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Overview Mission Profile Science Objectives Lunar Prospector, the first dedicated lunar mission in 25 years, has already been a tremendous success. Following a near flawless launch, a four day journey to the Moon and entry into lunar orbit, the tiny spin-stabilized spacecraft has been sending data back to Earth since January 6th of this year. Lunar data from the circular polar mapping orbit has been arriving since January 15th. On March 5th, 1998 Prospector captured the public imagination by announcing the discovery of a definitive signal for water ice at both of the lunar poles. At that time, a conservative analysis of the available data indicated that a significant quantity of water ice, possibly as much as 300 million metric tons was mixed into the regolith (lunar soil) at each pole, with a greater quantity existing at the north pole. The first competitively selected Discovery class mission had conclusively demonstrated that, not only could a cost-capped, fast development mission succeed, it could do ground-breaking science in the process. The first operational gravity map of the Moon was announced at the same time. Since then, Lunar Prospector has taken advantage of its own science results and the gravity data have been used to facilitate orbit maintenance. With nearly two thirds of Prospector's one year primary mission completed, the most recent look at Prospector's data reveal several remarkable insights into lunar science and resources.   Doppler Gravity Experiment - The gravity field of the Moon strongly influences the altitude of a spacecraft in low-circular orbit. The most dramatic example is the Apollo 16 subsatellite. After being deployed in a near-circular orbit from the command and service module, the eccentricity increased quickly and the spacecraft impacted the lunar surface 35 days after the release strictly due to the force of the gravity field. Understanding the precise nature of a planet's gravity field is vital to all exploration and experimentation.           Gamma Ray Spectrometer- Lunar Prospector's gamma-ray spectrometer (GRS) is mapping the abundances of ten elements on the Moon's surface: thorium (Th), potassium (K), uranium (U), iron (Fe), Oxygen (O), silicon (Si), aluminum (Al), calcium, Ca), magnesium (Mg), and titanium (Ti). It is especially sensitive to the heavy, radioactive element thorium and the light element potassium. These are particularly plentiful in the last part of the crust to solidify. Thus, mission scientists are able to determine the global distribution of KREEP (K-potassium, Rare Earth Elements, and P-phosphorous), a chemical "tracer" of sorts which helps to tell the story of the Moon's volcanic and impact history. The data produced by the GRS will help scientists understand the origins of the lunar landscape, and may also tell future explorers where to find useful metals like aluminum and titanium.     Magnetometer/Electron Reflectometer - The magnetometer and electron reflectometer aboard the Lunar Prospector are taking valuable data to help unravel puzzles that have intrigued scientists for a quarter of a century. What kind of magnetic field(s) exists on the Moon? What kind of natural resources are buried in the Moon's crust and is there a core? If so, what are its characteristics? Can we build a lunar base? How did the Moon form and evolve - what is its history?     Neutron Spectrometer - Lunar Prospector mission scientists devised the neutron spectroscopy experiment to search for water ice at the poles of the Moon. As the world found out on March 5, 1998, at the mission's first science data return press conference, preliminary results from the experiment were indeed positive: Water ice does exist on the Moon, and there appears to be more of it at the North pole than at the South pole. Lunar Prospector had detected a significant amount of hydrogen which is inferred to be in the form of water. This was the first direct evidence of the presence of water ice at the Moon's frigid poles. Lunar Prospector is also the first interplanetary mission ever to use the neutron spectroscopy technique to detect water. ProspectorÕs neutron spectrometer (NS) works by detecting hydrogen, by way of subatomic particles called neutrons.     Alpha Particle Spectrometer - The Apollo series of missions revealed that the Moon had not been perpetually cold and dead, as once believed, but rather was host to a series of dramatic volcanic eruptions in which vast seas of molten lava flooded much of the lunar surface. While the majority of such activity most likely occurred very early in the Moon's history, over three billion years ago, the Moon is thought to still harbor some remnant volcanic and tectonic activity. Outgassing events, in which alpha-particle emissions of radon leak out from the lunar interior, are scientific evidence of such activity. Determining where and when such gas release events take place will tell scientists just how active the Moon actually is, as well as helping to identify the source(s) of the Moon's small and tenuous atmosphere.