Ancient Meteorites from Mars Unlock Secrets of Red Planet's Early Atmosphere

Scientists may be learning a bit more about Mars' atmosphere by studying meteorites. They've examined 40 of these space rocks that fell to Earth from the Red Planet and have unlocked the secrets of the ancient Martian atmosphere through chemical signatures.

The meteorites themselves are igneous rocks that formed on Mars. These rocks were ejected into space when either an asteroid or comet hit the planet. Hurled forcefully from the planet, these rocks eventually landed on Earth. The oldest meteorite that the researchers examined is about 4.1 billion years old, and was formed when the solar system was just in its infancy.

By studying meteorites that range in ages, the researchers can understand the evolution of the Martian atmosphere. This, in turn, can reveal clues about what Mars might have been like in the distant past. The Mars rover Curiosity has actually discovered evidence that there was once water on the planet, which may mean that there was also once life.

So what did the scientists find? They found sulfur, so they tracked the sulfur isotopes in the meteorite samples. In the end, they were able to identify some sulfur as a product of photochemical processes in the Martian atmosphere. In addition, they found that the chemical reactions involving sulfur were very different than took place in Earth's early geological history.

"Climate models show that a moderate abundance of sulfur dioxide in the atmosphere after volcanic episodes, which have occurred throughout Mars' history, could have produced a warming effect which may have allowed liquid water to exist at the surface for extended periods," said Heather Franz, one of the researchers, in a news release. "Our measurements of sulfur in Martian meteorites narrow the range of possible atmospheric compositions, since the pattern of isotopes that we observe points to a distinctive type of photochemical activity on Mars, different from that on early Earth."

The findings reveal a bit more about the Martian atmosphere, and allow the researchers to compare it to that of Earth.

The findings are published in the journal Nature.