NASA’s Messenger mission will live on for at least one year past its planned expiry date. The spacecraft entered orbit around Mercury, the solar system’s innermost planet, on March 18, and its primary mission had been scheduled to conclude on March 17, 2012. “We are still ironing out the funding details, but we are pleased to be able to support the continued exploration of Mercury,” said Ed Grayzeck, a mission program scientist. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) collects UV to near-IR wavelengths to measure atmospheric gases and surface minerals on the solar system’s innermost planet. In this color composite created from individual observations from the first Mercury solar day in orbit, red is 575-nm reflectance, green is the spectral slope from the visible to the near-IR, and blue is a ratio of spectral slopes (the UV/visible slope over the visible/near-IR slope). This combination, notably the blue-purple-pink ranges, indicates areas where the ultraviolet variations correlate with geological features. (Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington) The spacecraft’s unprecedented orbital science campaign is providing the first global close-up of the planet closest to the sun and has revolutionized scientific perceptions of it. The extended mission will allow scientists to learn even more about Mercury, said principal investigator Sean Solomon of the Carnegie Institution of Washington. “During the extended mission, we will spend more time close to the planet than during the primary mission, we’ll have a broader range of scientific objectives, and we’ll be able to make many more targeted observations with our imaging system and other instruments,” he said. “Messenger will also be able to view the innermost planet as solar activity continues to increase toward the next maximum in the solar cycle. Mercury’s responses to the changes in its environment over that period promise to yield new surprises.” The spacecraft carries several instruments with which it gleans new information about the tiny, parched planet. Among them are the Mercury Dual Imaging System, which maps landforms, tracks variations in surface spectra and gathers topographic information; the Gamma-Ray and Neutron Spectrometer, which seeks emissions from radioactive elements on Mercury’s surface and from surface elements that have been stimulated by cosmic rays; the Mercury Laser Altimeter, which charts the planet’s topography; and the Mercury Atmospheric and Surface Composition Spectrometer, which measures atmospheric gases and surface minerals. The extended mission has been designed to answer six scientific questions, each of which has arisen only recently as a result of discoveries made from orbit: • What are the sources of surface volatiles on Mercury? • How late into Mercury’s history did volcanism persist? • How did Mercury’s long-wavelength topography change with time? • What is the origin of localized regions of enhanced exospheric density at Mercury? • How does the solar cycle affect Mercury’s exosphere and volatile transport? • What is the origin of Mercury’s energetic electrons? “Advancements in science have at their core the evaluation of hypotheses in the light of new knowledge, sometimes resulting in slight changes in course, and other times resulting in paradigm shifts, opening up entirely new vistas of thought and perception,” said Messenger project scientist Ralph McNutt of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. For more information, visit: www.nasa.gov/mission_pages/messenger/main/index.html