Vesta appears in a splendid rainbow-colored palette in new images obtained by NASA's Dawn spacecraft. The colors, assigned by scientists to show different rock or mineral types, reveal Vesta to be a world of many varied, well-separated layers and ingredients. Vesta is unique among asteroids visited by spacecraft to date in having such wide variation, supporting the notion that it is transitional between the terrestrial planets -- like Earth, Mercury, Mars and Venus -- and its asteroid siblings.
This video includes images from NASA's Dawn framing camera instrument. The hill is about 26 miles (42.5 kilometers) long by about 17 miles (28 kilometers wide), and appears to be sculpted by impact craters.
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
This image combines two separate views of the giant asteroid Vesta obtained by NASA's Dawn spacecraft. The images were taken by Dawn's framing camera. The far-left image uses near-infrared filters where red is used to represent 750 nanometers, green represents 920 nanometers and blue represents 980 nanometers. The image on the right is an image with colors assigned by scientists, representing different rock or mineral types on Vesta. The data reveal a world of many varied, well-separated layers and ingredients. The reddish color suggests a steep visible spectral slope, and areas of fresh landslides in the inner walls of the crater show deeper green colors.
Credit:NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
These Dawn FC (framing camera) images show part of the ejecta blanket from Vesta's "Snowman" craters in the northern hemisphere. The ejecta blanket fills the whole image and is identified by its hummocky yet smooth texture. The hummocky texture is due to the undulating hills and depressions across the image. But apart from these hills and depressions the surface is rather smooth. This smoothness is due to the generally small size of particles in ejecta blankets. The left image is an albedo image, which is taken directly through the clear filter of the FC. Such an image shows the albedo (e.g. brightness/darkness) of the surface. The right image uses the same albedo image as its base but then a color-coded height representation of the topography is overlain onto it.
This image using color data obtained by the framing camera aboard NASA's Dawn spacecraft shows Vesta's southern hemisphere in color, centered on the Rheasilvia formation. Rheasilvia is an impact basin measured at about 290 miles (467 kilometers) in diameter with a central mound reaching about 14 miles (23 kilometers) high. The black hole in the middle is data that have been omitted due to the angle between the sun, Vesta and the spacecraft.
Scientists assigned different colors for the ratios of two wavelengths of radiation detected by the framing camera to indicate areas that are relatively redder or bluer. The red indicates wavelengths at 750 nanometers divided by 440 nanometers. Blue indicates areas at 440 nanometers divided by 750 nanometers. Scientists are still studying why certain areas look redder or bluer. Green indicates areas at 750 nanometers divided by 920 nanometers, suggesting the presence of the iron-rich mineral pyroxene or large-sized particles.
Scientists assigned different colors for the ratios of two wavelengths of radiation detected by the framing camera to indicate areas that are relatively redder or bluer. The red indicates wavelengths at 750 nanometers divided by 440 nanometers. Blue indicates areas at 440 nanometers divided by 750 nanometers. Scientists are still studying why certain areas look redder or bluer. Green indicates areas at 750 nanometers divided by 920 nanometers, suggesting the presence of the iron-rich mineral pyroxene or large-sized particles.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
This mosaic was assembled using images obtained during Dawn's approach to Vesta, at a resolution of 480 meters per pixel.
In images from Dawn's framing camera, the colors reveal differences in the rock composition associated with material ejected by impacts and geologic processes, such as slumping, that have modified the asteroid's surface. Images from the visible and infrared mapping spectrometer reveal that the surface materials contain the iron-bearing mineral pyroxene and are a mixture of rapidly cooled surface rocks and a deeper layer that cooled more slowly. The relative amounts of the different materials mimic the topographic variations derived from stereo camera images, indicating a layered structure that has been excavated by impacts. The rugged surface of Vesta is prone to slumping of debris on steep slopes.
Dawn scientists presented the new images at the American Geophysical Union meeting in San Francisco on Monday, Dec. 5. The panelists included Vishnu Reddy, framing camera team associate, Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany; Eleonora Ammannito, visible and infrared spectrometer team associate, Italian Space Agency, Rome; and David Williams, Dawn participating scientist, Arizona State University, Tucson.
This mosaic was assembled using images obtained during Dawn's approach to Vesta, at a resolution of 480 meters per pixel.
In images from Dawn's framing camera, the colors reveal differences in the rock composition associated with material ejected by impacts and geologic processes, such as slumping, that have modified the asteroid's surface. Images from the visible and infrared mapping spectrometer reveal that the surface materials contain the iron-bearing mineral pyroxene and are a mixture of rapidly cooled surface rocks and a deeper layer that cooled more slowly. The relative amounts of the different materials mimic the topographic variations derived from stereo camera images, indicating a layered structure that has been excavated by impacts. The rugged surface of Vesta is prone to slumping of debris on steep slopes.
