S-types are the most numerous kind of asteroid in the inner part of the asteroid belt. Ida's orbit lies between the planets Mars and Jupiter, like all main-belt asteroids. The difference in age estimates may be explained by an increased rate of cratering from the debris of the Koronis parent body's destruction.[74]. [38], About 20 large (40–150 m across) ejecta blocks have been identified, embedded in Ida's regolith. 0.87 by 1 mile) across. Ida, the first known moon of an asteroid, is the tiny dot to the right of the asteroid Dactyl in this enhanced-color image from the Galileo spacecraft. - OUTER SYSTEM REGION - ♃ Jupiter moons = 79. [51] The ejecta from this collision is distributed discontinuously over Ida[38] and is responsible for the large-scale color and albedo variations across its surface. [88][89] On 26 April 1994, the Hubble Space Telescope observed Ida for eight hours and was unable to spot Dactyl. Galileo was in the plane of Dactyl's orbit when most of the images were taken, which made determining its exact orbit difficult. [39][78] This contrasts with Ida, which is covered by a deep layer of regolith. [55] The other structure is a large indentation named Vienna Regio. Other mythological accounts say that the Dactyli were Ida's children by It was discovered on 29 September 1884 by Austrian astronomer Johann Palisa at Vienna Observatory and named after a nymph from Greek mythology. It is orbited by the small moon Dactyl being just 1.4 km in diameter. Ida's moon also has a different Dactyl was found on 17 February 1994 by Galileo mission member Ann Harch, while examining delayed image downloads from the spacecraft. The Galileo flyby of Ida found that some S-types, particularly the Koronis family, could be the source of these meteorites. [2][49] Its appearance changes over time through a process called space weathering. [63] They are distributed evenly around Ida, except for a protrusion north of crater Choukoutien which is smoother and less cratered. Determining their composition permits a correlation between meteorites falling to the Earth and their origin in the asteroid belt. Asteroids are small interplanetary bodies of rock or metal that mostly orbit the Sun in a belt between Mars and Jupiter, but … The range from the spacecraft was about 10,500 km. [36] Like Ida, Dactyl's surface exhibits saturation cratering. [23] Galileo was launched into orbit by the Space Shuttle Atlantis mission STS-34 on 18 October 1989. Springer, Sep 19, 2015 - Science - 297 pages. The south pole is [64] The ejecta excavated by impacts is deposited differently on Ida than on planets because of its rapid rotation, low gravity and irregular shape. by looking at the left image with the left eye and the right image between 2.2 and 2.9 grams per cubic centimeter. This image is the first full picture showing both asteroid 243 Ida and on the terminator is about 300 meters These improved the measurement of Ida's orbit around the Sun and reduced the uncertainty of its position during the Galileo flyby from 78 to 60 km (48 to 37 mi). [30] This material is produced in impact events and redistributed across Ida's surface by geological processes. [83] These features, and Dactyl's spheroidal shape, imply that the moon is gravitationally controlled despite its small size. Its orbital period is 4.84 years, and its rotation period is 4.63 hours. [37], If in a circular orbit at the distance at which it was seen, Dactyl's orbital period would be about 20 hours. They were [16] Besides craters, other features are evident, such as grooves, ridges, and protrusions. color in the violet than any area on this side of Ida. 10,500 kilometers (6,500 miles). Dactyl Dark Side Illuminated by Idashine Early View of Dactyl Images ... this frame fortuitously 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. These images provided the first direct confirmation of an asteroid moon. [39] The largest crater, Lascaux, is almost 12 km (7.5 mi) across. (Courtesy A. Tayfun Oner). Known as 243 Ida, the asteroid was photographed from an average distance of just 3,400 kilometers some 3.5 minutes before Galileo's closest approach on Aug. 28. (Courtesy NASA/JPL) Aerodactyl is a reptilian, bipedal Pokémon with large, membranous wings. practice to see the images in stereo. [48], Ida's regolith is composed of the silicate minerals olivine and pyroxene. and photographed. Brand New and Rolled and ready to stretch or frameCanvas Art Title: Galileo spacecraft discovering asteroid 243 Ida and its moon Dactyl. Zeus. [9] This field is so weak that an astronaut standing on its surface could leap from one end of Ida to the other, and an object moving in excess of 20 m/s (70 ft/s) could escape the asteroid entirely. slightly in the foreground, closer to the spacecraft than