View from the Edge

“April showers bring may flowers” is a silly child’s rhyme that I think is familiar to most my readers. Like most such rhymes, its a teaching tool for young minds, allowing us to explain complex ideas in simple fun ways. That simple little rhyme that many of us learned as very small children helps us understand and conceptualize the changing of the seasons, the emergence of new life, and even such basic concepts as the value of water to life itself. Its something we don’t often think about, but water is one of the most fundamental aspects of everything we’ve ever seen that we called life … it is so fundamental that “life as we know it” simply couldn’t exist without water. Thats not QUITE to say that life can’t exist without water, but if it does, we have no conception of how that would work in practice.

And thats what makes the recent discovery of Gliese 581-C so exciting to extra-solar life geeks like me … the first evidence of an extra-solar planet that is both close to the right size, and right temperature to have liquid water on the surface. It should be noted that there is no evidence of water at this point, only conditions that make liquid water possible, but even that is a first for astronomers who look for planets around other stars. Until the discovery of Gliese 581-C, the only other planets found outside our solar system were gas giants like our outer solar system or bigger … while there are tantalizing clues to life on moons like Titan in our outer solar system, it would be life in a way that is wholly foreign to life on earth. With Gliese 581-C, scientists have found the first planet outside our solar system that has the chance of life like our own … as yet, there is no direct evidence of life or water, but even the discovery of a place where that is possible is exciting.

One of the more fascinating things about Gliese 581-C is that although it is the most earth-like extra-solar planet found, it actually isn’t really all that earth like. Discovered by measuring minute variations in the parent star’s (Gliese 581) spectral pattern caused by orbiting planets (and as the C might have already alerted you, this is actually the third planet discovered around Gliese 581), its neighbours are a giant approximately the size of Neptune that hugs close to its parent star in a tight orbit of less than 6 days, and on the other side is a big brother approximately 8 times the size of earth leisurely orbiting Gliese 581 in 82 days. The current planet that has everyone excited is actually much closer to Gliese 581 than earth is to the Sun, but as a red dwarf Gliese 581’s total heat output is far less than our own sun, and given that difference, the 13-day orbit of C is perfect for the “habitable zone” of the star, the zone where liquid water is possible on the surface of a planet. C (there is no other name as of yet) is also larger than earth, at about 1.5 times the diameter and 5 times the mass, and scientists say that will likely translate to about twice the gravity of earth for someone standing on the surface. Add that to the strange environment around a red dwarf, which would probably include less visible light than we are used to and far more of what we would call “radiation” (which, of course, is often just higher or lower wavelengths of light than we can see), and its likely that any life found on Gliese 581-C will have to be different than life on earth.

We don’t know anything about atmosphere, so I won’t speculate about that at all, and we are assuming water. The higher gravity is almost certain to produce stronger, shorter, stockier creatures. Animals that had internal skeletons similar to us would tend to be lower to the ground and more spread out … tall and thin designs would tend to be very difficult to maintain in a higher gravity environment. Exoskeletons very low to the ground, like crabs, might be more common in such an environment. The radiation of a red dwarf might present a huge impediment to life, but it might not as well … life around thermal vents on our own earth, deep in our own oceans (and incidentally, life that some scientists speculate may have been the first life on earth, shielded deep in the ocean from earth’s primordial, radiation filled environment) exists completely independently of sunlight, as do many species that have evolved wholly inside cave systems and other underground species. Even if such radiation is completely toxic to life as a whole, deep oceans, or life deep within the mantle of the planet, still based on water as we see here on earth, could still exist independent of the star and the radiation at the surface. That said, there are also many other forms of extremophiles on earth that thrive in conditions of super-toxic heat and acid (such as the geysers and vents of Yellowstone park), as well as in extreme cold, radiation, and other conditions once thought “toxic to life” in general. Even the bizarre radiation of a red dwarf isn’t, by default, toxic to “life as we know it” since life as we know it, on earth, has expanded pretty dramatically through research in the past few decades. There was a time not so many years ago when respectable scientists would have considered you a bit strange and eccentric, and ultimately wrong, if you’d suggested that vast communities of tube worms might live miles below the ocean, around vents spewing forth water at hundreds of degrees full of the most vile and toxic chemicals. Yet, there they are.

Its hard to imagine what the life of Gliese 581-C might look like if it does exist … we are very often stunned to the point of speechlessness by what we find here on our own planet, so predicting what we might find on another is pretty much a crap-shoot. But the simple fact that its the right size and temperature for liquid water is an exciting discovery. It will probably be some time yet before more is known about the actual conditions, but its the first indication we’ve had of a couple of things. First, its the first time we’ve found another planet even remotely like our own, outside our two immediate neighbours, and that in itself is significant. But second, its also an indication that such small, rocky planets in that zone that supports life might be fairly common. Its an exciting find for space geeks like me … I’m looking forward to a time when we can learn a bit more about this new planet.

The April showers, May flowers, and Gliese 581-C by View from the Edge, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Share Alike 2.5 Canada License.