Did Mars have an oxygen-rich atmosphere 4 billion (4000 million) years ago? New research investigating the differences between rocks studied by NASA’s Spirit rover and Martian meteorites is suggesting just such a thing. The differences in composition between the two can be explained with the idea that Mars possessed an oxygen-rich atmosphere about 4 billion years ago — that’s 1.5 billion years before the development of an oxygen-rich environment on the Earth.
Specifically, the researchers from Oxford University compared the compositions of Martian meteorites that have been found on the Earth and data on surface rocks in the Gusev crater on Mars that was obtained by the Spirit Mars rover. “The fact that the surface rocks are five times richer in nickel than the meteorites was puzzling and had cast doubt on 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,” stated Professor Bernard Wood, of Oxford University’s Department of Earth Sciences.
“This result is surprising because while the meteorites are geologically ‘young’, around 180 million to 1400 million years old, the Spirit rover was analysing a very old part of Mars, more than 3700 million years old.”
It is a possibility though that Mars may vary considerably in geological composition depending on the region, but the researchers think that that is less likely than if the differences are the result of the of subduction — when surface material is recycled into the interior, and then eventually brought to the surface via volcanic activity. The researchers suggest that “the Martian surface was oxidized very early in the history of the planet and that, through subduction, this oxygen-rich material was drawn into the shallow interior and recycled back to the surface during eruptions 4000 million years ago. The meteorites, by contrast, are much younger volcanic rocks that emerged from deeper within the planet and so were less influenced by this process.”
Professor Wood stated: “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 colour it is likely that the ‘red planet’ was wet, warm and rusty billions of years before Earth’s atmosphere became oxygen rich.”
An interesting thought — wonder what the planet would have looked like? Possibly like the Earth?
The new research was just published in the journal Science.