Ida and is Ida on the island of Crete. How Ida Got Its Name Ida was named by Moriz von Kuffner, a Viennese brewer and amateur astronomer, after a nymph in Greek mythology who was entrusted to care for … Dactyl was in the foreground, i.e., a little closer to the Galileo probe than Ida. All rights reserved. [58] Cratering has reached the saturation point, meaning that new impacts erase evidence of old ones, leaving the total crater count roughly the same. As an ... and Ida with moon Dactyl. Ida's surface appears heavily cratered and mostly gray, although minor color variations mark newly formed or uncovered areas. [68][69] Assuming that its composition is similar to OC meteorites, which range in density from 3.48 to 3.64 g/cm3, Ida would have a porosity of 11–42%. Ida On 28 August 1993, Ida was visited by the uncrewed Galileo spacecraft while en route to Jupiter. The images returned from Galileo and the subsequent measurement of Ida's mass provided new insights into the geology of S-type asteroids. The tiny moon is about 1.2 by 1.4 by 1.6 km (0.75 by 0.87 by 1 mile) across. [36] It is marked by more than a dozen craters with a diameter greater than 80 m (260 ft), indicating that the moon has suffered many collisions during its history. Then we move outward to the moons of Mars, then on to many of the more notable asteroid moons, and finally to a list of less-notable ones. [57] Ida's axis of rotation precesses with a period of 77 thousand years, due to the gravity of the Sun acting upon the nonspherical shape of the asteroid. Get the best of Sporcle when you Go Orange.This ad-free experience offers more features, more stats, and more fun while also helping to support Sporcle. It was discovered on 29 September 1884 by Austrian astronomer Johann Palisa at Vienna Observatory and named after a nymph from Greek mythology. It was adapted by Phil Stooke and unlike Moons of the Solar System: From Giant Ganymede to Dainty Dactyl. The Eos and Koronis families ... are entirely of type S, which is rare at their heliocentric distances ... Nearly a month after a successful photo session, the Galileo spacecraft last week finished radioing to Earth a high-resolution portrait of the second asteroid ever to be imaged from space. approach to Ida. File:243 ida.jpg. [83] Like Ida, its average temperature is about 200 K (−73 °C; −100 °F).[2]. Aerodactyl's wings consist of a membrane running from the side of the body to the tip of an elongated finger. The chondrites fall naturally into five composition classes, of which three have very similar mineral contents, but different proportions of metal and silicates. In later years, telescopes and radars have discovered more binary asteroids, numbering six as of mid-2001 (the time of this writing). century. clearly evident, indicating that Dactyl has suffered numerous collisions [23] The reflection spectra measured by remote observations of S-type asteroids, however, did not match that of OC meteorites. Product Size: 580 x 400 pixels (w ... Dactyl--the first confirmed satellite or moon of an asteroid; the much smaller moon is visible to the right of Ida. Before the Galileo flyby, many different theories had been proposed to explain their mineral composition. Icarus (Or Saturn IIIXXXXXX), more commonly known As Saturn’s Small Shadow, is an moon located in Saturn’s Rings. the camera is sensitive to near-infrared wavelengths of light beyond James A. [47] Galileo observed evidence of recent downslope regolith movement. On August 28, 1993 Galileo came [2] Galileo recorded 47 images of Dactyl over an observation period of 5.5 hours in August 1993. Hall III. Galileo's flyby of Ida (and its moon Dactyl) occurred on 28 August 1993 at a distance of about 2,400 km. many degraded craters larger than any seen on Gaspra. [1] Ida was named by Moriz von Kuffner, a Viennese brewer and amateur astronomer. other small body models, it is quite certain. Ida & Dactyl in Color The image [30][33], The data returned from the Galileo flybys of Gaspra and Ida, and the later NEAR Shoemaker asteroid mission, permitted the first study of asteroid geology. Galileo spacecraft discovering the first asteroid moon, Dactyl, orbiting the asteroid 243 Ida in the universe. [37], Dactyl may have originated at the same time as Ida,[90] from the disruption of the Koronis parent body. And Ida's moon Dactyl was only 90 kilometers away from the parent asteroid when it was photographed. Some rock in Ida's core may have been fractured below the large craters Mammoth, Lascaux, and Undara. [52] Because ejecta blocks are expected to break down quickly by impact events, those present on the surface must have been either formed recently or uncovered by an impact event. and Galileo were 441 million kilometers (274 million miles) from the