Derbin and one of its (sub)satellites, Derminmus, seen from an observatory on the surface of Mesbin.

Name: Derbin

Designation: Kaywell A d I

Discovery (Kerbin): Transit.

Rediscovery (Mesbin): Folklore/General Knowledge and Naked Eye Object.

The largest and furthest satellite of Mesbin, and arguably a planet in its own right, Derbin is practically the opposite of Mesbin. While they are both massive terrestrial planets, the similarities end there. Derbin is tidally locked to Mesbin, and so it rotates very slowly over the course of its orbit. Since it was never over-spun, it never lost its thick atmosphere, and retains a dense, reflective cloud cover. The clouds obscure the surface features of Derbin, making it very difficult to map the world, but it is not likely that there exists a particularly friendly environment on the other side of the cloud deck anyway--but who knows? For all we know, a vast planetary rainforest awaits any space probe that braves the journey!

Physical Properties

• Radius = 1,267,600 meters = 0.19896 Earth Radii = 2.1127 Kerbin Radii
• Mass = 5.116 x 10^23 kg = 0.0857 Earth Masses = 9.6683 Kerbin Masses
• Surface Gravity = 2.167 Gee
• Albedo = 0.6
• Rotation Period = 1548189.96 seconds (17 days 22 hours 3 minutes 10 seconds)

Orbital Properties

• Parent Body = Mesbin.
• Semi Major Axis = 259,000,000 meters
• Orbital Period = 1548189.96 seconds (17 days 22 hours 3 minutes 10 seconds)
• Eccentricity = 0.12
• Inclination = 3.7°
• Longitude of Ascending Node = 73°
• Argument of Periapsis = 2°
• Mean Anomaly At Epoch = 289°

Moons

Derbin has two subsatellites or "moonmoons." (Or arguably just, satellites and moons).

• Derminmus: The small chocolate-minty satellite of Derbin, and again quite rich in volatiles.
• Dermun: The larger, dryer, and more geologically complex of the two satellites.

Atmospheric Properties

Derbin kept its primordial atmosphere for the most part, except it did lose almost all of its hydrogen.

Composition:

• Helium: 46%
• Carbon Dioxide: 30%
• Hydrogen: 13%
• Nitrogen: 10%
• Water: 1%

Other:

• Pressure at Sea Level: 7.8 atm .
• Temperature at Sea Level: 100.85° Celsius.
• Greenhouse Effect: 93.88° Celsius.
• Atmosphere Limit: 58,000 meters.

Geology

Spoilers for what's below the clouds...

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Beneath the clouds, Derbin's surface is barren and hot, though there are regions--at high altitudes and latitudes--that it is at habitable temperatures and pressures. The terrain is very much like that of Kerbin and Kerbmun, with continents, mountains, and hills. Derbin has no seas or oceans, other than the clouds of water vapor and steam which cover the scorching lowlands. Occasional hot rains pour from the higher altitude clouds, but there are no permanent bodies of water. In the lowlands, or "Maria," tectonic rifts, trenches, and ridges show the same sort of tectonic evolution that happens underwater on Kerbin and Kerbmun.

Derbin has several quite tall volcanoes as well, many of them likely to be active.