A four-billion old meteorite that originated near the surface of Mars points to the warm and wet temperature of the planet Mars in the past, at about 18 degrees Celcius or 64 degrees Farenheit.

Researchers at the California Institute of Technology (Caltech) determined that the carbonate minerals in the meteorite were formed at about 18 degrees Celcius, which is neither cold nor particularly hot.

The temperature was measured using the Martian meteorite ALH84001 which was discovered in 1984 in the Allan Hills of Antartica. The potato-shaped rock was theorized to have been blown off from the surface of Mars towards the Earth when another meteorite struck the area.

This finding was contained in the research paper "Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 ± 4 °C in a near-surface aqueous environment," which was published online in the Proceedings of the National Academy of Sciences (PNAS).

At present, Mars has an average temperature of -63 degrees Celius. However, the evidence that Mars once had a warmer temperature and had liquid water is crucial to understanding the planet's history.

This corroborates previous findings of Mars rovers and orbiting spacecraft that have found ancient deltas, rivers, lakebeds, and mineral deposits that suggested the presence of water.

Woody Fischer, assistant professor of geobiology and co-author of the research paper noted that there were all the ideas about a warmer and wetter Mars but there was little data to prove it until the study on the meteorite.

"It's proof that early in the history of Mars, at least one place on the planet was capable of keeping an Earthlike climate for at least a few hours to a few days," says a co-author of the paper, Johh Eiler, who is a Robert P. Sharp Professor of Geology and professor of geochemistry.