The last time I saw Bob Zubrin, at a conference of the Mars Society of which he's president, he was, as usual, passionately advocating for manned missions to Mars. "If we send robotic machines ahead of humans to synthesize rocket fuel from the planet's soil and atmosphere, we can cut NASA's $400 billion cost estimate by 90 percent," he insisted. His plan for utilizing in situ resources notwithstanding, we're still a long way from putting humans on Mars, but that hasn't dimmed his passion for the subject — he's written five books and hundreds of papers about mankind's future on the red planet.
Which is why I was surprised by his latest paper, which at first blush has no Martian connection. Titled "Interstellar Communication Using Microbes: Implications for SETI," it's brilliant, funny, mind-expanding, well worth a few minutes of your time and available for free online. He starts by questioning the rationale behind the 58-year-long unsuccessful Search for Extraterrestrial Intelligence (SETI). SETI scans the heavens for possibly artificial — i.e. patterned — radio waves, since a pattern could mean ET origin. Zubrin points out the unlikelihood of ETs sending radio signals and of us receiving them, the signal-to-noise ratio being so low, even with huge transmitting and receiving dishes operating at gigawatt levels.
We're looking in the wrong place, he suggests. The smart way for ETs to get their message out into the galaxy is to encode it in spaceworthy microbial form, what the Swedish Nobel-winning chemist Svante Arrhenius dubbed panspermia (Greek for "all seed") more than 100 years ago. What message? Genetic information, of course. If you're really interested in communicating beyond your homeland, you don't send a "Wazzup, bro?" message out into the void, you send life. What sort of life? Tiny microbes that can survive, evolve and propagate in new planetary surroundings. They travel much slower than radio waves' light speed, of course, but time isn't of the essence when you're seeding a 13-billion-year-old galaxy.
There's good reason to believe that panspermia — microbial life from space, whether of artificial (ET) or natural origin — is what started life here on Earth some 4 billion years ago. The most primitive life forms found on Earth are bacteria but bacteria are already incredibly complicated structures. For instance, they propagate themselves using DNA, which is as complex a molecule as we can imagine. Why do we find no precursor life forms here? Because, argues Zubrin, life didn't start on Earth by an improbable series of chemistry-to-biology steps, it came right out of the starting gate already viable as tiny (1-10 microns diameter) microbes raining down on early Earth from space. Which is why life began here almost as soon as conditions allowed, not a billion years later.
In order to test the panspermia hypothesis, we need to find an environment in which these putative seeds of life that found their way into the early solar system have been unsullied by later evolution. What better place to look than in deep groundwater on Mars? (Now I see Zubrin's interest in this — you need humans there to drill down maybe a kilometer beneath the surface.) Mars and Earth were sister planets 3.5 billion years ago, so finding traces of DNA-based life but no earlier precursor life-forms (as on Earth) would be strong evidence for space-borne panspermia seeding life on both planets long ago. And if — big if — such DNA encodes what Zubrin calls "forward-looking traits" that could only have been put there by intelligent beings, we would finally have the answer to the big question: Are we alone?
Barry Evans (firstname.lastname@example.org) dreams of terraforming Mars into a second Earth.