Fossils? From what? There has never been life on Mars and they never will be, until we arrive that is and find the same thing we found when we landed on the Moon... Nothing!
The idea that life exist somewhere out there isn’t unthinkable... The idea that life out there somewhere will be anything remote to life as it is on earth is unthinkable and highly unlikely. We are the perfect distance from the sun to allow for life to exist... And of the hundreds of millions of lifeforms that have existed here on earth... How many are self aware? One... Human. Hate to burst the bubbles of all those star trek fans... There are no other intelligent forms of life out there... We are it, the end, the one and only.
The universe is pretty big, out of curiosity what’s your source on this?