Saturday’s launch of NASA’s Gravity Recovery And Interior Laboratory (GRAIL) twin spacecraft, a carefully choreographed mission to precisely map the moon’s gravitational field, could help scientists understand fundamental questions about the moon’s composition, internal structure and evolution.

GRAIL’s principal investigator — Maria Zuber, the Earle A. Griswold Professor of Geophysics and Planetary Science at MIT — becomes the first woman to lead a planetary spacecraft mission. 

Following the launch of the twin GRAIL spacecraft and a four-month journey, GRAIL-A is scheduled to enter orbit around the moon Dec. 31; GRAIL-B will enter lunar orbit the following day. GRAIL’s 90-day scientific mapping mission will begin in March 2012. 

“Technologically, it is blazing the trail for other planetary missions,” says Zuber, the head of MIT’s Department of Earth, Atmospheric and Planetary Sciences. “Using dual spacecraft in tight-formation flight, doing precise timing and gravity measurement, you could envision future planetary missions to Europa [one of Jupiter’s moons] to map currents in its subsurface ocean; to Venus to map the circulation of its atmosphere; and to Mars to observe the seasonal carbon dioxide cycle between its atmosphere and its surface.”

Analysis of data from the paired spacecraft will allow GRAIL to map the lunar gravitational field with unprecedented accuracy and resolution. The precise distance between the two spacecraft can be accurately measured using radio interferometry and tracking beacons with ultra-stable oscillators. 

By precisely measuring changes in the distance between the twin orbiting spacecraft as they traverse the moon’s gravitational field, scientists expect to create a lunar gravity model up to 1,000 times more accurate than previous models. “The ability to calibrate observations in space and time brings a lot of value to scientific investigation,” Zuber says.