Mercury Messenger sends home new views of tiny planet
By Amanda Jermyn



The Romans named the planet Mercury after their messenger god, so it seems appropriate that NASA’s spacecraft now orbiting this planet should be called Messenger. After orbiting Mercury for the past seven months its extraordinary messages have revolutionized scientific thinking about our Solar System’s smallest and innermost planet. Built and operated by the Johns Hopkins Applied Physics Laboratory, Messenger has provided the first direct measurements of the chemical composition of Mercury’s surface, the first close-up views of the planet’s “hollows,” and new evidence that flood volcanism is widespread on Mercury.

The new data show huge expanses of volcanic plains surrounding the north polar region, covering over 6% of the total surface of the planet. According to James Head, of Brown University, lead author of a report in the journal Science, the lava deposits in some places are up to 1.2 miles thick. Vents up to 16 miles long have also been discovered. These appear to be the source of huge volumes of hot lava that have flowed over the surface of Mercury, carving valleys and creating teardrop-shaped ridges on the terrain. According to Head, such lavas may have been typical of an early period of Earth’s history.

Images observed during the earlier Mariner 10 mission and Messenger flybys showed that the floors and central mountain peaks of some impact craters are very bright and are bluer than other areas of Mercury. These were considered unusual because no craters with similar characteristics have been found on the moon. Now Messenger’s recent close-up images show the bright areas, termed “hollows,” to be composed of small irregular-shaped depressions often found in clusters. Many of these shallow depressions have not accumulated small impact craters, and are thus assumed to be relatively young. There is also evidence that they are still forming.

The new data also rule out most existing models for Mercury’s formation. Measurements by Messenger’s Gamma-Ray and X-Ray Spectrometers indicate that its surface composition is very different from the moon and other rocky planets, and that it is similar to that of metal-rich chondritic meteorites, material left over from the formation of our solar system. Given the fascinating data obtained so far, one can only wonder what new messages from Mercury this NASA mission might yet unveil.

This month join the Springfield STARS Club on Tuesday, November 22nd at 7:30pm at the Springfield Science Museum for an evening honoring Dr. Richard Scott’s 90th birthday and his contributions to the Springfield Science Museum and STARS Club over the past 56 years. A Springfield native, Dr. Scott graduated from Harvard Medical School, and practiced general surgery in Springfield from 1955 on. He was the first surgeon in the Springfield area trained in pediatric surgery. He and Frank Korkosz, who built the first optical projection planetarium in the US, built the Foucoult Pendulum for the Springfield Science Museum. Together with Korkosz, Warren Filmore, Ed Wood and others, Dr. Scott also helped build the 20” diameter telescope that now graces the Science Museum’s observatory. At this month’s STARS Club meeting refreshments will be served, and the public is welcome free of charge. For more information, visit http://www.reflector.org or call (800) 336-9054.