smart1_science We've visited it in person. We've studied it with robots in orbit. We've even crashed into it on purpose to try and kick up something interesting. Yet our nearest celestial neighbor the Moon still holds mysteries.
Exactly how the Moon evolved, and thus how the Earth came to be, is not fully understood. And scientist suspect -- but are not certain -- that the Moon harbors water ice at its south pole, something that could determine whether colonies are ever established there.
In response to the dearth of data, several upcoming missions are
being planned. The first spacecraft to visit the Moon after a four-year-drought will be SMART-1, the European Space Agency's maiden voyage to Earth's only natural satellite.The robotic craft is slated for launch in April 2003.
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 | An artist's rendering of the SMART-1 spacecraft orbiting the Moon. IMAGE: ESA
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| NASA's Clementine spacecraft gathered 1,500 images that went into this mosaic of the Moon's south pole and about 777 miles (1,250 kilometers) outward. Note the large, shadowed, depressed region near the south pole; it may hold water ice. IMAGE: NASA
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| During the Apollo 17 mission, astronaut Harrison "Jack" Schmitt rakes up Moon rocks during a panoramic image taken by Eugene Andrew Cernan. SMART-1s infrared imager will "sample" the surface from an orbital position. IMAGE: NASA
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|  | TODAY'S DISCUSSION | | |
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The six-month orbital mission -- SMART-1 won't land on the Moon -- is touted as a technology test bed for an electric propulsion mechanism and for the viability of miniature instrumentation in space. But SMART-1 will also tote a scientific payload keener than most any other used before at the Moon, helping to gain insight into its composition and the evolution of the Earth-Moon system. The crafts findings could help pave the way for a human return to the lunar surface and exploration further into space.
Much of what's known about the Moons composition comes from the 841.5 pounds (381.7 kilograms) of
lunar samples scooped up during six Apollo missions. But a truly representative sampling of the Moon is missing. All but two collections were made from or near the lunar maria landing sites on the Moons near side, close to the equator. Yet the collections were revolutionary. Astronaut Harrison "Jack" Schmitt on the Apollo 17 mission in 1972 collected a variety of lunar rock and soil with the help a special gripping rake.
"Apollo 17 was a very good mission, but it was limited and time consuming," says Giuseppe Racca, SMART-1s project manager. On the other hand, "The infrared instrument on SMART-1 is like sending a bunch of astronauts all over the Moon."
SMART-1s Infrared Spectrometer (SIR) will map the entire lunar surface at a spatial resolution that project manager Andrea Marini compares to a small chocolate box, in 266 varying infrared wavelengths. The orbiting Clementine mission in the mid-1990s, by comparison, could only resolve features larger than a football field and distinguished just seven different colors in the infrared range.
SIRs infrared map will allow scientists to distinguish between subtypes of lunar minerals made from different geologic processes. So-called feldspar minerals form at lower temperatures than pyroxenes and olivines, for example. Thus the instrument will reveal what kind of geologic processes have occurred on the Moon, and how long the Moon has been the mostly dead orb it is now.
The leading theory for the Moon's formation holds that it was made from a giant impact, when a Mars-sized object slammed into the nascent Earth, melting and ejecting a huge amount of molten rock into the sky. Yet the specifics of the impact and the processes the Moon and Earth went through after the
first 24 hours of chaos are mostly speculative.For instance, it's known that after the Moon assembled itself, it melted again as it evolved. But its unknown how long that process lasted, and how much of it melted, said Paul Spudis, a scientist at the Lunar and Planetary Institute in Houston.
SMART-1s Demonstration of a Compact Imaging X-ray Spectrometer instrument, or D-CIXS, will reveal more about the formation process by make the first global map of the relative abundance of surface elements, especially aluminum, iron, and magnesium.
Spudis explained that if the surface contains a lot more magnesium than iron, then melting of the Moon must have been slight. But if magnesium and iron are more equally represented, then the Moons secondary melting may have lasted for a long time.
Clementines contributions to science were significant, especially its discovery of hydrogen types that indicated there might be water ice at the Moons south pole. In the late 1990s, Lunar Prospector helped confirmed this finding. But some doubts remain, and no spacecraft have been to the Moon since Lunar Prospector was
crashed into the surface on purpose in 1999, ending the project in a dramatic long shot that failed to kick up useful chemical signs to view from Earth, as hoped.Scientists had long speculated whether or not frozen water existed on the Moon. If it's there, it was likely because comets had brought it there. But researchers figured that the combination of the Suns energy and the lack of gravity would have evaporated the water, except at the dark polar regions. High mountains veil the Moons south pole. Very little sunlight reaches beyond those peaks, setting up a possible natural ice chest but also making observations of the low-lying areas nearly impossible.
An instrument called a neutron spectrometer would be needed to verify if the hydrogen found there is actually bound in water molecules; hydrogen can exist in other forms.
SMART-1 is not carrying a neutron spectrometer, but it is carrying an asteroid-Moon Imager Experiment, or AMIE, which will make the first detailed study of the region in the visible light spectrum at varying angles. The images will rely on the tiny amount of light that is bounced around the peaks of the mountains.
"AMIE will be seeing if there are the right morphological conditions for water to be held there," Racca said.
The resulting maps will be important for another reason. Spudis and his colleague Ben Busse have found an area at the south pole that may just be in permanent sunlight. "The place would be valuable real estate. Wed want to go there because it would be great for solar power ... and close to water. Its possible that its kind of like an oasis."
Other researchers have suggested these peaks would be the perfect spot to locate a Moon base.
SMART-1 will test pint-sized tools and a new propulsion system that could later be used on more ambitious flights to Mercury and beyond. Yet SMART-1 could produce some valuable science along the way. Clementine, too, was a technology test bed and orbited the Moon for only 71 days.
"We have a long way to go before there is a possibility of colonizing and exploration of the Moon," said Marini. "But a first step is exploring with our small instruments and high tech to get a better understanding of the Moons southern pole and whether or not there is water there."
Editor's Note: SMART-1 was originally slated for launch in 2002, but the date was pushed back to allow more development time for the craft's clever propulsion system. Return tomorrow to learn more about this in our Tech Wednesday feature presentation.
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