To those that ask I have to say, none whatsoever. In fact, there’s not even evidence there was ever any kind of life on Mars and that’s what the Perseverance Rover is there to find out.
Here’s what we do know. There was water on Mars once. We don’t know if life ever developed, but we do know that if it did it would not have been enough time for anything to develop beyond single cell organisms and that’s what NASA is looking for: evidence that microbes once lived on Mars.
We don’t have any hope of finding fossilized bones, fossilized vegetation, fossilized leaves, or anything of that sort because we know Mars never sustained a warm climate with liquid water long enough for that to evolve. What we do hope to find is chemical evidence that single-celled organisms may have lived in or near an old lakebed inside the crater where the Perseverance Rover was just landed. Aren’t you following the news?
We do know that Mars never supported any multicellular life. There were never any plants, animals, people or civilization and there are certainly no ruins. Sometimes here on Earth when you look up into the clouds you can see shapes that remind you of animals and other things. Untrained lay persons who are not well informed look at pictures of rocks on Mars and speculate that these rocks were carved by intelligent beings. It isn’t so.