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Pax Abyssi

Science // Arid worlds

Arid worlds, Mars and its kind

Rocky planets with thin, dry air, the kind Mars is, and the most numerous planets you can land on in Pax Abyssi. Each is built from its own science: its terrain from its type, its caps from its own temperature, its tint from its own albedo, and ground you can walk on to the horizon.

01 // In flight

Arid worlds as you see them from orbit

In the game2,195 planets, all landable

Frames from the game, the HUD off, each planet lit by its own star at its true colour. Select a frame to see it full size.

An orange planet half lit on the right, pale salt pans in its basins and a dark channel winding down towards them, open full size
HYG 11971 I at 77 Ceti, an evaporated ocean. Salt lies in the deepest basins where the last water dried, old shorelines ring them, and channels run downhill into the pans.
In-game capture, pre-alpha, HUD off
Mars half lit on the right of the frame, a great round shield volcano standing on the line between day and night near the top, open full size
Mars at half phase, a shield volcano of the Tharsis rise on the terminator. Mars is the one arid world drawn from its own layout: the old southern highlands, Tharsis and its shields, Valles Marineris, Hellas and the caps.
In-game capture, pre-alpha, HUD off
A rust-red planet on the left of the frame, lit from the right, with a crater in a bright rayed halo and a broad pale basin in a darker collar below it, open full size
HYG 27941 II, a rust plains world at 500 K: hematite-red dust, a crater in a bright halo of ejecta and a wide basin floored with dust.
In-game capture, pre-alpha, HUD off
A grey-brown planet half lit, its surface packed with craters, a bright rayed crater low on the left, open full size
HYG 110366 II, a cratered highland: an old crust saturated with craters, as the Moon's highlands are, with a young rayed crater near the limb.
In-game capture, pre-alpha, HUD off
A pale ochre planet half lit, faint rings of buried craters showing through a smooth mantle of dust, open full size
HYG 85166 I, an ochre regolith world. A mantle of pale dust lies over its craters, and their rims show through as faint rings.
In-game capture, pre-alpha, HUD off
A small half-lit orange planet with tan smudges of haze across its rust ground, against the stars, open full size
HYG 56940 II at 3 Draconis, a hot clouded rust desert: 593 K under half a bar of carbon dioxide. The tan smudges are dust haze, about a third of its sky.
In-game capture, pre-alpha, HUD off
02 // Two kinds of air

Thin and clear, or clouded with dust and ice

The science sorts arid worlds by their air first. Thin air leaves the ground bare to the sky; a few tenths of a bar is enough for cloud, haze and storms.

Thin air

0.0005 to 0.12 bar

1,408 planets with Mars's kind of air, carbon dioxide, most of them at a few millibar: too thin for liquid water to last and too thin to hide the ground. Their colour is the rock's and the dust's: rust, ochre, grey-brown or near-black basalt.

Clouded

0.02 to 0.8 bar

786 planets with enough air for weather. The cool ones grow water-ice cloud and polar caps. The hot ones, above about 500 K, never see frost, and what veils their ground is dust.

Mars

6 millibar

Sol IV at its true radius of 3,389.5 km, built from its own layout. Land at the foot of the Olympus Mons scarp, among the hills of Gale crater, on the ice in Korolev crater or at the rim of Coprates Chasma.

In the game11 terrain templates and MarsIn the gamecaps from each planet's own temperatureIn developmentthe dust haze seen from orbitIn developmentevaporated oceans across the galaxyPlannedcaps that grow and shrink with the seasons
03 // Every planet its own

A terrain from its type, the rest from the planet

An arid world takes its terrain from its type. Eleven templates, one for each terrain, hold the ground: the craters and basins, the dune fields, the shields and lava flows, the salt pans and old shorelines. Each planet wears its terrain at its own true radius, turned to a heading of its own, so no two rust plains worlds show you the same face.

Then the planet's own numbers dress it. Its brightness follows its measured albedo, which runs from 0.12 to 0.25 within a single type. On the hottest thin-air worlds, above about 600 K, the iron oxides in the dust bake to hematite and the ground turns redder.

No arid world has open water. Below about 6 millibar, ice that warms turns straight to vapour and liquid water cannot last. Where a world once had a sea, the game draws what the sea left: salt in the deepest basins, shorelines where the water stood, and the channels that fed it.

The ice comes from the planet. A thin-air world colder than 320 K wears polar caps sized by its own surface temperature: at 180 K they reach down to about 66 degrees of latitude, and at 300 K only a small cap is left near the pole. The north and south caps differ, as Mars's do. Each stands as a layered plateau 0.5 to 3 km thick, ringed by frost and pitted where the ice has turned to vapour. 513 of the 1,408 thin-air planets are cold enough to wear them.

There are 2,194 arid planets around the catalogue stars, in 1,415 systems, and you can land on every one of them, and on Mars.

04 // Every look

17 looks, sorted by terrain

In the game17 looks in the game

Eleven terrains and Mars. The polar-ice looks are the same terrains under their caps, which a planet wears when it is cold enough.

