From: Andrew Goldman
To: General George Collins
Re: Plantary Research Assessment
Date: July 13, 1978

Contained in this memo, is the revised analysis you requested on Ganymede, the moon which the CCA have colonised. I have also included similar data on it's neighbouring moon Callisto, which may be another possible Bio-Metal site.

Io, Europa, Ganymede and Callisto, make up the Galilean moons, the former are the smaller, inner two. It is highly unlikely that the CCA will choose to venture to Io, as any Bio-Metal deposits would have surely be covered by the Sulpur deposits from it's volcano, and we cannot expect to find any more scrap on this moon, this is mainly why I believe that Callisto is the next most likely subject.



GANYMEDE:

Position: Satellite of Jupiter, fifth planet from the Sun
Distance from Sun: 5.2 Astronomical Units
Minimum Distance from Earth: ~630 Million Kilometres
Surface Gravity (Earth = 1): 0.145
Surface Composition: Dirty Ice, Silicate Rock
Atmospheric Pressure (Earth = 1): 0.023
Mean Surface Temperature: -156 Celsius
Axis Rotation: Static
Orbit Period: 2.7 days
Jupiter Orbit Period: 7.155
Diameter: 5268 Kilometres

Ganymede is the largest natural satellite in the Solar system, and is bigger than Pluto and Mercury. One worry is it's large Gravity, which attracts heavy cratering from the asteroid belt which shares Jupiter's orbit. It isn't often that an asteroid collides with Ganymede, but it would be a terrible disaster if it did occur.

Ignoring this factor, Ganymede is a perfect applicant. It's distance from Jupiter, and large gravity, mean that a considerable amount of Bio-Metal will have deposited on it's surface. The surface is largely Water-Ice, and more recently it has been discovered, that Ganymede has a thin atmosphere of pure oxygen. It seems that the CCA's risk to mine on Ganymede could have been justified.

The surface is made of a mixture of two types of terrain. 60% is covered by a light, grooved terrain, and the remaining 40% is a darker, rougher, and highly cratered. The grooves themselves contain very few craters, so probably developed at the expense of the darker crust, and are younger rock.



CALLISTO:

Position: Satellite of Jupiter, fifth planet from the Sun
Distance from Sun: 5.2 Astronomical Units
Minimum Distance from Earth: ~630 Million Kilometres
Surface Gravity (Earth = 1): 0.127
Surface Composition: Dirty Water Ice
Atmospheric Pressure (Earth = 1): 0
Mean Surface Temperature: -147 Celsius
Axis Rotation: Static
Sun Orbit Period: 4332.7 days
Jupiter Orbit Period: 16.689
Diameter: 4806 Kilometres

Callisto is similar to Ganymede in many ways; and in many ways is very different. It is large, icey, and cratered. Although it is smaller in mass, having a slightly reduced gravity from Ganymede, it suffers even more from cratering, as it is the outermost of the Galilean moons. Callisto is the third largest satellite, and probably the darkest object in the Solar System too. One of the moon's main features is a multi-ring structure, called Valhalla.

As with Europa, the surface of Callisto is icey, and our scientists have reason to believe that the ice may melt at some depth, revealing a "salty ocean", below the surface. This ice would provide water and oxygen. In all, Callisto is not a very safe sight for Bio-Metal gathering, but under the circumstances, this would be the CCA's next choice for Bio-Metal.


We have moved Skyeye-Io into an orbit around Ganymede, and then Callisto, and have found CCA activities on only the former. I believe that if all Bio-Metal sources on the other moons had become depleted, Ganymede would have been the NSDF's 8th choice of moon, as the Impact-risk ( from asteroids ) is much lower. Callisto, however is more of a problem. I am not promising we will need to land on Callisto; however, this is likely to be the destination if the CCA find their position Ganymede undefendable, or if resources become depleted.

I would like to wish yourself, and the NSDF luck on this mission. I personally believe the CCA have a nerve to try this, and although our forces may not be as strong as the CCA's, our will to win is greater. I wish every soldier who fights in this war luck, and every commander success.