Click to enlarge. Image from Too Much Zerging
Here's a quick outline planets by type as described in Star Control II:
- Huge balls of gas composed of light elements (hydrogen, helium)
- Ships can't attempt landings since there's no solid surface
- It's possible that massive "scoop ships" could harvest elements
- No intelligent life has been found on/in a gas giant...yet...
- Large, rocky planets with nickel-iron cores, fluid mantels and covered in water (Earth-like)*
- Distance from parent star determines whether water is liquid,gaseous, or locked up in ice
- Life is common on these worlds
- Surface temp ranges 0-100 degrees centigrade
- Small, not dense, composed of light elements and metals
- Rarely have atmosphere
- Comparable to Luna, Earth's moon
- Surfaces composed of silicates and metal oxides
- Little or no usable mineral deposits
- Thin atmosphere may support minimal eco system
- Like water worlds, but covered in inorganic hydrocarbons like ethanol
- Small deposits of useful minerals
- Known for ability to support life
- Large, rocky have metal core with silicate sheath
- Dense atmosphere of carbon dioxide makes for hot, volatile surface conditions
- Usually found in the first or second orbital position
- Lighter materials have often burned off leaving small dense core of heavy metals and minerals exposed
- Highly valuable for the natural resources, but may have intense gravity fields
- Similar to water world but surface gas is not oxygen, but methane and ammonia**
- Contains higher surface concentration of radioactive elements
- Higher amounts could indicate uncommon gas composition or mantle convection process
The manual indicates that there are other "less common" types of planets spread throughout the game and encourages you to seek them out.
When planets are encountered in-game, players (starship captains) typically scan them for minerals, lifeforms, artifacts, etc. Scanning brings up a stat-block of the following attributes:
- Planet Type: (As covered above)
- Orbital Radius: Distance from primary star in astronomical units (A.U.s)
- Temperature: Surface temperature; hotter worlds make for dangerous landings
- Tectonics: Seismic activity; rated 1-8 "classes" which seems to follow the Volcanic Explosivity Index not the Richter Scale
- Weather: Measures force and density of disturbances and measured similar to tectonics (8 classes); lightning is most dangerous weather effecting landings
- Atmospheric Pressure: Measured in "standard Earth units" and adds more flavor than function in the game
- Mass: Total mass measured in Earth units, 1 = 1 Earth
- Radius: Also measured in Earth units; mass combined with radius determines a planet's gravity attribute
- Gravity: Measured in Earth units and determines how much fuel it costs to land (and leave) a planet
- Length of Day: How long it takes for planet to revolve on its axis, not a large in-game consideration
- Axial Tilt: Difference between a planet's rotational axis and axis of orbit, determines planets seasons (which likely affects weather patterns/overall climate)
In Star Control, it's important to understand most of these attributes, while a few seem to be more geared toward rounding out the game's aesthetic. I appreciate the amount of thought that went into crafting the planet classification and I could see actually making use of all of these in a paper and pencil RPG.
Whereas SC2 sorta' auto-calculates the danger to your crew when you attempt landings, attributes like Length of Day, Atmospheric Pressure and Weather could be used to greater effect in a home campaign of your own making. They might influence how PCs choose to expose them selves to the elements and for how long.
All in all, I think this is an excellent to classify planets. It gives nice snapshot of each planet encountered. Might be worth an attempt to do something similar in an X-plorers, Star Frontiers, or other scifi game.
*Star Control II came out before the notion of "Super Earths" was widely known by the public. In the game, Earth is considered a larger, rocky planet. Venus, Mars, and Mercury are typically small-to-medium sized worlds.
**Manual; says "oxygen" here, should really be referred to as "nitrogen" or an "oxygen/nitrogen mix."