OCOTILLO WELLS, Calif.—The area of the Southern California desert we were standing in made for a decent visual fill-in for the Red Planet—simply change the tint of the landscape and get rid of the sparse scrub on the nearby hillsides. At this site, in a large, open-air mine near the Salton Sea, a few people in hard hats were gathered around a tall stand with a tether in the middle that dropped into a small hole in the ground.

The area was silent except for the hum of a large compressor. "That's for cooling," explained Kris Zacny, an engineer for Honeybee Robotics. "We won't need cooling on Mars."

But the process also provided information about possible future drill designs. The soft gypsum powder created by the drill tended to clump and cake up inside the drill, making it hard to empty out the sample holding space without heavy human involvement. Obviously, that wouldn't be an option on Mars. As a solution to that problem, Zacny suggested they could design a drill with very deep channels—think of a regular drill bit with spirals that are so deep that the volume occupied by the bit is mostly air.

The bit itself would then carry the debris to the surface, where it could be removed simply by rotating the drill against a scraper and/or brush, a simple mechanical process that would be easy to implement. A scoop below the cleaning area could capture some of the debris for a more detailed analysis.

Another key lesson came up at an earlier drilling attempt at the same site. "After drilling about 30, 34 feet, we ran into a very inhospitable layer," Scharra said. "It happened to be wet clay here, but who knows, it might be a buried meteorite on Mars or an impenetrable layer."

The owners of the quarry, US Gypsum, stepped in to help out. A mobile industrial drill was dispatched and, within minutes, reached the clay at 10 meters and confirmed it extended far enough that the drilling site wasn't very good for testing. Honeybee's drill was then pulled out and shifted to a nearby site in the mine.

That experience told the team that the hardware couldn't just be set up on a permanent stand, limited to drilling where it landed. It needed to be mobile. "It can't be just a one-trick pony," Shara said. "It's got to be able to hit something really bad and say 'this doesn't look good,' come back up to the surface... and then move maybe just 20-30 feet and do it again and have the ability to do that several times. If we have an initial failure, the whole experiment isn't off."

If it's mobile and robust enough, the drill could potentially be used on multiple sites.

Where no drill has gone before

The general concept for the drill works. The drill has easily handled two different sites in the mine, gone down to depths where all the hardware was operating underground, and returned samples from meters deep that were ready for chemical analysis. "These samples are actually being analyzed," Zacny told Ars. "We sent samples already to NASA-JPL, our partner on future drill development, and they found organic material. They showed that there's enough organics in a surface to validate that this is good stuff."

Although finding life at the bottom of a borehole on Mars is still an iffy bet, the ability to recover and analyze material from well below the surface would almost guarantee we'd learn something interesting. Because these deposits built up gradually over time, drilling into them acts as a bit of a time machine. "Going not just a few inches below the surface, but going hundreds of feet, hundreds of meters," Zacny said, "[is] going into the past of the planetary body." We could track changing conditions on Mars as its atmosphere and water were lost and potentially find evidence that life was around in the past.

Until we put the hardware on Mars, however, we can't be sure what we'll find. "What's it going to be like down deep on Mars? 100, 300, 500 feet down on Mars?" Shara asked. "The answer is we have no idea. And we're never going to have any idea until we go look."

Listing image by Honeybee Robotics