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[ music fades up ]
[ narrator ] Polar lunar craters are of interest for future space exploration because
potential resources, including water ice, have been found to exist
there. However intriguing recent calculation from
NASA's Lunar Science Institute team indicate a possible
new obstacle to reaching those resources, and the implications are
a bit shocking.
[ Bill Farrell ] Well in a nutshell, what we're finding, is that the polar
craters are very unusual electrical environments.
And in particular there can be large surface charging
at the bottom of these polar craters.
[ narrator ] Because the Moon is only slightly tilted to the Sun, landscapes at the
lunar poles have several unique characteristics. With sunlight
coming in sideways, tall polar peaks reach out and receive almost
constant sunlight, while deep polar craters hide surfaces that
may not have seen light for millions of years. The orientation
of these dark craters to the Sun may allow them to trap water ice
but it may also be charging them to hundreds of volts.
[ Farrell ] Well the solar wind is actually a relatively tenuous gas.
that's emitted from the Sun, but it's not a neutral gas, like the gas
in this room, it's actuall a gas that's really, for the most part, free
ions and free electrons, it's really two components. And so you have this electrical
gas if you will. And then as it passes by the Moon,
the electrons behave slightly differently than the ions, of course the
electrons are very low mass, the ions are more mass, again we don't think
of an ion as being something real heavy, but compared to these little, flimsy electrons
they really are. So as you pass by, for example, a polar crater
the electrons will actually fill into the crater, ahead of the
ions. Now as it turns out, as it does that, you create an
electric field, it's called an ambipolar electric field, and that electric field then
drives in the ions.
[ narrator ] So while it is already known that human or robotic explorers searching
within these dark craters would face temperatures that plunge below minus
400 degrees farenheit, this new computer model suggests
they may have to contend with a dangerous electrical environment as well.
Static discharge could short out sensitive electronics,
while the static cling of sticky and extremely abrasive lunar dust
could wear out spacesuits and other equipment.
Astronauts and instruments within these craters would need to be
electrically grounded to avoid such hazards.
[ Farrell ] Well that is actually the crux of the whole problem, what is
the electrical ground on the Moon? You actually have a surface on the Moon
that has the conductivity, it's almost like candle wax, you know, you're not going to get
a charge out of the ground. So you're really grounded to the plasma.
And when you're out in the solar wind, you know, on the surface of the Moon,
not in these craters and not in these mountains, okay you're grounded. But when you start heading into
these craters, you've now lost touch with your electrical ground, so that means you take a step
and you might have to wait a hundred seconds before that charge that you just
accumulated disapates away. That's a long time to be stepping around.
So you really do have to worry about human systems going into these craters.
[ narrator ] The next steps for the Lunar Science Institute team include more complex
computer models. There are still many questions to answer about where the
Moon's key polar resources lie, how they got there, and whether
or not future explorers will be able to reach them.
To learn more about NASA news and research visit
www.nasa.gov