Mars Mission is a subtheme of LEGO Space theme, which debuted in August 2007, and ended in 2009. There were 17 sets made in the theme.
The Humans are a group of astronauts that have come to Mars in search of green energy crystals found on the Martian surface. In the storyline they are using them to power their futuristic devices, unfortunately for them the Aliens want them too. The Human structures consist of two colors, orange and white. There are a range of astronaut members in the Mars Mission line, according to LEGO Battles, they are led by Biff and Gemm.
The aliens have came from an unknown place in the universe, also searching for the crystals, they are not from Mars (according to the LEGO magazine and LEGO battles). The aliens themselves are transparent green and glow in the dark. Alien Commanders are the leaders of the alien army. The aliens are shown to live in underground hives. In 2008, it appeared that the aliens have been found, and the hives were destroyed. According to LEGO Battles, there is an Alien Queen. The alien queen has looks like an alien commander, but her legs are the same as a Spy Clops.
LEGO revived an older, forgotten feature in this new theme. The pump system, which was pioneered in one of the previous space ranges Life on Mars. In Mars Mission, it is white and orange, instead of the purple, tan, and other rare colors or Life on Mars.
The crystals are one of the main reasons that the Humans and Aliens came to Mars. Both races wish to use these crystals for power sources, which can be used to supply energy to all of their respective vehicles and other systems. These energy crystals are similar in function to those of Life on Mars.