Some scientists in the UK have discovered structures in meteorite fragments which look a hell of a lot like fossilized algae.
These algae are indigenous to the rock....that's alien algae people!!!!
Technology review write up here: http://www.technologyreview.com/view/512381/as…
Original paper here: http://arxiv.org/abs/1303.1845
Fossilized or not, this may be our first real glimpse of an alien life form.