Practicing on Earth

Called the Earth-Mars Cave Detection Program, the project is preparing to enter phase 2, during which scientists will test their approach in "Mars analogue" sites, terrestrial environments with similarities to Martian landscapes. These sites will include dry, blistering deserts, such as the Mojave in California and the Atacama in Chile, as well as frigid environments like Iceland and Antarctica.

During the first phase of the project, the researchers acquired the thermal signatures of a dozen caves in Arizona and New Mexico using an experimental infrared detector flown aboard an airplane, called the Quantum Well Infrared Photodetector (QWIP), as well as data collected on the ground using a handheld thermal camera.

Cave detection using QWIP works by spotting regions in the landscape where temperatures are different from the surroundings. Inside a cave, temperatures are nearly constant due to lack of sunlight. Outside, temperatures fluctuate with the rising and setting of the Sun. At a cave entrance, these two temperature regimes mix together to create a unique thermal signature that, depending on the time of day, can be either warmer or cooler than the surrounding environment.

"The caves show up as hotspots in a sea of cold, or as cold spots in a sea of warmth," said study team member Murzy Jhabvala, chief engineer of the Instrument Systems and Technology Center at NASA's Goddard Space Flight Center.

The data, still being analyzed, look promising. In one series of images, the researchers snapped thermal images of Xenolith Cave in New Mexico over a 24-hour period. The cave opening can be seen clearly in some of the images.

"It jumps out at you," said Jut Wynne, a biospeleologist (cave biologist) with the U.S. Geological Survey and Northern Arizona University. "It lights up like a Christmas tree in the predawn and in the late-night shots. It's a bit more ephemeral during the day shots."

In Phase 2, the researchers will tweak their technique to figure out the best wavelengths to use and optimal times during the day for cave hunting. "In so doing, we're going to take these applications and then apply them to an orbiter platform for Mars," said Wynne, who is also the Earth-Mars Cave Detection Program project leader.

Segue: http://www.space.com/scienceastronomy/0 ... caves.html