Mars had an oxygen-rich atmosphere more than a billion years before the Earth, say scientists. An examination of meteorites and rocks on the planet suggests that oxygen was affecting the Martian surface four billion years ago.
On Earth, oxygen did not build up to appreciable quantities in the atmosphere for at least another 1.5bn years.
The researchers compared Martian meteorites that have crashed onto the Earth with data from rocks examined by Nasa's Spirit Mars rover. Differences in their composition can best be explained by an abundance of oxygen early in Martian history.
We have known that Mars had flowing water at one point in it's history. Now we know that it also had an oxygen rich Atmosphere! This begs the question that many Sci-Fi stories have asked over the years: Was Mars habitable? If it WAS habitable, was there sentient life on the planet?
Given enough time, could signs of civilization be wiped out before we could ever get to it? 1.5 Billion years is a long time, and even most metals will decompose after enough time. So the real question is if this is the case, how would we even know if there was life on Mars?
So many factors make it impossible to tell, but perhaps there are others who are more educated in the decomposition of materials than I am. Even still, it's something to think about!