Sciency Words: Cold Trap

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Today’s post is part of a special series here on Planet Pailly called Sciency Words. Every Friday, we take a look at a new and interesting scientific term to help us all expand our scientific vocabularies together. Today’s word is:


My04 Lunar Water 1The Moon has a lot in common with the planet Mercury, and just like Mercury, the Moon has trouble retaining its volatiles.

Water is a volatile, meaning it’ll spontaneously evaporate or sublimate at relatively low temperatures and/or pressures. Without the protection of an atmosphere or a magnetic field, volatiles like water tend to be swept off into space by the solar wind.

The only way the Moon can hold on to its water is to keep it well hidden from the Sun’s heat. Regions of the Moon (or Mercury) that are dark enough and therefore cold enough to retain water ice are informally known as cold traps.

The Moon’s best cold traps lie near its south pole, within the basins of large craters that remain in perpetual shadow, never seeing the Sun. Temperatures there hover around 100 Kelvin (a.k.a.: -170 degrees Celsius or -280 degrees Fahrenheit or simply “@&%$, that’s cold!”).

Similar craters exist near the Moon’s north pole, but they’re generally smaller and shallower and might not serve as effective cold traps.

My04 Lunar Water 2But just because the Moon has cold traps, that doesn’t prove it has water ice. On Monday, we’ll go exploring one of the Moon’s most famous and controversial cold traps: Shackleton Crater. Feel free to bring your ice skates, but I can’t guarantee you’ll get to use them.

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Today’s post is part of Moon month for the 2015 Mission to the Solar System. Click here for more about this series.



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