Seven Marbles (TRAPPIST-1) System - Pre-Colonisation

Red dwarf system 40 ly from Sol

Seven Marbles
Image from The Astronomer
The Seven Marbles system, showing the star, Resonance (TRAPPIST-1)
The Seven Marbles system is a planetary system around a very small and dim red dwarf star known as Resonance (originally known as TRAPPIST-1). This system was colonised in 865 AT by the GAIA-assisted arkship The Maid. This article describes the system as it existed when The Maid and her colonists first arrived.

Seven Marbles (TRAPPIST-1) System - Data Panel

SystemSeven Marbles
PrimaryResonance (TRAPPIST-1)
Location- Distance from Iota: 10.466 ly (J2000)
- Distance from Sol: 40.541 ly (J2000)
StarResonance (TRAPPIST-1)

Physical characteristics:
- Mass: 1.770E+29 kg (0.089 x Sol)
- Radius: 84,180 km (0.121 x Sol)
- Luminosity: 0.000522 x Sol (bolometric)
- Temperature: 2,511 Kelvin
- Spectral type: M8V
- Age: 7.6 billion years
Resonance illuminates the Seven Marbles. It is a solitary late M-type main-sequence star near the lower stellar mass limit. Despite being around 7.6 billion years old, the star rotates quickly, completing one revolution in just 3.3 Terran days, but the star does not produce frequent nor particularly strong flares. Large starspots are common and can cause subtle temperature changes on the planets.

Resonance is surrounded by seven roughly Earth-sized planets linked in a near-resonance chain, and a cold SubNeptunian planet lurks well beyond, separated by a large gap populated by the few asteroids that survived the system's long history.
Senrau, showing the atmospheric currents which transfers heat from one hemisphere to the other.
TRAPPIST 1b Name: Senrau:

Orbital characteristics:
- Semi-major axis: 1,728,000 km (0.011 AU)
- Orbital period: 1.511 days

Physical characteristics:
- Type: Vesperian MesoAzurian Ydratian AquaCytherean
- Mass: 6.074E+24 kg
- Radius: 7,141.9 km
- Density: 3,980 kg/m^3
- Gravitational acceleration: 7.947 m/s^2 (0.810 g)
- Rotation period: Tidally-locked
- Albedo: 0.291
- Average surface temperature: 1,058 K

- Surface pressure: 1.460 GPa
- Composition: 86.9% water, 11.2% carbon dioxide, 1.6% oxygen, 0.2% hydrogen, 0.1% methane, trace amounts of ammonia, neon, and helium
Senrau's large volatile reservoir and high insolation gave it a thick steamy atmosphere dominated by water and carbon dioxide, with trace amounts of other gases leftover from the formation. The planet's dayside was too hot for cloud formation, giving the planet its deep blue color, with minimal haze visible near the edge of the planet disk. On the night hemisphere, where the temperatures were cooler, clouds of sulfuric acid could form, and be brought into the dayside through the leading hemisphere via the planet's rotation. These clouds rapidly dissipate under the heat. Due to the heat and pressure at the boundary between the atmosphere and the rocky layer, the planet's lithosphere was thin, soft, and plastic. Mantle plumes - exceedingly common thanks to induction heating - melted parts of the crust, forming large pools of magma on the surface.
Visne and Reyik
Visne and Reyik
TRAPPIST 1c Name: Visne:

Orbital characteristics:
- Semi-major axis: 2,366,000 km (0.016 AU)
- Orbital period: 2.422 days

Physical characteristics:
- Type: Vesperian Acidian Minervan AquaCytherean
- Mass: 6.904E+24 kg
- Radius: 6,901.2 km
- Density: 5,014 kg/m^3
- Gravitational acceleration: 9.674 m/s^2 (0.986 g)
- Rotation period: Tidally-locked
- Albedo: 0.682
- Average surface temperature: 822 K

- Surface pressure: 46.1 MPa
- Composition: 72.4% carbon dioxide, 18% oxygen, 8.2% water, 1.4% nitrogen, trace amounts of hydrogen, methane, sulfur dioxide, argon, helium, ammonia, neon, and nitric acid
From space, Visne appeared as a featureless cream-colored ball not unlike Venus, but a closer inspection revealed a much wetter and thicker atmosphere. Visne was extremely geologically active thanks to high surface temperature which weakened the crust, and induction heating caused by the planet's interaction with the stellar magnetic field which melted the planet's upper mantle. No mountain on Visne could rise high before their weight depresses the soft crust down, allowing vast basalt flats to dominate the planetary surface. Much of the surface was relatively new as a result. The thick atmosphere and constant surface renewal meant that impact craters were nearly nonexistent.
TRAPPIST 1d Name: Reyik:

Orbital characteristics:
- Semi-major axis: 3,333,000 km (0.022 AU)
- Orbital period: 4.050 days

