Mars had oxygen even before Earth. Early Mars had an oxygen-rich environment and water, a new study suggests.

The findings of oxygen on Mars come from an Oxford University study. The researchers compared meteorites and surface rocks and discovered Mars had oxygen.

The study paints a picture of a Mars that was "warm, wet, and rusty" - and possibly could host life.

Much of the data about possible oxygen on Mars was taken from NASA's Spirit rover.

Scientists found that surface rocks on Mars were five times richer in nickel than the meteorites.  They think that long ago, Mars' surface was oxidized, which may explain its red color.

This may be because of subduction, a process by which material is recycled into the planet's interior. The meteorites are younger rocks, and contain much less nickel.

He said that oxidation may have given Mars its color, and that the planet was "warm, wet and rusty" long before Earth.

Dr. Bernard Wood, a lead researcher in the study, said, "The principal way we would expect to get oxygen is through photolysis of water - water vapour in Mars' atmosphere interacting with radiation from the Sun breaks down to form hydrogen and oxygen.

"Most of that hydrogen and oxygen recombines back to water. But a small fraction of the hydrogen is energetic enough to escape from the planet. A small amount of hydrogen is lost leaving an oxygen excess.

"But the gravity on Mars is one third of that on Earth, so hydrogen would be lost more easily. So the oxygen build-up could be enhanced on Mars relative to Earth."

Wood also further explained subduction, saying "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."

Wood added, "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."

Thus, Mars may have once had oxygen and water...meaning Mars may have hosted life?