Mission to Callisto

Uploaded on Jan 6, 2010
Callisto (pronounced /kəˈlɪstoʊ/,or as Greek Καλλιστώ) is a moon of the planet Jupiter, discovered in 1610 by Galileo Galilei.
It is the third-largest moon in the Solar System and the second largest in the Jovian system, after Ganymede.
 Callisto has about 99% the diameter of the planet Mercury but only about a third of its mass. It is the fourth Galilean moon of Jupiter by distance,
 with an orbital radius of about 1 880 000 km. It does not form part of the orbital resonance that affects three inner Galilean satellites—Io, Europa and Ganymede—
 and thus does not experience appreciable tidal heating. Callisto rotates synchronously with its orbital period, so the same face is always turned toward Jupiter.
 Callisto's surface is less affected by Jupiter's magnetosphere than the other inner satellites because it orbits farther away.
Callisto is composed of approximately equal amounts of rock and ices, with a mean density of about 1.83 g/cm3. Compounds detected
spectrally on the surface include water ice, carbon dioxide, silicates, and organic compounds. Investigation by the Galileo spacecraft 
revealed that Callisto may have a small silicate core and possibly a subsurface ocean of liquid water at depths greater than 100 km.
The surface of Callisto is heavily cratered and extremely old. It does not show any signatures of subsurface processes such as plate tectonics,
earthquakes or volcanoes, and is thought to have evolved predominantly under the influence of impacts. Prominent surface features include multi-ring structures,
variously shaped impact craters, and chains of craters (catenae) and associated scarps, ridges and deposits. At a small scale, the surface is varied and consists of small,
 bright frost deposits at the tops of elevations, surrounded by a low-lying, smooth blanket of dark material. This is thought to result from the sublimation-driven degradation 
 of small landforms, which is supported by the general deficit of small impact craters and the presence of numerous small knobs, considered to be their remnants.The absolute ages
 of the landforms are not known.
Callisto is surrounded by an extremely thin atmosphere composed of carbon dioxide[6] and probably molecular oxygen, as well as by a rather intense ionosphere. Callisto is thought 
to have formed by slow accretion from the disk of the gas and dust that surrounded Jupiter after its formation. Its slowness and the lack of tidal heating prevented rapid differentiation.
 The slow convection in the interior of Callisto, which commenced soon after formation, led to partial differentiation and possibly to the formation of a subsurface ocean at a depth of 100150 km and a small, rocky core.
The likely presence of an ocean within Callisto indicates that it can or could harbor life. However, this is less likely than on nearby Europa. Various space probes from 
Pioneers 10 and 11 to Galileo and Cassini have studied the moon.
 Callisto has long been considered the most suitable place for a human base for future exploration of the system of Jupiter.

Discovered by G. Galilei
S. Marius
Discovery date January 7, 1610
Designations 
Alternate name Jupiter IV 
Adjective Callistoan, Callistian 
Orbital characteristics 
Periapsis 1 869 000 km[b] 
Apoapsis 1 897 000 km[a] 
Mean orbit radius 1 882 700 km
Eccentricity 0.007 4 
Orbital period 16.689 018 4 d
Average orbital speed 8.204 km/s 
Inclination 0.192° (to local Laplace planes)
Satellite of Jupiter 
Physical characteristics 
Mean radius 2410.3 ± 1.5 km (0.378 Earths) 
Surface area 7.30 × 107 km2 (0.143 Earths) 
Volume 5.9 × 1010 km3 (0.0541 Earths)
Mass 1.075 938 ± 0.000 137 × 1023 kg (0.018 Earths)
Mean density 1.834 4 ± 0.003 4 g/cm3[3] 
Equatorial surface gravity 1.235 m/s2 (0.126 g) 
Escape velocity 2.440 km/s
Rotation period synchronous
Axial tilt zero 
Albedo 0.22 (geometric)
Surface temp.
K[4] min mean max 
80 ± 5 134 ± 11 165 ± 5 

Apparent magnitude 5.65 (opposition)
Atmosphere 
Surface pressure 7.5 pbar 
Composition ~4 × 108 cm−3 carbon dioxide
up to 2 × 1010 cm−3 molecular oxygen
Category
Science & Technology
License
Standard YouTube License

Model of Callisto’s internal structure showing a surface ice layer, a possible liquid water layer, and an ice–rock interior.

 Credit: NASA/JPL

Interior density structures created by an outer solar system late heavy bombardment onto Ganymede (top row) and Callisto (bottom row).

 Credit: SwRI

Voyager 1 image of Valhalla, a multi-ring impact structure 3800 km in diameter. Credit: NASA/JPL

New Horizons Long Range Reconnaissance Imager (LORRI) captured these two images of Jupiter’s outermost large moon, Callisto,

 during its flyby in February 2007. Credit: NASA/JPL

Artist’s impression of a base on the icy surface of Callisto. Credit: NASA

This video examines the most iconic small scale feature of Callisto which are its ice towers, also known as ice knobs.
 I examine the evidence behind how such features form. The most likely explanation found is that they are mostly eroded crater rims.
 But how can things erode on Callisto's surface which is largely geologically inactive and on top of that is airless? Well,
 probably through the sublimation of ices along with maybe some small contribution of small meteorites hitting the surface. 
 The images that were used in this video to piece together the puzzle of how Callisto's surface works were captured
 by NASA's Galileo spacecraft, however there is much more left to uncover and sadly the Juno spacecraft didn't even 
 do a single flyby of Callisto so far.(10-2024)