In Pax Abyssi: every sphere is the game's own frame of a planet wearing that look, from its fast-travel stop 40 degrees from its star. Hover or focus a tile for its name.

  • In the game
  • In development
  • Planned

Rust and ochre plains

4 looks · 4 in the game

The commonest arid worlds: a few millibar of carbon dioxide over dusty plains. Rust plains are hematite red with big haloed craters and dust-floored basins; on ochre regolith a pale mantle of dust buries the old relief. Below 320 K each wears polar caps sized by its own temperature.

  • Rust plains, arid world TAW-RD-RP: Hematite-red plains, big craters in grey haloes, dust-floored basins. 238 planets. In the game.TAW-RD-RP
  • Ochre regolith, arid world TAW-RD-OR: A pale ochre dust mantle over buried craters, a few dark windows. 262 planets. In the game.TAW-RD-OR
  • Rust plains with polar frost, arid world TAW-PI-RI: The rust plains under caps pitted by sublimation. 75 cold rust plains planets. In the game.TAW-PI-RI
  • Ochre regolith with thin frost, arid world TAW-PI-OI: Ochre dust under a thin frost cap. 90 cold ochre planets. In the game.TAW-PI-OI

Cratered highlands

4 looks · 4 in the game

Old crust that has kept every impact: grey-brown ground saturated with craters, multi-ring basins and rayed young craters. The ancient crust is the same ground older and softer, its rims rounded and its crater floors dark. The commonest arid type in the catalogue, and the coldest.

  • Cratered highland, arid world TAW-CH-CH: Dark grey-brown, crater on crater, rayed young craters. 364 planets. In the game.TAW-CH-CH
  • Ancient crust, arid world TAW-CH-AC: Warm brown, soft rounded rims and dark crater floors. 352 planets. In the game.TAW-CH-AC
  • Cratered highland with polar ice, arid world TAW-PI-CI: The highland under thick clean caps. 148 cold highland planets. In the game.TAW-PI-CI
  • Ancient crust with polar ice, arid world TAW-PI-AI: The ancient crust under its caps. 128 cold ancient crust planets. In the game.TAW-PI-AI

Volcanic basalt worlds

2 looks · 2 in the game

Near-black lava sheets, broad shield volcanoes and fans of tephra, with few craters because the lava is young. They hold more air than the other thin arid worlds, a median 36 millibar.

  • Volcanic basalt, arid world TAW-VB-VB: Dark lava sheets, shield volcanoes, tephra fans. 192 planets. In the game.TAW-VB-VB
  • Volcanic basalt with polar ice, arid world TAW-PI-VI: The shields and flows under polar caps. 72 cold basalt planets. In the game.TAW-PI-VI

Evaporated ocean

1 look · 1 in the game

A world that once had a sea and lost it. The water went in stages, so the old shorelines stand at the levels it fell through, salt lies in the deepest basins, and channels run down into the pans. Most of the low ground is old sea floor, smooth and nearly free of craters.

  • Evaporated ocean, arid world TAW-EO-EO: Salt pans in bathtub rings, old shorelines, channels. HYG 11971 I at 77 Ceti. In the game.TAW-EO-EO

Clouded arid worlds

5 looks · 5 in the game

Deserts under 0.02 to 0.8 bar of carbon dioxide, a median 0.35 bar: enough air for weather. The cool ones carry water-ice cloud and polar caps. Above about 500 K there is no ice at all, and the veil is dust.

  • Clouded rust desert, arid world TAC-RD-SD: Muted rust under water-ice cloud, a great canyon and volcanoes. 185 planets. In the game.TAC-RD-SD
  • Clouded basalt highland, arid world TAC-BH-SD: Dark basalt plateaus over rust lowlands, long rifts, thin frost. 174 planets. In the game.TAC-BH-SD
  • Clouded ochre dust, arid world TAC-OD-SD: Ochre sand seas and mesas under amber haze, small caps. 169 planets. In the game.TAC-OD-SD
  • Hot clouded rust desert, arid world TAC-RH-SD: Rust from pole to pole under dust haze, no ice. 123 planets. In the game.TAC-RH-SD
  • Hot clouded ochre dust, arid world TAC-OH-SD: Ochre sand seas and yardangs under dense dust haze, no ice. 135 planets. In the game.TAC-OH-SD

Mars

1 look · 1 in the game

The one arid world drawn from its own layout rather than a template: the southern highlands and the northern lowlands, Tharsis and its shields, Valles Marineris, Hellas, and Mars's own caps, at its true radius of 3,389.5 km.

  • Mars, arid world MARS: Sol IV, the real one. In the game.MARS

Rocky worlds smothered by thick air are greenhouse worlds; those hot enough for their rock to melt are lava worlds; airless and icy ones are on barren and ice worlds.

In the wikiArid worldDry habitable worldAtmospheric escapePlanet classification
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