Analysis of Candidate Mars Analog Sites in the Equatorial Alpine from Orbital Infrared Data

We propose that equatorial alpine regions on Earth may represent a valuable Mars analog environment for several reasons. Nearer to the equator, seasonal variations in temperature are minimal, and at high elevations, conditions can persist below the freezing point of water year-round. These regions tend to host alpine glaciers, many of which have been retreating in recent decades. Although these regions may not reach the extreme cold of modern Mars, the consistently sub-freezing temperatures should limit the amount of liquid water available, as sublimation may be a more dominant process than melting. We have identified several candidate sites, where high elevations coupled with fairly low annual precipitation may represent viable Mars analog environments. These are Pico de Orizaba, Mexico (19.0°N, 97.3°W); Nevado Siula Grande and Yerupajá, Peru (neighboring peaks near 10.3°S, 76.9°W); and Illimani, Bolivia (16.6°S, 67.8°W). Using infrared data from multi- and hyper-spectral orbital instruments, we characterize each summit area by mapping (1) glacier extents, (2) soil/bedrock composition, and (3) estimated land surface temperatures (LST). Glacier extents and LST are derived from multispectral imagery (Enhanced Thematic Mapper Plus [ETM+] on Landsat 7 and the Operational Land Imager [OLI] and Thermal Infrared Sensor [TIRS] on Landsat 8). For glacier mapping, we use the ratio of the panchromatic and short-wave infrared bands to identify regions of glacier retreat. LST is estimated from thermal infrared imagery using simple atmospheric corrections and surface classifications derived from the Normalized Difference Vegetation Index (NDVI). Multispectral surface mapping of the summit at Pico de Orizaba has revealed two primary regions of glacier retreat and several locations where soil temperatures persist at <-10°C year-round. In addition, we have identified images from the hyperspectral Hyperion instrument on the now-decommissioned Earth Observing 1 spacecraft (EO-1) that will be used to characterize the composition of these summits (or nearby areas depending on data availability), including soil and bedrock properties. Once the mapping of all three candidate regions is complete, we will assess each as a Mars analog based on soil/bedrock compositions and surface temperatures.