The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).
This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo..
Voir l'image PIA01072: Galileo's First Image of Amalthea sur le site de la NASA.
These images of Jupiter's moon Amalthea were taken with NASA's Galileo and Voyager spacecraft. Recent findings show that Amalthea is almost pure water ice, hinting that it may not have formed where it now orbits. This information challenges long-held theories about how moons form around giant planets.
The image on the left shows the escape velocities color-coded on a shape model of Amalthea with the same viewpoint as the Voyager spacecraft image in the middle panel. Blue represents the lowest escape velocity, barely 1 meter per second (about 3 feet) near the anti-Jupiter end, while red (barely visible) shows the region of much higher escape velocity, nearly 90 meters per second (295 feet). The low escape velocities result from the low density of Amalthea and from its rapid rotation as it orbits Jupiter.
The middle image is a composite from both Galileo and NASA's Voyager spacecraft (see PIA02530) and shows Amalthea from the anti-Jupiter side. The visible area is about 150 kilometers (93 miles) across. The Sun is behind the spacecraft, resulting in loss of visible shadows. The brighter markings on the ends of a ridge are prominent in this view.
On the right is a Galileo image of Amalthea, (see PIA02532), with the bright spots on the end of Amalthea seen from the leading side of the satellite. Here the Sun is to the left and topography, such as the impact crater at the right, is visible.
Amalthea is Jupiter's fifth largest moon. It orbits about 181,000 kilometers (112,468 miles) from Jupiter, considerably closer than the Moon orbits Earth. It measures about 168 miles in length and half that in width. Galileo passed within about 99 miles of the moon on Nov. 5, 2002. After more than 30 close encounters with Jupiter's four largest moons, the Amalthea flyby was the last moon flyby for Galileo. The mission began orbiting the planet in 1995.
Additional information about the Galileo mission is available online at: http://galileo.jpl.nasa.gov/. Voyager information is available at: http://voyager.jpl.nasa.gov/.
These two images of Jupiter's small, irregularly shaped moon Amalthea, obtained by the camera onboard NASA's Galileo spacecraft in August 1999(left) and November 1999 (right), form a "stereo pair" that helps scientists determine this moon's shape and the topography of its surface features. Features as small as 3.8 kilometers (2.4 miles) across can be resolved in these images, making them among the highest-resolution images ever taken of Amalthea.
The large impact crater visible in both images, near the right-hand edge of Amalthea's disk, is about 40 kilometers (about 29 miles) across; two ridges, tall enough to cast shadows, extend from the top of the crater in a V-shape reminiscent of a "rabbit ears" television antenna. To the left of these ridges, in the top center portion of Amalthea's disk, is a second large impact crater similar in size to the first crater. To the left of this second crater is a linear "streak" of relatively bright material about 50 kilometers (31 miles) long. In previous spacecraft images of Amalthea taken from other viewing directions, this bright feature was thought to be a small, round, bright "spot" and was given the name Ida. These new images reveal for the first time that Ida is actually a long, linear "streak." This bright streak may represent material ejected during the formation of the adjacent impact crater, or it may just mark the crest of a local ridge. Other patches of relatively bright material can be seen elsewhere on Amalthea's disk, although none of these other bright spots has Ida's linear shape.
In both images, sunlight is coming from the left and north is approximately up. Note that the north pole of Amalthea is missing in the right-hand image (it was cut off by the edge of the camera frame). The bright streak, Ida, is on the side of the moon that faces permanently away from Jupiter, and the crater near the right-hand edge of the disk is in the center of Amalthea's leading side (the side of the moon that "leads" as Amalthea moves in its orbit around Jupiter).
The images are, from left to right: Amalthea taken on August 12, 1999 at a range of 446,000 kilometers (about 277,000 miles) and on November 26, 1999 at a range of 374,000 kilometers (about 232,000 miles).
The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).
This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.
Voir l'image PIA01074: Four Galileo Views of Amalthea sur le site de la NASA.
These images of the inner Jovian moons Thebe, Amalthea, and Metis (left to right), taken in January 2000 by the camera onboard NASA's Galileo spacecraft, are the highest-resolution images ever obtained of these small, irregularly shaped satellites.
The images resolve surface features as small as 2 kilometers (about 1.2 miles) across for Thebe; 2.4 kilometers (about 1.5 miles) across for Amalthea, and 3 kilometers (about 1.9 miles) across for Metis. In late 1999 and early 2000, near the end of a two-year mission extension known as the Galileo Europa Mission, the Galileo spacecraft dipped closer to Jupiter than it had been since it first went into orbit around the giant planet in 1995. These maneuvers allowed Galileo to make three flybys of the volcanically active moon Io and also made possible these new high-quality images of Thebe, Amalthea, and Metis, which lie very close to Jupiter, inside the orbit of Io.
