Prof.’s team analyzes Mercury’s mysteries

Tuesday, February 5, 2008

Nearly three and a half years after it was launched from Cape Canaveral, Fla., NASA’s MESSENGER spacecraft gave scientists their first glimpse of Mercury in more than 30 years. For Professor of Geological Sciences James Head PhD’69 and his team of undergraduate and graduate students, the flyby, which occurred on Jan. 14, provided the team with a trove of data and images of areas of the planet that have never been seen before. But this data is just a preview of what will be available once the spacecraft goes into orbit around Mercury in March 2011.

MESSENGER was selected as the seventh mission in NASA’s Discovery Program, which allows scientists from around the country to propose and manage unmanned, scientific space missions, and carries instruments to support research on the geological, geophysical, chemical and magnetic characteristics of Mercury. The mission plan calls for the craft to fly by Mercury two more times before entering orbit in 2011.

As chair of the project’s geology group, Head oversees a team of 10 that is trying to shed light on the planet’s history. The team is trying to determine whether Mercury’s morphological features were caused by volcanic activity.

With older data, scientists weren’t able to determine whether volcanic activity had occurred on the planet. Mercury is covered in large, flat plains dotted with craters. Unlike Earth’s moon, Mercury’s surface does not have dark spots and light spots. When viewed from space, most geological features blend into the ground, so scientists can’t see many of the surface’s features, such as evidence of volcanoes.

“But with our high-resolution data coming in,” Head said, “we’re starting to see features that look volcanic – flows and things like that.”

In addition, the planet’s proximity to the sun prevents scientists from using either Earth-based telescopes or the orbiting Hubble Space Telescope to examine the planetary surface, for fear of damaging the equipment. Mariner 10 was the last mission to Mercury, and it flew by the planet three times – the last of them in March 1975. Many scientists have been waiting for a chance to return to the planet since that final pass.

The data MESSENGER recently sent back revealed far more of the planet than was visible from Mariner 10. Until now, scientists have been restricted to studying less than half the planet because Mariner 10 was only able to photograph one side. In addition, the images were relatively dark and the resolution fairly low. The images taken on MESSENGER, however, show significantly more of the planet. Imagery from the two remaining fly-bys and the craft’s eventual orbit should provide even more valuable data.

Already, the Brown team has found some interesting geological features on Mercury’s surface. Among them is a formation that has been named “The Spider,” a network of troughs radiating from a central dark feature. At the center is a crater approximately 40 kilometers in diameter. According to Caleb Fassett GS, the team believes that the Spider may have resulted from a magmatic process with a super-imposed impact crater. Since the crater is not exactly in the center of the troughs’ radiation, the two features’ formations do not seem to be connected.

Head’s graduate student team has been working on the data as it is relayed from MESSENGER to Earth. An “away team” of four people heads down to the Johns Hopkins University Applied Physics Lab as the data returns. They work with another group, which stays at Brown, to analyze the information.

“We basically get involved when data comes back,” Laura Kerber GS said. “We got to go down and meet a bunch of the scientists whose papers we had been reading. We were with them when the first images came down and some of these people had been waiting for 34 years.”

“This first wave is just discovery,” she added. “No matter what you normally study, you are just looking at the images and asking, ‘What is this tectonic activity? What is this volcanism?'”