Traces of massive floods found on Mars

NASA scientists have discovered evidence of "gigantic floods" on Mars that carved deep channels into the red planet in the past 500 million years.
NASA's Mars Reconnaissance Orbiter has provided images allowing scientists for the first time to create a 3-D reconstruction of ancient water channels below the Martian surface.
The spacecraft took numerous images during the past few years that showed channels attributed to catastrophic flooding in the last 500 million years. During this period, Mars had been otherwise considered cold and dry.
These channels are essential to understanding the extent to which recent hydrologic activity prevailed during such arid conditions. They also help scientists determine whether the floods could have induced episodes of climate change.

"Our findings show the scale of erosion that created the channels previously was underestimated and the channel depth was at least twice that of previous approximations," said Gareth Morgan, lead author on the paper.
"This work demonstrates the importance of orbital sounding radar in understanding how water has shaped the surface of Mars," Morgan said in a NASA statement.

The channels lie in Elysium Planitia, an expanse of plains along the Martian equator and the youngest volcanic region on the planet, according to the findings reported in Science Express.
Extensive volcanism throughout the last several hundred million years covered most of the surface of Elysium Planitia, and this buried evidence of Mars' older geologic history, including the source and most of the length of the 1000-kilometre-long Marte Vallis channel system.

Marte Vallis' morphology is similar to more ancient channel systems on Mars, especially those of the Chryse basin.
The team from NASA, the Smithsonian Institution in Washington, and the Southwest Research Institute in Builder, was able to map the buried channels in three dimensions with enough detail to see evidence suggesting two different phases of channel formation.
One phase etched a series of smaller branching, or "anastomosing," channels that are now on a raised "bench" next to the main channel.
Scientists said these smaller channels flowed around four streamlined islands. A second phase carved the deep, wide channels.