Outmigration: Candidate Lineup

Assuming a minimum of 1 acre per person (including arable land) total space required for any of our colonies, and assuming an initial colony of 1000 individuals capable of expanding to 10,000 individuals, in each case we need 4 square km of habitable space initially which can be expanded to 40 square km of living space eventually. Each of these candidates have the potential to accomplish this.

Low Orbtal Toroidal Station

Distance ~ 1000 km from surface (ISS is 500 km)
Gravity: 1.0G, or whatever is desired
Escape Velocity ANY
Braking: Thrust only
Existing life potential: none
Resources: None
Radiation: Low
Asteroid vulnerability: low to moderate

Advantage: Easiest access of any candidate, full gravity
Disadvantage: All materials to build must come from earth.

L4 or L5 Langrangian Orbit Toroidal Station

Distance 400,000 km
Gravity: 1.0G, or whatever is desired
Escape Velocity ANY
Braking: Thrust only
Existing life potential: none
Resources: None
Radiation: High
Asteroid vulnerability: moderate to high

Advantage: Stable orbit, could build very large without need for propulsion, full gravity
Disadvantage: All materials to build must come from earth or moon.

Peary Crater (Moon)

Distance 400,000 km
Gravity: 0.2G
Crater Diameter 73 km
Escape Velocity 2.38 km/sec
Braking: Thrust only
Existing life potential: none
Resources: Rock, iron, limited water
Radiation: Low
Asteroid vulnerability: Low

Advantage: Close, ample resources for small colony
Disadvantage: Size of colony self-limiting, few similarly ideal locations on moon

Mars

Distance Variable, ~100,000,000km
Gravity 0.4G
Escape Velocity 5.03 km/sec
Weak atmospheric braking, high winds
Existing life potential: very low
Resources: Rock, iron, water
Radiation: Low
Asteroid vulnerability: Low

Advantage: Very large settlements possible, most "earth-like" of candidates
Disadvantage: Unless we find substantial fossil deposits, not much incentive to stay on Mars

Callisto

Distance ~800,000,000km
Gravity 0.1G
Escape Velocity 2.44 km/sec
Braking: Thrust only
Existing life potential: very low
Resources: Rock, iron, water
Radiation: Low
Asteroid vulnerability: Moderately High

Advantages: Good outpost for study of rest of Jupiter system
Disadvantages: Other than research, not much incentive to colonize

Enceladus

Distance 1,300,000,000km
Gravity 0.01G
Escape Velocity 0.24 km/sec
Braking: Thrust only
Existing life potential: moderate to high
Resources: Water
Radiation: Low
Asteroid vulnerability: High

Advantages: Gravity light enough that a rotating toroid built (or landed) on Enceladus could provide full gravity for inhabitants, while surface gravity sufficiently low for many low-G applications. LOTS of water ice. Great view. Good outpost for research of Titan.

Disadvantages: Very far away.


Tomorrow we'll look at some of the potential motivations to colonize, and from this make a best guess of which candidate would best serve each motive.