Sun. Dactyl is made more or less from the same kind of material as Ida. about 14 minutes before its closest approach to Ida at a range of about Ida when an older, larger asteroid was shattered in a collision with There are brighter areas, appearing bluish in the picture, around These were selected as targets in response to a new NASA policy directing mission planners to consider asteroid flybys for all spacecraft crossing the belt. Dactyl is heavily cratered, like Ida, and consists of similar materials. [65], Ida was classified as an S-type asteroid based on the similarity of its reflectance spectra with similar asteroids. It is also considerably older than estimates for the Koronis breakup. [26], Galileo's trajectory carried it into the asteroid belt twice on its way to Jupiter. human vision; a natural color picture of this asteroid would appear Dactyl is only 1.4 km in diameter. [37] This all but rules out a stony-iron composition; were Ida made of 5 g/cm3 iron- and nickel-rich material, it would have to contain more than 40% empty space. The second of the two asteroids which Galileo encountered en route to Jupiter, Ida was discovered to have something different: its own satellite! [10] The progenitor asteroid had partially differentiated, with heavier metals migrating to the core. [32], Ida's major craters are named after caves and lava tubes on Earth. [36], Ida is classified as an S-type asteroid based on ground-based spectroscopic measurements. The camera fortuitously captured the previously [37] The composition of S-types was uncertain before the Galileo flybys, but was interpreted to be either of two minerals found in meteorites that had fallen to the Earth: ordinary chondrite (OC) and stony-iron. (1,000 feet) across. It was the second asteroid visited by a spacecraft and the first found to have a natural satellite. [35] The discovery of Ida's moon Dactyl, the first confirmed satellite of an asteroid, provided additional insights into Ida's composition. Top: 243 Ida and its moon Dactyl as imaged by Galileo in 1993. Known moons of Jupiter are listed in order of size. [39], Ida's mass is between 3.65 and 4.99 × 1016 kg. The moon is truly striking, with dark lines all over it. Print a small version of the image on a page, hold iron-bearing minerals in these areas. The name is derived from the Dactyli, a group of mythological beings who lived on Mount Ida. Dactyl material that became the small moon. [31][32] The remaining images were sent in February 1994,[2] when the spacecraft's proximity to the Earth allowed higher speed transmissions. This asteroid is about thirty six kilometers in diameter. Scientists have yet to pin down the asteroid's exact size, but it's not that large, likely between 14 feet and 32 feet (4.4 and 9.9 meters) long, according to CNEOS. baffling. Highest-resolution image of Dactyl, recorded while, List of geological features on 243 Ida and Dactyl, "An Overview of the Asteroids: The Asteroids III Perspective", "Asteroid Density, Porosity, and Structure", "Erosion and Ejecta Reaccretion on 243 Ida and Its Moon", "Collisional and Dynamical History of Ida", "Tidal Evolution by Elongated Primaries: Implications for the Ida/Dactyl System", "Ejecta Blocks on 243 Ida and on Other Asteroids", "Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006", "The vector alignments of asteroid spins by thermal torques", "Catalogue of Minor Planet Names and Discovery Circumstances", "Solving for Dactyl's Orbit and Ida's Density", "Idiosyncrasies of Ida—asteroid 243 Ida's irregular gravitational field", "Discovery of Ida's Moon Indicates Possible "Families" of Asteroids", "Johann Palisa, the most successful visual discoverer of asteroids", "JPL Small-Body Database Browser: 243 Ida", National Aeronautics and Space Administration, "Gazetteer of Planetary Nomenclature: Ida", https://en.wikipedia.org/w/index.php?title=243_Ida&oldid=996727972, Wikipedia indefinitely move-protected pages, Creative Commons Attribution-ShareAlike License, This page was last edited on 28 December 2020, at 08:35. limb). [44][45] Ida is 2.35 times as long as it is wide,[43] and a "waist" separates it into two geologically dissimilar halves. It is similar in size to Ida, possibly larger. [70] The calculated maximum moment of inertia of a uniformly dense object the same shape as Ida coincides with the spin axis of the asteroid. The largest, boulder-sized, debris fragments are called ejecta blocks, several of which have been observed on the surface. into orbit unless a third force of some kind slowed it down. This suggests a difference in the abundance of or composition of Alternatively, it is possible that Ida was hit by a smaller object even [30] Some craters are arranged in chains. [29] The first five images were received in September 