Structural and biological analysis of faults in basalts in Sheepshead Mountains, Oregon as an Earth analogue to Mars

Abstract

Endoliths and chasmoendoliths, organisms that live in rock fractures, rely on connected open spaces in rocks for fluid and nutrient circulation on Earth and perhaps other planetary bodies. These life forms are not visible from orbit or easily detectable by rover cameras, but the fracture networks and scarp morphologies associated with fracture networks are measurable. We conducted a field analogue study of 92 normal fault scarps in the Sheepshead Mountains, Oregon to examine the correlation between scarp morphology and vegetation growth in the Steens Basalt of the Columbia River Flood Basalts. While vegetation is not expected on Mars or other bodies, the fracture networks that sustain vegetation are the same that would support and protect endoliths. Structural variables measured in the field are: percent of fault scarp that is fault surface and talus surface, scale of columnar jointing, consistency in location of columns, talus size and sorting, fault lengths, distance to hot springs and playa lakes, and strike and dips of fault surfaces, talus surfaces, and flow bedding. Infrared spectra of fault scarps were measured using a handheld multispectral camera and Normalized Difference Vegetation Index (NDVI) were calculated from these images in ArcGIS™. Statistical analysis of the scarp morphologic parameters indicate that interconnectedness of fractures is key for elevated NDVI and is represented by a range of parameters including bedding strike, talus sorting, and proximity to playas. Results support a model for ideal slopes to investigate for preserved biological activity on Mars.