A lake once filled the 96-mile wide crater currently being explored by NASA's Mars rover Curiosity, providing evidence that the planet most like Earth in the solar system was once suitable for microbial life.
The findings combine more than two years of rock data collected by the rover since landing inside Gale Crater back in August 2012.
Scientists discovered rocks containing water-deposited sediments inclined towards the crater's center, which now has a three-mile mound called Mount Sharp. This would mean that Mount Sharp didn't exist during the period of time some 3.5 billion years ago when the crater was filled with water.
"Finding the inclined strata was a complete surprise," said lead scientist John Grotzinger, with the California Institute of Technology in Pasadena, according to Reuters.
"Sedimentary geology is the cutting edge for trying to understand the Earth. When oil companies collect seismic surveys across places, they are looking for inclined strata because then you get geometry that tells you where the rocks are that you're looking for," he added.
Not long after landing, Curiosity found that Mars once had the chemical ingredients and environmental conditions needed in order to support microbial life, those fulfilling the main goal of its mission.
The rover then started driving toward Mount Sharp to search for other habitable spots and learn if life-friendly environments existed long enough for life to evolve.
"The size of the lake in Gale Crater and the length of time and series that water was showing up implies that there may have been sufficient time for life to get going and thrive," said NASA's Mars Exploration Program scientist Michael Meyer, according to Reuters.
The studies, which haven't been published yet, point to a series of wet and dry times at Gale Crater, challenging the previously believe notion that Mars' period of warm climate was early and short-lived.
"All that driving we did just didn't get us to Mount Sharp. It gave us the context to appreciate Mount Sharp," Grotzinger said of the rover, which has traveled about 5 miles since landing on Mars.