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Mars had materials rich in oxygen about 4 billion years ago

A new study suggests that Mars had an oxygen-rich environment long ago -- even before Earth. 

Oxford University researchers, led by Professor Bernard Wood of Oxford University's Department of Earth Sciences, compared meteorites and surface rocks before coming to this conclusion. 

The team studied meteorites from Mars and rocks found by NASA's Spirit rover on Mars' surface. They found that the surface rocks were five times richer in nickel than the meteorites. 

They believe this is the case because of subduction, where material is recycled into the planet's interior. The study says that Mars' surface was oxidized long ago, and through subduction, materials rich in oxygen went into the planet's interior and were recycled back to the surface about 4000 million years ago. Earth didn't experience a rise in atmospheric oxygen until 2500 million years ago. 

The meteorites, though, are younger rocks that came from deep within the red planet. Hence, they are unphased by this subduction. 

"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 Wood. "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."

Spirit, a golf cart-sized, solar-powered robot geologist that was sent to Mars in 2004, spent six long years traveling the Martian surface. But after enduring many harsh winters on Mars, Spirit finally fell silent in 2010, and was removed from the mission in mid-2011. 

NASA has been relying on rover Curiosity to dig up new info on the red planet now. It landed on Mars in August 2012, and has found rock samples that suggest life on Mars and questionable radiation levels that could determine human travel to Mars. 

Source: Science Daily

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By delphinus100 on 6/23/2013 1:22:39 AM , Rating: 2
There are moons with thick atmospheres so it is not gravity. I would say gravity does play a role but a small one.

How well a planet (or other body) can hold an atmosphere is a function of gravity, the molecular weight of the gases in question, and the speed of those molecules (temperature) at the 'top' of its atmosphere.

Titan, Saturn's largest moon, can hold a substantial atmosphere in spite of being much less massive than Mars because it's mostly fairly heavy methane and nitrogen molecules, and because it's cold way out there. The chances are small that any of those heavy molecules will be kicked up to escape velocity. If you brought it closer to the Sun, that would go away fairly quickly.

The gas giant planets, however, are massive enough to hang onto light hydrogen molecules. The extrasolar 'hot Jupiters' we know to be out there are likely massive enough to keep significantly hydrogen atmospheres, even though within spitting distance of their stars.

Venus is pretty hot, has no real magnetic field either, but is massive enough to hang onto its mostly CO2 atmosphere, in spite of also being even closer to the source of the solar wind.

It's no surprise that colder but lighter Mars retains heavy carbon dioxide molecules as well.

It's not all about planetary magnetic fields and solar winds...

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