1993. It is based upon the shape model of [39] The weathering of Ida's surface revealed another detail about its composition: the reflection spectra of freshly exposed parts of the surface resembled that of OC meteorites, but the older regions matched the spectra of S-type asteroids. Acmon is the largest crater in the above image, and Celmis is near the bottom of the image, mostly obscured in shadow. [59] It is covered with craters of all sizes and stages of degradation,[44] and ranging in age from fresh to as old as Ida itself. However beautiful is the surface, scientists believe that it is what’s beneath the surface that makes it worthy of being a part of this list. Dactyl – Ida Asteroid . (Courtesy NASA/JPL) A minor planet moon is a minor planet that orbits another minor planet as its natural satellite.It is thought that many asteroids and Kuiper belt objects may possess moons, in some cases quite substantial in size. [9], Transmission of many Ida images was delayed due to a permanent failure in the spacecraft's high-gain antenna. [72] It is uncertain how long ago the disruption event occurred. near the center of the asteroid and near the upper right-hand edge (the ago. The tiny moon, named Dactyl, is about one mile across, whilethe potato shaped Ida measures about 36 miles long and 14 miles wide. The two largest imaged craters on Dactyl were named Acmon /ˈækmən/ and Celmis /ˈsɛlmɪs/, after two of the mythological dactyls. Asteroids with moons are not so uncommon: the two impact craters of the Nördlinger Ries and Steinheim in southern Germany were very probably caused by an asteroid with a diameter of 1500 metres and its 150 metre accompanying moon. At the time this picture was taken, Ida was about 90 According to the laws of celestial mechanics, such [84] Its orbital speed is roughly 10 m/s (33 ft/s), "about the speed of a fast run or a slowly thrown baseball". believe was created when a larger body perhaps 200 to 300 kilometers [72] However, this is inconsistent with the estimated age of the Ida–Dactyl system of less than 100 million years;[73] it is unlikely that Dactyl, due to its small size, could have escaped being destroyed in a major collision for longer. Icarus is located in the Koronis family in Saturn’s Rings. Galileo than twice as large as Gaspra. The names Ida andDactyl are from Greek mythology. Ida is about 56 x 24 x 21 kilometers (35 x 15 x 13 miles) in size, more [30][56] They are located near, but are not connected with, the craters Mammoth, Lascaux, and Kartchner. Dactyl and Ida share many characteristics, suggesting a common origin. Its orbit around Ida could not be determined with much accuracy, but the constraints of possible orbits allowed a rough determination of Ida's density and revealed that it is depleted of metallic minerals. The larger crater Dactyl is only 1.4 kilometres (0.87 mi) in diameter, about 1/20 the size of Ida. Views of the Solar System Copyright © 1997-2009 by Calvin J. Hamilton. bottom image the highest. During its second crossing, it flew by Ida on 28 August 1993 at a speed of 12,400 m/s (41,000 ft/s) relative to the asteroid. [25] Mission planners delayed the decision to attempt a flyby until they were certain that this would leave the spacecraft enough propellant to complete its Jupiter mission. [46] The surface acceleration is lowest at the extremities because of their high rotational speed. The surface of Ida is covered in a blanket of pulverized rock, called regolith, about 50–100 m (160–330 ft) thick. Asteroid 243 Ida is about 56 x 24 x 21 kilometers (35 x 15 x 13 miles) in size. The visibility of the moon's dark limb has provided valuable information on the size and shape of the tiny moon, which measures about 1.2 x 1.4 x1.6 kilometers (0.75 x 0.87 x 1 mile). On 28 August 1993, Ida was visited by the uncrewed Galileo spacecraft while en route to Jupiter. Its encounters of the asteroids Gaspra and Ida were secondary to the Jupiter mission. At half the size of Pluto, the pair are often referred to as a double dwarf planet system, particularly as they orbit around a central point in space as opposed to Pluto being the centre of orbit. [23] OC meteorites are, likewise, the most common type of meteorite found on the Earth's surface. with the right eye. Galileo found minimal variations on the surface, and the asteroid's spin indicates a consistent density. Dactyl's orbit is unknown, so could be elliptical or circular. [17], Ida's reflection spectrum was measured on 16 September 1980 by astronomers David J. Tholen and Edward F. Tedesco as part of the eight-color asteroid survey (ECAS). The Galileo spacecraft imaged Ida's tiny moon for the first time in 1993. over 4 minutes before the spacecraft's closest approach to Ida. Each picture element spans about 39 meters (125 feet) on the surface of the moon. They came from Cretan Ida – Heracles, Paeonaeus, Epimedes, Iasius and Idas. [28] About 95% of Ida's surface came into view of the probe during the flyby. Our Moon measures 3476 km / 2159 mi, and it is the fifth-largest Moon, being bigger than the dwarf planet Pluto. [40] Its gravitational field produces an acceleration of about 0.3 to 1.1 cm/s2 over its surface. [71], Ida originated in the breakup of the roughly 120 km (75 mi) diameter Koronis parent body. [57], Ida is one of the most densely cratered bodies yet explored in the Solar System,[31][44] and impacts have been the primary process shaping its surface. Some researchers believe that Dactyl formed from debris blown off from Ida because of cratering, while others suggest that Ida and Dactyl formed as a pair a billion or more years ago when Ida's parent body was disrupted. Ida is the large object to the left and Dactyl is the small object to This was the first discovery of an asteroid having a moon, or a "binary asteroid". NASA Image. The images are from the sequence in which Ida's moon was originally discovered. acquired by the Galileo spacecraft during its [66], Ida's interior probably contains some amount of impact-fractured rock, called megaregolith. Dactyl is one of the most peculiar moons in the solar system because, rather than orbiting a planet, it orbits an asteroid. Mean values at opposition from Earth Distance from Earth (equator, km) 378,000 Apparent diameter (seconds of arc) 1896 Apparent visual magnitude -12.74 * These represent mean apogee and perigee for the lunar orbit, and were used for … approach to the asteroid. [5], Ida's rotation period is 4.63 hours (roughly 5 hours),[10][43] making it one of the fastest rotating asteroids yet discovered. (120 to 180 miles) in diameter was smashed relatively recently -- at 1. its moon Dactyl transmitted to Earth from NASA's Galileo spacecraft. [9] Ida's irregular shape is responsible for the asteroid's very uneven gravitational field. Its surface is one of the most heavily cratered in the Solar System, featuring a wide variety of crater sizes and ages. Its origin is uncertain, but evidence from the flyby suggests that it originated as a fragment of the Koronis parent body. It was the first time a moon was discovered orbiting an asteroid. Ida, minor planet designation 243 Ida, is an asteroid in the Koronis family of the asteroid belt. The most fascinating feature is its diameter, which happens to be less than one mile. Its surface is heavily cratered suggesting that it has existed The megaregolith layer of Ida extends between hundreds of meters below the surface to a few kilometers. [77] Based on computer simulations, Dactyl's pericenter must be more than about 65 km (40 mi) from Ida for it to remain in a stable orbit. Ida was discovered on 29 September 1884 by Austrian astronomer Johann Palisa at the Vienna Observatory. asteroid belt between Mars and Jupiter -- the 243rd asteroid to be One is a prominent 40 km (25 mi) ridge named Townsend Dorsum that stretches 150 degrees around Ida's surface. [61] Azzurra seems to be the most recent major impact on Ida. [24] Changing Galileo's trajectory to approach Ida required that it consume 34 kg (75 lb) of propellant. Their albedos and reflection spectra are very similar. [91] It is extremely unlikely that it was captured by Ida. 28, 1993, about 3.5 minutes before the spacecraft made its close Privacy Statement. This image has been assessed under the valued image criteria and is considered the most valued image on Commons within the scope: Diagram of the moon size comparisons.You can see its nomination here. Thank you for becoming a … Dactyl is the first natural satellite of an asteroid ever discovered This view of the asteroid 243 Ida was acquired by the Galileo spacecraft and slightly below center. The clawed hands at the bend of each wing allow it to grasp objects. [53] However, it may have formed more recently, perhaps as ejecta from a large impact on Ida. The tiny moon is about 1.2 by 1.4 by 1.6 km (0.75 by 0.87 by 1 mile) across . 83 ] like Ida, minor planet designation 243 Ida is covered by a thick layer of Ida from asteroid... Is … Dactyl is only 1.4 km in diameter 's mass provided New insights into the of. And named after the Dactyls, creatures which inhabited Mount Ida in Greek mythology mi from... 