Mars: Feel the Vibe!
The long history of false alarms about life on Mars illustrates our willingness to find such signs.
I am writing this on a transatlantic flight, and was just handed a Dutch candy bar with the label “Mars: Feel the Vibe” – appropriate for a day when my morning inbox was inundated with dozens of messages asking me if life has really been found on Mars. That’s what I get for taking a day off: Every time life is discovered on Mars, I seem to miss it. When Martians were announced at a White House press conference in 1996 I was briefly offline, relaxing in the mountains, and was astounded to see newspaper headlines declaring “Life on Mars”. That time, behind the hype, there was a significant discovery – tiny, segmented structures in a meteorite from Mars which might be microfossils, though skeptics declared they were simply quirky mineral formations. This debate is still unresolved.
And now the media is again declaring “NASA Announces Life Found on Mars”! And, once again, if you cut through the cloud of hype, you can find an important discovery. Methane. Found with much more rigorous methods than previous, disputed detections over the past few years. Methane is a big deal, because it shouldn’t be there. Sunlight and atmospheric chemistry would make short work of it, so there must be an active supply, which implies that something is up on Mars. Something chemical which could be geological or even biological. What is really new is maps showing seasonal patterns and localized sources. Methane is concentrated in the summer, in certain locations that may be associated with unusual geology.
A few discrete methane sources tied to unusual geologic areas – if that’s what we are seeing – does not support the existence of a globally pervasive biosphere, even a buried one, but may be more consistent with the “surviving oases” model of life – pockets of organisms hanging on in a few remaining areas, remnants of an ancient glorious biosphere.
This provides a test of our notion that we might detect life on distant exoplanets by finding anomalous gases in their atmospheres. One thing that bothers me about the methane on Mars is that it is anomalous enough. Earth’s atmospheric chemistry is thrown drastically out of whack by life. Oxygen is not just a trace gas but one fifth of our air. With every breath we take in oxygen that has been produced by plants and use it to burn organic food and get energy to live, returning CO2 to the air, where plants can use it to make more food. Earth’s atmosphere is integral to our biosphere – a conduit transferring chemical gradients between, for example, oxygen producers and oxygen breathers. It is much more than a passive dump for occasional waste gases. Mars, with its ancient immobile surface and its nearly pure CO2 atmosphere does not seem like a planet with a global biosphere. But could it have isolated pockets of underground life?
Even seemingly isolated niches of underground life on Earth are evolutionary offshoots of a biosphere that has thrived and co-evolved with our planet over billions of years, and exist within a planetary crust that has been radically transformed and re-made by life. If a global biosphere is like a living organism, requiring homeostasis and the complex simultaneous interplay of many systems, then finding isolated life on an otherwise dead planet might be as unlikely as finding a beating heart without a warm body.
If life exists on Mars today, it is a very different beast from Earth life, and has a completely different relationship with the rest of its planet. We seem to really want Mars to be another Earth, but it just isn’t – and hasn’t been for at least three and a half billion years. Perhaps it will be again one day in the future. Eventually, in the case of Mars, wishing may make it so. Its only a matter of time before there really are Martians. We’ll keep announcing them until we actually find them or, failing that, eventually become them ourselves.