Washington DC
NASA is going back to the Moon鈥攁nd this time, the space agency is
looking for water. On 5 January, if all goes well, the Lunar Prospector will
lift off from Cape Canaveral. Over its 18-month mission, the probe will study
the composition of the lunar crust and should determine whether or not there are
deposits of ice in some of the Moon鈥檚 shadowy craters.
In 1994, a Department of Defense satellite called Clementine obtained some
tantalising radar reflections from deep within craters at the lunar south pole
that looked remarkably like those from water ice. The $63-million Lunar
Prospector mission should find out whether these images were more than
mirages.
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On one of three booms that jut out from the orbiter there is a spectrometer
that will measure the speed of neutrons that skitter into space when cosmic rays
strike the Moon鈥檚 surface. Neutrons are slowed down by hydrogen and, by
comparing the proportion of fast, hot neutrons to the slower, cold ones,
scientists will measure the amount of hydrogen on the Moon鈥檚 surface. 鈥淎nd if
there鈥檚 an excess of hydrogen in polar regions, it must be bottled up as water,鈥�
says Alan Binder, an astrophysicist with the Lunar Research Institute in Gilroy,
California, principal investigator on the Lunar Prospector mission.
Another instrument will record gamma rays released by the decay of
radioactive elements such as thorium and uranium. The frequencies of the gamma
rays will reveal the proportions of each element in the Moon鈥檚 crust. And this
will give scientists a hint as to how and when the Moon formed. 鈥淭his is the
highest science priority,鈥� says Binder. 鈥淭hese are the key data to understand
the origin and evolution of the Moon.鈥�
Other instruments will map the Moon鈥檚 irregular magnetic field, which should
give planetary scientists an insight into the processes occurring in the Moon鈥檚
core. The probe may also detect gases that occasionally spurt from the Moon
during a moonquake, which will tell scientists more about lunar seismic
activity.
The main uncertainty surrounding the mission is the launch vehicle鈥攁
new rocket from Lockheed Martin called Athena II. On one test flight, an Athena
II rocket veered out of control and self-destructed. Lunar Prospector鈥檚
scheduled September launch was delayed several times for 鈥渞igorous testing鈥� of
the launcher. But NASA officials say they are now confident of the rocket鈥檚
reliability.