Around 3.3-3.8 billion years ago, a series of streams and lakes existed on the Red Planet, filling the Gale Crater with sediment deposited as layers that formed the foundation for the mountain named Mouth Sharp, an Indian-origin scientist has revealed.
According to Ashwin Vasavada, project scientist with NASA's Mars Science Laboratory (MSL), the Red Planet appears to have had a more massive atmosphere billions of years ago than it does today, with an active hydrosphere capable of storing water in long-lived lakes.
The MSL team has concluded that this water helped to fill Gale Crater, Curiosity's landing site.
"Observations from Curiosity rover suggest that a series of long-lived streams and lakes existed at some point in the past, delivering sediment that slowly built up the lower layers of Mount Sharp," explained Vasavada.
Using Curiosity data, MSL scientists have pieced together an increasingly coherent and compelling story about the evolution of this region of Mars.
Before Curiosity landed on Mars, scientists proposed that Gale Crater had filled with layers of sediments.
Some hypotheses implied that the sediments accumulated from wind-blown dust and sand whereas others focused on the possibility that sediment layers were deposited in ancient streams and lakes.
The latest results indicate that these wetter scenarios were correct for the lower portions of Mount Sharp.
"During the traverse of Gale, we have noticed patterns in the geology where we saw evidence of ancient fast-moving streams with coarser gravel as well as places where streams appear to have emptied out into bodies of standing water," Vasavada emphasised.
The prediction was that we should start seeing water-deposited, fine-grained rocks closer to Mount Sharp.
"Now that we have arrived, we are seeing finely laminated mudstones in abundance. These silty layers in the strata are interpreted as ancient lake deposits," he pointed out.
"These finely laminated mudstones are very similar to those we see on Earth," added Woody Fischer, professor of geobiology and coauthor of the paper.
The mudstone indicates the presence of bodies of standing water in the form of lakes that remained for long periods of time, possibly repeatedly expanding and contracting during hundreds to millions of years.
These lakes deposited the sediment that eventually formed the lower portion of the mountain.
A lingering question surrounds the original source of the water that carried sediment into the crater.
For flowing water to have existed on the surface, Mars must have had a thicker atmosphere and warmer climate.
Curiosity has been exploring Gale Crater since August 2012.
In mid-September 2014, the rover reached the foothills of Mount Sharp. Curiosity has been exploring the base of the mountain since then.
The new findings were published in the journal Science.
