Mars once had salt lakes similar to the ones on Earth and has gone through wet and dry periods, according to a new study.
The researchers from Texas A&M University College in the US examined Mars' geological terrains from Gale Crater, an immense 95-mile-wide rocky basin that is being explored by the NASA Curiosity rover since 2012 as part of the MSL (Mars Science Laboratory) mission, according to the study published in the journal Nature Geoscience.The results show that the lake, which was present in Gale Crater over three billion years ago underwent a drying episode, potentially linked to the global drying of Mars.
Gale Crater was formed about 3.6 billion years ago when a meteor hit Mars.
"Since then, its geological terrains have recorded the history of Mars, and studies have shown Gale Crater reveals signs that liquid water was present over its history, which is a key ingredient of microbial life as we know it," said study co-author Marion Nachon from Texas A&M University.
"During these drying periods, salt ponds eventually formed. It is difficult to say exactly how large these ponds were, but the lake in Gale Crater was present for long periods of time - from at least hundreds of years to perhaps tens of thousands of years," Nachon said.
According to the researchers, Mars probably became drier over time, and the planet lost its planetary magnetic field, which left the atmosphere exposed to be stripped by solar wind and radiation over millions of years.
"With the atmosphere becoming thinner, the pressure at the surface became lesser, and the conditions for liquid water to be stable at the surface were not fulfilled anymore, so liquid water became unsustainable and evaporated," Nachon said.The salt ponds on Mars are believed to be similar to some found on Earth, especially those in a region called Altiplano, which is near the Bolivia-Peru border.
Nachon said that the Altiplano is an arid, high-altitude plateau where rivers and streams from mountain ranges "do not flow to the sea but lead to closed basins, similar to what used to happen at Gale Crater on Mars.
"This hydrology creates lakes with water levels heavily influenced by climate. During the arid periods Altiplano lakes become shallow due to evaporation, and some even dry up entirely," she said.
Nachon added that the study shows that the ancient lake in Gale Crater underwent at least one episode of drying before "recovering."
It's also possible that the lake was segmented into separate ponds, where some of the ponds could have undergone more evaporation.
These results indicate a past Mars climate that fluctuated between wetter and drier periods, the researchers said.