William Atkins
Friday, 01 May 2009 21:10
Science -
Space
Page 3 of 4
With respect to the impact basin, the floor of the Rembrandt impact basin has showed terrain that has never been seen before because normally they are buried by volcanic lava flows and not exposed as with this basin.
Thomas Watters (Smithsonian Institution) states,
"This basin formed about 3.9 billion years ago, near the end of the period of heavy bombardment of the inner solar system. Although ancient, the Rembrandt basin is younger than most other known impact basins on Mercury."
This second visit involved over 1,200 high-resolution, color images of the planet, including about one-third of the planet’s surface area that had never been seen before by Earth probes. These images have given scientists a better picture of the crust formed on Mercury—with about 40% covered by smooth plains that followed from lava flows, which are similar to those found on Mars.
Dr. Solomon states,
"The discovery of a large and unusually well preserved impact basin shows concentrated volcanic and deformational activity."
In addition, MESSENGER’s Mercury Atmospheric and Surface Composition Spectrometer (MASCS) detected the element magnesium in the exosphere of Mercury. Its presence was not a surprise to mission scientists, however, the amount found and its distribution was quite surprising. MASCS also observed the elements calcium and sodium within the Mercurian exosphere and aluminum, iron, and silicon from its surface.
The Science article
MESSENGER Observations of Mercury’s Exosphere: Detection of Magnesium and Distribution of Constituents states
“Mercury is surrounded by a tenuous exosphere that is supplied primarily by the planet’s surface materials and is known to contain sodium, potassium, and calcium."
The exosphere is the uppermost layer of an atmosphere.
The U.S. team continues to say,
“Observations by the Mercury Atmospheric and Surface Composition Spectrometer during MESSENGER’s second Mercury flyby revealed the presence of neutral magnesium in the tail (anti-sunward) region of the exosphere, as well as differing spatial distributions of magnesium, calcium, and sodium atoms in both the tail and the nightside, near-planet exosphere.”
And,
“Analysis of these observations, supplemented by observations during the first Mercury flyby, as well as those by other MESSENGER instruments, suggests that the distinct spatial distributions arise from a combination of differences in source, transfer, and loss processes.”
Page four concludes.
