An ancient Martian meteorite discovered in the Sahara desert may give scientists a clue about the ancient climate pattern of the red planet.
Looking at the chemical clues locked inside the rock, scientists are in the process of finding out whether Mars - now a cold, dry place - was once a warm, wet planet that sustained life.
The team found evidence for the climate shift in minerals called zircons embedded inside the dark, glossy meteorite.
Zircons, which are also abundant in the earth's crust, form when lava cools.
"When you find a zircon, it is like finding a watch. A zircon begins keeping track of time from the moment it is born," said Munir Humayun, a professor of geochemistry at Florida State University.
The zircons in the meteorite are an astonishing 4.4 billion years old.
"The secret to Mars' climate lies in the fact that zircons (ZrSiO4) contain oxygen, implying that it formed during the red planet's infancy and during a time when the planet might have been able to sustain life," Humayun explained.
On Mars, oxygen is distributed in the atmosphere (as carbon dioxide, molecular oxygen and ozone), in the hydrosphere (as water) and in rocks.
"First we learned that about 4.5 billion years ago, water was abundant on Mars and now we have learned that something dramatically changed that," Humayun maintained.
The conditions that we see today on this dry Martian desert, must have persisted for at least the past 1.7 billion years.
"We now know that Mars has been dry for a very long time," Humayun concluded in a paper appeared in the journal Nature Geoscience.
