NASA has created a 3D reconstruction of ancient water channels below the surface of Mars, revealing evidence of a catastrophic flood in the last 500 million years.
Images from the Mars Reconnaissance Orbiter (MRO) show that the flood was as big as the ancient mega-flood that created the Channeled Scablands in the US Pacific Northwest. Mars had been believed to be cold and dry during this period.
"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," says Gareth Morgan, a geologist at the National Air and Space Museum's Center for Earth and Planetary Studies in Washington. "This work demonstrates the importance of orbital sounding radar in understanding how water has shaped the surface of Mars."
The channels lie in Elysium Planitia, an expanse of plains along the Martian equator, and the youngest volcanic region on the planet. Extensive volcanic activity throughout the last several hundred million years has covered most of the surface of Elysium Planitia with lava, burying most of the 620-mile-long Marte Vallis channel system.
Not much is known about Marte Vallis, although it's similar to more ancient channel systems on Mars, especially those of the Chryse basin. Many scientists think the Chryse channels likely were formed by the catastrophic release of ground water, although others suggest lava as the cause.
To map the Marte Vallis channels, the researchers used MRO's Shallow Radar (SHARAD), spotting 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. These smaller channels flowed around four streamlined islands. A second phase carved the deep, wide channels.
"In this region, the radar picked up multiple 'reflectors,' which are surfaces or boundaries that reflect radio waves, so it was possible to see multiple layers, " says Lynn Carter of NASA's Goddard Space Flight Center. "We have rarely seen that in SHARAD data outside of the polar ice regions of Mars."
The mapping also shows that the floods carving the channels originated from a now-buried portion of the Cerberus Fossae fracture system. The water could have accumulated in an underground reservoir and been released by tectonic or volcanic activity.
"While the radar was probing thick layers of dry, solid rock, it provided us with unique information about the recent history of water in a key region of Mars," says Jeffrey Plaut of NASA's Jet Propulsion Laboratory.