THIS PROPOSAL WILL LEVERAGE KNOWLEDGE OF BEHAVIOR OF LIFE IN DUNES ON EARTH TO ANSWER THE QUESTIONS ABOVE BY CONDUCTING A QUANTITATIVE TERRESTRIAL FIELD EXPERIMENT IN A US DUNE FIELD. IN TASK 1 WE WILL MEASURE THE FOLLOWING ENVIRONMENTAL CONDITIONS AT FOUR DISCRETE DEPTHS WITHIN FOUR DUNES: TEMPERATURE MOISTURE GRAIN SIZE NITROGEN OXYGEN AND TOTAL ORGANIC CARBON. DISCRETE LAYERS WILL BE DETERMINED ON SITE USING GROUND PENETRATING RADAR. FOR TASK 2 WE WILL ESTABLISH A MORE NUANCED MEASUREMENT OF HABITABILITY WITHIN THE DUNE INTERIORS BY EXAMINING NOT ONLY BACTERIAL ABUNDANCE BUT ALSO METABOLIC ACTIVITY AND GENE EXPRESSION. GENOMIC METABOLOMIC AND METATRANSCRIPTOMIC ANALYSES WILL BE PERFORMED ON SAMPLES PROCURED ALONG WITH THE MEASUREMENTS OF TASK 1. THIS INFORMATION IS CRITICAL TO INTERPRETING THE RELATIVE IMPORTANCE OF THE ENVIRONMENTAL CONDITIONS MEASURED IN TASK 1. FOR TASK 3 WE WILL DETERMINE CORRELATIONS BETWEEN THE ENVIRONMENTAL AND BIOLOGICAL FACTORS AND VARIANCE OF THAT CORRELATION WITH DUNE INTERIOR POSITION OR POSITION IN THE DUNE FIELD. THESE RESULTS WILL SPECIFICALLY INFORM THE DESIGN AND INTERPRETATION OF FUTURE MEASUREMENTS I.E. ESTABLISHING HOW REPRESENTATIVE A SHALLOW SAMPLE OR SAMPLE AT THE EDGE OF A DUNE FIELD IS OF THE ENTIRE DUNE OR THE ENTIRE DUNE FIELD. OUR PROPOSAL DIRECTLY RESPONDS TO THE HABITABLE WORLDS SOLICITATION AS OUR RESULTS WILL IMPROVE SCIENTIFIC UNDERSTANDING OF HOW IN SITU MEASUREMENTS AT ANALOG SITES CAN [...] IMPROVE OUR UNDERSTANDING OF THE POTENTIAL FOR THE ENVIRONMENT TO SUPPORT LIFE ELSEWHERE. OUR FINDINGS OF HOW ENVIRONMENTAL AND BIOLOGICAL FACTORS VARY WITHIN A DUNE AND BETWEEN DUNES OF THE SAME FIELD WILL HAVE IMPLICATIONS FOR SAMPLING STRATEGIES AT MARS OR TITAN. FURTHERMORE BY TYING THE ENVIRONMENTAL FACTORS TO DIFFERENT ASPECTS OF BIOLOGICAL ACTIVITY WITHIN DUNE INTERIORS WE WILL DETERMIN[E] PROCESSES AND CONDITIONS THAT CREATE AND MAINTAIN HABITABLE ENVIRONMENTS PROVIDING NEW INSIGHT FOR INVESTIGATING DUNES AS TARGETS FOR THE POSSIBILITY OF EXTANT LIFE BEYOND THE EARTH.