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MESSENGER Mission News
July 20, 2010

AGU Selects MESSENGER Paper as Eos Research Spotlight

Click on the thumbnail image for a larger version.

The American Geophysical Union has selected a research paper detailing observations of Mercury’s magnetosphere during the probe’s third flyby as a “Research Highlight” in today’s issue of Eos, the AGU’s weekly online and print newspaper.

“Observations of Kelvin-Helmholtz waves along the dusk-side boundary of Mercury's magnetosphere during MESSENGER’s third flyby,” by Scott Boardsen and coauthors, originally published in Geophysical Research Letters, is available online at http://www.agu.org/pubs/crossref/2010/2010GL043606.shtml.

In it, Boardsen, an associate research scientist at the Goddard Earth Sciences and Technology Center, and his colleagues report the first detection at Mercury’s magnetospheric boundary of Kelvin-Helmholtz waves, surface waves that form when two fluids with different speeds move past one another. Such waves can be created along a planet’s magnetopause when solar wind plasma interacts with the magnetosphere.

During MESSENGER’s previous flybys, no such waves were detected. But during the third flyby, 15 crossings of the dusk‐side magnetopause were observed in the magnetic field data over a two-minute period, during which the spacecraft traveled a distance of 0.2 Mercury radii.

“The quasi‐periodic nature of the magnetic field variations during the crossings, the characteristic time separations of about 16 s between pairs of crossings, and the variations of the magnetopause normal directions indicate that the signals are likely the signature of surface waves highly steepened at their leading edge that arose from the Kelvin‐Helmholtz instability,” Boardsen and coauthors wrote. “At Earth, the Kelvin‐Helmholtz instability is believed to lead to the turbulent transport of solar wind plasma into Earth's plasma sheet. This solar wind entry mechanism could also be important at Mercury.”

Highlighted Team Member: Engineer Keeps MESSENGER in the Right Position at the Right Time

As the lead engineer of the guidance and control team for the MESSENGER spacecraft, Dan O’Shaughnessy works continually to ensure that the spacecraft and its instruments are in the right position at the right time. To find out more about O’Shaughnessy, go online to http://messenger.jhuapl.edu/who_we_are/member_focus.html.

Featured Image: Mercury's Firdousi Honors the Persian Poet

The crater in the center of this image was named Firdousi in March 2010 in honor of Hakīm Abu'l-Qāsim Firdawsī Tūsī (940-1020), a revered Persian poet and author of the Shāhnāmeh, the national epic of the Persian people. MESSENGER imaged this crater as the spacecraft approached Mercury for its third flyby. Firdousi is notable for the distinctive chains of small secondary craters that radiate outward from the main impact site. That these chains of secondary craters can still be seen and have not been obliterated by subsequent impact events indicates that Firdousi is a relatively young crater on Mercury's surface.

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

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