Gliese 581d

Gliese 581d

I've been very intrigued by the recent news that an extrasolar planet has been discovered in the so-called Goldilocks zone of a nearby star. The Goldilocks zone is the region around a particular star (based on its size and type) where the radiation (heat and light, essentially) would be right for Earth-like life. Gliese 581 is a red dwarf star "only" 20 light years away, and 581d is tidally locked in its orbit, meaning that--like our moon's relationship with Earth--the same side of the planet always faces its star.

Lots of people are calling Gliese 581d "Earth-like" or potentially so. I think that's true in some respects, but not others. Since it's a rocky planet in the Goldilocks zone, it's pretty likely there's liquid water there. Plus, it's not so much larger than Earth that gravity would be too crushing. Unlike much more hostile worlds, you don't have to come up with extraordinarily exotic life form ideas to imagine life on such a planet. Liquid water and moderate temperatures in certain regions make it a place that we can wrap our minds around--sort of. It's still pretty weird and wild there, most likely.

The side facing the star would be far too hot to be hospitable. Likewise, the dark side, gripped in perpetual night, would be too cold. In between, however, there would be region of perpetual twilight where temperatures might be reasonable, if not downright comfortable, to creatures like we're used to. There are regions of our own planet, for example, that experience long periods of twilight, for example, such as northern Canada.

As my friend Bruce Cordell was quick to point out, however, because you've got a hot region right next to a cold region, that in between area is going to be wracked by storms. Storms that never stop, and are likely far, far worse than any storm known on Earth. But maybe all that potential liquid water is held in deep Gliesean seas. Deep down under the surface, it might be pretty comfortable for aquatic life to flourish.  Perhaps that life would not just adapt to the situation (as life does), but would go a step further and use it to its best advantage.

For example, imagine an organism with different life stages, each needing and flourishing in a different environment. A larval stage that needed warm waters and exposure to sunlight to grow, dwelling on the edges of the day side of the planet, staying near the surface of the water that eventually matures into a different stage that needs cool temperatures (maybe to aid in reproduction), so it migrates to the night side.

The fact that Gliese doesn't have a daytime and nighttime would make for a very alien intelligence that looked at time very differently than we do. Day and night wouldn't be related to time, they'd be related to place. Our migratory multi-stage organism, if intelligent, would think of "day" and "night" as the first and second halves of its life. Shorter spans of time might be measured in terms of sleep periods or periods between needing to eat, although the strange nature of the planet and the creature might make those things very different from what we're used to as well. For example, because there's no natural light-dark cycle force upon it, perhaps our intelligent aquatic being wouldn't have a sleep or eating cycle anything like ours. Perhaps it would hibernate for long periods and then awake to eat after a long fast. Maybe in its larval stage it would never sleep or eat, deriving all of its energy from sunlight, but in the adult stage it would sleep and eat a lot to survive in the cold.

It's fun to speculate. I've got even more ideas, but now that my creative juices are flowing I'm starting to think about putting them into a story.

Yay, science!