Uranium, thorium and potassium, appear hyper-abundant on Mars surface

Natural nuclear fission reactor 

https://www.iaea.org/newscenter/news/meet-oklo-the-earths-two-billion-year-old-only-known-natural-nuclear-reactor

https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

https://www.researchgate.net/publication/340952315_EVIDENCE_OF_A_MASSIVE_THERMONUCLEAR_EXPLOSIONS_ON_MARS_IN_THE_PAST_The_Cydonian_Hypothesis_and_Fermi's_Paradox

Thorium and radioactive potassium appear concentrated in the northern Mare Acidalium in the region of the large, shallow depression north of Acidalia Colles., with a small concentration at the approximate antipode of this region on the other side of the planet

sible archeological artifacts. ...