That is the evidence. Science is often done indirectly. We know that the Sun is made up of hydrogen gas but no one has been there. We know black holes exist, and that the big bang took place 15 billion years ago, that atoms are made up of protons, electrons and neutrons, and that gravitational waves ripple through spacetime. No one has directly seen these things, but we know them to be true based on indirect evidence.
Similarly, the above list of facts is indirect evidence for life on Mars.
