With the GRAIL data, the astronomers were able to map the gravity field both in and around over 1,200 craters on the lunar far side. This region--the lunar highlands--is our Moon's most heavily cratered, and therefore oldest, terrain. Heavily cratered surfaces are older than smoother surfaces that are bereft of craters. This is because smooth surfaces indicate that more recent resurfacing has occurred, erasing the older scars of impact craters.
Dr. Carolyn Porco, a planetary scientist and leader of the Imaging Science team for Cassini, explained to the press in March 2012 that "More than 90 jets of all sizes near Enceladus's south pole are spraying water vapor, icy particles, and organic compounds all over the place. Cassini has flown several times now through this spray and has tasted it. And we have found that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth's oceans."
"Makemake is in the class of rare Pluto-like objects, so finding a companion is important. The discovery of the moon has given us an opportunity to study Makemake in far greater detail than we ever would have been able to without the companion," Dr. Parker continued to explain.