any part of any star is highly disordered. There is zero (0) chance life could exist there.

0 chance? you can not do these kind of asseverations without prove it.

Even scientists said that is possible cross a wall walking without touch it if you try an infinite number of times.

You can said that is highly improbable. then I will be agree.

But what about material structure that we dont know? What about different quarks structures? What about electromagnetism or other forces.

I am glad that you use the concept of entropy to describe life. But when you said that life require low entropy, this is in the case of life as we know it.

In fact what life do is take energy from outside, produce work and reduce its internal entropy, all this would increase the total universe entropy. So I dont find any logic rule to demonstrate that life can not exist.

And "I guess" that the light that plants absorb is in a higher entropy state that the elements inside a star.

I can said that in the center of the star there is a black hole, and inside the black hole there is life. And you can not refute becouse we dont know how a black hole looks from inside.

[hawkinator]

I would say that if it had an oxygen-nitrogen based atmosphere with no excessively toxic trace elements present, not only could it sustain life as we know it, but humans from Earth could (given time) adapt to live there. What we know about long term spaceflight suggests that exposure to higher gravity would cause the reverse effect, muscles and bones getting stronger to cope, and the circulatory system getting stronger as well.

As for having a large moon/twin planet also capable of supporting life, that could work as well. A large planet like that would most likely carry a much stronger magnetic field, possibly allowing the twin planet to carry an atmosphere without being as large as it would otherwise need to be to carry an atmosphere. Remember that without our magnetosphere, Earth would have an atmosphere similar to Mars. Make the twin fairly close to it's big brother, and/or give it a magnetosphere of it's own, and I would say that atmosphere, oceans, and life would all be plausible.

Now, the next issue would be the tides. You have a few basic options:

1. Give them a tidally locked orbit to where they always have the same side facing one another (like Duna and Ike). In this scenario, the two planets would bulge slightly towards one another (not enough to cause major problems), and gravity on the side facing the other would be weaker. Rockets taking off from one planet could take advantage of this to get more efficient launches, potentially making space more accessible to the people on the big brother planet. The oceans would always be bulging in the same places, meaning there would be no tides (the oceans would always stay at more or less the same level everywhere).

2. No tidal locking would mean that both planets would have extremely high tides. This would make life difficult near the shores, however still possible.

3. One or the other could only show one face to the other. Then one of the planets would have conditions like #1 above, and the one would have conditions described in #2.

As for the naysayers that say that planets could never form like that, firstly, whenever fiction is written, the author becomes the god of their own mini universe, the omnipotent, omniscient, omnipresent being who created this universe and is in control of all events within it. The physical laws of this universe are solely up to the author. All resemblance to reality exists because the god of that universe wants it there. In the end, these planets were never "formed", and the life here never "evolved", they were all created, by you, the god of this universe. Maybe your characters are atheists, maybe not, in either case let them work out some way of explaining how their universe got there. How they think they got there is really the more important thing anyway, because the truth is that you put them there.

[Deathsoul097]

Hmm... Food for thought.

We are trying to follow real physics as much as possible, the only major exception being how I have solved the speed of light barrier.(Basically, ripping a hole into another dimension and back again, but in a different relative location. I know that sounds OP, but it is balanced out by requiring an immense amount of power, and the further away the destination is, the more power it requires, so with even the biggest ships you can usually only jump 10 to 100 Light years at a time. Also the size of the ship doesn't matter, the portal consumes a marginal amount less if you were to open one a micrometre across than one a kilometre across, limiting smaller ships to jumping between a couple of star systems at a time, and waiting for a recharge to optimal power levels before jumping again.) Either way, I do want to see whether the major alien's homeworld can be physically possible.

Don't laugh at me for this but the main aliens in the series are person sized and looking(ish) two tailed squirrels. (These aliens also gifted humanity with the afore mentioned warp tech, known as a Sabier Drive) Their moon (Tallifrae) Is rich in resources, along with being inhabited by the imaginatively named Tallifraeans. (Think blue half person half shrimp marine aliens.)

EDIT: The planet is known as Gaia, to all races including Humanity, the Wagshee (The two-tailed squirrel people[Pronounced Wog-she]), and the Tallifraeans.

EDIT EDIT: I was thinking that it would be option two, but the planet/moon would be just far enough away that tides n both would be comparable to earth. Also, the atmosphere on both should be hospitable to humans on both the moon and the planet, if a slight reduction in life expectancy from a slightly higher content of noble gasses, such as xenon and argon on the moon.

Edited December 2, 2013 by Deathsoul097