Physical characteristics:
- Type: Vesperian Hydronian Ydratian AquaAbyssal
- Mass: 1.774E+24 kg
- Radius: 4,994.9 km
- Density: 3,398 kg/m^3
- Gravitational acceleration: 4.745 m/s^2 (0.484 g)
- Rotation period: Tidally-locked
- Albedo: 0.819
- Average surface temperature: 596 K

- Surface pressure: 53.6 MPa
- Composition: 48.7% oxygen, 30.6% carbon dioxide, 19.5% water (vapor), 1.1% nitrogen, trace amounts of hydrogen, methane, argon, ammonia, nitric acid, and neon.
Like Visne, Reyik was featureless when viewed from afar, although the water clouds give it a slightly bluer appearance. Reyik's nightside becomes cold enough to form iridescent ice clouds. Under atmospheric pressure thousands of times higher than the Terran atmosphere, Reyik sports a foggy ocean of compressible water beneath its atmosphere. Although the sea level is not hot enough, deep down the temperature exceeds the supercritical temperature of water and the ocean begins to boil. Bubbles of supercritical water from this layer rises up to the surface, cooling off along the way until they condense back into compressible fluid.
Fulno and Eunna
Fulno and Eunna
TRAPPIST 1e Name: Fulno:

Orbital characteristics:
- Semi-major axis: 4,381,000 km (0.029 AU)
- Orbital period: 6.099 days

Physical characteristics:
- Type: Vesperian Rhean Agonian / Vesperian Rhean AquaGaian (Conlectic Glacial)
- Mass: 4.611E+24 kg
- Radius: 5,797.6 km
- Density: 5,648 kg/m^3
- Gravitational acceleration: 9.155 m/s^2 (0.933 g)
- Rotation period: Tidally-locked
- Albedo: 0.264
- Average surface temperature: 258 K

- Surface pressure: 5.89 kPa
- Composition: 91.4% nitrogen, 5.6% carbon dioxide (vapor), 2.9% argon, 0.1% oxygen, trace amounts of water (vapor), neon, carbon monoxide, and helium.
As a tidally-locked terrestrial planet, Fulno was split into the hot, Mars-like dayside, and the frigid nightside. Nearly the entirety of the nightside was covered in a single gigantic ice cap that stores nearly all of Fulno's surface volatile content, while dried out lakes and rivers dating back to various time periods in the recent past scattered near the terminator on dayside. These features pointed to episodic melting of Fulno's ice cap, which released nearly all of its carbon dioxide, enough to triple the amount of carbon dioxide in the atmosphere, and some water which created brief Gaian conditions. During the intervals, Fulno lacked any surface liquid, but local sandstorms triggered by sublimating carbon dioxide glaciers were common. Although mostly free of clouds, wispy water polar clouds near the terminator at high latitudes were present.
TRAPPIST 1f Name: Eunna:

Orbital characteristics:
- Semi-major axis: 5,765,000 km (0.039 AU)
- Orbital period: 9.206 days

Physical characteristics:
- Type: Vesperian Tholian Rhean AquaThalassic (Tundral)
- Mass: 5.578E+24 kg
- Radius: 6,664.1 km
- Density: 4,500 kg/m^3
- Gravitational acceleration: 8.383 m/s^2 (0.855 g)
- Rotation period: Tidally-locked
- Albedo: 0.217
- Average surface temperature: 276 K

- Surface pressure: 193 kPa
- Composition: 96.6% nitrogen, 3.1% carbon dioxide (vapor), 0.2% oxygen, 0.1% argon, 0.1% water (vapor), trace amounts of ammonia (vapor), methane, neon, hydrogen cyanide, helium, carbon monoxide, and hydrogen
A tholin haze, a feature it shared with its twin planet Matow, obscures much of Eunna's surface features. The only exceptions were the eyes of the twin permanent storms bordering the equatorial wind flow on the dayside. Although it received less than half of Terran irradiance, the planet's atmosphere, almost twice as thick as the Earth's, retained and distributed enough heat to allow a cold ocean of water-ammonia liquid solution to exist on its dayside, while ice sheets formed at the nightside. Oceanic currents and wind created by Eunna's rotation animated the ocean, the ice cap, and the atmosphere. The equator region was constantly in motion as the strong equatorial current dragged icebergs across the circumference, while the glacier sheets at middle latitudes were more stable. At the nightside, the colder temperatures and the calmer winds encouraged organic particles to trickle down from the sky, in a phenomenon called tholin snow.
Matow and Eunna
Matow and Yaudel
TRAPPIST 1g Name: Matow:

Orbital characteristics:
- Semi-major axis: 7,013,000 km (0.022 AU)
- Orbital period: 12.354 days

Physical characteristics:
- Type: Vesperian Tholian Rhean CapnoArean (Tundral) + AquaGanymedean
- Mass: 6.856E+24 kg
- Radius: 7,313.9 km
- Density: 4,183 kg/m^3
- Gravitational acceleration: 8.554 m/s^2 (0.872 g)
- Rotation period: Tidally-locked
- Albedo: 0.221
- Average surface temperature: 223 K

