According to scientists Mars likely had three distinct eras:
If Mars had been hospitable to life, it would only have been in its early, wet years, according to the researchers led by Jean-Pierre Bibring of France's Institute for Space Astrophysics.
The planet formed about 4.6 billion years ago. During the first era, clay materials, which need abundant water and moderate temperatures, formed, the researchers said.
Then, starting about 4 billion years ago a second era began, marked by volcanic activity spewing sulfur into the environment. That was the start of a drying out of the planet.
Between 3.2 billion years ago and 3.5 billion years ago the third era began. It was marked by minerals dominated by ferric oxides, which have not been formed or altered by water, the researchers said. That increasingly dry and acidic environment was "not a pleasant place for any form of life, even a microbe," said John Mustard, a Brown University geologist who was a co-author of the paper.