Mars Science Laboratory Shakedown in the High Arctic
|Andrew Steele of the Carnegie Institution of Washington checks out the red beds from Sverrefjelle.
Image credit: AMASE
Members of the AMASE team (AMASE stands for Arctic Mars Analog Svalbard Expedition) last month completed their fourth field season on the Arctic island of Spitsbergen. They went to test out instruments similar to those that will fly on an upcoming mission to Mars, and to perform a field test of a prototype rover, Cliff-bot, that is capable of climbing up and down 80-degree slopes.
Spitsbergen is the largest island in the Norwegian Svalbard archipelago, which lies between the northern tip of Norway and the northern polar ice cap. It is an inviting destination for astrobiology researchers because it contains several Mars analog sites: geologic formations that resemble, in various ways, ones on Mars.
One such site contains Devonian-age redbeds, formed between 408 and 360 million years ago. Such red-rock formations are a familiar sight in the American southwest, although there they are typically older. The redbeds in Svalbard, composed of rust-colored fluvial sandstones and mudstones, which contain the iron-bearing mineral hematite, are reminiscent of regions of layered terrain seen on Mars in images taken by orbiting spacecraft.
Svalbard’s "blueberry site" was selected because sulfate-bearing sandstones there contain small spherical concretions similar to the "blueberries" found by NASA’s Opportunity rover in Meridiani Planum. The martian concretions, which contain hematite, helped scientists confirm the former presence of liquid water on Mars. The Svalbard concretions do not contain hematite; they are rich in sulfate and carbonate minerals that also form in the presence of liquid water. Interestingly these concretions contain evidence of cryptoendolithic communities.
A third site contains carbonate globules embedded within volcanic rocks, similar to carbonate globules found in the martian meteorite ALH84001. Work done by the AMASE team during the 2005 field season, which focused extensively on these globules, determined that they formed purely through non-biological processes, when a volcano erupted, about one million years ago, up through an overlying glacier. A paper describing these findings has been accepted by the journal Meteoritics and Planetary Science.
A primary goal of this year’s field work was to test two instruments similar to those selected to fly aboard NASA’s upcoming Mars Science Laboratory (MSL). MSL, a rover scheduled to launch in the fall of 2009, will reach Mars in October 2010. It will look for signs of habitable environments, places where life could have gained a foothold in the past, or could still be surviving today.
MSL’s CheMin (Chemistry and Mineralogy) instrument will be capable of performing both X-ray diffraction and X-ray fluorescence analyses of powdered rock samples. It will catalog the chemical and mineral composition of rocks it examines. MSL’s SAM (Sample Analysis at Mars) instrument will contain both a GCMS (gas chromatograph-mass spectrometer) and a tunable laser spectrometer. SAM will search for organics. Together, the two instruments will enable scientists to go a step beyond what the Mars Exploration Rovers, Spirit and Opportunity, have achieved. Those rovers, still active on the martian surface, were designed to find evidence of liquid water. MSL will be able to assess habitability.
|Diagram of the CheMin instrument.
Image credit: LANL
The principal investigators for both CheMin (David Blake, NASA Ames Research Center) and SAM (Paul Mahaffy, NASA Goddard Space Center) participated in this year’s AMASE expedition. By working with each other in the field – their activity in Svalbard was the first time they had done so – and by comparing their instruments’ results
"It just gives us more experience with a variety of analog samples, and some of the decision-making processes that we would be going through on the surface of Mars. It’s a good way of really getting out in the field and understanding how decisions are made and interpreting the data, at some level, rapidly. It’s good experience just to kind of get our feet wet and operate a little bit like we’re going to be operating with MSL," said Mahaffy.
The AMASE team brought with it not only the CheMin and SAM instruments, but also several additional instruments used commonly in biotechnology laboratories. These included PCR (polymerase chain reaction) equipment, which duplicates DNA; instruments capable of detecting ATP and cell-wall components; and a microarray that can detect proteins, which is scheduled for inclusion on ExoMars, a future European Space Agency mission to the red planet.
This extra equipment gave the SAM and CheMin teams additional information to help them interpret the results from their instruments, said AMASE Project Scientist Andrew Steele, of the Carnegie Institution of Washington. Although the biotechnology techniques will not be available for the samples MSL analyzes, the experience the scientists are gaining now will help them recognize patterns in the data they do receive from MSL.
For example, one set of samples was collected from weathered peridotite outcrops at the carbonate globule site. CheMin showed that the mineralogy of the sample indicated an environment that could support life, and SAM detected organics and amino acids in the sample. On Mars, this is all the information that will be available. But the additional biotech instruments were able to confirm a viable life signature in the Svalbard sample. They gave the SAM team confidence that the organic signature they saw was valid.
Another sample, taken from oil-rich dolomite, was correctly identified by CheMin as a calcite-dolomite mixture. SAM again detected a lot of organics in the sample, similar to what one would expect to show up in oil shale. But the additional biotechnology techniques showed only small amounts of viable life present. Conclusion: the organic signal was evidence of past life.
"Just throwing one technique at a sample gives you an overview. Throwing two, three, four, five techniques all correlating the data sets, gives you much more confidence that you’re actually looking at something that’s there and that’s potentially life," said Steele. "We can look to see how the instruments all perform on a similar sample set, get the teams talking together to begin to understand what the limitations of somebody else’s technique and how that fits into their analysis."
Avoiding and detecting contamination is a problem the AMASE 2006 team spent a lot of time addressing. It’s nearly impossible to eliminate every single microbe from one’s test equipment. So there’s always the possibility that an organic signal seen in a rock on Mars comes from bacteria that were missed during the spacecraft cleaning process on Earth.
"By doing this on Earth now with a group of samples that are analogous to those that we’ll be looking at on Mars, what we’re able to do is, if there’s a significant input from contamination, then the SAM team, because it’s worked on all these samples on Earth, will be able to distinguish the signals that they’re seeing a lot easier. They’ll have a lot more experience at looking at mixed signals and taking them apart," Steele said.
The AMASE team also gained valuable experience in sample acquisition and preparation. "Each technique needs a slightly different sample preparation," Steele said. "Many of the kind of really simple, down-to-Earth things like sample prep, and how you run it cleanly – all these things get lost in the mud, usually, and are left to figure out sometimes until too late, when the mission’s started."
|Trapped mineral fragments associated with microbial communities appear inside blue ice.
Photo: Kjell Ove Storvik/AMASE
Indeed, from Steele’s perspective, the most important accomplishment of AMASE 2006 was not the specific analyses that were performed, but rather the team-building that occurred. Not only did the science teams for different MSL instruments get a chance to work together in the field, but the scientists worked closely with the rover drivers, so that they got a sense of how the entire cycle – from scientific goal, to rover request, to sample acquisition, to data return and analysis – needs to be integrated.
"That was the biggest challenge," said Steele, "to get 30 scientists and engineers working together as a team. And that happened. For me, the biggest highlight is we forged a team to do that."
AMASE is arranged by Physics of Geological Processes (University of Oslo) in collaboration with the Norwegian Space Center. Its expedition leader is Hans E.F. Amundsen of PGP. This was the first year AMASE received funding from NASA’s ASTEP (Astrobiology Science and Technology for Exploring Planets) program. Steele is the Principal Investigator for the ASTEP grant. The ASTEP funding will continue for two more years. Next year, the AMASE team plans to explore more challenging sites, and to integrate a coring device and additional scientific instruments, including deep-UV and Raman spectrometers, onto the Cliff-bot rover. The also plan to control the rover remotely, to more closely simulate a real-time Mars mission.