Under a slate-gray sky, Mono Lake in eastern California seems to be dying as it gradually evaporates to reveal strange, towering rock formations hidden for hundreds, even thousands of years.
The structures, called tufa, are spires of calcium carbonate formed long ago when calcium-bearing fresh water bubbled up into the alkaline lake rich in carbonates. Scientists think this evaporating basin paints a picture akin to what may have existed on Mars about four billion years ago, as some planet-wide catastrophe began desiccating Martian lakes, rivers and streams—perhaps leaving behind calcium carbonate formations similar to those at Mono Lake. Studying the mineralogy, chemistry and biology of the deposits that remain from an evaporating basin on Earth helps scientists better understand what to look for in the geologic record on Mars—specifically, how Martian rocks today may have preserved evidence of ancient microbial life.
And that is a key reason why Mono was chosen as a testing ground for new Mars rover technology designed to drill cores in rock and cache them securely for an eventual return to Earth. A Mars sample-return mission, regarded by many researchers as the "Holy Grail" of robotic Mars exploration, is estimated to cost at least $6 billion. It could launch as early as 2018 if the Space Studies Board of the National Academies makes it a top priority. The national agenda for Mars exploration should become clearer in March, when the board publishes its Planetary Science Decadal Survey.
The technological challenges are enormous but not insurmountable, according to a team of scientists and engineers that converged at Mono Lake October 3 to 7 for the first field tests of a new drilling and caching system developed at the Jet Propulsion Laboratory in Pasadena. JPL engineers teamed up with researchers at the Carnegie Institution for Science in Washington, D.C., and the NASA Goddard Space Flight Center in Greenbelt, Md., who are involved in the Arctic Mars Analog Svalbard Expedition, or AMASE—an ongoing program in Norway to test instruments for the exploration of Mars under its current conditions as well as study the habitability of extreme environments to learn about how life may exist on the Red Planet today.
Concluding the field tests at the lake, Andrew Steele, a Carnegie researcher and principal investigator for the test (as well as co-investigator for AMASE), says, "The major success is that we drove the rover up to a real-world sample, cored it, cached it and capped it. Done. Ready to go. That is a big step forward, and I think that will enable a greater degree of confidence in future planning," he adds.
A cold rainstorm at Mono Lake and forecasts of possible snow delayed field tests for three days. But by October 6 the storm clouds cleared long enough for the rover system to make its debut in "Martian" terrain.
The drilling and caching system architecture employs an automated device called a SHEC (short for Sample Handling, Encapsulation and Containerization). During the test, JPL engineers demonstrated that a handling arm could autonomously extract a sample tube from a full drill bit and transfer it to a sample canister where it is then capped and secured. On Mars, once the canister is filled with core samples, the rover's arm would lift it from the SHEC and place it on the ground where a second rover would retrieve and transport it to a vehicle that would be launched for a rendezvous with an orbiter for the return flight to Earth.
Although that is a rough sketch of a potential sample-return mission, the researchers at Mono deemed the first drill and SHEC test a critical step in the quest. "The visceral understanding of the behavior of coring tools and rock cores, once you're inside the rock, is worth any amount of laboratory testing," says Pamela Conrad, an astrobiologist at Goddard and a principal co-investigator on the AMASE project with Steele.
Counting on an automated rover from hundreds of millions of miles away is, of course, fraught with perils. At least one potential problem became apparent at Mono Lake: The scientists discovered that moisture inside the rock, combined with drilling heat, can transform the rock into clay and eventually gum up the bit. Whereas such moist conditions are unlikely on Mars, the test helped the researchers anticipate the unexpected. Among other unsettled issues raised are how to avoid cross-contaminating samples when using a drill to core samples more than once.
Next year, the team plans to return to the field, possibly Mono Lake, with a more automated and robust drill and cache system.
View a slide show of NASA technology tested at Mono Lake for a potential Mars sample-return mission