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October
7, 2009: NASA is figuring out how to make water from
moondust. Sounds like magic?
"No
magic--" says Ed Ethridge of NASA's Marshall Space Flight
Center "-- just microwaves. We're showing how microwaves
can extract water from moondust by heating it from the inside
out."
 The
recent
discovery of water on the Moon's surface has inspired
researchers like Ethridge to rev up the development of technologies
to capture it. Some of them believe the small amounts of frozen
water mixed in lunar topsoil are just the tip of the iceberg.1
If so, Ethridge has figured out a way to retrieve it.
Right:
Apollo 12 astronaut Alan Bean holds up a thermos full of moondust.
Could this be transformed into a thermos of moonwater? NASA
scientists are working on it. [larger
image]
"We
believe we can use microwave heating to cause the water ice
in a lunar permafrost layer to sublimate – that is, turn into
water vapor. The water vapor can be collected and then condensed
into liquid water."
"Best
of all, microwave extraction can be done on the spot. And
it requires no excavation -- no heavy equipment for drilling
into the hard-frozen lunar surface."
He
calls his first mining experiment the "Moon in a bottle."
"We
filled a bottle with simulated lunar permafrost [fake moondust
containing water ice] and heated it in a microwave oven. The
microwaves heated the simulant enough to extract water, even
though the soil was as cold as it would be on the Moon."
At
least 95 percent of the water added to the simulant was extracted
(vaporized out of the soil) with 2 minutes of microwaving.
"And
we were able to capture 99 percent of the vaporized water
in our cold trap," says collaborator Bill Kaukler of
the University of Alabama-Huntsville. "It works."
Above:
Ed Ethridge's experimental setup at the Marshall Space Flight
Center in Huntsville, Alabama. [larger
image]
Then
Ethridge and his team moved beyond the oven to beaming microwaves
into the simulant – the way it would have to be done on the
Moon. The beamed microwaves were absorbed into the soil and
heated it sufficiently to extract water.
"This
was an important demonstration. We had to make sure the microwaves
wouldn't reflect off the surface," Ethridge explains.
"It worked beautifully."
What's
next?
"We've
asked for some genuine soil from the Apollo missions,"
says Ethridge. "We want to test the real thing and calculate
how fast the water vapor will come out. That's an important
piece of information."
 Right:
Click on the image to launch a 10 hour 3D animation showing
how a 1KW microwave source entering from the top produces
heating in a cubic meter simulated lunar soil. Colored bands
represent locations of constant temperature. Credit: Ed Ethridge/NASA/MSFC
[movie]
"There
are other things we need to know, like how much ice is at
the poles, how deep it is, where it is -- is it only in the
craters or is it everywhere?" This Friday morning, Oct.
9th, LCROSS
(the Lunar Crater Observation and Sensing Satellite) could
answer some of the questions about moonwater when it plunges
into crater Cabeus at the lunar south pole to unearth signs
of H2O.
If
ample water ice does exist on the Moon, how would lunar residents
collect it?
"They'd
have to beam microwaves into the soil and collect the water
vapor in a cold trap," he explains. "We want to
build a prototype water prospecting experiment to demonstrate
the technique we’d like to see used in a lunar water mining
facility."
He
stops talking, looks up, and smiles. "I'd be willing
to go up and set up the first Lunar Water Works -- if they'd
let me."
Author: Dauna Coulter
| Editor:
Dr. Tony Phillips | Credit: Science@NASA
| footnotes
and credits |
| Footnote:
1Several days ago, NASA announced that the
Moon Mineralogy Mapper, or M3, an instrument
aboard the Indian Space Research Organization's Chandrayaan-1
spacecraft, discovered water molecules in the polar
regions of the Moon. NASA's Cassini spacecraft and NASA's
Epoxi spacecraft confirmed the find.
Ethridge says: "The data [from the three aforementioned
spacecraft] dealt with water detected from the top 1
or 2 mm of soil from regions like the Apollo sites,
which are known to be "depleted" of any water
(i.e., water produced from solar wind protons). But
their data also shows much higher signals for water
from the polar regions. The best locations for water
ice are permanently shadowed craters near the poles.
The water at the poles may be underneath a 1 cm depleted
layer that overlies a higher concentration of water
down to a meter deep. A few years ago, Lunar Prospector
and Clementine produced data for hydrogen that translates
to average concentrations estimated to be from 1 to
4.6 % water over large areas at the poles. Assuming
an average 2 percent concentration, that translates
to maybe 40 pounds -- about 5 gallons -- of water in
a cubic meter of moon soil. (2 percent of a 1 ton is
40 pounds. A cubic meter of lunar soil is approximately
1 ton.)"
Credits:
Dr. William Kaukler of the University of Alabama-Huntsville
was instrumental in the experimental and hardware setups
for these experiments. Frank Hepburn of Marshall led
the dielectric property measurements. Southern Research
Institute is doing some measurements for team on the
gas permeability of compacted lunar soil.
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