NASA is creeping toward confirmation of alien life on Mars. It's about as close as we can get until a sample return mission.

https://journals.sagepub.com/doi/epub/10.1177/15311074261417...

Yes there's been a series of soft reveals. A visible macro fossil might be the only way a rover could prove past life, but that seems unlikely given lack of water erosion to be expose such things.

They found some organic compounds now, from that they estimate a high ammount of them a lot time ago. I guess it's a bad calculation instead of aliens.