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Images: Ida and Dactyl

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Ida and Dactyl

Asteroid Ida and its moon Dactyl. Scientists found the moon - the first discovered orbiting and asteroid - when the Galileo spacecraft flew past Ida in 1994. *Image Credit*: NASA, Jet Propulsion Laboratory

NASA Identifier: SPD-SLRSY-887

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Date Taken:09.18.2009

Date Posted:10.10.2012 16:13

Photo ID:707596


Size:47.24 KB

Location:WASHINGTON, DC, USGlobe

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  • This image is the most detailed picture of Dactyl, a natual satellite (moon) of asteroid 243 Ida. Dactyl was the first moon found orbiting an asteroid. NASA's Galileo spacecraft discovered the tiny moon during a 1993 flyby of Ida while en route to Jupiter.  This frame captured the previously unknown moon at a range of about 3,900 kilometers (2,400 miles), just over 4 minutes before the spacecraft's closest approach to Ida.   More than a dozen craters larger than 80 meters (250 feet) in diameter are clearly evident, indicating that the moon has suffered numerous collisions from smaller solar system debris during its history. The larger crater on the terminator is about 300 meters (1000 feet) across. The satellite is approximately egg-shaped, measuring about 1.2 x 1.4 x 1.6 kilometers (0.75 x 0.87 x 1 mile). The Galileo project, whose primary mission was the exploration of the Jupiter system, is managed for NASA's Office of Space Science by the Jet Propulsion Laboratory.  *Image Credit*: NASA, Jet Propulsion Laboratory

NASA Identifier: SPD-SLRSY-883
  • This image is a closeup of the newly discovered moon of the asteroid Ida, provisionally designated '1993 (243) 1.' This is a magnified, processed version of the single view of the natural satellite transmitted so far by the Galileo spacecraft to Earth. Only 1.5 kilometers (1 mile) across in this view, the overall shape, size, rotation and orbital motion of the natural satellite are still unknown. The sun's illumination is coming from the upper right. The black 'gouge' in the body's shape toward the lower left is probably more apparent than real and is mostly a part of the shadowed night side of the little moon. A rugged landscape, including one or two craters, appears to be present, although the smallest features that can be detected in this picture are about 1/7th the diameter of the natural satellite. This picture was taken by Galileo during its flyby of Ida on August 28, 1993. Later in the spring of 1994, scientists hope to receive other views of Ida's moon which are currently stored on Galileo's onboard tape recorder; one of those images is expected to be at least three times sharper than this one. The Jet Propulsion Laboratory manages the Galileo Project for NASA's Office of Space Science.

NASA Identifier: P43732
  • This composite image shows the asteroid 243 Ida as seen from the Galileo spacecraft during its approach on August 28, 1993. The six views were shuttered through the camera's green filter and show Ida's rotation over a period of about 3 hours 18 minutes. The asteroid makes a complete rotation every 4 hours 38 minutes; therefore, this set of images spans about 3/4 of Ida's rotation period and shows most of Ida's surface. By combining the information in these views with that from the highest resolution images returned from the spacecraft in September 1993, the size and shape of this irregular body can now be determined accurately The asteroid appears to be about 58 kilometers (36 miles) long and about 23 kilometers wide, with a very irregular shape and volume of some 16,000 cubic kilometers. The images are arranged in chronological order from a time 3 hours 51 minutes before closest approach (upper left), through upper right, middle left, middle right lower left and lower right (33 minutes before closest approach). The six images show Ida at the same scale throughout. Ida's rotation axis is roughly vertical in these images, and the rotation causes the right-hand end of Ida to move toward the viewer as time progresses. The first image was taken from a range of about 171,000 km (106,000 miles) and provides an image resolution of about 1,700 meters per pixel (the highest resolution achieved for Ida is about 25 meters per pixel). The second, taken 70 minutes later, is from 119,000 kilometers, followed by 102,000 kilometers, 85,000 kilometers, 50,000 kilometers, and 25,000 kilometers. The features on Ida are less sharp in the earlier views because of the greater distances. Prominent in the middle three views is a deep depression across the short axis of the Asteroid. This feature tends to support the idea that Ida may have originally been formed from two or more separate large objects that collided softly and stuck together. Also visible in the lower left view is an apparent linear albedo or reflectance boundary. Color images yet to be returned from the Galileo spacecraft may help resolve the question of whether or not the two ends of Ida are made of different materials.

NASA Identifier: PLAN-PIA00137
  • Asteroids are material left over from the formation of the solar system. One theory suggests that they are the remains of a planet that was destroyed in a massive collision long ago. More likely, asteroids are material that never coalesced into a planet. In fact, if the estimated total mass of all asteroids was gathered into a single object, the object would be less than 1,500 kilometers (932 miles) across, less than half the diameter of our Moon.  The asteroid belt lies in the region between Mars and Jupiter. The Trojan asteroids lie in Jupiter's orbit, in two distinct regions in front of and behind the planet.   *Image Credit*: Lunar and Planetary Institute

NASA Identifier: SPD-SLRSY-850


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