Why colonize the Moon before going
to Mars? NASA scientists give their reasons.
by Trudy E. Bell and Dr. Tony
NASA has a new Vision
for Space Exploration: in the decades ahead, humans will land on
Mars and explore the red planet. Brief visits will lead to longer
stays and, maybe one day, to colonies.
First, though, we're
returning to the Moon.
Why the Moon before
"The Moon is a
natural first step," explains Philip Metzger, a physicist at
NASA Kennedy Space Center. "It's nearby. We can practice living,
working and doing science there before taking longer and riskier
trips to Mars."
The Moon and Mars have
a lot in common. The Moon has only one-sixth Earth's gravity; Mars
has one-third. The Moon has no atmosphere; the Martian atmosphere
is highly rarefied. The Moon can get very cold, as low as -240o
C in shadows; Mars varies between -20o and -100o
Even more important,
both planets are covered with silt-fine dust, called "regolith."
The Moon's regolith was created by the ceaseless bombardment of
micrometeorites, cosmic rays and particles of solar wind breaking
down rocks for billions of years. Martian regolith resulted from
the impacts of more massive meteorites and even asteroids, plus
ages of daily erosion from water and wind. There are places on both
worlds where the regolith is 10+ meters deep.
equipment in the presence of so much dust is a formidable challenge.
Just last month (Feb 2005), Metzger co-chaired a meeting on the
topic: "Granular Materials in Lunar and Martian Exploration,"
held at the Kennedy Space Center. Participants grappled with issues
ranging from basic transportation ("What kind of tires does
a Mars buggy need?") to mining ("How deep can you dig
before the hole collapses?") to dust storms - both natural
and artificial ("How much dust will a landing rocket kick up?").
Photo credit: International Space Station
astronaut Leroy Chiao.
Moon, an alien world in Earth's backyard.
Answering these questions
on Earth isn't easy. Moondust and Mars dust is so ... alien.
Try this: Run your
finger across the screen of your computer. You'll get a little residue
of dust clinging to your fingertip. It's soft and fuzzy - that's
Lunar dust is different:
"It's almost like fragments of glass or coral - odd shapes
that are very sharp and interlocking," says Metzger.
"Even after short
moon walks, Apollo 17 astronauts found dust particles had jammed
the shoulder joints of their spacesuits," says Masami Nakagawa,
associate professor in the mining engineering department of the
Colorado School of Mines. "Moondust penetrated into seals,
causing the spacesuits to leak some air pressure."
In sunlit areas, adds
Nakagawa, fine dust levitated above the Apollo astronauts' knees
and even above their heads, because individual particles were electrostatically
charged by the Sun's ultraviolet light. Such dust particles, when
tracked into the astronauts' habitat where they would become airborne,
irritated their eyes and lungs. "It's a potentially serious
Dust is also ubiquitous
on Mars, although Mars dust is probably not as sharp as moondust.
Weathering smooths the edges. Nevertheless, Martian duststorms whip
these particles 50 m/s (100+ mph), scouring and wearing every exposed
surface. As the rovers Spirit and Opportunity have revealed, Mars
dust (like moondust) is probably electrically charged. It clings
to solar panels, blocks sunlight and reduces the amount of power
that can be generated for a surface mission.
For these reasons,
NASA is funding Nakagawa's Project Dust, a four-year study dedicated
to finding ways of mitigating the effects of dust on robotic and
human exploration, ranging from designs of air filters to thin-film
coatings that repel dust from spacesuits and machinery.
The Moon is also a good testing ground
for what mission planners call "in-situ resource utilization"
(ISRU) - a.k.a. "living off the land." Astronauts on Mars
are going to want to mine certain raw materials locally: oxygen
for breathing, water for drinking and rocket fuel (essentially hydrogen
and oxygen) for the journey home. "We can try this on the Moon
first," says Metzger.
flies from the tires of a moon buggy, driven by Apollo
17 astronaut Gene Cernan. These "rooster-tails"
of dust caused problems, which the astronauts solved using
Both the Moon and Mars are thought
to harbour water frozen in the ground. The evidence for this is
indirect. NASA and ESA spacecraft have detected hydrogen - presumably
the H in H2O - in Martian soil. Putative icy deposits
range from the Martian poles almost to the equator. Lunar ice, on
the other hand, is localized near the Moon's north and south poles
deep inside craters where the Sun never shines, according to similar
data from Lunar Prospector and Clementine, two spacecraft that mapped
the Moon in the mid-1990s.
Apollo 17 astronaut digs a trench to study the mechanical
behavior of moondust.
If this ice could be
excavated, thawed out and broken apart into hydrogen and oxygen
... Voila! Instant supplies. NASA's Lunar Reconnaissance Orbiter,
due to launch in 2008, will use modern sensors to search for deposits
and pinpoint possible mining sites.
"The lunar poles
are a cold place, so we've been working with people who specialize
in cold places to figure out how to land on the soils and dig into
the permafrost to excavate water," Metzger says. Prime among
NASA's partners are investigators from the Army Corps of Engineers'
Cold Regions Research and Engineering Laboratory (CRREL). Key challenges
include ways of landing rockets or building habitats on ice-rich
soils without having their heat melt the ground so it collapses
under their weight.
Testing all this technology
on the Moon, which is only 2 or 3 days away from Earth, is going
to be much easier than testing it on Mars, six months away.
So ... to Mars! But
first, the Moon.