A Wet Run for a Dry Planet: NASA Tests Drilling Technology in the Desert with Mars Sample Return in Mind [Slide Show]
Despite a gummed up drill bit and three days of very un-Martian precipitation, engineers pronounced the test a success--and learned to expect the unexpected, whether it be in the California outback or on Mars
Credit: Bruce Lieberman
HOLY GRAIL Many planetary scientists view a successful Mars sample-return mission as a kind of "Holy Grail" of solar system exploration—an unprecedented opportunity to bring pristine pieces of another planet directly back to labs on Earth for in-depth analysis. Under current designs for a drilling and caching system, rock cores would measure about five centimeters long and one centimeter in diameter. Pictured here is one such core sample from a target rock at Mono Lake, along with the unsealed metal sample tube that held it.
A SAMPLE PLAN On a Mars sample-return mission, the rover would do all the work drilling cores and caching rock samples for a return flight. But during field tests it is all about learning in stages how the technology should be developed for its ultimate mission. Jennifer Eigenbrode (pictured), an organic bio-geochemist from Goddard, and Steele, from Carnegie, examine the tailings they just collected from a bore hole.
GETTING GUMMED UP Moisture inside a target rock can cause problems for drilling operations, engineers discovered during their field tests at Mono. The drill bit generates heat from friction as it bores into the rock, and water combines with core tailings to create clay that can gum up the drill. Engineers discussed designing a way for the drill to disconnect from the bit if it becomes stuck—allowing the rover to cut its losses and move on to another target.
AUTOMATED CACHING Team members examine the rover's SHEC (Sample Handling, Encapsulation and Containerization) system as a handling arm inside extracts a sample tube filled with a rock core from the rover's drill bit and inserts it into a canister, where it is capped and sealed. The SHEC system, designed by Younse at JPL, houses four drill bits for coring rock and 19 sample tubes cached in a canister the size of a stout coffee mug. During a sample-return mission envisioned by engineers and scientists, the rover's arm would lift the filled canister and place it on the ground. A second rover would retrieve the container and transport it to a launch vehicle; once loaded it would blast off and rendezvous with a Mars orbiter. The orbiter would then rocket the cached rock cores back to Earth. Pictured
[far left] is Andrew Steele, a Carnegie astrobiologist and co-principal investigator for AMASE. Also pictured, [left to right] are Conrad, Younse and DiCicco. Bruce Lieberman Advertisement
TUFA The NASA team worked at the western shoreline of the lake, where volcanic pumice boulders caked with a layer of calcium carbonate pock the landscape. In other places around the lake geologic formations called tufa, formed underwater and now exposed in the evaporating lake, make Mono Lake's shoreline an eerie sight. Tufa are created over hundreds, even thousands of years when spring water bearing calcium bubbles up through alkaline lake water rich in carbonates. The calcium and carbonates combine, creating limestone towers that grow around the mouth of the underwater spring.
DRILL BABY, DRILL The evaporative environment at Mono Lake, revealing calcium carbonate formations that were once submerged, may have characterized Mars' ancient past. Evidence of past life may be entrained in such geologic formations.
CONTACT! Once a microscopic imager on board the rover photographs the drill site on a target rock, a tungsten carbide drill bit at the end of the rover's arm moves into position and bites into the rock. The drill employs both percussion, like a jackhammer, as well as rotation to extract a core. A drilling session can take several minutes—the drill starts and stops in bursts lasting several seconds. Boring into hard substances like basalt can take some time. The bit is designed to penetrate about five centimeters into the rock. Engineers monitor the levels of electrical current powering the drill; a surge can mean the drill is binding or otherwise stuck.
ZEROING IN Pamela Conrad, an astrobiologist at Goddard, contemplates the rover's next move as it inches closer to a rock targeted for coring. The dark rock is pumice dating back to a volcanic eruption below the lake about 1,700 years ago. It is partially covered with a layer of calcium carbonate that formed when the rock was submerged below the surface of the lake. Scientists believe this evaporating basin is similar to what may have existed on Mars about four billion years ago. Conrad is a principal co-investigator for NASA's ongoing Arctic Mars Analog Svalbard Expedition (AMASE) to test technology for Mars exploration and study the habitability of extreme environments.
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READY TO ROVE Engineers from the Jet Propulsion Laboratory in Pasadena carry a Mars-class rover toward the western shoreline of Mono Lake in California. During the first week of October, a team of researchers from JPL, NASA Goddard Space Flight Center and the Carnegie Institution for Science conducted its first field test of a drilling and caching system that could be used on a Mars sample-return mission proposed for 2018. Pictured [
left to right] are software engineer Matt DiCicco; mechanical engineer Paulo Younse; electrical engineer Ron Morgan (in the blue jacket); and engineering supervisor and principal investigator for development of sample acquisition and caching technology, Paul Backes. Bruce Lieberman Advertisement