Another possibility is growing rocks. Rocks that are living creatures, but not like we know them to be. I remember many years ago (4-6) William Rutledge...an astronaut now living in Rwanda spoke about his experience during his Apollo 20 mission. He said he saw yellow living rocks on the abandoned cigar shaped UFO in Deporte crater on the moon. He said they grew in size and a useful liquid chemical came out of them.
NASA urls below.
Scott C. Waring - Taiwan
Photo .5: Sol 1830 left http://marsrovers.jpl.nasa.gov/gallery/all/2/n/1830/2N288828136EFFB000P0625R0M1.JPG