Planet Size & Life

>>8148944
What life (as we know it) needs is liquid water. Planet size isn't an important factor.

>>8148949
I thought gravity would play a big part in it.

Wouldn't smaller planets struggle to keep an atmosphere? ie. Mars? Or is there another reason that Mars no longer has an atmosphere?

>>8148957
Mars no longer has an atmosphere (a very thin one remains) for two intricate reasons :
- No magnetic activity : Earth's core is active and create a magnetic field around the planet that protect it against solar winds. The same solar winds that can blow the atmosphere out of the planet.
- After the majority of Mars's atmosphere was blown away, the remaining air wasn't creating a suffisant pressure on the surface to keep water liquid. Water evaporates and is blown away, no water remains.

I'm not an expert in this, so someone see something wrong please correct.

Yes, because size is also a matter of multiple things: where it forms in the solar system (Venus is .82 Earth mass, Mars is only .11). What elements it retains, i.e. we're losing Helium and it will be too expensive to use before 50 years are up, and Mars is a dustbowl. Astral bombardment: You want enough foreign material to diversify iron and shit, but too much heavy metals would poison a lot of life, and also increase the planets mass beyond a reasonable amount.

Ironically more massive would probably be a lot better than less massive. Most life can handle being close to the ground, although plants would be stumpier. A higher mass would entail either a higher density core, which could lead to strange plate tectonics, or a lower density core, which would likely reduce a magnetic field to a level unsuitable for multicellular life (though there are radiation hardened organisms). The "Daisy World" is actually a significant thing which might be the most important factor in whether or not a planet can sustain life:

https://science.slashdot.org/story/16/06/08/027258/researchers-say-the-aliens-are-silent-because-they-are-extinct


>>8148949
Listen here you little shit, life takes a long time, a stupidly fucking long time.

>>8148976
"where it forms" is a cause, "what elements it retains" is an effect, pick what you're talking about.

>>8148991
Choosing both you stupid nigger. Learn to read.

>>8148976
>Listen here you little shit, life takes a long time, a stupidly fucking long time.
Yes. But not his original question. Size matters in the variables you listed, but isn't the main modifier. As I said, it's not an important factor. You can have a giant telluric planet being more likely hit by comets, but if it's too close or too far from it's star and dosen't have suitable surface temperature, it's not even worth trying.

>>8148996
>size is a matter of multiple things
>is a matter of
Meaning a consequence of. Learn to write, toughguy.

>>8148944
>Would a planet need to be a similar size to Earth to be able to produce plant and animal life as we know it on Earth?
Yes.

Sufficient gravity is essential to keeping water and air. Too small planet means too little gravity and water and air is lost. Too much and gravity becomes too crushing for complex life.

>>8148971
I'm a geology student but that sounds perfect. A planet that's too small just can't retain an atmosphere. No atmosphere = no water, no water = no life.

If we find something living in the methane pools of Titan I'll change my tune but so far as I'm concerned life requires water.