[codesushi42]

>It's pretty much our only opportunity to see if life emerged twice in the same planetary system under similar conditions.

You mean carbon based life. Methane based life may be a possibility, and you wouldn't have found it on Mars. You might find it on Titan.

[dredmorbius]

Methane is an organic (carbon-chain) molecule: CH4.

Titan would have a low-temperature carbon-based chemistry, but it would remain carbon-based if focused on methane.

Alternative hypothetical biochemistries usually focus on silicon.

[codesushi42]

True. But a methane based lifeform would be radically different than the carbon based lifeforms found on Earth, and would have emerged separately.

[dredmorbius]

Oddly, that wasn't your claim.

[codesushi42]

It was. Read the OP's claims about Mars.

Mars alone does not provide the answer about whether or not life evolved independently in our solar system.

[hdfbdtbcdg]

Can you elaborate?

[codesushi42]

They would not have cell membranes with phospholipids for one thing.

[hdfbdtbcdg]

Why not? Methane is a hydrocarbon. We are made of hydrocarbons.

I just can't understand what the chemical difference is. Are these differences because of oxygen? I.e. life forms of C+H vs lifeforms of C+H+O?

[codesushi42]

Yes. Phospholipids are not viable outside of water; they would not be strong enough to perform well in liquid methane.