- Surface pressure: 133 kPa
- Composition: 98.5% nitrogen, 1.2% carbon dioxide (vapor), 0.2% argon, 0.1% carbon monoxide, trace amounts of oxygen, methane, neon, hydrogen, helium, and ammonia (vapor).
Beneath the tholin haze, Matow, whose surface was completely frozen, offered a different scenery from Eunna. Its ice shell was varied in thickness. On the dayside, the crust was as thin as a few kilometers, while on the nightside it was usually tens of kilometers thick. Matow experienced the strongest tidal stressing of all seven inner planets, serving to fracture the icy crust. Convection within the subsurface ocean dragged plates around, creating plate tectonics, which resulted in a large number of rifts, faults, mountain ranges, and most spectacularly, cryovolcanoes. Matow's tectonic activities were most prominent on the dayside, while the nightside, although somewhat less active, possessed the glacial equivalent of supercontinent cycles, each cycle lasting between a few centuries and millennia. Similar to Eunna, tholin snow occured on Matow's nightside.
TRAPPIST 1h Name: Yaudel:

Orbital characteristics:
- Semi-major axis: 9,265,000 km (0.062 AU)
- Orbital period: 18.768 days

Physical characteristics:
- Type: Vesperian Rhean CapnoChionian (Tundral) + AquaGanymedean
- Mass: 1.977E+24 kg
- Radius: 4,924.8 km
- Density: 3,951 kg/m^3
- Gravitational acceleration: 5.440 m/s^2 (0.555 g)
- Rotation period: Tidally-locked
- Albedo: 0.259
- Average surface temperature: 161 K

- Surface pressure: 14.7 kPa
- Composition: 98.1% nitrogen, 1% argon, 0.7% carbon monoxide, 0.2% carbon dioxide (vapor), 0.1% neon, trace amounts of methane (vapor), hydrogen, oxygen, and ammonia (vapor)
Yaudel was a smaller and colder version of Matow, although these two factors set it apart from the bigger planet. Its tholin haze was thin enough that features on the surface could be observed in visible light, although slightly blurred. Unlike its bigger sibling, Yaudel's ice shell was thick and stagnant, with few fractures mainly caused by tidal stressing and impacts. Low internal heat meant that its subsurface ocean was not nearly as active as Matow's, further discouraging any sort of tectonic activity. The atmosphere on Yaudel was cold enough that nearly all carbon dioxide was locked in glaciers in night side lowlands and basins. Being even colder and with calmer winds, haze precipitated at the night side. Tholin dust storms fueled by subliming glaciers were a common phenomenon on Yaudel capable of depositing organic particles on the dayside, dyeing the whole planet reddish.
Asteroid zoneThe Resonantine Gap:

Total mass: 4.727E20 kg
Much of the remaining asteroidal mass that survived the system's old age orbits in the large expanse of space between Yaudel and Maria's orbits, commonly known as the Resonantine Gap. The largest asteroids are no more than a hundred kilometer in diameter. Most asteroids in this region are carbonaceous with large fractions of volatiles, becoming more common further from the star, while some siliceous asteroids orbit closer to the star. It is possible for some of the outer volatile-rich objects to encounter Maria, sending them towards the star and becoming comets, although there are few and short-lived, forming a small fraction of comets in the Seven Marbles system.
Maria and Selene
Maria and Serene
TRAPPIST 1h Name: Maria:

Orbital characteristics:
- Semi-major axis: 264,639,000 km (1.769 AU)
- Orbital period: 7.886 Julian years
- Eccentricity: 0.017

Physical characteristics:
- Type: CryoNeptunian YmirJotunnian
- Mass: 3.562E+25 kg
- Radius: 16,560.2 km
- Density: 1,872 kg/m^3
- Gravitational acceleration: 8.668 m/s^2 (0.884 g)
- Rotation period: 55,577 s (15.438 hr)
- Albedo: 0.278
- Average temperature (1 bar): 61 K

1) Serene: Type: Apnean, Semi-major axis = 204,169 km, Orbital period = 4.351 days, Eccentricity = 0.000, Inclination = 2.075°, Mass = 3.538E+21 kg, Radius = 749.4 km, Albedo = 0.326
Maria is the largest planet in the Seven Marbles system, although it is on the smaller side of the planets of its type, weighing in at measly 6 times Earth's mass. It is a typical CryoNeptunian planet, with few streaks of frozen clouds floating over a deep blue globe.

Its largest satellite, Serene, is the ice giant's sole spherical satellite. Due to the lack of perturbing bodies with significant gravity, its orbital eccentricity dropped to nearly zero. With the diminishing eccentricity comes reduced tidal heating, and the moon quickly cooled down, becoming geologically dead within a hundred million years.
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Development Notes
Text by The Astronomer, Dangerous Safety
Additional material by Steve Bowers
Initially published on 03 June 2020.