Jengus IV was the inhabited fourth planet in its star system and homeworld of the Scrubble, a silicate humanoid species. It had at least one moon. Its surface was rocky, with many pinnacles and caves; the latter were occupied by a type of "cave bug".
Believing the remote planet to be uninhabited, in the 24th century the Federation established Outpost 76 on Jengus IV for scientific research. The intrusion of the scientists apparently incensed the Scrubble, who began a conflict in 2381 using psychic mines that turned their victims to stone. Responding to the outpost's distress call, Captain Murakami of the USS Hood was able to broker a tentative peace treaty.
The USS Cerritos and USS Carlsbad subsequently coordinated to relocate the outpost and dispose of the psychic mines. In the course of doing so, their away teams discovered that the conflict between the Scrubble and the scientists had in fact been contrived between them for a scheme to harvest sensitive Starfleet intelligence and sell it on the black market. (LD: "Mining The Mind's Mines")