I hunt microbes for a living, so it shouldn’t surprise anybody to hear that every time I see news coverage of a Mars mission, I ask: “why isn’t this mission looking for microbes?” When Avi Loeb recently pointed out a 2019 Scientific American essay by Gilbert Levin entitled “I’m Convinced We Found Evidence of Life on Mars in the 1970s” I immediately clicked the link — in hope that the essay might teach me what some of the hangups have been. Sadly, Levin’s essay just leaves me feeling more mystified than ever.
Levin is a respected engineer and inventor who served as principal investigator for the “controversial” labeled-release experiments designed to detect life on the 1976 Viking mission to Mars. In 2012, Levin published a formal white paper proposing an improved version of the experiment, in which released metabolites would be checked for chiral chemistry and for Carbon-14 content (classic hallmarks of living organisms). The technical details of the white paper are complicated — and outside my area of expertise — so I’ll simply recommend Levin’s elegant Scientific American essay for further info.
Even after poking around on the internet, I’ve been unable to find any sensible counter-arguments that could help me understand why NASA never pursued the exciting follow-up experiment Levin has been advocating for more than a decade.
In his essay, Levin cites evidence supporting the idea that Earth and Mars might have occasionally exchanged biota over the past few billion years. A testable prediction of the biota-exchange hypothesis is that life on Mars would be expected to use the same DNA chemistry as every living thing on Earth. The power of DNA sequencing technology has grown by leaps and bounds in the 21st century, including remarkable advances in miniaturization. A sequencing device called a Nanopore is small and sturdy enough that it can be packed along for remote off-grid hiking expeditions. Automating the extraction and amplification of DNA from Martian soil samples presents a bit of a technical challenge, but it’s certainly well within the realm of tractability. These are rocket scientists we’re talking about.
When the pandemic forced me to work from home, tech-savvy “trainees” in the lab trained me how to fire up a large-scale bioinformatic project where I trawled petabytes of public deep-sequencing data looking for viral sequences. It’s grimly hilarious that when the pandemic stopped me from driving or flying anywhere, I suddenly developed the carbon footprint of a Bitcoin miner. I’d argue I got a lot better mileage out of my carbon emissions.
One of the most interesting finds came from an obscure dataset in which NASA sequenced air filters from the clean room where the Phoenix Mars Lander was assembled in 2007. The dataset contained an exotic polyomavirus that I’m pretty sure infects the types of dust mites that typically inhabit human skin. Over to Swift:
So, Nat’ralists observe, a Flea
Hath smaller Fleas that on him prey,
And these have smaller yet to bite ‘em,
And so proceed ad infinitum
In short, NASA used advanced DNA sequencing technology to discover exotic microbes hidden in the Phoenix Mars Lander clean room, but it somehow never occurred to anybody to load advanced sequencing technology onto the lander. Mystifying.
I can conceive of the possibility that Levin is wrong and the old labeled-release results really were just a trick of some lifeless chemistry we don’t fully understand. Or it’s possible Levin is right about the labeled-release results but the living things on Mars use some other genetic material that’s incompatible with currently available DNA sequencing technology. Looking for DNA on Mars could be considered a long shot, but if all we ever fund are timid experiments guaranteed to only make incremental advances then science will never make giant leaps.
This story is cross-posted on my Medium page