[Brookhaven]

The problem is, we know that there ought to be organic molecules on Mars. Asteroid and comet impacts will have put them there.

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What?

And where would the asteroids and comets get “organic” molecules? Let’s assume the didn’t get them from the Earth (the only place we currently know for sure “organic” stuff exists.) Why would there be not just an expectation, but an assumption that asteroids contain organic material?

[count-your-change]

I think when the term “organic” is used in chemistry it simply means “carbon based”. Carbon based molecules can exist without life but life doesn't exist with carbon molecules.

[MyTwoCopperCoins]

You are mistaking “organic” chemicals to mean those produced by living beings. It’s not true. Benzene is an organic compound. It can be produced in the lab out of completely inorganic compounds. Same happens with asteroids and ther objects in space, when carbon, oxygen and hydrogen molecules interact.

[Filo]

Why would there be not just an expectation, but an assumption that asteroids contain organic material?

Because they do.

Organic material isn't anything special. It's just carbon compounds that can, and do, form naturally.