Juno 10 was a planet purchased by Jack for its branzine. He imported Halflings to mine the mineral, creating a twenty metre wide hole in the process. He delivered shipments of branzine via rocket ships that launched from the planet.
The Second Doctor, Jamie McCrimmon and Zoe Heriot visited Juno 10 and met Jack, who was pretending to be there to warn visitors of the health and safety risk the hole posed. Zoe persuaded Jack to allow them to inspect the hole but, as they did so, a second hole opened behind the trio and they fell in. Their fall was broken by the slimy ground underfoot and they made their way to Jack's rocket and Zoe bypassed the keypad to gain access. Worried by the danger they posed to his haul, Jack launched the rocket and was startled to find that it exploded in mid flight. The Doctor, Zoe and Jamie had escaped in the ship's ejector seats and confronted Jack as he inspected the wreckage.