Gravity mapping has delineated seven new gravity anomalies

Lunar Prospector: Mapping the Moon

Lunar Prospector is providing a global map of the composition of the moon and analyzing the moon's gravity and magnetic fields. It has been in a polar orbit around the moon since January 16, 1998.

What the Data Show

Neutron flux data show that there is abundant hydrogen, and hence probably abundant water ice, in the lunar polar regions. Gamma-ray and neutron data reveal the distribution of iron, titaniuim, and other major and trace elements on the moon. The data delineate the global distributions of a key trace element, rich component of lunar materials called KREEP, and of the major rock types. Magnetic mapping shows that the lunar magnetic fields are strong antipodal to Mare Imbrium and Mare Serenitatis and has discovered the smallest known magnetosphere, magnetosheath, and bow shock complex in the solar system. Gravity mapping has delineated seven new gravity anomalies and shown that the moon has a small iron-rich core of about 300 km radius.

The Moon's Composition

The early evolution of Earth and the moon are closely coupled. It is generally though that the moon formed about 4.4 billion years ago from debris produced when a large (Mars-sized) planetesimal collided with the proto-Earth. Much of the early record of this event is preserved on the moon, where most of the crust is older than about 3 billion years and the only subsequent major crustal deformation was produced by impacts from comets and asteroids. In contrast, plate tectonics on Earth have destroyed most of the evidence of this event. Even after many years of study, however, we still have limited information on the global composition and interior structure of the moon at sufficient resolution to derive a detailed model of its origin. Mapping and sampling during the Apollo and Luna landing missions identified the major lunar terranes, ages, and rock types and provided our first glimpse of the farside of the moon. But coverage of the lunar poles was poor, and global selenophysical data were not obtained or were at low resolution. The recent Clementine mission produced global multispectral data that resulted in a map of iron and titanium concentrations. Clementine radar data also provided a tantalizing hint that the polar regions might be harboring ice.

Improving Our View and Understanding of the Moon

The goal of the Lunar Prospector (LP) mission is to test and extend these results by obtaining gravity, magnetic, and compositional data at high resolution of the entire moon. These data will enhance our view of the surface and interior of the moon and will improve our understanding of its origin and evolution.

Lunar Prospector is the first NASA-supported lunar mission in 25 years and the third mission in NASA's Discovery Program. LP was launched on January 7, 1998, and has been mapping the moon since January 16, 1998, from its 118-minute, circular, polar orbit 100 km above the moon's surface. The main mapping mission will continue until January 1999. Then LP will map for 6 months at 25 km. The mission is expected to end in July 1999 when LP impacts the moon.

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