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Computer generated image of
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| Title |
Computer generated image of Apex high-altitude research sailplane in flight |
| Description |
This computer-generated image depicts the current design concept of the Apex high-altitude research aircraft being developed by Advanced Soaring Concepts (ASC) for NASA's Environmental Research Aircraft and Sensor Technology program, based at NASA's Dryden Flight Research Center, Edwards, California. The Apex High-Altitude Flight Experiment is expected to explore the aerodynamics of controlled flight at very high altitudes near 100,000 feet. The Apex will be hoisted aloft tail-first from Dryden by a large high-altitude balloon and released at about 110,000-feet altitude. As it gradually descends, its instrumentation will collect aerodynamic data. The remotely-piloted, semi-autonomous Apex will combine a modified ASC sailplane fuselage design with a new wing designed at the Massachusetts Institute of Technology. The wing will have a special airfoil designed for high subsonic speeds at extreme altitudes. A device extending behind the right wing is a "wake rake," which will measure aerodynamic drag behind a test section of the wing, while a rocket pack mounted beneath the fuselage will assist the Apex in transitioning to horizontal flight. Research flights were expected to begin in mid-1998, but a series of technical problems delayed them. In the spring of 1999, Apex entered mothball status. This continued for a year, and in the spring of 2000 NASA selected Apex as part of phase 1 of the Revolutionary Concepts effort. |
| Date |
01.01.1997 |
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Europa Impact Crater
PIA02561
Jupiter
Near Infrared Mapping Spectr
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| Title |
Europa Impact Crater |
| Original Caption Released with Image |
A newly discovered, city-sized impact crater viewed by NASA's Galileo spacecraft may shed new light on the nature of the enigmatic icy surface of Jupiter's moon Europa. This false-color image reveals the scar of a past major impact of a comet or small asteroid on Europa's surface. The bright, circular feature at center right has a diameter of about 80 kilometers (50 miles), making it comparable in size to the largest cities on Earth. The area within the outer boundary of the continuous bright ring is about 5,000 square kilometers (nearly 2,000 square miles). The diameter of the darker area within the bright ring is about 29 kilometers (18 miles), which is large enough to contain both the city of San Francisco and New York's Manhattan Island, side by side. The brightest reds in this image correspond to surfaces with high proportions of relatively pure water ice, while the blue colors indicate that non-ice materials are also present. The composition of the darker materials is controversial, they may consist of minerals formed by evaporation of salty brines, or they may be rich in sulfuric acid. The bright ring is a blanket of ejecta that consists of icy subsurface material that was blasted out of the crater by the impact, while the darker area in the center may retain some of the materials from the impacting body. Further study may yield new insights about both the nature of the impactor and the surface chemistry of Europa. Europa's surface is a question of great interest at present, since an ocean of liquid water may exist beneath the icy crust, possibly providing an environment suitable for life. Geologic investigations of Europa's surface are underway, and a new spacecraft mission, the Europa Orbiter, is planned. Impact craters with diameters of 20 kilometers (12 miles) and larger are extremely rare on Europa, as of 1999 only 7 such features were known. The rarity of larger impact craters on Europa lends greater significance to the discovery of this one. Impact crater counts are often employed to estimate the ages of the exposed surfaces of planets and satellites, and the small number of craters found on Europa implies that the surface may be quite young in geological terms. Thus the discovery of this feature may provide additional insights into questions about the age and level of geological activity of Europa's surface. Impact craters are expected to form with greater frequency on the "leading" sides of satellites that always turn the same face to their primary planet, in this case, Jupiter. The process is much like the effect of running through a rainstorm. The "apex" of Europa's leading side is located on the equator at 90 degrees West longitude, only about 10 degrees removed from the feature shown. Europa's leading side does not receive a continuous bombardment by ionized particles carried along by Jupiter's rapidly rotating magnetosphere (as is the case for the trailing side), which may allow greater preservation of the chemical, signatures of the impacting object. To the east of the bright ring-like feature are two, or perhaps three, similar but less well-defined quasi-circular features, raising the possibility that this crater is one member of a catena, or chain of craters. This would lend still greater interest to this area as a potential target for focused investigations by later missions such as the Europa Orbiter. The near-infrared mapping spectrometer on board Galileo obtained this image on May 31,1998, during that spacecraft's 15th orbital encounter with Europa. The image data was returned to Earth in several segments during both the 15th and the 16th orbital periods. Merging and processing of the full data set was accomplished in 1999. Analysis and interpretation are ongoing. Galileo has been orbiting Jupiter and its moons since December 1995. Its primary mission ended in December 1997, and after that Galileo successfully completed a two-year extended mission. The spacecraft is in the midst of yet another extended journey called the Galileo Millennium Mission. More information about the Galileo mission is available at:http://galileo.jpl.nasa.gov [ http://galileo.jpl.nasa.gov ]JPL manages Galileo for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena. |
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