Planetary Science Questions

[travisjames]

I'm writing a collection of short stories and I'm about to begin one about survival on another planet. I have a lot of research to do for this and I was hoping someone educated in this field could tell me if my fictitious planet could exist. Thanks!

What I'd like in the planet:

A terrestrial planet covered by ice/snow
Breathable atmosphere (for humans)
temperature above -20 celsius?
Gravity similar to Earth
Ore-rich (though not under constant bombardment by meteors anymore)
Liquid water underground
Tidal locked (if possible)
Currently undergoing cooling and destined to lose its atmosphere or freeze solid in the far future. Perhaps it was once warmer.
Hydrothermal vents
Yellow/brown dwarf sun?
Would there be strong winds? Precipitation?

Are there any other special considerations for such a planet?

[LAW]

You'd need an active iron core to maintain a magnetosphere and a reasonable distance from its star, or perhaps it could be a bit more exotic? It could be an icy, earth sized asteroid which is reaching escape velocity, it's atmosphere and tectonic activity is formed by friction from tidal gravity from the planet/star it is orbiting.

If it was orbiting a planet like Jupiter solar wind wouldnt be a huge problem, very similar to some of its inner moons.

[ZeroID]

Sounds like the planet Hoth, see 'Star Wars' for details ..

Tidal locked is not good for temp etc management.

[mental4astro]

Hi Travisjames,

I think such conditions would be plausible. Short answer is yes, but good to know how and why.

Current thinking would suggest your most likely prototype would be Mars to meet your parameters!

Many of your parameters are interlinked too.

A cooling planet would mean a cooling and solidifying iron core for the atmosphere to be lost. The molten iron core in a rotating planet creates a magnetic field around it, its magnetosphere. It is this magnetosphere that protects the atmosphere of the atmosphere stripping charged particles from the planet's host star. A cooling core would result in a weakening magnetosphere and the protection it offers. The atmosphere will begin to be slowly stripped away, and as a result cooling it as its density decreases. A "reverse greenhouse" with no way back. The gravity of the planet (assuming same mass for it to have the same gravity as Earth), would only slow the process compared to Mars. A frozen planet could occur first due to gravity, but the atmosphere would be slowly stripped and thinned.

The stripped atomsphere would also increase the amount of ultraviolet radiation reaching the surface of the planet. This would lead to the breakdown of water molecules in the atmosphere, decreasing percipitation, and the eventual total loss of all water, other than that underground permafrost. Yes, liquid water could exist for some time deep underground, insulated from the cold surface, and kept warm from the remaining internal heat. It will all eventually freeze.

Breathable oxygen goes out the window too with the UV. The stripped water molecules, Hydrogen is lost into space, and the higher energy creates Ozone, O3, not breathabe Oxygen, O2. O3 is toxic.

Hydrothermal vents? Hmmm, maybe. These deep underground reservoirs would come under "techtonic" pressure. Crust movement would cause ruptures in the rock surrounding these reservoirs, giving you your hydrothermal vents. Much like underground oil and gas being realeased to the surface here on Earth.

Ore rich, yes, as per your prescription, can happen. Ores as such more likely to have occured from the creation of the planet rather than meteor bombardment, but not exclusive. Rare ores more likely to be from bombardment, and at impact sites and surrounds in the deposited impact detrious (like the ray craters on the Moon).

Yellow dwarf star? Yes. But for the planet to be in the "Goldilocks Zone", the planet would need to be much closer to the star, making the star appear larger in the "sky" than our Sun. Brown dwarf star may not have enough energy to sustain life. Another thing about a Yellow Dwarf, these stars are very, very long lived, longer than our Sun. The planet in question would sooner freeze than be a victim to any of the Dwarf's death throes.

Tidal locking may be possible. This would mean for the planet that one face would be always facing the host star. One half would have pertetual daylight, and the other pertetual night. Bugger of a situation though! Cabin fever to boot on the dark side!

High winds? You bet! Just about all the time if planet is tidally locked and with an atmosphere. These winds would be the only relief that the daylight locked half would have from constant heating.

If habitable, there would be very different animals adapted to the "midday" half of the planet to that along the "sunset" perimeter, and even more so on the "night-time" half. A cooling planet would upset the balance, forcing the night-time creatures to venture closer to the daylight.

Not a happy place.

[Dave2042]

Hope you're still watching the thread. I thought the following link would interest if you haven't already seen it.

http://www.smh.com.au/technology/sci-tech/planets-worlds-apart-orbit-one-distant-star-20120622-20s01.html

Regards