Pluto

The outer edge of the system, with a wisp of nitrogen for an atmosphere, one moon, and a radio problem no dish solves.

The numbers

These are the figures the map's card shows when you hold your finger on Pluto, plus the two speeds that decide what a flight there costs. Low orbit speed is how fast you must be going, sideways, to stay up just above the surface. Escape speed is how fast you must be going to leave altogether. Sphere of influence is how far Pluto's pull reaches before something bigger takes over.

Stationary orbit is the height where one trip round takes exactly one of the world’s days, so a ship there hangs over the same spot on the ground. See Stationary orbits.

What it is made of

What the world is built from. It is not something a ship measures, but it is why the ground looks and behaves as it does — an ice moon takes an impact differently from an iron one.

The air

Nitrogen, at roughly a hundred-thousandth of Earth's pressure and 44 K. It is thin enough to do nothing to a lander and real enough that the world has air bands to survey, which no other world this small has.

Pressure falls off as you climb: every 9,912 m of height, there is half as much air around you. A Barometer reads that fall directly, and a Thermometer reads the cooling beside it — 0.4 K for every kilometre, until the air bottoms out at 38 K (−235 °C) and stops getting colder.

What the air is made of

The mix changes with height. Each column is a measured level; between two of them the game blends one into the other, and above the top one there is nothing left to breathe. A Mass Spectrometer reads this table itself: its figure is the mean molar mass of the mix where the reading is taken, and beside it the line names the biggest gases it found. See the Mass Spectrometer.

The ground

Pluto's surface is divided into biomes — bands running round the world, each with its own colour, its own typical height and its own roughness. Which one you come down in is recorded in your flight log, and the first reading taken in each one pays.

Where is the band's place round the world, in degrees from the world's own 0°, running out to ±180° on the far side. Typical height is where that biome's ground sits against the datum the map measures altitude from, and roughness is how far it wanders either side of that.

On the map Pluto is drawn from a painted picture, and the five biomes are its five sectors, 72° each: the dark red-brown Dark Belt faces 0°, the white Ice Mountains and the Cratered Uplands run round one side, and the pale Nitrogen Plains and the bright Heart, the smoothest ground on the world, round the other. The colour under you as you come down is the colour of that sector.

Named landforms

Pluto's ground is drawn from a table of named features rather than noise alone, as every world you can stand on is. Where you come to rest is recorded by name, which is why some achievements ask for a summit, a crater floor or a plateau rather than just a landing. All 9 of them are below, in order round the world, from the far side back to 0° and on round.

Where is the landform's place round the world, and height is how far it stands above (or below) the ground around it. Flat ground is the level run it promises — the width of the ledge, floor or summit a ship can set down on.

Its moons

One moon goes round Pluto, inside its sphere of influence. It has a sphere of its own, and reaching it is a small transfer inside the big one.

Getting there

Radio is what stops you here, not fuel. The best dish and the best Comm Station each reach 500.00 Gm, and Pluto's orbit is wider than that, so a ship with nobody aboard arrives out of touch unless a relay is parked where the geometry helps. A crew needs no link at all. Reaching its sphere of influence pays Pluto Is a Planet.

What a ship leaving Earth's pad needs, in total change of speed, to do each of these:

What it pays

Every place nobody has measured before pays discovery the first time an instrument reads it, and how much depends on how far from home the world is. Pluto counts as 6.00 against Earth's 1.00, so every place on it pays that many times what the same place at home would.

A place is a world, a band of altitude and — on the ground — the biome you are standing in, and each instrument surveys each place separately. Science and readings explains the whole of it.

What it pays out for

One achievement names Pluto: Pluto Is a Planet.

The full list, with what each one pays, is on the Achievements reference.