The moons are shown in their correct relative sizes, with sunlight coming from the right. We are viewing the side of each moon that faces permanently away from Jupiter, and north is approximately up in all cases. The prominent impact crater on Thebe is about 40 kilometers(about 25 miles) across and has been given the provisional name Zethus. The large white region near the south pole of Amalthea marks the location of the brightest patch of surface material seen anywhere on these three moons. This unusual material, which sits inside a large crater named Gaea, has been greatly overexposed; accordingly, the white area on this image is somewhat larger than the actual bright area on Amalthea. Note also the "scalloped" or "sawtooth" shape of Amalthea's terminator (the line between day and night, at the left-hand edge of Amalthea's disk), which indicates that parts of this satellite's surface are very rough, with many small hills and valleys.
The images are, from left to right: Thebe taken January 4, 2000 at a range of 193,000 kilometers (about 120,000 miles); Amalthea taken January 4, 2000 at a range of 238,000 kilometers (about 148,000 miles); Métis taken on January 4, 2000 at a range of 293,000 kilometers (about 182,000 miles).
These are the best images of the small inner satellites of Jupiter taken by the solid state imaging (SSI) system on NASA's Galileo spacecraft. From left to right and in order of decreasing distance to Jupiter are Thebe, Amalthea, Adrastea, and Metis, shown at the same scale as Long Island which is 190 kilometers long. Since these satellites are so small, their surface gravities are very low: a person weighing 150 pounds on Earth would weigh about 1 pound on Amalthea, and about an ounce on Adrastea. Large craters 35 to 90 kilometers (20 to 55 miles) across which are the result of impacts by fragments asteroid and comet debris are conspicuous on the surface of the larger satellites.
The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.
This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://solarsystem.nasa.gov/galileo/. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo.">http://www.jpl.nasa.gov/galileo/sepo.
The upper series of images represents the best yet of the four small inner satellites of Jupiter taken by the camera on NASA's Galileo spacecraft. From left to right, in order of decreasing distance to Jupiter, are Thebe, Amalthea (the largest moon), Adrastea (the smallest), and Metis. The images represent the first time that the shapes of Adrastea and Metis have been resolved by a spacecraft camera.
The views are presented at a common scale but were taken at somewhat different original resolutions, ranging from 5.4 kilometers (3.3 miles) per picture element for Amalthea, to 7.5 kilometers (4.6 miles) per picture element for Thebe and Metis. Individual craters, 35 to 90 kilometers (20 to 55 miles) across, are visible on Thebe and Amalthea. While no craters are visible in these images of Adrastea and Metis, the overall irregular shape of Metis indicates it has suffered major collisions. Jupiter is to the right.
Viewing positions are slightly different from the views of the models in the bottom row, which depict the shapes of the small satellites viewed from the direction of satellite motion ("leading sides") and presented at a common scale. These shape models have been calculated from the outlines of the satellites and locations of shadows in individual images, as well as from stereoscopic images taken by the Galileo's camera during different orbits. The models emphasize the highly irregular shapes caused by a history of impacts by fragments of small asteroids and comets. Jupiter's strong gravitational pull on these objects at relatively close distances accelerates the objects to very high velocities, making such impacts very energetic.
JPL manages the Galileo mission for NASA's Office of Space Science, Washington, DC.
The images are posted on the Internet at http://photojournal.jpl.nasa.gov/ and at http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at: http://www.jpl.nasa.gov/galileo/sepo
Voir l'image PIA01624: Shapes of the Small Inner Satellites of Jupiter sur le site de la NASA.
The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).
This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.
Voir l'image PIA01076: Family Portrait of the Small Inner Satellites of Jupiter sur le site de la NASA.
A montage of images of the small inner moons of Jupiter from the camera onboard NASA's Galileo spacecraft shows the best views obtained of these moons during Galileo's 11th orbit around the giant planet in November 1997. At that point, Galileo was completing its first two years in Jupiter orbit--known as the Galileo "prime mission"--and was about to embark on a successful two-year extension, called the Galileo Europa Mission.
The top two images show the moon Thebe. Thebe rotates by approximately 50 degrees between the time these two images were taken, so that the same prominent impact crater is seen in both views; this crater, which has been given the provisional name Zethus, is near the point on Thebe that faces permanently away from Jupiter.
The next two images show the moon Amalthea; they were taken with the Sun directly behind the observer, an alignment that emphasizes patterns of intrinsically bright or dark surface material. The third image from the top is a view of Amalthea's leading side, the side of the moon that "leads" as Amalthea moves in its orbit around Jupiter. This image looks "noisy" because it was obtained serendipitously during an observation of the Jovian satellite Io (Amalthea and Io shared the same camera frame but the image was exposed for bright Io rather than for the much darker Amalthea). The fourth image from the top emphasizes prominent "spots" of relatively bright material that are located near the point on Amalthea that faces permanently away from Jupiter. The bottom image is a view of the tiny moon Metis.
In all the images, north is approximately up, and the moons are shown in their correct relative sizes. The images are, from top to bottom: Thebe taken on November 7, 1997 at a range of 504,000 kilometers (about 313,000 miles); Thebe on November 7, 1997 at a range of 548,000 kilometers (about 340,000 miles); Amalthea on November 6, 1997 at a range of about 650,000 kilometers (about 404,000 miles); Amalthea on November 7, 1997 at a range of 475,000 kilometers (about 295,000 miles); Metis on November 7, 1997 at a range of 637,000 kilometers (about 396,000 miles).