GOLDEN, Colo. — Reports that NASA’s Curiosity Mars rover had relayed some potentially history-making findings touched off a frenzy of interest even as mission scientists sought to temper expectations in advance of a formal announcement. Contrary to rampant speculation, Curiosity has not made an earth-shaking find just a few months into its mission, agency officials said Nov. 29.
At the epicenter of all the speculation was that Curiosity’s Sample Analysis at Mars (SAM) instrument had found organic compounds in soil samples it gathered.
John Grotzinger, lead mission investigator for the Curiosity rover, set the rumors in motion during an interview with NPR the week of Nov. 19, saying, “We’re getting data from SAM … this data is gonna be one for the history books. It’s looking really good.”
Expectations had been running high that whatever history-making news there was to report, Curiosity scientists would deliver the goods at the American Geophysical Union’s meeting Dec. 3-7 in San Francisco.
On the agenda is a discussion of Curiosity’s search for organic molecules on Mars with its Gas Chromatograph-Mass Spectrometer — a key instrument to help explore the surface and subsurface of Mars, seeking traces of prebiotic or biological activity. NASA said Nov. 29 not to expect “major new findings.”
“Rumors and speculation that there are major new findings from the mission at this early stage are incorrect,” the agency’s Jet Propulsion Laboratory in Pasadena, Calif., said in the statement. “The news conference will be an update about first use of the rover’s full array of analytical instruments to investigate a drift of sandy soil.”
Most scientists contacted for this story believed that Curiosity’s SAM had detected organic chemical compounds. Other experts cautioned that the rover’s findings were being overhyped.
“This is going to be a disappointment,” said Chris McKay, a NASA space scientist at the Ames Research Center in Mountain View, Calif. “The press description of the SAM results as ‘earthshaking’ is, in my view, an unfortunate exaggeration. We have not (yet) found anything in SAM that was not already known from previous missions: Phoenix and Viking.”
But James Garvin, chief scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and a member of Curiosity’s Mars Science Laboratory (MSL) science team, had a different take.
“What John Grotzinger was saying as our very capable project scientist on MSL is exactly the case,” Garvin said. “The analytical payload on MSL — in particular, SAM as a suite — has been making unprecedented measurements of solid material samples with incredible implications about Mars, but which require, as in all science, demonstration of reproducibility and adequacy of calibration/validation.”
Curiosity landed inside Mars’ huge Gale Crater Aug. 5, beginning a two-year mission to determine if the planet could ever have hosted microbial life. The rover carries 10 different instruments, but SAM is the heart of Curiosity, taking up more than half of its science payload by weight. Garvin said the SAM team, plus the wider MSL science team (including Grotzinger), “are working industriously to have consistent results for the world to revel in as soon as possible.
“It is more akin to waiting for test results from one’s doctor. … We want to be sure they are valid and properly interpreted and explained.”
Unlike imaging and related experiments, highly sensitive results from SAM’s instruments, which include mass spectrometers, tunable diode laser spectrometers and gas chromatographs, require very great care in calibration, validation and interpretation, Garvin said.
“MSL with its Curiosity rover really is analogous to the Hubble Space Telescope in the impact it can and will have — we just have to be patient,” he said.
Similar to Hubble, Garvin added, “We have to be patient to use our tools to look at the ‘right stuff.’ Stay tuned. … Mars will not disappoint and nor will MSL.”
Also awaiting the word from the Curiosity science team was Michael Mumma, a planetary scientist at NASA Goddard, where he is founding director of the Goddard Center for Astrobiology.
“It clearly relates to the first soil sample analyzed by SAM. I suspect the delay means that a second sample is being analyzed to confirm findings from the first,” Mumma said.
Given that SAM’s Tunable Laser Spectrometer (TLS) methane data were not released until a third and fourth batch of samples had been analyzed, Mumma said he doubted there would be much to hear for several weeks.
“Remember that TLS will sample gas — water, methane — from pyrolyzed soil, while SAM’s [Gas Chromatograph-mass Spectrometer] samples the mass spectrum,” Mumma said.
In Mumma’s view, “blockbuster findings” could include the discovery of a major release of methane from pyrolyzed soil, with measurements of certain intriguing chemical variations called isotopologues. A finding of complex hydrocarbons or of a type of chemical compound called polymers would also be a major discovery.
“I think the minimum finding that could get Grotzinger to describe it as ‘historic’ is complex organic compounds,” said Gilbert Levin, an adjunct professor at Arizona State University in Tempe.
Levin was a life detection experimenter on NASA’s Viking mission to Mars in 1976. Levin and co-experimenter Patricia Ann Straat led the Viking Labeled Release investigation, which returned data from Mars indicating the presence of microbial life, the team asserts.
“I have already pointed out that the Viking [Pyrolytic Release experiment] showed that simple organics are continually being formed on Mars, so they would be no big deal for Curiosity,” Levin said. “I doubt SAM could have detected proof of living microorganisms. But, slowly, ineluctably, NASA is being dragged into the mire of life on Mars, and will ultimately, maybe soon, have to reverse its opinion on the results of the Viking Labeled Release.”
If Curiosity has found organics, Levin said, it would confirm that the Gas Chromatograph-mass Spectrometer was not sensitive enough to rule out the positive findings of the Viking Labeled Release.
“The failure of the Viking [Gas Chromatograph-mass Spectrometer] is the only remaining obstacle to acceptance of the Mars [Labeled Release] having detected existing microbial life. That obstacle would be removed by the Curiosity finding of organics. Whether that will turn the consensus in favor of life, I do not know, but any rationale against it would be difficult to maintain,” Levin concluded.Ultimately, the world will have to wait just a little bit longer to find out what Curiosity knows.
“Curiosity’s science team is analyzing data from SAM’s soil inspection, but not ready to discuss yet,” said Guy Webster, a spokesman for the Curiosity Mars rover science team at the Jet Propulsion Laboratory in Pasadena, Calif.
This is no change from the policy with past results from the mission, such as SAM’s atmosphere analysis or CheMin’s [Chemical and Mineralogy instrument] soil sample analysis, Webster said. “The scientists want to gain confidence in the findings before taking them outside of the science team.”
Webster said that Grotzinger was delighted about the quality and range of information coming in from SAM and similarly delighted by results at other points during the mission so far.
“The characterization of new findings as earthshaking did not come from anyone on the mission’s science team,” Webster said.