Mars Had a Much Thicker Atmosphere in the Past

The meteorite that the Mars rover Opportunity discovered a few weeks ago is shedding more and more light on the past composition and state of the atmosphere on the planet. Following thorough investigations, experts have been able to infer that the gaseous mix was a lot thicker in the past than it is now. The conclusion has been drawn from the fact that the piece of cosmic rock, dubbed Block Island, reached the surface of the Red Planet largely intact, when it should have disintegrated in mid-air.

According to estimates based on Martian atmosphere readings collected from NASA's missions, a meteorite the size of Block Island falling towards the surface nowadays would burn up and fall apart high above the ground. Only an object about ten times smaller than this rock would make it to the surface without being damaged or destroyed. This seems to hint at the fact that the atmosphere was a lot thicker and denser in the past.

“The fact that this meteorite is still intact tells you that the atmosphere must have been denser to slow it down for the fall,” NASA Jet Propulsion Laboratory planetary geologist Matt Golombek told Discovery News.

Block Island is estimated to have slammed into Mars a few billion years ago, when the environment was probably more acidic than it is today. The iron-nickel meteorite shows signs similar to those that would appear if you etched it with acid. Additionally, the team also believes that no water existed in the area where it fell. Back on Earth, when such objects touch water, they rust in a few years. Over billions of years, little would have remained from it.

Finding the new point of interest marked the first time when Opportunity had to backtrack in order to get a closer look at something it went by. The rover is, at this time, scheduled to spend another week or so probing the meteorite with its microscopic cameras. Other readings could yield even more clues on how Martian atmosphere developed over time, and also on the conditions that the object had to undergo in its billions of years spent on the sandy surface of Mars.