Earth's aged, crater-pocked, and
bone dry-appearing moon may well sport a wet look.
That outlook is gaining momentum via
a treasure-trove of new scientific measurements gleaned by an international
armada of moon-orbiting scientific scouts, including a report last week that
craters near the lunar poles, always in shadow, may
harbor water ice.
What's more is that such a prospect
could fuel those eager to return human explorers to the moon, to establish a
base camp there, and to hone talent and hardware for jumping off to other
destinations.
History in the making
Locating, then mining and processing
polar deposits of water ice on the moon, it is reasoned, would add up to a useful
resource for future lunar inhabitants.
The idea of ice in the floors of
sunlight-shy polar lunar craters was first aired in 1961 by Caltech researchers
Kenneth Watson, Bruce Murray, and Harrison Brown. And in the late 1970s, James
Arnold of the University of California, San Diego, suggested that comets and
water-rich asteroids crashing into the moon could deposit water to the lunar
surface.
Still, is the chatter about new
lines of evidence supportive of water ice at the lunar poles a slam dunk
situation?
"If ice is found we have to further
explore it with landers, rovers, coring drills to assess its distribution
and composition," explained Bernard Foing, the European Space Agency (ESA) project
scientist for the now defunct ESA SMART-1 lunar orbiter. He is also the
director of the International Lunar Exploration working Group (ILEWG).
Following that appraisal, Foing said
that the next task is to organize how ice could be partly exploited on-the-spot
in some areas to ease the next steps of human exploration towards an international
lunar base.
Lunar natural parks
Foing also underscored the
scientific merit of any ice find. That is, the lunar ice should be left
intact in some "lunar natural parks" as a precious historical record of impacting
comets and water-rich asteroids that have delivered the goods to the moon.
Foing paints a view of what might be
found, in terms of water ice at the poles.
"I would expect the water ice could
come in thin layers separated by layers of covering protective dust layers," he
told SPACE.com. "The ice thickness would vary with the history of
bombardment of comets and water rich asteroids, but also could come in patches
on the surface."
How could water ice have stayed
frozen inside shadowed craters, without sublimating into the lunar exosphere?
According to Foing, layers at colder
temperatures than 80 degrees Kelvin would take billion of years to sublimate,
if protected early enough from sputtering by meteorites or from energetic solar
wind particles. Last week, NASA announced that its Lunar Reconnaissance Orbiter
had found temperatures as low as minus 397 degrees Fahrenheit (minus 238 Celsius) in some shadowed craters, making them possibly the coldest
place in the solar system.
"The next challenge for future
missions will be to land in the permanently shadowed bottom of a polar crater
and extract a few meters core of soil," Foing said, possibly sampling at once
layers of comet material -- or water rich asteroids -- that impacted the moon
in the past three billion years.
Uniform or patchy?
Similar in view is Clive Neal, a professor of civil
engineering and geological sciences at the University of Notre Dame in Indiana. He is also chair of NASA's Lunar Exploration Analysis Group (LEAG)
and also sits on the Planetary Science Subcommittee of the NASA
Advisory Council.
"If the water ice is a slam dunk
situation," Neal told SPACE.com, "we will need to know the distribution
within the craters...is it uniform or patchy?"
If such a find it is to be used to
support future
moon exploration, Neal said that the magnitude of the deposits will also
need to be quantified.
"We will also need to figure out
where this stuff came from, which means sampling and analyzing the deposits...a
non-trivial thing!"
So whatever is new and forthcoming
regarding Earth's celestial next door neighbor, Neal has a bottom line: "This
is an exciting time of discovery for the moon!"
Developing
story
Observations
that signatures of water ice have been detected on the moon that are robust,
sound, and hold up within scientific circles may take a while.
That's the
sense of Wendell Mendell, Chief of the Office for Lunar & Planetary
Exploration, Constellation Systems Program Office at the NASA Johnson Space Center in Houston, Texas. He added that this view is a personal judgment and in
no way reflects NASA policy or plans.
If the
resource is found lurking within darkened craters, how do you get to it and
extract either the ice or the water from some process?, Mendell asked.
Follow-on
questions are many, Mendell told SPACE.com: In that kind of environment,
how do you get mechanical systems and electronic systems to work? How do you get
to the bottom of the crater? You are not going to drive...are you going to fly
in? What will the rocket blast do to the ice deposits?
"Enthusiasts
may tell you that all of these questions are just details left to the
engineers," Mendell said. "If so, when will the infrastructure be available to
deal with these challenging design and operational issues?"
At first
blush, even if water ice truly exists on the moon, it will be a curiosity,
Mendell added. "I also will not believe it just from remote sensing data."
Sage advice
comes from space scientist Alan Stern, former head of NASA's space science
office.
"This is a
developing story. My view is that much more will be known in a few months. So
what looks tantalizing or even confusing today will be more compelling or more
definitive soon," Stern said.
Leonard
David has been reporting on the space industry for more than four decades. He
is past editor-in-chief of the National Space Society's Ad Astra and Space
World magazines and has written for SPACE.com since 1999.
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