Washington, Oct 30 : The NASA Messenger spacecraft, which is gliding over the surface of Mercury for the second time this year, has revealed previously unseen territory on the planet.
After completing a critical gravity assist to keep it on course to orbit Mercury in 2011, Messenger unveiled 30 percent of Mercury's surface never before seen by a spacecraft.
"The region of Mercury's surface that we viewed at close range for the first time this month is bigger than the land area of South America," said Sean Solomon, principal investigator and director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington.
"When combined with data from our first flyby and from Mariner 10, our latest coverage means that we have now seen about 95 percent of the planet," he added.
The probe's Mercury Laser Altimeter, or MLA, measured the planet's topography, allowing scientists, for the first time, to correlate high-resolution topography measurements with high-resolution images.
"The MLA collected altimetry in regions where images from MESSENGER and Mariner 10 data are available, and new images were obtained of the region sampled by the altimeter in January," said Maria Zuber, co-investigator and head of the Department of Earth, Atmospheric, and Planetary Sciences at the Massachusetts Institute of Technology.
"These topographic measurements now improve considerably the ability to interpret surface geology," she added.
Spacecraft images also are revealing for the first time vast geologic differences on the surface.
"Now that Messenger's cameras have imaged more than 80 percent of Mercury, it is clear that, unlike the moon and Mars, Mercury's surface is more homogeneously ancient and heavily cratered, with large extents of younger volcanic plains lying within and between giant impact basins," said co-investigator Mark Robinson of Arizona State University in Tempe.
According to Brian Anderson of the Johns Hopkins University Applied Physics Laboratory, known as APL, in Laurel, Maryland, "The previous flybys by Messenger and Mariner 10 provided data only about Mercury's eastern hemisphere."
"The most recent flyby gave us our first measurements on Mercury's western hemisphere, and with them we discovered that the planet's magnetic field is highly symmetric," he added.