Space Exploration

The spacecraft twins, GRAIL-A and GRAIL-B, are flying aboard a Delta II rocket launched from Florida. The twins' circuitous route to lunar orbit will take 3.5 months and cover approximately 2.6 million miles (4.2 million kilometers) for GRAIL-A, and 2.7 million miles (4.3 million kilometers) for GRAIL-B. In lunar orbit, the spacecraft will transmit radio signals precisely defining the distance between them. Regional gravitational differences on the moon are expected to expand and contract that distance. 

GRAIL scientists will use these accurate measurements to define the moon's gravity field. The data will allow mission scientists to understand what goes on below the surface of our natural satellite. "GRAIL will unlock lunar mysteries and help us understand how the moon, Earth and other rocky planets evolved as well," said Maria Zuber, GRAIL principal investigator from the Massachusetts Institute of Technology in Cambridge. 

NASA's Artist Concept of the GRAIL's Twin Spacecraft fly in Tandem Around the Moon

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the GRAIL mission. The Massachusetts Institute of Technology, Cambridge, is home to the mission's principal investigator, Maria Zuber. The GRAIL mission is part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems, Denver, built the spacecraft. Launch management for the mission is the responsibility of NASA's Launch Services Program at the Kennedy Space Center in Florida. JPL is a division of the California Institute of Technology in Pasadena. 

GRAIL's primary science objectives will be to determine the structure of the lunar interior, from crust to core and to advance understanding of the thermal evolution of the Moon. As a secondary objective, GRAIL will extend knowledge gained from the Moon to the other terrestrial planets.  Science investigations will include:

• Map the structure of the crust and lithosphere

• Understand the Moon's asymmetric thermal evolution

• Determine the subsurface structure of impact basins and the origin of mascons

• Ascertain the temporal evolution of crustal brecciation and magmatism

• Constrain deep interior structure from tides

• Place limits on the size of a possible solid inner core