Remote Hyperspectral Imaging of Endolithic Biofilms Using a Robotic Probe

Abstract

Many scientists on Earth have concentrated their searches for extraterrestrial life on robotic probes sent to nearby planets and moons. These robotic probes are able to analyze conditions on the planets and transmit data back to Earth. One branch of astrobiology is devoted to duplicating the specified conditions of remote planets and moons on Earth, and identifying the life that survives there under the assumption that similar life might exist elsewhere. Earth analogs for Mars are found in the deserts of Antarctica, and perhaps beneath glaciers, for example. Earth can serve as a useful test bed for robotic probe technology. Cyanobacteria are one of the oldest forms of life on Earth, and similar forms of life may have developed on other planets like Mars as well. NASA has sent several missions to Mars intended to investigate the environment or to search for life, including the Mars Pathfinder / Sojourner mission. While the Pathfinder mission transmitted some of the best data obtained from the Martian surface to date, the long Martian winters and rough terrain limit the amount of data that can be obtained from different locations using a rover that must drive up to a target to sample it. The two Mars Exploration Rovers scheduled to arrive in January 2004 will feature a longer range to search for signs of liquid water. The search for life near locations where water may be intermittently present demands ability to sense life farther from the rover. Hyperspectral imaging can be used to identify astrobiologically interesting sites from a distance. The rover can then drive up to the site and conduct further sampling. The cyanobacterium (a blue-green alga) lives in harsh environments where water is intermittently available. Gloeocapsa produces mycosporine-like compounds that serve as a UV sunscreen and that can be used as a chemical marker for presence of biofilms. In this study, reflectance measurements made by a visible - near-IR / IR imager mounted on a battery-powered robot were used to detect the growth of cyanobacterial colonies on a prepared limestone surface at a distances up to 20 meters.