Today, Mars is a dry place, but modern science indicates that it wasn’t always that way. Concentrated river deposits scattered throughout the planet’s surface tell a story about early-Mars’ soggy past, in which water flowed across the surface between 3-4 billion years ago.
River deposits occur when water pushes minerals from one place to another. Discovering them on Mars is a sign that water once flowed where they reside. While this wouldn't be the first time that researchers have found river deposits on Mars, perhaps the most striking fact is how densely-packed some of them are.
Image Credit: B.T. Cardenas et al., Geological Society of America Bulletin
A new study carried out by researchers from the Jackson School of Geosciences at the University of Texas at Austin now contends that Aeolis Dorsa preserves some of the most densely-packed river deposits ever found on Mars to date. They’ve published their findings in the journal GSA Bulletin.
High-resolution images captured by both the Context Camera (CTX) and High-Resolution Imaging Science Experiment (HiRISE) instrument on NASA’s Mars Reconnaissance Orbiter, coupled with topographic data collected by the Mars Orbiting Laser Altimeter (MOLA) on NASA’s Mars Global Surveyor, led the researchers to their results.
An analysis of the data revealed how the river deposits at Aeolis Dorsa underwent a process known as ‘topographic inversion.’ During this process, flowing water slowly exhumed the deposits through the process of erosion and formed the ridges can we make out in satellite imagery today.
River deposits occur naturally on Earth too, so the researchers were able to use what they’ve learned from studying similar features on Earth to draw conclusions about early-Mars’ mysterious past, including how long ago and in what direction the water flowed.
The team discerned that the rivers flowed in a south-easterly direction and found patterns pointing to incised valleys where water levels both rose and fell regularly. Not much is known yet about what might have caused the water levels to fluctuate so much, but that’s a question that additional research may help to answer.
The findings are particularly important to planetary scientists because they tell a story of a time when the Mars may have been habitable. Moreover, the data can help us learn more about how Mars evolved over the years, transforming from the wet, habitable planet into the desolate wasteland it is today.
It should be interesting to see what kinds of conclusions planetary scientists will draw next and whether we'll unlock the mysteries behind Mars before sending astronauts to explore the red planet in person.