Humanity has been wondering about whether life exists beyond our little backwater planet for so long that we’ve developed a kind of cultural bias as to how the answer to this central question will be revealed. Most of us probably imagine that NASA or some other space agency will schedule a press conference, an assembled panel of scientific luminaries will announce the findings, and newspapers around the world will blare “WE ARE NOT ALONE!” headlines. We’ve all seen that movie before, so that’s the way it has to be, right?
Probably not. Short of an improbable event like an alien spacecraft landing while a Google Street View car was driving by or receiving an unambiguously intelligent radio message from the stars, the conclusion that life exists now or once did outside our particular gravity well is likely to be reached in a piecewise process, an accretion of evidence built up over a long time until on balance, the only reasonable conclusion is that we are not alone. And that’s exactly what the announcement at the end of last year that the Mars rover Perseverance had discovered evidence of organic molecules in the rocks of Jezero crater was — another piece of the puzzle, and another step toward answering the fundamental question of the uniqueness of life.
Discovering organic molecules on Mars is far from proof that life once existed there. But it’s a step on the way, as well as a great excuse to look into the scientific principles and engineering of the instruments that made this discovery possible — the whimsically named SHERLOC and WATSON.