Read my comment above this. They learned from that and now there are very few people who can stop it, and putin has surrounded himself with people as loony as he is, and likely lies to them a lot to keep them scared and more likely to follow said orders.

They learned from that. Very few men can stop the order. Very, very, very few. Iirc it is pretty much two buttons at putins disposal. "Fire nukes" "run test firing nukes that is indistinguishable from the real thing to lower levels"

His legacy is all he cares about. I suspect he is also legitimately delusional and sees a huge threat to Russia itself.

Yes, oxygen is highly reactive. Tends to react with iron pretty often in the universe, often being either metal oxides or water. Geological processes can transfer oxygen too without it being in elemental form.

So to answer your question, it came from space, likely reacted in space then came down from asteroids. So this iron was likely like this before Mars came to be. But also the very surface over billions of years WILL come into contact with elemental oxygen in space.

Where do you think the little oxygen that Mars got from space/internal processes went? After a few billion years even a tiny amount will cause that.