Gigantic groundwater outbursts created the largest flood channels in the solar system on Mars, 3.2 billion years ago.
For many years it was thought that this was caused by the release of water from a global water table, but research led by J. Alexis P. Rodriguez of the Planetary Science Institute reveals regional deposits of sediment and ice emplaced 450 million years earlier to be the source.
“The flooding is due to regional processes, not global processes,” said Rodriguez, a Senior Scientist at the Planetary Science Institute and lead author of “Martian outflow channels: How did their source aquifers form, and why did they drain so quickly?” that appears in a Nature Scientific Reports. “Deposition of sediment from rivers and glacial melt filled giant canyons beneath a primordial ocean contained within the planet’s northern lowlands. It was the water preserved in these canyon sediments that was later released as great floods, the effects of which can be seen today.” [More at link]