While the Curiosity rover is chugging along on the surface of Mars, NASA is making other discoveries from samples taken from other Mars rovers. This time around, looking at rock samples from NASA's Spirit rover, scientists have discovered that Mars had an oxygen-rich atmosphere some four billion years ago, which was long before when Earth developed oxygen in its atmosphere.
Based on this timeline, it's said that Earth didn't build up oxygen to appreciable levels in the atmosphere until around 1.5 billion years after Mars built up its atmosphere full of oxygen. The rocks taken from the Mars surface are said to be over 3.7 billion years old and show signs of early exposure to oxygen.
These rocks were perfect samples for the scientists too, as they were buried deep into the red planet's interior and then eventually spat out in volcanic eruptions. By being buried deep underground, much of the oxygen elements were left untampered with. Scientists compared their rock samples with Martian meteorites that have crashed into Earth in the past to find the link between the two.
Obviously, this means that there could've been life on Mars, but it's still uncertain as to what kind of life. There may have been plants, water, and other lifeforms, but actual humans? It's a long shot, but it's too early to tell at this point. Of course, Mars gets its now-rusty and dry look due to oxidation, but scientists think that the planet was once warm and festered with life at some point in its past.
VIA: The Guardian