The Mars environment over 3.5 billion years ago was able to support liquid water at the surface, says a study.
River deposits exist across the surface of Mars and a region of Mars named Aeolis Dorsa contains some of the most spectacular and densely packed river deposits seen on the Red Planet, according to the study published in the Geological Society of America (GSA) Bulletin.
These deposits are observable with satellite images because they have undergone a process called "topographic inversion" where the deposits filling once topographically low river channels have been exhumed in such a way that they now exist as ridges at the surface of the planet, the researchers said.
With the use of high-resolution images and topographic data from cameras on orbiting satellites, Benjamin T Cardenas and colleagues from Jackson School of Geosciences at the University of Texas at Austin, identified fluvial deposit stacking patterns and changes in sedimentation styles controlled by a migratory coastline.
They also developed a method to measure river paleo-transport direction for a subset of these ridges.
Together, these measurements demonstrated that the studied river deposits once filled incised valleys.
On Earth, incised valleys are commonly cut and filled during falling and rising eustatic sea level, respectively.
The researchers concluded that similar falling and rising water levels in a large water body forced the formation of the paleo-valleys in their study area.
"We present evidence that some of these fluvial deposits represent incised valleys carved and filled during falls and rises in base level, which were likely controlled by changes in water-surface elevation of a large lake or sea," the study said.
They observed cross-cutting relationships at the valley-scale, indicating multiple episodes of water level fall and rise, each well over 50 metres, a similar scale to eustatic sea level changes on Earth.
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