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Water on Mars May Be Trapped in the Planet's Crust, Not Lost to Space
Mars had water—until it didn't. Scientists thinks that about four billion years ago, the planet had substantial amounts of liquid water on its surface, enough to form rivers, lakes, seas, and even oceans—and perhaps also to support life. But something happened in the following billion years, triggering the loss of this water from the surface until all that was left was the cold, dry wasteland of a world that we see today. Why and how that happened remains somewhat of a mystery. "We don't exactly know why the water levels decreased and Mars became arid," says Eva Scheller of the California Institute of Technology.
In recent years, results from NASA's Mars-orbiting MAVEN spacecraft suggested the driver of this water depletion may have been atmospheric loss. Long ago, for reasons unknown, Mars lost its strong magnetic field, exposing the planet to atmosphere-eroding outbursts from the sun. As a result, much of Mars's air escaped to space, presumably carrying away most of the planet's water with it. But in a new paper published this week in the journal Science, Scheller and her colleagues argue this process alone cannot explain Mars's modern-day aridity. Instead they say that a substantial amount of the planet's water—between 30 and 99 percent—retreated into the crust [open, DOI: 10.1126/science.abc7717] [DX], where it remains today, in a process known as crustal hydration.
Also at NYT, Reuters, National Geographic, and Yahoo News.
(Score: 0) by Anonymous Coward on Monday March 22 2021, @01:09AM (1 child)
Crustal hydration requires that a large chunk of the crust LOSES water through dehydration, and then, because it’s now lighter, floats higher on the underlying magma, and water gets under the floating crust. This requires a molten core. That molten core’s rotation would generate a protective magnetic field around the pl.
The core freezes, no more magnetic field, and no more plate tectonics, so no more crystal hydration. The water vapour gets stripped to hydration and oxygen, and is lost in space. Not stored under the crust, because the dehydrated crust is no longer subjected to plate tectonics.
Wishful thinking.
So why did Mars lose it’s magnetic field? Probably too small to have a large enough core with a supply of fissile elements that could keep generating heat from atomic decay for billions of years. Because size matters.
(Score: 2) by hendrikboom on Monday March 22 2021, @04:34AM
And no big moon to churn subsurface lava by tidal forces.