Mars Rivers Carved by Lava, Not Water
A controversial theory is being revived: lava carved Mars channels. This could discourage hopes to find life on the red planet.
On The Conversation, volcanologist Robin Wylie (University College, London) says a new paper by Giovanni Leone (Swiss Federal Institute of Technology) supports the interpretation that the many river-like channels on Mars, including the giant Valles Marineris, were formed by lava flows, not water. Leone studied thousands of images from the Mars Reconnaissance Orbiter (MRO) at extremely high resolution (up to 25 cm per pixel) to draw his conclusions.
The morphology of the lava flows Leone encountered suggest that the lava actually incised the valleys and channels in the first place. The MRO images seem to show that channels formed by the freshly erupted lava were later deepened and widened by the passage of liquid rock. This type of erosion, Leone argues, can explain the existence of the valleys and outflow channels without the need to invoke significant amounts of liquid water.
Leone also found collapsed lava tubes and other indications of lava flows at all stages. Volcanic origin of the channels used to be the consensus interpretation back in the 1960s, Wylie says, but for the last 25 years, the consensus had shifted to the view that water carved the channels.
The “radical conclusions” will be hard to accept for astrobiologists eager to find evidence of life. Leone’s interpretation does not rule out the presence of water, but gives it a less prominent geological role. Future missions looking for life may be more likely to find dry volcanic rock, like the Spirit rover did in Gusev Crater. That crater had been theorized to be the terminus of a water-carved outflow channel, but only lava was found, to the disappointment of some.
The war between the wet-Marsers and dry-Marsers still carries on. Give Mars all the water they want, and they will still never find life emerging from nonliving material. It didn’t happen here, and it can’t happen there, or anywhere.