THE SOUTHWORTH PLANETARIUM
207-780-4249   www.usm.maine.edu/planet
70 Falmouth Street   Portland, Maine 04103
43.6667° N                   70.2667° W 
Altitude:  10 feet below sea level
Founded January 1970
Julian Date: 2458876.16
2019-2020:  XCIII
                 "Sweater:  garment worn by a child when its mother is feeling chilly."
                             -Ambrose Bierce

THE DAILY ASTRONOMER
Tuesday, January 28, 2020
Moon Water?


Last week we tried to discourage one of the subscribers from escaping to a nearby nebula in order to escape relatives and creditors.     This week, another subscriber who aspires to one day live on the moon, asked a question about the lunar water resources.   He believed that the moon couldn't possibly retain any water resources because of its searing heat and low gravity.

"Hello!   I read your article about going to the Helix Nebula.   I was thinking I could get away from everyone simply by moving to the moon.    As I was reading about the moon, I saw where there are water reserves on it.   How is that even possible?  Isn't the day time temperature above 200 degrees and isn't its gravity weak?   The water should have vaporized long ago and escaped into outer space.  Besides, how could it even get water in the first place?"     -Displaced Marvin

The notion of moon water has always encouraged aspiring lunar colonists who have realized that living on the moon necessitates the conveyance of EVERYTHING humans need to sustain life:  food, water, oxygen, et cetera.    The cost of transporting such necessities for even a quaint lunar village would prove prohibitive.    How much more convenient and cost effective would it be if water were already present.   Not only could it be used as water, but it could also be used to extract oxygen: two vital necessities from a single resource.

While the existence of lunar water (as opposed to moon water, a delectable treat for the discerning Pagan) has been discussed for years, recent explorations, notably by the Lunar Reconnaissance Orbiter, have discovered evidence consistent with the presence of water in the south polar region.    That's the rub.   Some parts of a southern polar crater could be perpetually steeped in shadow.    In such a dark area, temperatures would remain well below zero and any water would be trapped as ice.     (Any ice on the moon's lit region would rapidly vaporize and the water's constituent molecules would escape.)  

Water could be delivered to the moon (and other places in the solar system) by comets, generally believed to be composed of water.     These impacts have likely happened repeatedly during the moon's long lifetime.    Most of the water these impacts delivered has long since dissipated as they occurred in lunar regions exposed to sunlight.      Only water derived from comets that struck the shadowed lunar regions could still remain on the moon's surface.

An important issue pertaining to moon water relates to the form it assumes.  Could it be gathered in large chunks, like glaciers, or would it be distributed over wide regions, like a thin coating of frost?    Lunar colonists would prefer the first option, as the water would be localized and therefore readily accessible.    

In 2022, NASA aims to deploy VIPER , the Volatiles Investigating  Polar Exploration Rover, to the moon to map its water reserves.   Apart from its array of on-board scientific instruments, VIPER will also drill into the lunar surface in search of water reserves.


When you feel to the moon, you might discover great reserves water, albeit frozen solid at temperatures averaging -200 degrees F.     Still, that puts you in a better position than the person who might still be contemplating self-exile in the Helix Nebula



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