Patatanlis

Mass Effect & Mass Effect 3
Patatanlis is a large rock world, with an unusually thin atmosphere of hydrogen and carbon monoxide. The frigid world's crust contains extensive deposits of uranium, and occasional lodes of naturally occurring plutonium. With a total mass more than four times that of Earth, Patatanlis should have a significantly thicker atmosphere. This unusual feature has flagged it as worthy of scientific investigation, but the need for expensive amounts of radiation shielding has deterred interest.