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.