Dawn scientists presented the new images at the American Geophysical Union meeting in San Francisco on Monday, Dec. 5. The panelists included Vishnu Reddy, framing camera team associate, Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany; Eleonora Ammannito, visible and infrared spectrometer team associate, Italian Space Agency, Rome; and David Williams, Dawn participating scientist, Arizona State University, Tucson.
Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI
"Vesta's iron core makes it special and more like terrestrial planets than a garden-variety asteroid," said Carol Raymond, Dawn's deputy principal investigator at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The distinct compositional variation and layering that we see at Vesta appear to derive from internal melting of the body shortly after formation, which separated Vesta into crust, mantle and core."
The presentation also included a new movie, created by David O'Brien of the Planetary Science Institute, Tucson, Ariz., that takes viewers on a spin around a hill on Vesta that appears to be made of a distinctly darker material than the rest of the crust.
Dawn launched in September 2007 and arrived at Vesta on July 15, 2011. Following a year at Vesta, the spacecraft will depart in July 2012 for the dwarf planet Ceres, where it will arrive in 2015.
Fresh Impacts on Vesta
This image combines two separate views of the giant asteroid Vesta obtained by NASA's Dawn spacecraft. The images were taken by Dawn's framing camera. The far-left image uses near-infrared filters where red is used to represent 750 nanometers, green represents 920 nanometers and blue represents 980 nanometers. The image on the right is an image with colors assigned by scientists, representing different rock or mineral types on Vesta, revealing a world of many varied, well-separated layers and ingredients.
The fresh impact craters in this view are located in the south polar region, which has been partly covered by landslides from the adjacent crater. This would suggest that a layer of loose material covers the Vesta surface.
"Vesta's iron core makes it special and more like terrestrial planets than a garden-variety asteroid," said Carol Raymond, Dawn's deputy principal investigator at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The distinct compositional variation and layering that we see at Vesta appear to derive from internal melting of the body shortly after formation, which separated Vesta into crust, mantle and core."
The presentation also included a new movie, created by David O'Brien of the Planetary Science Institute, Tucson, Ariz., that takes viewers on a spin around a hill on Vesta that appears to be made of a distinctly darker material than the rest of the crust.
Dawn launched in September 2007 and arrived at Vesta on July 15, 2011. Following a year at Vesta, the spacecraft will depart in July 2012 for the dwarf planet Ceres, where it will arrive in 2015.
This image combines two separate views of the giant asteroid Vesta obtained by NASA's Dawn spacecraft. The images were taken by Dawn's framing camera. The far-left image uses near-infrared filters where red is used to represent 750 nanometers, green represents 920 nanometers and blue represents 980 nanometers. The image on the right is an image with colors assigned by scientists, representing different rock or mineral types on Vesta, revealing a world of many varied, well-separated layers and ingredients.
The fresh impact craters in this view are located in the south polar region, which has been partly covered by landslides from the adjacent crater. This would suggest that a layer of loose material covers the Vesta surface.
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
This image combines two separate views of the giant asteroid Vesta obtained by NASA's Dawn spacecraft. The images were taken by Dawn's framing camera. The far-left image uses near-infrared filters where red is used to represent 750 nanometers, green represents 920 nanometers and blue represents 980 nanometers. The image on the right is an image with colors assigned by scientists, representing different rock or mineral types on Vesta. The data reveal a world of many varied, well-separated layers and ingredients. The reddish color suggests a steep visible spectral slope, and areas of fresh landslides in the inner walls of the crater show deeper green colors.
Credit:NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
These Dawn FC (framing camera) images show part of the ejecta blanket from Vesta's "Snowman" craters in the northern hemisphere. The ejecta blanket fills the whole image and is identified by its hummocky yet smooth texture. The hummocky texture is due to the undulating hills and depressions across the image. But apart from these hills and depressions the surface is rather smooth. This smoothness is due to the generally small size of particles in ejecta blankets. The left image is an albedo image, which is taken directly through the clear filter of the FC. Such an image shows the albedo (e.g. brightness/darkness) of the surface. The right image uses the same albedo image as its base but then a color-coded height representation of the topography is overlain onto it.
Credit:NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The topography is calculated from a set of images that were observed from different viewing directions, allowing stereo reconstruction. The various colors correspond to the height of the area. The white area in the center of the image is the highest area and the blue area in the top of the image is the lowest area. The topography image shows that there are not large height differences between the hills and depressions. But, the topographically high area of ejecta, which is colored white, does become apparent in the topography image.
