Well... after first shock and a feeling of desolation our space traveller finds out that the rocks are in fact blue cheese. The microbes making that cheese work differently and produce not CO2, but O2.
After communicating this to earth, scientists quickly find out that this could be one solution for the climate change.
The ongoing press releases make markets react and prices for blue cheese rise to astromomical heights.
With money drawn from subscrition warrants on blue cheese finally a very fast rescue operation could be financed.
In the meantime the astronaut has become obese by eating cheese the whole time. As well his olfactory sense has become strange...