Devan Nisson¹, Thomas L Kieft², Oliver Warr³, Clifford C Walters⁴, Esta van Heerden⁵, Errol Duncan Cason⁶, Julio Castillo Hernandez⁷, Jan-G Vermeulen⁷, Barry M Freifeld⁸, Hiroshi Ogasawara⁹, Raymond J Durrheim¹⁰, Barbara Sherwood Lollar¹¹, Bennie Liebenberg¹² and Tullis C Onstott¹³, (1)Princeton University, Princeton, NJ, United States, (2)New Mexico Institute of Technology, Department of Biology, Socorro, NM, United States, (3)University of Toronto, Department of Earth Sciences, Toronto, ON, Canada, (4)ExxonMobil Research and Engineering Company, Annandale, NJ, United States, (5)North-West University, Mahikeng, South Africa, (6)University of the Free State, Department of Microbial, Biochemical and Food Technology, Bloemfontein, South Africa, (7)University of the Freestate, Department of Microbial, Biochemical and Food Technology, Bloemfontein, Free State, South Africa, (8)Lawrence Berkeley National Laboratory, Berkeley, CA, United States, (9)Ritsumeikan University, Kusathu, Japan, (10)University of the Witwatersrand, School of Geosciences, Johannesburg, South Africa, (11)University of Toronto, Earth Sciences, Toronto, ON, Canada, (12)Independent Consultant, Orkney, South Africa, (13)Princeton University, Department of Geosciences, Princeton, NJ, United States