Despite the poo-flinging here...
It is indeed quite likely that very long duration space missions, and certainly deep space colonies, might recycle human bodies into the local ecosystem.
That this almost certainly not be true of a mission as short as a Mars mission doesn't negate the concept, or render it somehow unfit for discussion. I suspect that actual Mars colonies might do things like this.
Many cultures on Earth did some form of "returning to nature" of their loved ones, some more blatant than others.
...Like all Loonies, we conserve our dead--and am truly glad that barbaric custom of burial was left back on old Earth; our way is better. But Davis family does not put that which comes out of processor into our commercial farming tunnels. No. It goes into our little greenhouse tunnel, there to become roses and daffodils and peonies among soft-singing bees. Tradition says that Black Jack Davis is in there, or whatever atoms of him do remain after many, many, many years of blooming.
Is a happy place, a beautiful place.
--Robert A. Heinlein, "The Moon is a Harsh Mistress"