Geology and ClimateEdit
The Terran Federation used Exbar as a penal colony for Grade 4 offenders, but unlike Cygnus Alpha the inmates had a degree of contact with outside planets, up to and including having visitors from outside.
Roj Blake's uncle Ushton was sent to Exbar, where Blake visited him as a boy. At some point in the next few years the Federation withdrew from Exbar leaving the inmates to fight amongst themselves for food and resources. The population level after a few years reached the point where a single cache of food concentrates was able to feed the entire population.
Travis later went to Exbar in search of Ushton and his daughter Inga, knowing of Blake's affection for them and intending to use them as hostages. He was, as usual, unsuccessful but his visit indirectly resulted in access to a cache of food that would greatly improve living standards on the planet. (B: Hostage)