June 16, 2011

MESSENGER Provides New Data About Mercury

NASA said on Thursday that its MESSENGER spacecraft completed its first perihelion passage from orbit around Mercury.

The spacecraft entered orbit around Mercury on March 18, 2011, becoming the first spacecraft ever to do so.

The space agency said tens of thousands of images of major features of the planet are now available in sharp focus, along with measurements of the chemical composition of Mercury's surface.

MESSENGER has helped provide maps of the planet's topography and magnetic field, which is revealing clues to Mercury's interior dynamical processes.

The spacecraft completed is its first superior solar conduction from orbit and its first orbit-correction maneuver this week.

"Those milestones provide important context to the continuing feast of new observations that MESSENGER has been sending home on nearly a daily basis," MESSENGER Principal investigator Sean Solomon of the Carnegie Institution of Washington said in a statement.

The spacecraft has also revealed irregular pits on the planet's surface that are surrounded by diffuse halos of higher-reflectance material.  These pits are found near central peaks, peak rings, and rims of craters.

"The etched appearance of these landforms is unlike anything we've seen before on Mercury or the Moon," Brett Denevi, a staff scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., said in a statement.

"We are still debating their origin, but they appear to have a relatively young age and may suggest a more abundant than expected volatile component in Mercury's crust."

The X-ray Spectrometer, one of MESSENGER's instruments, has made important discoveries as well, according to NASA.

This instrument has helped space agency see that Mercury's surface is not dominated by feldspar-rich rocks, but instead magnesium/silicon, aluminum/silicon, and calcium/silicon ratios averaged over large areas of the planet's surface.

"We are assembling a global overview of the nature and workings of Mercury for the first time, and many of our earlier ideas are being cast aside as new observations lead to new insights," Solomon said in a statement.

"Our primary mission has another three Mercury years to run, and we can expect more surprises as our solar system's innermost planet reveals its long-held secrets."


Image Caption: The same scene as that in Image 1.3a is shown after the application of a statistical method that highlights differences among the eight color filters, making variations in color and composition easier to discern. Credit: NASA/The Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington


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