The recent indirect discovery of a planet orbiting red dwarf Gliese 581 raised strong ripples of interest and speculation. The smallest exoplanet yet discovered, it has been called earth-like based on three attributes: its calculated radius is one and a half times that of earth; its orbit appears to be inside its star’s habitable zone (by definition, the region where water can remain liquid); and its conjectured temperature falls within terrestrial norms.
“Sunset from the Surface of Gliese 581c” by Karen Wehrstein
The planet’s other intrinsics are quite un-earthly. Ten times closer to its dim, flare-racked primary than earth is to the sun, Gliese 581c completes an orbit in 13 days. It is five times the mass of earth, making its gravity about twice as strong. Because of its proximity to its star, it is probably tidally locked, with hurricane winds raking the twilight zone, and tides several hundred times the strength of terrestrial ones tugging its seas, if it has any. Nevertheless, the planet may also harbor a stable atmosphere – and if that is combined with the presence of water, the question of life automatically rears its head.
Most scientists were ecstatic that a small planet (probably rocky, possibly containing oceans) had finally been discovered, taking us one more step to the right across the terms of the Drake equation. Hopeful artists created wishful views of the planet. But there were some interesting negative reactions as well.
Adherents of the Singularity scenario argued that such planets are beside the point, because by the time a rocket reaches the Gliese system (just 20 light years away, yet still a journey of millennia with our present propulsion means), we will have evolved past our present “carbon-bound” configuration. Others warned of the dangers of sending out long-generation colonists without supervision, so to speak. Still others recalled the Fermi paradox, and lamented that if earth-like planets are as common as this, the deafening silence that SETI has garnered bodes ill for the frequency of advanced life or the surivival of technological civilizations in our galaxy.
The naysayers, in their sophistication, missed a crucial point. Whether Gliese 581c is so hospitable that we could live there or so hostile that we could only visit it vicariously through robotic orbiters and rovers, if it harbors life – even bacterial life, often mistakenly labeled “simple” – the impact of such a discovery will exceed that of most other discoveries combined. Unless supremely advanced Kardashev III level aliens seeded the galaxy like the Hainish in Ursula LeGuin’s Ekumen, this life will be an independent genesis, enabling biologists to define which requirements for life are universal and which are parochial.
At this point, we cannot determine if Gliese 581c has an atmosphere, let alone life signatures. If it has developed non-technological life, without a doubt it will be so different that we may not recognize it. Nor is it a given, despite our fond dreaming in science fiction, that we will be able to communicate with it if it is sentient. In practical terms, a second life sample may exist much closer to home – on Mars, Europa, Titan or Enceladus. But those who were enthusiastic about this discovery articulated something beyond its potential seismic impact on biology and culture: the desire of humanity for companions among the sea of stars, a potent myth and an equally potent engine for inner and outer exploration.
Athena Andreadis is Associate Professor of Cell Biology in the
Shriver Center for Mental Retardation at University of Massachusetts Medical School, and the author of
To Seek Out New Life: The Biology of Star Trek.
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