Lava, Not Water Made Mars' Canyons

The massive canyons that cover the surface of Mars were likely formed by lava flow, not water, according to a recent study.

The study, published in the Journal of Volcanology and Geothermal Research, details how it appears unlikely that the massive gorges Noctis Labyrinthus and Valles Marineris on Mars were formed by rushing water, as the total amount of water on Mars could not have been enough to carve both canyons.

According to a press release accompanying the study,  Giovanni Leona, a specialist in planetary volcanism, closely examined the two gorges, which, when combined, would span the complete length of the United States from east to west. For perspective, the Grand Canyon, one of the Earth's largest canyons, only takes up a small portion of the state of Arizona.

Leona set out to conclusively determine how these canyons had formed. A past theory is that rushing water slowly cut a path through elevated bed-rock. Another, more modern theory was that the canyons were formed through massive shifts along Mars' tectonic plates.

However, according to an analysis of the images from the US Geological Survey of Mars, both these theories were very far off the mark. Liquid rock, Leone writes, was the only force powerful enough to have carved out these massive canyons.

"The typical indicators of erosion by water were not visible on any of them," Leone said in a press release. "One must therefore ask oneself seriously how Valles Marineris could have been created by water if one cannot find any massive and widespread evidence of it."

The scientist also roughly estimated how much water would have been needed, and at what force, to carve out these canyons. The answer, he said, was fantastical.

Instead, Leone found evidence that the canyons were actually formed by the repeated collapse of massive volcanic tubes that race like veins through the Martian surface during volcanic eruptions. Once an eruption subsided, these tubes would be left hollow and could potentially collapse, creating small canyons. Additional eruptions could widen the canyons until they were the size of the Martian valleys we see now.

The implications of this study can easily be overlooked.

According to Leone, if researchers accept that Mars had about as much water as we currently see on it, it is far less likely that it ever would have been able to support life, utterly debunking past theories that Mars was once much like Earth.

The study was published in the Journal of Volcanology and Geothermal Research on May 1.