For a long time, the scientific community has debated whether Mars had an ocean in its northern hemisphere. Using topographic data, a research team was able to show definitive evidence of an approximate 3.5-billion-year-old coastline.
The team, led by Benjamin Cardenas analyzed terrain maps of Mars, the team tracked the sedimentary accumulation in specific areas that could be consistent with the levels present in ocean shoreline accumulation.
Just as on Earth, where ancient sedimentary basins contain the stratigraphic records of the evolution of climate and life, on Mars this system could be applied to find a record of the life and, according to Cardenas, an ocean as large as this would be a good place to start.
Rock formations, as well as the thickness of the ridge system, elevations, locations and possible directions of sedimentary flow, helped the team understand the evolution of the paleogeography of the area.
The new topographic maps revealed strong evidence that there was an ocean on Mars consistent with a widespread warm, wet climate. It was about 900 meters thick and covered hundreds of thousands of square kilometers.
The area once believed to have been ocean is known as Aeolis Dorsa and, according to experts, contains the densest collection of river ridges on the planet. Cárdenas said that «the rocks at Aeolis Dorsa capture fascinating information about what the ocean was like. Sea level rose significantly. Rocks were being deposited along its basins at an accelerated rate. A lot of changes were occurring here.»
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They traced the evidence together to present a stratigraphy of an ancient ocean’s margin. The researchers mapped over 6,500km of fluvial ridges, basically signs of sediment that gets deposited by flowing water, and grouped them into 20 systems.
«What immediately comes to mind as one of the most important points here is that the existence of an ocean of this size means greater potential for life,» said Benjamin Cardenas, assistant professor of geosciences at Penn State and lead author of the study published recently in the Journal of Geophysical Research.
