This is a quick glance at the different types of planets you are likely to encounter in the Elite galaxy, in a manner similar to that of the Star Systems page. Each has been listed with a short description and any other points to note.
World with indigenous life and oxygen atmosphere:
Naturally life-supporting worlds, usually these are found around type G planets, but there are so many exceptions (Red Giants, Type K, Type F, Type A) that this is clearly not the standard. There are usually one or two at most, but Taygete (32,32) has 4, with at least one more world for terraforming. May be up to 2 Earth masses, but usually not less than about 0.3. Earth is the best example of this type for obvious reasons. Temperature extremes range from 347K to perhaps as low as 251K.
Terraformed world with introduced life:
These are worlds that have the capability to support life, in that if sufficient levels of Carbon Dioxide, Oxygen and water are made available then life can be introduced. Usually these have a surface temperature of a value such that once the raw ingredients are introduced, nature can be left to continue the process. These can be up to 2 Earth masses or perhaps one tenth in some cases. Examples can be found throughout the galaxy, especially Epsilon Indi, Alioth and Achenar. Planets ripe for terraforming are those with some form of water/Carbon Dioxide atmosphere.
Small sustained terraformed world:
The best example of this is Mars. Small worlds with a thin atmosphere comprising mostly of Carbon Dioxide may have genetically modified but simple photosynthesising plants introduced to initiate atmosphere change. Because of the thin atmosphere, to support humans unaided the density of the atmosphere must be dramatically increased as part of the terraforming process. How this is done (or could, in theory be done) I am not sure. If you have seen the film Aliens, where massive automated atmosphere purifiers are created then this could be one way, but the actual physics of it is still pretty much in the realms of pure fiction, as the gravity of Mars is too low. The sustaining process is unclear.
Rocky world with thick corrosive atmosphere:
Extremely unpleasant worlds, mostly characterised by high surface temperatures, and sulphur/Carbon Dioxide atmosphere where the density has run amok somewhat. Venus is the best example, to terraform this would be tremendously difficult: the high temperatures would be prohibitive and removing excess sulphur from the atmosphere would be far too complex. This sort of planet is generally about the mass of Venus.
World with methane weather system and corrosive atmosphere:
Titan is a good example of this. Why Titan has methane locked in its atmosphere is anybody's guess. On the whole they seem similar to worlds like Venus except with a much lower temperature that supports methane in its liquid form. Not a good idea to land here but I can't say I've bothered trying yet. Methane occurs as a result of a number of reactions: hydrogenation of carbon oxide, the action of water on aluminium carbide or by the heating of sodium ethanoate with alkali. Worlds like this MAY support life because the essential molecules are there, in some form or another, especially as methane is given off by decomposing organic matter. Worlds like this have uses in industry too.
World with ammonia weather system and corrosive atmosphere:
Taygete (32,32) has three of these in its system. Ammonia, or Nitrogen Hydroxide is a corrosive gas, it is also used as a refrigerant, and can be used to manufacture fertilizer, nitric acid and explosives. Nitric acid itself has many uses in the chemical industries. Planets like this, although not contenders for terraforming may be used to support fledgling industries.
World with water weather system and corrosive atmosphere:
An ideal contender for terraforming, but it would be difficult. It depends a lot on what makes the rest of the atmosphere so corrosive, as although water itself is essential to life, it is also arguably THE most corrosive chemical in existence. Water will, in some form or another react on a chemical level with just about anything, it will dissolve, or at the very least, badly oxidise almost all metals, especially iron. If terraforming attempts fail, then the industrial uses for this planet could be far-reaching. About 1 in 6000 parts of water will be deuterium oxide, a compound that is being looked at as a main fuel to power fusion power stations. Temperatures on these worlds vary considerably, obviously not more than 373K but can be as low as 251K where water can exist as a liquid in a supercooled state, unless disturbed or an ice crystal is added.
Rocky planet with a thin atmosphere:
Planets like this are ripe for terraforming; Mars in its current state falls under this category, and in the Frontier universe serves as the headquarters of most of the major corporations within the Federation. Obviously this is assuming that the atmosphere is primarily carbon dioxide, additional carbon dioxide can be added to increase atmospheric density, and then 'seeded' with simple photosynthesising plants. The problems have been looked at in 'Small sustained terraformed worlds'.
Highly volcanic world:
Generally the surface of these worlds is constantly changing and is very unstable. For some reason there are only 2 or 3 examples of this in FE2 or FFE. The instability of these worlds is (I think) caused by its proximity to a massive object - look at Io and Lucifer, these are both in extremely close proximity to a massive object, Jupiter and Sirius B respectively in the case of these examples, and the tidal forces generated are immense enough to heat the planet up internally resulting in the spectacular volcanoes and constantly changing surface due to lava flows.
Small barren sphere of rock:
Exactly this really. MAY be of use to those developing a career in mining though, check the inner planets of systems with an MB4 to see what they hold. This may be something reasonably useful like a metal seam (gives metal alloys, although it may hold precious metals!) or it may simply be water ice. These are generally similar to very small planetoids such as Ceres.
Barren rocky planetoid:
Objects such as Mercury, the Moon, etc. Can be useful for mining in a similar sense to that of the small barren spheres of rock described above. Obviously, actually mining these specific planets is illegal.
Like Phobos and Deimos. May be blasted with a 30MW mining laser to release minerals, although the release of precious metals has been documented. Needs to be used in combination with fuel scoop + cargo scoop conversion (FE2) and/or Tractor beam cargo scoop (FFE). May also be used to increase Elite rating for those who can't be bothered :-)
Small gas giant:
Large (relatively, compared to Earth) planet whose atmosphere consists of predominantly of light gases such as hydrogen, helium and methane. Can be useful if you have a fuel scoop and a hydrogen drive for the exploration of distant worlds, if there are no gas giants then you will have to resort to scooping fuel from the star. Not recommended for novices. Examples of these gas giants are Uranus and Neptune, with their characteristic colours caused by traces of methane in the atmosphere.
Medium gas giant:
In FE2 and FFE these are depicted as always having some sort of prominent ring system, much like that of Saturn, although many gas giants of any type have some form of ring system, this could be caused by the break up of an asteroidal body, or meteors that are caught in its gravitational field. Atmosphere similar to that of small gas giants, but with the possibility of trace amounts of ammonia, ethane and phosphine. Can also have hydrogen fuel scooped from it. Saturn is (perhaps) unique in having an overall density less than that of water.
Large gas giant:
Jupiter, for example. Again, may have hydrogen fuel scooped from it. In addition to the gases found in medium gas giants, there may also be found carbon monoxide, acetylene and perhaps water vapour. Also the prospect of scooping hydrogen fuel. Generally relatively warm as high rotational speeds and large coriolis effects generate heat.
Very Large gas giant:
Larger version of large gas giants, imaginatively enough. Because of their size friction within the planet caused by gravitational contraction generates a remarkable amount of heat, so these planets are generally much warmer than expected. Again, there is the prospect of scooping hydrogen fuel.
Brown dwarf substellar object:
Very strange objects, almost like protostars except lacking the necessary mass and therefore gravitational collapse to initiate fusion of light elements such as hydrogen and helium within its core. Most have been observed only indirectly, although one or two have been detected directly. Most are comprised of hydrogen, helium and large quantities of methane, apparently, and are around 20 to 50 times the mass of Jupiter, the critical mass to initiate fusion is around 80 times the mass of Jupiter.
Thanks to Stuart Wilson for the information on this page.