New maps of Mars’ topography provide evidence for the existence of an ocean on the planet in its ancient history, with implications for its ability to once support life.
A map of the Martian region known as Aeolis Dorsa – a boundary that separates the high, cratered southern highlands from March of the planet’s northern smooth lowlands – strongly suggests a shoreline left by a huge ocean.
The map of the region reveals that the Red Planet once experienced sea level rise consistent with a hot, humid climate in stark contrast to the frozen, dry Martian landscape seen today.
“What immediately comes to mind as one of the most important points here is that the existence of an ocean of this size means a higher potential for life,” said Benjamin Cardenas, professor geoscience assistant at Penn State University and head of research. in a statement. (opens in a new tab) “It also tells us about the ancient climate and how it evolved. Based on these findings, we know that there must have been a time when it was warm enough and the atmosphere was thick enough to support so much liquid water at a time.”
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While planetary scientists are certain that Mars was once a much waterier planet than it is today, a debate has raged over whether a the ocean existed in the northern hemisphere of the planet.
Cardenas and his colleagues were able to answer this question by using topological data to show evidence of a coastline around 3.5 billion years old. One aspect of this geologic feature was the substantial accumulation of sediment covering hundreds of thousands of square kilometers and approximately 3,000 feet (900 meters) thick.
“The big novelty we did in this paper was thinking about Mars in terms of stratigraphy and sedimentary record,” Cardenas said. “On Earth, we trace the history of waterways by looking at the sediments that are deposited over time. We call this stratigraphy, the idea that water carries sediment, and you can measure changes on Earth by understanding the way sediment accumulates. That’s what we’ve done here – but this is Mars.”
Scientists used software developed by the United States Geological Survey to evaluate Mars map data collected by the Mars Orbiter Laser Altimeter (MOLA) onboard NASA. Mars Global Surveyor (MGS) spacecraft, which orbited the planet between 1996 and 2006.
The data revealed more than 4,000 miles (6,500 kilometers) of river ridges, which are relics of ancient sediment-filled water channels that rise higher than the surrounding landscape. The team grouped these river ridges into 20 systems demonstrating that they likely formed from eroded river deltas or submarine channel belts that are remnants of an ancient coastline on Mars.
The researchers concluded that Cardenas Aeolis Dorsa must once have been covered by ocean, the remains of which can today be seen in the densest concentration of river ridges on the Red Planet.
“The rocks of Aeolis Dorsa capture fascinating information about the state of the ocean,” Cardenas explained. “It was dynamic. The sea level rose dramatically. Rocks were being deposited along its basins at a rapid rate. There were a lot of changes happening here.”
The team was able to understand the evolution of the paleogeography of the region by observing elements of the rock formation such as the thicknesses of the ridge system, elevations, locations and possible directions of sediment flow.
Because ancient sedimentary basins on Earth contain information about the evolution of our planet’s climate and the emergence and development of life, Cardenas believes that if scientists want a similar understanding of the same things on Mars, Aeolis Dorsa is a great starting point.
“A major objective for the The Mars Curiosity rover mission is to look for signs of life. He has always looked for water, traces of habitable life. It’s the largest to date,” Cardenas said. “It’s a giant body of water, fed by upland sediment, presumably carrying nutrients. If there had been tides on ancient Mars, they would have been here, gently bringing in and leaving water.
“It’s exactly the kind of place where ancient martian life could have evolved. »
The research has been published in Journal of Geophysical Research: Planets (opens in a new tab) October 12.
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