Chicago (IL) -A second NASA flyby of Mercury has revealed that the planet's atmosphere, magnetic field and geological past indicate "greater levels of activity" than scientists first suspected.
"This second Mercury flyby provided a number of new findings," explained Sean Solomon, the probe's principal investigator from the Carnegie Institution of Washington. "One of the biggest surprises was how strongly the dynamics of the planet's magnetic field–solar wind interaction changed from what we saw during the first Mercury flyby in January 2008. The discovery of a large and unusually well preserved impact basin shows concentrated volcanic and deformational activity."
The spacecraft also made the first detection of magnesium in Mercury's thin atmosphere, known as an exosphere. This observation and other data confirm that magnesium is an important constituent of Mercury's surface materials.
According to William McClintock, the discovery of magnesium will help researchers discover how the planet "formed and evolved." McClintock, who is from the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder, suspects that additional metallic elements from the surface, including aluminum, iron and silicon, also contribute to the exosphere.
Half of Mercury was unseen until a little more than a year ago. However, spacecraft images have enabled scientists to view 90 percent of the planet's surface at high resolution. The spacecraft's nearly global imaging coverage of the surface after the second flyby provided new insight into how the planet's crust was formed.
"After mapping the surface, we see that approximately 40 percent is covered by smooth plains," said Brett Denevi of Arizona State University in Tempe. "Many of these smooth plains are interpreted to be of volcanic origin, and they are globally distributed. Much of Mercury's crust may have formed through repeated volcanic eruptions in a manner more similar to the crust of Mars than to that of the moon."
Scientists continue to examine data from the first two flights and are preparing to gather more information from a third flyby of the planet on September 29.