[ProtectOurFreedom]

...the remains would first need to be burned to not contaminate the surface

OK, where do you get the precious oxygen to burn the body? Do you REALLY want to waste precious oxygen to do that on Mars?

Then, there's this..."a worst case scenario has been presented where the space fairing heroes..."

"Fairing"...

"Sea faring"...

"Space faring"...

What happened to the Queen's English? Did the Daily Mail fire all of its editors?

[SauronOfMordor]

Cremation does not necessarily require oxygen. Heating the body in an electric furnace until all possible bacteria are dead should be sufficient.

The ashes can then be used in inside gardens.