Mars Timeline Shows Three Eras, One Wet

Today’s cold, dry climate on Mars evolved about 3.5 billion years ago, ending a period when that planet had seen moist conditions, research indicates.

An international team of scientists developed a timeline for Mars’ geological evolution, reporting in Friday’s issue of the journal Science that the planet 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.

Between 3.2 billion and 3.5 billion years ago the third era began, marked by minerals dominated by ferric oxides, which have not been formed or altered by water, the researchers said.