Ancient Mars supported liquid water

Mars had a surface environment that supported liquid water about 3.5 billion years ago, according to a study of river deposits spread across the red planet. A region of Mars named Aeolis Dorsa contains some of the most spectacular and densely packed river deposits seen on the planet.

With the use of high-resolution images and topographic data from cameras on orbiting satellites, B T Cardenas and colleagues from the Jackson School of Geosciences in the U.S. 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.

Cardenas and colleagues conclude that similar falling and rising water levels in a large water body forced the formation of the paleo-valleys in their study area. Cross-cutting relationships are observed 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. The conclusion that such large water level fluctuations and coastline movements were recorded by these river deposits suggests some long-term stability in the controlling, downstream water body, which would not be expected from catastrophic hydrologic events

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