Instead of a warm, wet and possibly life-bearing planet, as some scientists contend, early Mars may have been a hostile and volatile place with frequent volcanic outbursts, a new study shows.
Earlier research had theorised that certain minerals detected on the surface of the Red Planet indicated the presence of clay formed when water weathered surface rock some 3.7 billion years ago.
This would also have meant the planet was warmer and wetter then, boosting chances that it could have nurtured life forms.
But new research by a team from France and the United States said the minerals, including iron and magnesium, may instead have been deposited by water-rich lava, a mixture of molten and part-molten rock beneath earth's surface.
Alain Meunier of the Universite de Poitiers and a team studied clay minerals at Mururoa atoll in French Polynesia that seem similar to Martian examples, and showed they were formed from precipitation of lava.
The same process has also occurred at other locations on earth, including the Parana basin in Brazil, said the study published on Sunday in Nature Geoscience.
"To crystallise, clays need water but not necessarily liquid water," Meunier said.
"In other words, clays are not exclusively typical of soils or altered rocks; they may crystallise also directly from magmas.
"Magmatic clays have no climatic significance. Consequently, they cannot be used to prove that the planet was habitable or not during its early history."