> The remaining eight mice are euthanized and preserved (formalin, ethanol or MELFI) for return to Earth to be weighed in order to ensure the mice have not lost weight over the course of their stay aboard the Rodent Habitat which will confirm that the supply of water and food was sufficient.

At first I thought "shouldn't you weigh them before altering their weight with preservatives?" but then I remembered that this is in a zero-g environment, making weighing mice a bit more difficult than on Earth. Maybe a "space scale" measuring inertial mass instead could work?