Spirit Embedded in Soft Soil on Mars as Engineers Devise Methods to 'Free Spirit'
Spirit Embedded in Soft Soil on Mars as Engineers Devise Methods to 'Free Spirit' © NASA 20 June, 2013

Mars had oxygen-rich atmosphere 4,000 million years ago

Differences between Martian meteorites and rocks examined by a NASA rover can be explained if Mars had an oxygen-rich atmosphere 4,000 million years ago, well before the rise of atmospheric oxygen on Earth 2,500 million years ago.

Scientists from the University of Oxford investigated the compositions of Martian meteorites found on Earth and data from NASA’s ‘Spirit’ rover that examined surface rocks in the Gusev crater on Mars. Surface rocks were found to be five times richer in nickel than the meteorites, perplexing scientists and casting doubt on whether the meteorites are typical volcanic products of the red planet.

Speaking about the research, Professor Bernard Wood said: “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. This result is surprising because while the meteorites are geologically ‘young’, around 180 million to 1,400 million years old, the ‘Spirit’ rover was analysing a very old part of Mars, more than 3,700 million years old.”

The researchers believe the differences are due to a process known as subduction, where a material is recycled into the interior. They suggest that the Martian surface was oxidised very early in the history of the planet and through subduction, this oxygen-rich material was drawn into the shallow interior and recycled back to the surface during eruptions 4,000 million years ago. The meteorites are understood to be much younger volcanic rocks which were less influenced by this process.

Wood added: “The implication is that Mars had an oxygen-rich atmosphere at a time, about 4,000 million years ago.”

The research was supported by the UK’s Science and Technology Facilities Council and the European Research Council and published in Nature magazine.