Astrobiology Frontiers

Mars gets a lot of press as the frontier in the search for extraterrestrial life on another orb. We Earthers have landed a bunch of probes, taken lots of pictures, and performed some in situ chemical analysis. We don’t know whether life existed once on Mars, although the working hypothesis is that early Mars was quite hospitable to life. The present red and rocky desert isn’t; but maybe life clings to existence in the subsurface. We have some very interesting and largely unexplored subsurface life right here on planet Earth.

 

In her recent book The Secret Life of the Universe, Nathalie Cabrol, director of the Carl Sagan Center at the SETI institute helped me broaden my frontier as to what’s interesting and potentially investigable in addition to Mars. She addresses the “veil of secrecy” of Venus and discusses possible habitable scenarios. I learned about new missions on the slate from NASA and ESA. She covers Mars, of course. But then she spends some time discussing Titan, Europa, Enceladus, Callisto and Ganymede. They’re all different, and each is uniquely interesting. I had previously heard or read about the first three as being interesting sites for finding life, but not the latter two.

 

But her book goes further afield. Ceres turns out to be quite interesting; it has geological seismic activity and possibly a liquid briny ocean beneath the ice. Pluto has “mountainous and glacial” terrain, and its partner Charon may have had a subsurface liquid ocean, I’m guessing made up of nitrogen and possibly ammonia (based on Pluto’s glaciers). I was previously under the impression that only planets in the “Goldilocks zone” of habitability where you were about the right distance from your sun to support liquid water were possible candidates for life. But Cabrol opened my gaze further afield. There could be very interesting and unique activity on a planet on a moon due to many factors, some of which might be conducive to complex chemistry arising.

 

One chapter is titled “Visions of Tatooine and Mordor”. Cabrol classifies the different exoplanets (over 5,500 and counting) into five categories, and then picks out specific examples of interest to astrobiologists. Kepler-16b is Tatooine – it has two suns. The gas giant Bespin could be Cloud City. And the ocean-world Kepler-22b could be Kamino. The interesting TRAPPIST system is also discussed. Cabrol discusses these many interesting orbs in the context of the Drake equation. Our ever-growing knowledge and discovery of so many planets, coupled with the possibility of the habitable zone being widened beyond the traditional Goldilocks parameters, suggests that E.T.’s existence is that much more likely.

 

I was particularly struck by her suggestion that “explaining the origin of life might not be enough to define it”. We’re blinkered by life-as-we-know-it, and it’s very difficult to imagine how else life might manifest. As to what it means to demonstrate the tasks of living, it may also be that “what life does is not what life is”. More questions, few answers. But it made me excited about potentially offering a course in astrochemistry. I’m certainly no expert, but it would be a great way to motivate myself to learn the material!