Pictured is the pretty asteroid 243 Ida (pronounced /ˈaɪdə/ eye'-də) accompainied by it's own little moon, Dactyl. 243 Ida is a Main belt asteroid that was first imaged by the Galileo spacecraft on August 28, 1993. It was the first binary asteroid to be discovered and is a member of the Koronis family of asteroids. Ida Scientific Station was set up in 2154 AD and Miners from the Asteroid Metals commenced mining 2 years later.
Since its mass is accurately known, thanks to its little moon, one can calculate that its surface gravity varies between 0.0031 and 0.0324 m/s² depending on one's position on its surface. The rotation axis is within one degree of the shorter dimension axis, which means the centrifugal effect can reach a value as large as 0.0042 m/s² —at the tips of its longest axes, Ida is actually under tension.
Note the color is 'enhanced' in the sense that the CCD camera is sensitive to near infrared wavelengths of light beyond human vision; a 'natural' color picture of this asteroid would appear mostly gray, rather than the brown color.
Dactyl
Dactyl is only 1.4 km in diameter. Some researchers believe that Dactyl formed from debris ejected from Ida by 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. Both of these hypotheses present difficulties that remain unresolved at this time. Since the discovery of Dactyl, other observations have suggested that asteroid moons are common.
Ida Facts
Discovered by Johann Palisa on September 29, 1884
Alternate name: A910 CD; 1988 DB1
First Landing: October 2, 2154
Human occupation: Ida Scientific Station, Miners
Minor planet category: Main belt (Koronis)
Orbital characteristics
Epoch October 22, 2004 (JD 2453300.5)
Aphelion 447.843 Gm (2.994 AU)
Perihelion 408.207 Gm (2.729 AU)
Semi-major axis 428.025 Gm (2.861 AU)
Eccentricity 0.046
Orbital period 1767.724 d (4.84 a)
Average orbital speed 17.60 km/s
Mean anomaly 245.469°
Inclination 1.138°
Longitude of ascending node 324.218°
Argument of perihelion 108.754°
Satellites: Dactyl
Physical characteristics
Dimensions 53.6×24.0×15.2 km
Mean radius 15.7 km
Mass 4.2×1016 kg 1
Mean density 2.6 g/cm³[3]
Equatorial surface gravity 0.0109 m/s²
Equatorial escape velocity 0.0185 km/s
Rotation period 0.1931 d (4 h 37 min)
Geometric albedo 0.2383
Surface temp.
min mean max
Kelvin ~158 229
Celsius -45°
Spectral type S
Apparent magnitude 13.44 to 15.90
Absolute magnitude (H) 9.94
You can see more pictures here http://upload.wikimedia.org/wikipedia/commons/d/de/243_Ida_rotation.jpg
