Niven is the third planet in the Ciro system and a member of the Galilean Planets. It is the seventh largest of eleven planets. Niven’s orbit brings it closer to Gael than any other planet, making it the easiest to reach in terms of delta-V expenditure.
"The beautiful orange sky here made mouths water on first observation. Kerbalkind knows that since it's closer to the star it's going to be a little warmer outdoors than anyone is accustomed to on Gael."
- Deep Sky Press
Although Niven has only 2/3 Gael’s radius, both planets have about the same total land area (approx. 2 million square kilometers). Niven’s surface is characterized by darkly colored lowlands, at elevations generally below 2,000 meters, and lightly colored terrain at higher elevations. The mean ground elevation is approximately 3,900 meters.
The dark lowland terrain comprises three biomes – Lowlands, Nivenean Trench, and The Drag. Together these biomes cover about 25% of Niven’s surface. They consist of mostly flat or slightly undulating terrain, though with an occasional mountain peak rising from the basin floor. The floor of The Drag is the point of lowest elevation on Niven (0 m). At the lowest elevations the ground is black.
The lightly colored high ground consists of a diversity of terrain types, ranging from plains, to hills, to mountains. The four largest biomes covering this area are Midlands, which covers about 40% of Niven’s total land area, Upper Plains (15%), Varicose (10%), and Sears (6%). The Midlands are mostly hilly or mountainous terrain, with a significant number of craters. The highest summits on Niven are found here (over 7,000 m). The Upper Plains are vast regions of flat or undulating terrain with some low hills. The Varicose are areas of large hills, often arranged in formations resembling a network of veins when viewed from high above. Sears are apparent scar areas, discolored with a dark border, consisting mostly of hilly terrain.
The remaining biomes are Crater Strain (a heavily cratered region), Poles (both north and south), and Ohio Spiral (a cold dusty desert covering the north pole, affectionately described by one kerbal astronomer as a giant fingerprint).
Niven has a thin, warm atmosphere composed mostly of Carbon Dioxide (88%), with a lesser amount of Nitrogen (6%) and other gases. The air pressure ranges from 0.12 to 0.05 atmospheres between Niven’s lowest and highest surface elevations. Of the twelve bodies that possess atmospheres, only the planet Hox has a lower air density at its surface. Niven likely had a thicker atmosphere in the past, but because of the planet’s low gravity and the presence of a strong solar wind, the once thick atmosphere was slowly stripped away.
Niven’s global temperature is listed as 52°C (325 K), but this is the theoretical mean taken at the planet’s datum. Since the mean surface elevation lies well above the datum, the actual globally averaged surface temperature is about 35°C. Niven’s hottest temperatures are found on the floor of The Drag near the equator. Here the mean daily temperature ranges from 33°C at night to 94°C during the day. The temperature at the poles averages -3°C. Temperature decreases by an average of about 4°C for every kilometer rise in elevation. Because Niven has a slightly inclined and elliptical orbit, it experiences a small seasonal temperature variation.
Niven’s surface has a low thermal inertia, meaning it heats up easily by day and cools off quickly at night. This produces a natural convection current in which air heated by the hot surface rises at the equator, flows poleward, descends at mid-latitudes, and then flows back toward the equator along the ground. As the air moves toward the equator, the Coriolis Effect deflects it toward the west. This generates winds blowing toward the equator out of the northeast in the northern hemisphere and out of the southeast in the southern hemisphere.
Niven likely had liquid water on its surface in the distant past, but over time the water evaporated and either escaped the atmosphere or was broken down by photo-dissociation. The water eventually disappeared, leaving Niven the dry planet it is today.
To be added.
Niven has 10 natural biomes:
- Upper Plains
- Crater Strain
- Nivenean Trench
- The Drag
- Ohio Spiral
- The Ohio Spiral provides a very large playground for low altitude vessels that can operate at length in Oxygen-less atmosphere.
- The Drag and Nivenean Trench both contain flat equatorial areas perfect for landing in and deploying an off-world base.
- In early versions of GPP, Niven had lakes near its poles. However, these were removed in version 1.0.2 after it was determined Niven’s atmosphere is too thin to support them.
- The Ohio Spiral is named after one of the mod’s developers.
- At first glance Niven is a Venus analog, but it also holds points for sharply resembling Titan, especially while it still had polar lakes.
Alongside Leto, Niven is a would-be parent body without a discrete flag and must share the flag of its neighbor. It may fall under the Gaeo Tao flag associated with Gael concerning their shared orange color.