Also crossing at and near the rim of Stickney are shallow, elongated depressions called grooves. Some of these boulders are enormous - more than 50 meters (160 feet) across. Individual boulders are visible on the near rim of the crater (D), and are presumed to be ejecta blocks from the impact that formed Stickney. This is the largest crater on Phobos, Stickney, 10 kilometers (6 miles) in diameter. The image shows several new features of this lumpy moon - features that are associated with the prominent crater seen in the upper left quarter of the image. This image is one of the highest resolution images (4 meters or 13 feet per picture element or pixel) ever obtained of the Martian satellite. Phobos was observed by both the Mars Orbiter Camera (MOC) and Thermal Emission Spectrometer (TES). The minimum distance between the spacecraft and Phobos was 1,080 kilometers (671 miles). "We hope this is the first of several observations that will help us understand Phobos and Deimos.This image of Phobos, the inner and larger of the two moons of Mars, was taken by the Mars Global Surveyor on August 19, 1998. "We want to get observations under all types of lighting - fully daylit, a small crescent, during eclipse," Hamilton said. With the first observation now in hand, plans are advancing for additional opportunities at different illumination phases of Phobos and Deimos. "There is heightened interest in Phobos because of the possibility that future astronauts could perhaps use it as an outpost." "We now have the capability of rotating the spacecraft for THEMIS observations," said Odyssey Project Scientist Jeffrey Plaut of JPL. The teams have adapted those procedures for imaging the Martian moons. ![]() In 2014, the spacecraft team at Lockheed Martin Space Systems, Denver and NASA's Jet Propulsion Laboratory, Pasadena, California and the THEMIS team at Arizona State University, Tempe, developed procedures to rotate the spacecraft for upward-looking imaging of a comet passing near Mars. In normal operating mode, Odyssey keeps the THEMIS camera pointed straight down as the spacecraft orbits Mars. 29 observation was completed to validate that the spacecraft could safely do so, as the start of a possible series of observations of Phobos and Deimos in coming months. Since Odyssey began orbiting the Red Planet in 2001, THEMIS has provided compositional and thermal-properties information from all over Mars, but never before imaged either Martian moon. ![]() Compositional information from THEMIS might help pin down their origin. One major question about Phobos and Mars' even smaller moon, Deimos, is whether they are captured asteroids or bits of Mars knocked into the sky by impacts. Observations in multiple bands of thermal-infrared wavelengths can yield information about the mineral composition of the surface, as well as the surface texture. Cameras on other Mars orbiters have previously taken higher-resolution images of Phobos, but none with the infrared information available from THEMIS. Phobos has an oblong shape with an average diameter of about 14 miles (22 kilometers). If it heats up very quickly, it's likely not very rocky but dusty instead." "As you go from predawn area to morning area you get to watch the heating behavior. "Including a predawn area in the observation is useful because all the heating from the previous day's sunshine has reached its minimum there," Hamilton said. As barefoot beach walks can confirm, sand warms or cools quicker than rocks or pavement. This provides information about how quickly the ground warms, which is related to the texture of the surface. Looking across the image from left to right presents a sequence of times of day on the Martian moon, from before dawn, to sunrise, to increasing amounts of time after dawn. "Part of the observed face of Phobos was in pre-dawn darkness, part in morning daylight," said THEMIS Deputy Principal Investigator Victoria Hamilton of the Southwest Research Institute, headquartered in San Antonio. Researchers have combined visible-wavelength and infrared data to produce an image color-coded for surface temperatures of this moon, which has been considered for a potential future human-mission outpost. ![]() The Thermal Emission Imaging System ( THEMIS) camera on NASA's Mars Odyssey orbiter observed Phobos on Sept. NASA's longest-lived mission to Mars has gained its first look at the Martian moon Phobos, pursuing a deeper understanding by examining it in infrared wavelengths.
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