The Not-So-Big Dig

With the equivalent power of an electric can opener, engineers try to do more than scratch the Martian surface.

A prototype of NASA's Phoenix Mars Scout stretches its 6.6-foot-long arm to scoop soil at Death Valley National Park in California. On Mars, the probe will dig a trench up to 20 inches deep to analyze the history of surface ice. (NASA)
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“It averaged 18 below Celsius (–3 Fahrenheit) and we found new ways to break and get stuck, and new failure modes and we spent a lot of time in the weather station, working on the drill. We finally drilled through ice and sandstone to two meters. We could drill about five inches in the sandstone in 20 minutes using 50 watts,” George said upon his return to Houston in mid-May. The NASA/BH drill has three motors – one to anchor the bottomhole assembly, another to apply down pressure, and the third to provide torque. As with the Raytheon/UTD rig, the drill winches up the cores and cuttings through the drill stem to be collected and analyzed on the surface.

“An interesting aspect of the core samples we got was that with all the concern about contaminating them with pieces of the bit, we now know that the interior of the core is intact and uncontaminated,” George said. “We trust that would be true on the moon or Mars” (see “Unwelcome Visitors,” left).

After seeking the most extreme Earth environments in which to test the drill, a return to the moon may provide the best opportunity to test Mars-bound rigs. The moon would provide “fantastic field-test opportunities,” says Suparna Mukherjee, technical lead for the Subsurface Access Base Technologies office at NASA’s Jet Propulsion Lab in Pasadena, California. When Mukherjee talks about inventing hardware for Mars, she occasionally arches her eyebrows and utters a contralto “cool.” She explains the meaning of Technology Readiness Levels 1, 2, and 3.

“TRL 1 is the draw-it-on-napkins level,” she says. “It’s physics and dreaming of possibilities.” TRL 2 finds scientists prowling hardware stores for off-the-shelf parts that become components for prototype systems. “The drills we tested in Idaho were TRL 3. We’ve gone from idea to hardware to proof-of-concept through field experimentation,” says Mukherjee. “You get hooked on the challenge.”
The most mature TRL 3 machines can drill through hard rock with less than 80 watts and bring samples to the surface. The next few hurdles for Mukherjee and the half-dozen other groups developing extraterrestrial drills is to miniaturize the rigs and get them to run autonomously. The drills also have to deliver samples to on-site instruments for analysis. “The mechanical engineering, with the various teams approaching problems from different angles, will be accomplished,” Mukherjee says, confidently.

Scientists from NASA’s Ames Research Center this summer ventured to the Canadian arctic to see whether artificial intelligence could control a Mars prototype drill. The Drilling Automation for the Mars Exploration (DAME) project bored into the Haughton Crater on Devon Island in Canada’s Nunavut Territory in late July to see if synthethic brainpower could keep the rig drilling for hours at a time without human interaction. The drill, built by Honeybee Robotics, ran on its own for a cumulative total of 43 hours, with the longest shift at 4.5 hours, and bored down 10.5 feet. Operating on 100 watts of power, the drill’s software also correctly responded to five of six known major fault modes. The experiment will help in designing drills for Mars, where robots will probably be able to “talk” with controllers on Earth only once or twice a day.

In a briefing at the Idaho National Laboratory last February, Arthur Lonne Lane, principal scientist of JPL’s Astrobiological Group, brought up several ancillary issues that NASA faces before sending drills to Mars. Data from the European Space Agency’s Mars Express orbiter has shown NASA places where it does —and doesn’t—want to drill.

Scientists would love, for example, to drill at the polar ice caps, where radar surveys by Mars Express indicate that water may be found just three feet down. But engineering hurdles prevent that, for now. NASA’s next rover, the Mars Science Laboratory, scheduled to be launched in 2009, will carry equipment to bore into rocks. But the spacecraft is restricted to landing 60 degrees north or south of the equator, partly because the frozen ground at the poles could hinder the heavy rover’s movement.
Lane speaks eagerly about the possibility of studying Martian biology, while acknowledging the frustration of looking at the planet. Mars, he says, is in many places covered with a kind of “organic crud.” The deepest any spacecraft has penetrated that crud is about 10 centimeters—just under four inches—when a wheel on NASA’s Opportunity lander was purposefully spun to make a trench in February 2004. The rover then pointed spectrometers into the trench to analyze heat signatures and minerals, and found spherical, glass-like pebbles the size of BBs.

The rewards of drilling on Mars are uncertain and nearly impossible to calculate. Boreholes on Earth—whether for oil, gas, or something else—are expected to pay off right away in new resources or scientific information. It costs about $20 a foot to drill a six-inch diameter water well on Earth. Drilling a two-inch diameter hole on Mars that just might turn up fossilized life? Priceless.

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