solar system with 3 habitable planets

[thekillman]

for a fanfic i created a solarsystem with 3 habitable planets.

all 3 are earth-like, all three can support human life.

my question is: how would their configurations be?


we need:

-Adequate heat
-Liquid Water
-sufficient gravity
-no harmfull particles


heat/liquid water depends on two things: atmosphere and distance to the sun. but what sunclasses are needed to support 3 planets?


i was thinking of this orbit configuration: two planets in the Liquid Water zone, one on the opposite side of the sun in the same orbit.

two act as eachothers moon, the third has a moon.


this is the basic story:

criminals were disposed on planet #1. they were left alone and they developed, and colonized planet #2, and eventually #3.

#2 is a colony, #3 is a mining planet.


terraforming based upon atmosphere is possible (ie, adding greenhouse gasses for increased heat, etc)

#1 absolutely needs to be human-sustainable.
#2 needs to be as close to human-sustainable as possible.
#3 can be less hospitable to human life, but if given the equipment, you can survive.


so how would 3 planets sustain life? there is some playing room, IE gravity does not have to be perfect, atmospheric condition doesnt have to be perfect, as long as you can ditch a human on it and he can survive, if needed by long-term adaption

[Splitsecond]

Well Venus, Earth and Mars should all be in the habitable zone, however it's suspected that a cataclysmic natural disaster stripped Mars of its capacity to hold onto its atmosphere and Venus has a composition that produces a very dense and acidic atmosphere. 'There but for the grace of God...'

[thekillman]

well, mars is too small to hold on an atmosphere. if it were bigger, it would be able to hold on the CO2 and thus sustain life.


venus is a whole different can of worms. its atmospheric composition is WAY off. its an acidic, dense atmosphere that creates insane temperatures. and ironically, the two combined would create a second earth:

mars: temperature and water.
Venus: sufficient size/gravity.




but would this configuration work? our "mars" would need an atmosphere denser than earth (or using more powerfull greenhouse gasses) to achieve earth temperatures.

our "venus" would need a heat-reflective atmosphere due to being closer to the sun. CO2 shields in two ways, but would you need a thick or thin layer?? or perhaps two large icecaps that reflect adequate sunlight??

[Splitsecond]

well, mars is too small to hold on an atmosphere. if it were bigger, it would be able to hold on the CO2 and thus sustain life.

That's not true. Current evidence suggests that roughly 4 billion years ago a Pluto-sized meteor hit Mars causing its magnetic field to collapse. As a result there was no magnetic field to deflect the solar winds produced by the Sun. The ionosphere was left exposed and was stripped away by the solar winds. This made the Mars atmosphere too thin, which means the atmospheric pressure is too low to support liquid surface water.

If it wasn't for that impact, there may have been intelligent life there, as it is there may still be life, but primitive life only. Also what if that meteor had hit us instead?

Venus just has the wrong composition, so it was done for from the start.

[thekillman]

actually mars is like half the size of earth. so it doesnt have adequate gravity. but your meteor impact story was probably the final blow. literally

[ManiacMike]

Well, you can have an earth-like planet (1), its colonized moon / livable moon (2) and a planet further away with a second sun. (3)

[Professor D.H.D. Puddlejumper]

i was thinking of this orbit configuration: two planets in the Liquid Water zone, one on the opposite side of the sun in the same orbit.

two act as each others moon, the third has a moon.

I'm somewhat skeptical of the idea that two earth-size planets could occupy the same orbit on opposite sides of the sun. Among other things I'd guess that the gravitional influence of other planets in the solar system would prevent a perfect orbital symmetry between the two. I found this link which might shed further light on the subject:

http://www.physicsforums.com/showthread.php?t=221505

But your idea of two earth-size planets orbiting each other is a bit more intriguing, especially if both were teeming with life. The gravitational influence that each would have on the other would, among other things, create enormous variances in ocean tides.

I also suppose that if Mars had been the same size and mass as Earth, then it might today harbor advanced life, albeit in a colder environment.

As for a planet closer like Venus, well, sci-fi writers used to depict the planet as teeming with steaming rainforests, continuous downpours, and lots of tropical creepies and crawlies. It didn't turn out that way but who knows? Maybe in another solar system, three such planets at similar distances could exist, all with life.

[thekillman]

so venus-earth-mars config IS possible?

[Crazy Tom]

If it's a stargate fic, go for the Jupiter Ignition project. They did it in 2001 Space Oddysey, and in Stargate.

[thekillman]

its for auvf, Multiworlds homesystem. Halkar Prime, Halcyn and Halion. i wanted a scientifical explanation.


moon has 1/6th the gravity of earth. meaning its 6x smaller. so for two planets, the gravitational interaction is 6x BIGGER. 10x further=100x less. due to R^2. so the planet has to be..... some 2.7x as far as the moon.

[lord groovy]

1 - I do agree with your opinion on twin planets on same orbit but at opposite sides. I think that they can't naturally form in a star system. If this was possible we may see a 'living' example in our solar systems with moons orbiting around one of the giant gas planets. But during the formation period, there would be some competition between the two planetoids and probably end into an asteroid belt.

At best, you could have a foreign body captured by the star's gravitational forces. It would make an additional story about the origin of the planet.

2 - I like the idea of twin planets orbiting around each other. I can't say if it could exist in real life. But well, wouldn't they have something like 24h nights (natural night + eclipse due to the other planet)?

3 - You could also have a closer gas planet (GP) at the limit of the livable zone with an Earth-size moon. If its revolution around the GP is synchronous with the GP rotation, it would always be facing the sun.

4 - About the weather, with adequate atmosphere composition, it could be the same on all your 3 planets. Thanks to greenhouse effect. On the other hand, the 3 planets would also have different gravity. The farther from the star, the stronger the gravity...

[Crazy Tom]

Twin planets are a killer, tidal lock means they always face each other and you have no tides, since both are of comparative size. No tides is very bad for all life as we know it.

its for auvf, Multiworlds homesystem. Halkar Prime, Halcyn and Halion. i wanted a scientifical explanation.

Aw come on killman! I thought these people were smart. You never put all your eggs in one basket, ever!

(I mean, if you insist, sure, but that's just extra handicap for them, where do you think Renette is heading next?)

[thekillman]

mmm. see the solar system as a flat surface.

the centre of the two planets orbiting eachother is C
the star is S


then the planets would rotate along the axis C-S.

the planets, in order to have the right amount of nights, would have to rotate normally, IE just like earth does. so they rotate along the axis at which C orbits the star, or at any angle from that orbit.

[Splitsecond]

There's no reason why a planet like Earth can't be orbiting at one of Earth's Lagrange points. There's nothing on our orbit, but Mars has 3 asteroids at it's Lagrange points and Jupiter is bracketed by groups of asteroids at two of its Lagrange points.

A Lagrange point is a point where a smaller body can remain stationary with respect to two larger bodies. So the planet will need to be smaller than Earth or the Sun.

[General_Finley]

If Mars was bigger and Venus was just a little bit closer to us then that would be an ideal layout for three habitable planets.