The source of water ice on the Moon could be traced to a seemingly unlikely source

The source of water ice on the Moon could be traced to a seemingly unlikely source

Comparatively, not much happens on the Moon. There is dust. There is rock. There are basalt plains, the product of extensive volcanism for much of the Moon’s history.

And, as we recently discovered, there is water. Lots of water. Encased in lunar regolith. Trapped in volcanic glass. Perhaps even in patches of ice on or just below the surface, hiding in craters at the poles that hide in permanent shadow, where it cannot be sublimated by the Sun’s heat.

Where this water could come from is still something of a mystery. But new research suggests an interesting source, a process we know has happened often on the Moon in the past: volcanoes.

Planetary scientists wonder if there would have been enough water molecules in the volcanic outgassing of the old Moon to fall back to the surface and form patches of ice in permanent shadow. Now it seems the answer is “yes”.

Our model suggests that [around] 41 percent of total H2The mass of O erupted during this period could have condensed as ice in the polar regions, with thicknesses of up to several hundred meters,” wrote a team of researchers led by planetary scientist Andrew Wilcoski. from the University of Colorado at Boulder in their article.

“Our work suggests that the period of volcanic activity of the early Moon would have been punctuated by short-lived collisional atmospheres that allowed the efficient sequestration of large amounts of water ice at the poles and the temporary daytime availability of ice at the poles. ‘water and steam at all. latitudes.’

The Moon seems quite serene these days, but once upon a time there was a hot mess. Those dark spots you see when you look at the full moon are vast plains of volcanic rock, from a period of large-scale volcanic activity that began perhaps 4.2 billion years ago and lasted until around 1 billion years ago, with most activity occurring during the first or so first two billion years of this period.

Tens of thousands of volcanoes spewed lava onto the Moon, blanketing the surface in volcanic landscapes (for context, the most volcanic body currently in the solar system is Jupiter’s moon Io, which has over 400 known volcanoes ).

Additionally, these eruptions would have included huge clouds of volcanic gases, mostly carbon monoxide and water vapor. These could have formed tenuous, transient atmospheres around the Moon that then dissipated into space. But, Wilcoski and his colleagues hypothesized, what if the water vapor didn’t dissipate entirely in the solar wind? What if part of it settles like gel?

They performed a model, based on an average rate of massive eruption of about once every 22,000 years. They then studied the rate at which volcanic gases escaped into space, compared to the amount that condensed, froze and deposited on the lunar surface.

They found that as the atmosphere persists – a period of about 1,000 years – about 15% of the water is deposited and forms a gel on the lunar night face, or about 8.2 quadrillion kilograms (18 quadrillion pounds). Some of this frost would sublimate in sunlight over time, but over billions of years enough could have remained to make up a significant proportion of the ice that remains today, the researchers said. .

That doesn’t mean it will be easy to find. Some of them may be buried meters below the lunar surface. But some of the water could have remained on the surface at lower latitudes long enough to interact with minerals there, or captured in volcanic glass that is remelted in meteorite impacts.

Such evidence of past water has already been identified on the Moon, giving us a starting point to search for evidence supporting ancient volcanic lunar frosts. Science is so awesome.

The team’s research has been published in The Journal of Planetary Science.

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