Clearly Visible below in this Hubble Space Telescope photo is the North Polar Opening of Mars.
It appears like a huge depression in the planet's surface like a giant crater, so big
you can see the clouds down inside on the sides of the polar opening.
NASA admits these are water "ice" clouds, so the interior of Mars must have water.
And if water, then very likely the interior of Mars could harbor life nurtured
by an interior sun.  Click here to see an image of Mars
where it's interior sun is lighting up the clouds over it's north pole
during winter when our Sun does not reach the north pole.