Episode 85 of The Trigan Empire
aka De maan Gallas II (Dutch title)
The Moon Gallas II (Dutch title, translated)
Written by Ken Roscoe
Illustrated by Gerry Wood
Alien Mission was originally published in 12 instalments in issues 1028 (21 November 1981) to 1039 (6 February 1982) of Look and Learn magazine.
To date it has not been reprinted in English.
Plot summary (Dutch)