We aim to provide crucial Earth analog setting methane flux data, as the scientific community explores patterns and constraints on Martian methane. We will: (1) quantify methane gas flux from the land surface at a weathered ultramafic landscape in northern California, USA; (2) measure concentrations of dissolved methane, acetate, and formate in related groundwaters; (3) constrain spatial differences in methane dynamics across the field area footprint through time; and (4) complete microbial membrane lipid profiling work on priority subsurface region to determine whether or not a significant biological methane ‘filter’ is at work in this setting. We will conduct this work in cold and warm seasons to detect seasonal variation and assess aqueous geochemical conditions that may play a role in methane escape from the deeply sourced groundwater system active at the target field locale. We will resolve methane flux and shifts in aqueous carbon species’ abundances to fill a gap in the scientific understanding of methane dynamics in natural ultramafic rock systems on Earth, and make comparisons to sites of extraterrestrial serpentinization more robust.