Ancient fluvial deposits exist on Mars and can be identified in satellite data by erosional landforms called fluvial ridges. River ridges are shaped like ancient river deposits and are useful for understanding the history of water on the Red Planet. However, NASA’s Curiosity rover in Gale Crater on Mars has observed fluvial deposits that are not associated with fluvial ridges, but rather bench and nose landforms generally not associated with ancient fluvial deposits. In a study published in the journal Geophysical Research Lettersplanetary scientists modified a computer model that generates river ridges from ancient fluvial deposits by adding a preferred direction for scarp retreat that may exist in craters on Mars because crater topography controls winds and wind currently controls erosion on Mars. The model generated benches and noses rather than ridges, proving that these landforms can be used as indicators of ancient ridge-like fluvial deposits in craters on Mars.
Bench and slope morphology imaged on Mars (top) and nose morphology from the ground on the Martian outcrop Mont Mercou (bottom). Image credit: NASA/Caltech-JPL/MSSS.
“We find evidence that Mars was probably a planet of rivers.” We see signs of this all over the planet,” Dr. Benjamin Cardenas, a researcher at Pennsylvania State University.
“We have everything we can learn about Mars by better understanding how these fluvial deposits can be interpreted stratigraphically, where we think of rocks today as layers of sediments deposited over time.”
“This analysis is not a snapshot, but a record of change. What we see on Mars today are the remnants of an active geologic history, not some landscape frozen in time.”
Previous studies of satellite data from Mars have identified erosional landforms called fluvial ridges as possible candidates for ancient river deposits.
Using data collected by the Curiosity rover in Gale Crater, Dr. Cardenas and his colleague Dr. Kaitlyn Stacey signs of fluvial deposits not associated with fluvial ridges, but rather with bench and nose-type forms that have never been associated with ancient fluvial deposits.
“This suggests that there may be undiscovered fluvial deposits elsewhere on the planet, and that an even larger part of the Martian sedimentary record may have been built up by rivers during the habitable period of Mars’ history,” said Dr. Cárdenas.
“On Earth, river corridors are so important to life, chemical cycles, nutrient cycles and sediment cycles. All indications are that these rivers on Mars behave similarly.”
In designing their computer model, the researchers found a new use for 25-year-old scans of Earth’s stratigraphy.
Scans of the Gulf of Mexico’s seafloor, collected by oil companies, provided an ideal comparison to Mars.
Scientists simulated Mars-like erosion using 3D scans of real, recorded stratigraphy on Earth.
When they ran the simulation, the model revealed eroded Martian landscapes that formed topographic benches and noses rather than river ridges that appeared almost identical to the landforms observed by the Curiosity rover inside Gale Crater.
“Our research shows that Mars may have had many more rivers than previously believed, which certainly paints a more optimistic view of ancient life on Mars,” said Dr. Cárdenas.
“It offers a vision of Mars where most of the planet once had the right conditions for life.”
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Benjamin T. Cardenas and Kaitlyn Stacey. Landforms associated with aspect-controlled exhumation of crater-filling alluvial strata on Mars. Geophysical Research Letters, published online August 8, 2023; doi: 10.1029/2023GL103618