Rocks of Vesta
The HED (howardite, eucrite and diogenite) meteorites are a large group of meteorites believed to originate from Vesta, a hypothesis that is consistent with current Dawn observations. The diogenites originated deep within the crust of Vesta and resemble rocks, both in texture and composition, which we find in the lower crust of the Earth. The QUE 99050 (left) and GRA 98108 (right) diogenites, pictured here, were recovered in Antarctica. These images are of thin slices of the meteorites as viewed through a polarizing microscope. The white bars in the images, each 2 millimeters long, indicate the scale. When polarized light passes through thin slices of rock, different minerals have different colors. QUE 99050 (left) consists of large gray and yellow crystals of pyroxene (magnesium-iron silicate) and is a subgroup of diogenite called "orthopyroxenitic diogenite" (orthopyroxenite is the name of a rock composed primarily of the mineral orthopyroxene). GRA 98108 (right) has a more mafic (i.e. magnesium and iron rich) mineralogy, consisting of roughly equal portions of pyroxene and the much brighter colored olivine, a silica-poor iron magnesium-iron silicate.
Credit: NASA/JPL-Caltech/Hap McSween (University of Tennessee), and Andrew Beck and Tim McCoy (Smithsonian Institution)
This olivine-rich "harzburgitic diogenite" (harzburgite is the name given to a rock composed of a mixture of the minerals orthopyroxene and olivine) is thought to represent the most deep-seated rocks from Vesta that we have in the meteorite collection. Diogenites like these comprise some fraction of Vesta's lower crust, and their compositions can be compared with observations from various instruments aboard Dawn. They can be compared with the VIR (Visible and Infrared Imaging Spectrometer) spectra to determine mineralogy and with the GRaND (Gamma Ray and Neutron Detector) observations to calibrate and interpret the GRaND instrument's responses. Similar rocks have likely been excavated by large impacts, such as the one that formed the Rheasilvia basin at the south pole of Vesta.
Credit: NASA/JPL-Caltech/Hap McSween (University of Tennessee), and Andrew Beck and Tim McCoy (Smithsonian Institution)
The HED (howardite, eucrite and diogenite) meteorites are a large group of meteorites believed to originate from Vesta, a hypothesis that is consistent with current Dawn observations. The eucrites are crystallized lavas that have the composition of basalt, the most common lava type on the Earth. The QUE 97053 (left) and EET 90020 (right) eucrites, pictured here, were recovered in Antarctica. These images are of thin slices of the meteorites as viewed through a polarizing microscope. The white bars in the images, each 2.5 millimeters long, indicate the scale.
Credit: NASA/JPL-Caltech/Hap McSween (University of Tennessee), and Andrew Beck and Tim McCoy (Smithsonian Institution)
The HED (howardite, eucrite and diogenite) meteorites are a large group of meteorites believed to originate from Vesta, a hypothesis that is consistent with current Dawn observations. The eucrites are crystallized lavas that have the composition of basalt, the most common lava type on the Earth. The QUE 97053 (left) and EET 90020 (right) eucrites, pictured here, were recovered in Antarctica. These images are of thin slices of the meteorites as viewed through a polarizing microscope. The white bars in the images, each 2.5 millimeters long, indicate the scale.
When polarized light passes through thin slices of rock, different minerals have different colors. QUE97053 (left) consists mostly of elongated gray crystals of feldspar (calcium aluminum silicate) and brightly colored grains of pyroxene (magnesium iron silicate). The texture of this rock is what would be expected from crystallization of a molten magma. EET90020 (right) has similar mineralogy but a recrystallized texture of equant grains formed by later heating. Equant grains have the same or roughly the same dimensions in all directions. Eucrites like these comprise some fraction of Vesta's surface. Their compositions can be compared with observations from various instruments aboard Dawn. They can be compared with the VIR (Visible and Infrared Imaging Spectrometer) spectra to determine mineralogy and with the GRaND (Gamma Ray and Neutron Detector) observations to calibrate and interpret the GRaND instrument's responses.
Dawn's mission to Vesta and Ceres is managed by JPL for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.
More information about the Dawn mission is online at: http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov.
Contacts and sources:
Priscilla Vega
Jet Propulsion Laboratory, Pasadena, Calif.
Dawn's mission to Vesta and Ceres is managed by JPL for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.
More information about the Dawn mission is online at: http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov.
Contacts and sources:
Priscilla Vega
Jet Propulsion Laboratory, Pasadena, Calif.
No comments:
Post a Comment