One of the best things about a good science fiction story is that it can take you to another world–literally! Well, not in the sense of actually physically taking you there, but if you want to experience the thrills of an alien world from the safety of your favorite chair, the best way to do it is to immerse yourself in a good space adventure story.
Planets are to science fiction what islands and continents are to fantasy. It’s possible to tell a story where no one ever sets foot on one, but then you’ve basically got a sea story (since space is an ocean, at least in most space opera). Even then, your characters are probably going to put into port from time to time, if for nothing else than a change of scenery to make things interesting. And if there’s anything science fiction interesting, it’s the wide variety of possible planet types.
For example, what would a planet be like if it were covered completely by water? If the world-ocean was so deep that there was no visible land? Assuming that the planet orbits within its sun’s habitable zone, where the temperature ranges allow water to exist as a liquid, then you would have a pretty interesting place. What would the hurricanes be like? A lot more intense than the ones here on Earth, that’s for sure.
Then again, suppose that the planet was a bit closer to its sun, and most of that water existed in the atmosphere as a gas. You’d have some pretty intense atmospheric pressures on the surface, but the density of the atmosphere would make it much easier to keep airships and flying castles aloft. In fact, that might be the most practical way to settle that kind of a world.
In our own solar system, there is an incredible amount of variety. On Mars, for example, glaciers of dry ice cover the southern pole, while the sun sets blue in a normally dirty brown sky. The tallest mountain actually summits above the atmosphere, and every few years, dust storms cover the whole world. And believe it or not, Mars is a lot more similar to Earth than anything else in our solar system.
On Titan, rivers of liquid methane flow down mountains of water ice, while black carbon dunes drift across a desert shrouded in orange haze. While the sun rises and sets with predictable regularity, the planet Saturn is suspended at the same point on the horizon and dominates a large portion of the sky. Don’t expect to see any rings, though–Titan orbits along Saturn’s ring plane, so the rings are mostly invisible.
Europa, one of the four Galilean moons of Jupiter, is also dominated by its host planet. Water ice covers the surface, but deep, deep below, there’s a massive liquid ocean that has never seen the light of the sun. What sort of monsters lurk in those depths–an ocean buried beneath a world?
Jupiter itself is pretty intense. A gas giant world with swirling bands of planet-sized clouds, it hosts a monstrous hurricane large enough to swallow at least two Earths. This vortex has been churning across the planet for over 150 years, and possibly as much as 350. I still remember the chills I got when I read 2001: A Space Odyssey, and the scientists’ probe dropped through the haze to a cloud deck as massive as one of our continents here on Earth.
Gas giant planets can be really interesting. They aren’t human habitable, since the gravity and pressure are so intense that anything man-made would be crushed before it could hit the surface, but those same forces can lead to some other interesting things. For example, at the lower levels, you may find storms that rain diamonds. Go further still, and you find an intense magnetic core that’s just on the verge of being able to sustain nuclear fusion. Detonate enough nuclear material down there, like they did in a short story from the Halo universe, and you can turn the planet into a star.
And that’s just our solar system. What about the hundreds of exoplanets that astronomers are now discovering? The first one to be confirmed, believe it or not, was orbiting of all things a pulsar! Imagine that–instead of the life-giving rays of a sun, the planet is bathed in highly lethal X-rays and gamma rays.
Of course, there are plenty of planets orbiting stars like our sun, but most of the ones discovered so far are hot Jupiters–gas giant worlds that orbit so close to their sun that the years are measured in hours. Some of these planets are so close that the sun is actually blasting the atmosphere away. We haven’t discovered the rocky core of a gas giant world that’s been destroyed in this manner, but theoretically it could exist.
Or what about the planets with highly elliptical orbits that traverse the habitable zone of their stars? Imagine: a world where the winters are so cold that the oceans freeze solid. After several of our Earth years, the spring brings a massive thaw. For a few short months the weather is actually quite balmy. Then, as spring turns to summer, the heat grows more and more intense, until the oceans begin to boil! When the summer reaches its zenith, the planet is nothing but a scorched desert wasteland. Soon, though, the autumn cool brings back the rains, with storms so intense that they refill the oceans in just a matter of months! Then, the deep freeze of winter begins, and the world returns to its long icy tomb.
One of my favorites, though, is the ribbon world that Asimov predicted in some of his stories. Worlds like this occur most commonly at class M red dwarf stars, which are so cool compared to our sun that planets within the habitable zone are tidally locked. This means that the sun neither rises nor sets, but remains stationary in the sky. The day side is burning hot, with either a barren desert wasteland or a giant hurricane large enough to cover most of the hemisphere. The night side, on the other hand, is so cold that all the water is completely frozen. The only habitable parts of the planet exist in a ribbon-like swath where the sun is just on the other side of the horizon, casting the land in perpetual twilight.
Believe it or not, we’ve actually discovered a planet like this in the Gliese system. Gliese 581g, or “Zarmina’s World” as the lead astronomer dubbed it, was discovered back in 2010. I was so excited by the discovery that I dedicated a blog post to it. Since then, the findings have not yet been confirmed, so it isn’t safe to call it a planet for sure, but if/when it ever is confirmed, it may be one of the first truly Earth-like planets to be discovered (at least, as Earth-like as a ribbon world can be).
In much of science fiction, there’s a tendency to make planets single biome only. Thus, you have your desert planets (Arrakis, Tatooine, Gunsmoke), your ice planets (Hoth, Gethen), your ocean planets (Calamari, Aqua), your jungle/forest planets (Dagobah, Lusitania, Kashyyyk), and even planets that are nothing but giant cities (Trantor, Coruscant). Some of the more recent series like Halo try to avert this, but even today it’s still fairly common.
If there’s anything that modern astronomy is showing us, though, it’s that the variety of planets and worlds out there is beyond anything we could possibly imagine. This is why I get a bit irked when an otherwise excellent series like Firefly makes out every planet to be like Wyoming. What about Gliese 581g? Kepler 22b? GJ 1214b? Kepler 16b?
As more exoplanets are discovered, I can’t help but believe that science fiction is going to experience a paradigm shift. What was once purely the realm of imagination is now being confirmed as reality. Alien worlds exist–alien Earths, even. And just as our conception of Mars changed from the Sword & Planet tales of Edgar Rice Burroughs’ Princess of Mars to the hard sf epics of Kim Stanley Robinson’s Red Mars, Green Mars, Blue Mars, so will our conception of other alien worlds.
I’ve got a lot of different planets in my own books, some borrowing a lot from the recent exoplanet discoveries, others leaning closer to the single biome worlds of classic space opera. In Desert Stars, Gaia Nova is kind of a cross between Arrakis and Trantor, with giant domed arcologies covering half the planet’s surface while the rest is mostly desert and wasteland. In Bringing Stella Home, Kardunash IV is (or rather, was) an Earth-like world, with forests, mountains, and oceans. In Stars of Blood and Glory, New Rigel is a straight up ocean world, while Ebitha from Star Wanderers is an ocean world tidally locked to its dwarf M class sun. I haven’t yet played with the elliptical planet, but I probably will someday.
One of the things I love most about a good science fiction story is that it takes me out of this world. With all the incredible new discoveries that astronomers are making, that aspect of the genre is only bound to get better. They’ve certainly enriched my own work, and will doubtless continue to do so in the future.