After a flurry of rumors that Curiosity discovered something that mission scientist John Grotzinger said would be “for the history books“, the internet has settled down into an odd blend of anticipation and disappointment about what will be revealed on Dec. 3. Here’s a bit of speculation about what will be revealed… why it’s not the stuff of some of your wildest dreams, but why it is nonetheless very, very, cool. Not just the sort of “cool” that gets us science geeks excited.
Let’s approach this by asking ourselves what’s the least interesting thing that might have been discovered. The SAM instrument is specifically designed to look for organic molecules in the Martian soil. So the odds are that this discovery has something to do with that. What’s the least interesting class of organic molecules that could be discovered? Easy. Organic molecules derived from meteorites. Those are “least interesting” because they are expected to be there, as a consequence of the slow but steady infall of meteorites to the Martian surface. However, it turns out that even this “least interesting” discovery would be pretty darn exciting.
Because this is not the first time that we have looked for organic compounds on the surface of Mars. The first and last time until now was in the late 1970s, after Viking 1 and Viking 2 landed on the surface of Mars in 1976. Then, as now, soil samples were analyzed by a sophisticated instrument package. Then, as now, organics derived from meteorites were expected.
But no natural organic molecules were found.
To explain this negative finding, it was hypothesized that the Martian soil contained an unidentified, powerful oxidant that destroyed organic molecules. As a consequence, the scientific community concluded that the Martian surface was hostile even to microbial life. The search for life on Mars shifted sharply. When the Viking mission was conceived, the surface of Mars was considered a possible – perhaps even a likely – abode for life today. After Viking, the emphasis turned to extinct life, and characterization of Mars’ surface habitability in the ancient past.
So even if Curiosity has “only” found organic molecules derived from meteorites, it will overturn a paradigm that has governed Mars exploration for over 30 years. It will validate those who have argued that the Viking organic analysis was erroneous, and that the Martian surface is, indeed, habitable today. It will revive the idea that we should search for microbes that eke out a living at the Martian surface today. Some will even argue that we need to reconsider the data from other experiments on the Viking mission, one of which provided tantalizing hints of active metabolism that were discounted largely because of the absence of organic compounds. But that’s a story for another day.
In the meantime, I’m betting we will need to rewrite those history books!
While this all seems to put the kibosh on exciting news, the language is a bit curious. The statement is that Curiosity has not found evidence of “Martian organics”. If this wording was carefully chosen, then it seems as though it leaves the door open to meteorite-derived organics. As outlined above, that would still be pretty darned interesting.
We’ll know more tomorrow. Live feed here. Fun times!