Well, yes, but it's another planet, see? Maybe that's what bacteria were
on mars.

Lots of Greetings!
Volker

So what? Let's write a fiction novel now! Let's assume then that bacteria
(for what it's worth posting this in sci.bio.microbiology :-)) on Mars were
huge, sevearl miles in diameter, made of invisible to our eye matter, and
had CO2 cell wall.When they rolled down on the surface of the planet, they
left markings that we now identify as "Channels", and then when they died,
they travelled to poles and decomposed there, leaving huge piles of
membranous CO2 behind to form what we call Polar Caps. Or, buy the way, they
might as well still live on Mars - under the surface - and use craters as
entry ports to their dens. :-)