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The Sun's Heliosphere & Heli
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| Title |
The Sun's Heliosphere & Heliopause |
| Explanation |
Where does the Sun's influence end? Nobody is sure. Out past the orbits of Neptune [ http://antwrp.gsfc.nasa.gov/apod/neptune.html ] and Pluto [ http://www.nineplanets.org/pluto.html ] extends a region named the heliosphere [ http://science.msfc.nasa.gov/ssl/pad/solar/heliosph.htm ] where the Sun's magnetic field [ http://science.msfc.nasa.gov/ssl/pad/solar/the_key.htm ] and particles from the Solar Wind [ http://science.msfc.nasa.gov/ssl/pad/solar/sun_wind.htm ] continue to dominate. The surface where the Solar Wind [ http://antwrp.gsfc.nasa.gov/apod/ap000318.html ] drops below sound speed [ http://antwrp.gsfc.nasa.gov/apod/ap010221.html ] is called the termination shock [ http://web.mit.edu/space/www/voyager/voyager_science/helio.review/axford.suess.html#Distance ] and is depicted as the inner oval in the above computer-generated illustration [ http://www.cs.indiana.edu/~soljourn/ ]. It is thought that this surface occurs as close as 75-90 AU [ http://neo.jpl.nasa.gov/glossary/au.html ] -- so close that a Pioneer [ http://spaceprojects.arc.nasa.gov/Space_Projects/pioneer/PNhome.html ] or Voyager [ http://voyager.jpl.nasa.gov/ ] spacecraft may soon glide through [ http://www.srl.caltech.edu/personnel/ace/recentpub/JGR_96/pap_preprint.html ] it as they exit the Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap020214.html ] at about 3 AU/year. The actual contact sheet between the Sun's ions [ http://www-istp.gsfc.nasa.gov/Education/wplasma.html ] and the Galaxy's ions is called the heliopause [ http://www-pw.physics.uiowa.edu/plasma-wave/voyager/heliopr.html ] and is thought to occur at about 110 AU. It is depicted above as the middle surface. The Sun's heliopause [ http://web.mit.edu/space/www/voyager/voyager_science/helio.review/axford.suess.html ] moves through the local interstellar medium [ http://antwrp.gsfc.nasa.gov/apod/ap020210.html ] much as a boat moves on water, pushing a bow shock [ http://antwrp.gsfc.nasa.gov/apod/ap001017.html ] out in front, thought to occur near 230 AU. |
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Spirit Hits a Home Run
PIA02187
Sol (our sun)
Panoramic Camera
| Title |
Spirit Hits a Home Run |
| Original Caption Released with Image |
This week, NASA's Mars Exploration Rover Spirit arrived at "Home Plate," a feature that, when seen from orbit, looks like the home plate of a baseball diamond. Home Plate is a roughly circular feature about 80 meters (260 feet) in diameter that might be an old impact crater or volcanic feature. The Spirit team has been eager to get to Home Plate and has been enjoying distant views of the feature and a curious "bathtub ring" of light-colored materials along its edges. The team has pushed the rover hard to get here before the deep Martian winter sets in. After scientists had identified Home Plate from orbit, they had many theories about what it could be and what they might see. But when Spirit's panoramic camera (Pancam) took this and other images, the science team was stunned. This Pancam image is of an outcrop nicknamed "Barnhill" and surrounding rocks on the north side of Home Plate, showing the most spectacular layering that Spirit has seen. Pancam and microscopic imager views of the layers in the rocks reveal a range of grain sizes and textures that change from the lower to the upper part of the outcrop. This may help scientists figure out how the material was emplaced. Spirit is also conducting work with its arm instruments to figure out the chemistry and mineralogy of the rocks. Scientists have several hypotheses about what Home Plate could be, including features made by volcanoes and impact craters, and ways that water could have played a role. They are busy trying to figure out what the data from Spirit is really telling us. As Spirit works at Home Plate during February, the science team is choosing informal names for rocks from the great players and managers of the Negro Leagues of baseball. This outcrop, "Barnhill," is informally named for David Barnhill, the ace of the New York Cubans' pitching staff during the early 1940s. He compiled an 18-3 record in 1941 and defeated Satchel Paige in the 1942 East-West all-star game. Other rocks in the area are informally named for Josh Gibson, "Bullet Joe" Rogan, and Cumberland Posey. Stay tuned this month, as the Baseball Hall of Fame elects more players from the Negro Leagues and Spirit continues to examine these spectacular rocks. Spirit took this mosaic of images using the panoramic camera on the rover's 746th day, or sol (Feb. 7, 2006), of exploring Mars. Scientists are acquiring and processing image data for more views of the same terrain in approximate true color. |
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MISR Participates in Aerosol
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PIA03404
Sol (our sun)
Multi-angle Imaging SpectroR
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| Title |
MISR Participates in Aerosol Characterization Experiment over Asia |
| Original Caption Released with Image |
Before scientists apply new spacecraft measurements to global climate change research, they must carefully test their understanding of the data under controlled conditions. During April 2001, a team of 200 investigators from 11 countries participated in the Aerosol Characterization Experiment (ACE) field campaign in Asia, deploying instruments aboard several ships, aircraft, and island stations in the waters surrounding Japan and Korea. They characterized meteorological conditions, measured the atmospheric energy balance, and directly sampled airborne dust and pollution particles while the Multi-angle Imaging SpectroRadiometer (MISR) and other satellite instruments flew overhead. These MISR images, centered just north of Shikoku Island in southwest Japan, were acquired on April 13, 2001 during Terra orbit 7015. They are two of nine simultaneous views obtained at different angles by the instrument, at 26 degrees aft of vertical (left) and 60 degrees forward of vertical (right). The entire west end of Honshu Island, which crosses the upper half of the images, is covered with broken clouds. Away from the clouds, the atmosphere looks hazier in the steeper MISR view, such differences reveal information about particles in the atmosphere. As these images were taken, the U.S. National Oceanographic and Atmospheric Administration (NOAA) Research Vessel Ron Brown and the National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) C-130 aircraft probed the environment near Oki island, in the upper left part of the images. At the same time, the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft made atmospheric chemistry and heat-balance measurements in the bottom-center region of the images. For more about ACE-Asia, see http://saga.pmel.noaa.gov/aceasia/ [ http://saga.pmel.noaa.gov/aceasia/ ] MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology. |
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