Early release

Centuries ago, the British would transport criminals across the oceans to Australia.
Recently, scientists came up with a plan to transport criminals to the moon.
Well, just the dangerous ones. The ones with life sentences and no possibility of parole.
The prison was automated, with robot guards, hydroponic oxygen and food generation farms, and so on.
The inmates were put to work building a moon colony for future residents.
Do a good job, and you earn a release.
And the plan worked. The colony was completed quickly,
The prisoners were all released… to the cold, airless surface of the moon.