1. The world’s most famous travertine terraces, in Pamukkale, Turkey http://www.aksityayincilik.com/turkphto2.htm

2. Photo by Larry Ulrich Mammoth hot springs at Yellowstone National Park Bruce Fouke and Nigel Goldenfeld’s group at the University of Illinois at Urbana-Champaign are studying whether or not microbial metabolic activity plays a significant role in the deposition of these travertine terraces by the degassing of CO 2. Can we use observation of certain geological structures to infer the existence of microbial life? On Earth? On Mars?

4. Angel Terrace VentApron and channel Ponds Proximal slope Distal slope Bacteria Bruce Fouke and Nigel Goldenfeld biocomplexity group at University of Illinois at Urbana-Champaign

5. ~ 10 cm Threads of microbes, encrusted with aragonite Bruce Fouke and Nigel Goldenfeld biocomplexity group at University of Illinois at Urbana-Champaign