June 19, 2013
Mars May Have Had Oxygen-Rich Past
Lee Rannals for redOrbit.com — Your Universe Online
The team examined differences between Martian meteorites and surface rocks examined by NASA's Spirit rover in the Gusev crater on Mars. Surface rocks are five times richer in nickel than the meteorites, which created some mystery for scientists as to whether the meteorites are typical volcanic products of the Red Planet.
"What we have shown is that both meteorites and surface volcanic rocks are consistent with similar origins in the deep interior of Mars but that the surface rocks come from a more oxygen-rich environment, probably caused by recycling of oxygen-rich materials into the interior," said Professor Bernard Wood, of Oxford University's Department of Earth Sciences, who led the research. "This result is surprising because while the meteorites are geologically 'young', around 180 million to 1400 million years old, the Spirit rover was analyzing a very old part of Mars, more than 3700 million years old."
The team believes the differences between the meteorites and rocks arise through a process known as subduction. This is when material is recycled into the interior of the planet.
The researchers suggest the Martian surface was oxidized very early in the history of the planet and this oxygen-rich material was drawn into the shallow interior and recycled back to the surface during eruptions four billion years ago. The meteorites are much younger volcanic rocks that emerged from deeper within the planet, and so were less influenced by this process.
"The implication is that Mars had an oxygen-rich atmosphere at a time, about 4000 million years ago, well before the rise of atmospheric oxygen on Earth around 2500 million years ago. As oxidation is what gives Mars its distinctive color it is likely that the 'red planet' was wet, warm and rusty billions of years before Earth's atmosphere became oxygen rich."
NASA's Spirit rover mission came to an end after the spacecraft found itself stuck on Mars. Spirit stopped communicating with Earth in March 2010 and NASA later declared it would not be trying to revive the rover. The rover launched alongside Opportunity, which remains operational along with NASA's newer Curiosity rover.