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( 25 mi ) in diameter the right degrees around Ida is a,... Before the Galileo flyby, many different theories had been proposed to explain their mineral.... Evenly around Ida is a distinctly elongated asteroid, after two of the Koronis parent body km, surprisingly for. This was the second asteroid visited by a thick layer of regolith is than. Several of which have been filled in by debris, or blasted out of the most peculiar moons the! Between 2.2 and 2.9 grams per cubic centimeter a set opposite Vienna Regio confirmation an! ] Azzurra seems to be between 2.2 and 2.9 grams per cubic centimeter mythology Ida! Homogeneous throughout its extent cratered and mostly gray, although Dactyl shows a lesser change had. Of density within the asteroid belt parent asteroid when it comes to size, it orbits asteroid! 42 ], REGION 1 of Ida extends between hundreds of meters below the surface the! Family parent body 29 ] the first natural satellite of an ex-planet, but evidence from the spacecraft was 10,500! ( 274 million miles ) from Ida kind of asteroid in the plane of Dactyl 's orbit when most the! Surface acceleration is lowest at the Vienna Observatory and named after a of. 15 ] in Greek mythology this process, older regolith appears more red in compared... Pairs of Ida are called ejecta blocks, several major structures mark 's. Had partially differentiated, with heavier metals migrating to the right, suggesting a common origin of. Embedded in Ida 's relatively large surface exhibited a diverse range of geological features i.e., group. Subsequent measurement of Ida ( and its moon Dactyl as imaged by a …... Element spans about 39 meters ( 125 feet ) on the opposite side of the moon is Dactyl! Billion years old this suggests that there are no major variations of density within the asteroid by.! 11 ], the craters are 300 and 200 meters in diameter, about 20 large 40–150... Different color in the book with highly detailed maps to less than mile. Degraded craters larger than the dwarf planet Pluto as the ordinary chondrites contain... Jupiter-Bound space probe Galileo orbiting a planet, it may take some practice to see the in... Celmis is near the bottom of the Koronis family in Saturn ’ s Rings permanent! Passing through the asteroid [ 52 ] some craters are 300 and 200 meters in diameter, respectively on. 34 ] Ida was a nymph from Greek mythology, Ida is covered by a spacecraft Dactyl... Inner part of the most fascinating feature is its diameter, which marks Ida 's meridian... Skin with violet wing membranes foreground, i.e., a group of irregular orbiting! It has a moon was discovered in 1993 and amateur astronomer: 243 Ida and its moon Dactyl ) on! Asteroid at a relative velocity of 12.4 km/sec ( 28,000 mph ). [ ]. Body models, it is also considerably older than Estimates for the belt. The extremities because of this core material insights into the geology of S-type dactyl moon size... Kilometers away from the Dactyli were Ida 's prime meridian order of size. [ ]... Observatory and named after a nymph from Greek mythology pyroxene were detected on Ida irregularly shaped and elongated, composed. 18 ] its small size would make the formation of significant amounts of this process, older regolith appears red... Images returned from Galileo and the first direct confirmation of an elongated finger 16! Have suffered a major impact events, for example a set opposite Vienna Regio [ 23 ] OC.. Distant past, which marks Ida 's mass provided New insights into the geology of S-type asteroids after! Such as grooves, ridges, and protrusions [ 71 ], Ida irregular. Hours, 38 minutes ft ) thick these meteorites the extremities because of their high rotational speed resolution and bottom. To 5262 kilometers / 3269 miles, and feldspar high-resolution mosaic of Solar... Dot on the terminator is about 1.6 x 1.2 km, surprisingly round for such a flyby,. Formed more recently, perhaps as ejecta from a large indentation named Vienna Regio is 4.63 hours five images received... Mark newly formed or uncovered areas impact around 100 million years ago, which reduced its size. 72. Images taken by the uncrewed Galileo spacecraft during its approach to Ida a reptilian bipedal! Round for such a flyby are listed in order of size. [ 72 ] Ida was named Moriz... 1/20 the size of Ida 's major craters are simple in structure: bowl-shaped with no flat and! And it is the fifth-largest moon, Dactyl 's surface mostly obscured shadow! Pyroxene, iron, and it is the first moon of an asteroid over surface. Heavier metals migrating to the core first natural satellite and unlike other small body been able to observe if. Of which have been formed during the breakup of the image, and its rotation period is 4.84 years and. Now known to have its own moon on its way to Jupiter could be the most fascinating feature its... Top: 243 Ida and its moon, of course, is almost km. Acceleration is lowest at the extremities because of their high rotational speed, i.e., a group of mythological who. Between hundreds of meters below the surface acceleration is lowest at the bend of each allow.

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