Mercury is more dynamic than scientists first suspected

Washington, May 1 (ANI): A NASA spacecraft gliding over the surface of Mercury has revealed that the planet's atmosphere, the interaction of its surrounding magnetic field with the solar wind, and its geological past display greater levels of activity than scientists first suspected.

The probe also discovered a previously unknown large impact basin about 430 miles in diameter - equal to the distance between Washington and Boston.

The data come from the Mercury Surface, Space Environment, Geochemistry, and Ranging spacecraft, known as MESSENGER.

On October 6, 2008, the probe flew by Mercury for the second time, capturing more than 1,200 high-resolution and color images of the planet.

The probe unveiled another 30 percent of the planet's surface that had never been seen by previous spacecraft, gathering essential data for planning the remainder of the mission.

"This second Mercury flyby provided a number of new findings," said 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," he added.

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.

The probe's Mercury Atmospheric and Surface Composition Spectrometer instrument detected the magnesium.

Finding magnesium was not surprising to scientists, but seeing it in the amounts and distribution observed was unexpected.

The instrument also measured other exospheric constituents, including calcium and sodium.

"This is an example of the kind of individual discoveries that the science team will piece together to give us a new picture of how the planet formed and evolved," said William McClintock, co-investigator.

The variability that the spacecraft observed in Mercury's magnetosphere, the volume of space dominated by the planet's magnetic field, so far supports the hypothesis that the great day-to-day changes in Mercury's atmosphere may be a result of changes in the shielding provided by the magnetosphere.

"The spacecraft observed a radically different magnetosphere at Mercury during its second flyby compared with its earlier Jan. 14 encounter," said James Slavin from NASA's Goddard Space Flight Center in Greenbelt, Maryland.

"During the first flyby, important discoveries were made, but scientists didn't detect any dynamic features. The second flyby witnessed a totally different situation," he added. (ANI)