The state of exoplanet sci-fi

Few recent findings have occasioned as much excitement as the detection of seven Earth-sized planets orbiting TRAPPIST-1, a red dwarf star about 40 light-years from Earth. Three of those planets lie in the habitable zone, a distance from the star that might support the existence of liquid water and therefore—just maybe—living organisms.

Despite all the enthusiasm, the TRAPPIST planets don’t resemble Earth in several important ways. TRAPPIST-1 is barely a tenth the size of the Sun. Its habitable-zone planets complete their orbits in 6 to 12 days and get pelted with UV radiation. Furthermore, the planets are tidally locked—the same side always faces their star. Such exotic conditions, and the tantalizing possibility that some extreme form of life could overcome those challenges, seem plucked straight out of science fiction.

Except that when it comes to exoplanets, it appears that sci-fi writers have some catching up to do. Stories over the past century have tended to focus on humans discovering and settling worlds that, despite some quirks, are perhaps too conveniently hospitable to our species. In science fiction, as in science, imaginations have been sparked by the possibility of a new Earth rather than a class of bizarre worlds that might nonetheless be able to support complex organisms. It may take the study of real exoplanets for the sci-fi community to rigorously explore what life might look like on a world that bears little resemblance to our home planet.

New planet, same atmosphere

Life-supporting exoplanets are a staple of sci-fi. Most tales begin long after the discovery of habitable planets outside our solar system, portraying humans and aliens with established civilizations that span galaxies—think Star Wars or Dune. A smaller group of stories specifically tackles exoplanet discovery and settlement.

One of the earliest entries in the canon is Edward Smith’s Skylark of Space, which was written beginning around 1915 and serialized for the magazine Amazing Stories in 1928. Smith’s book tells the story of Richard Seaton, a chemist who discovers a way to “liberate the intra-atomic energy of copper” using a newly discovered metal called X. He decides to use the new energy source to travel to the stars. Seaton and his friends eventually discover the planet Osnome, which is home to two races of humanoid aliens: the enlightened Kondal and the treacherous Mardonale.

Although the story was undeniably innovative for its time, Skylark has not aged well, particularly because of its clunky prose and the racial prejudices reflected in the descriptions of the “light” Kondal and “dark” Mardonale. Furthermore, Osnome is, in most ways, simply Earth in a new orbit. Seaton and his companions face few difficulties in landing on its surface or breathing its atmosphere.

In fact, most early fiction about exoplanets tended to take place on planets remarkably similar to Earth. For example, the explorers in the classic 1956 sci-fi movie Forbidden Planet find Altair-IV surprisingly welcoming, at least when it comes to a breathable atmosphere and sources of food. Twenty years before the film’s action begins, a scientific expedition to Altair-IV went missing. When Earth sends a new vessel to the planet, Commander John Adams finds Dr Edward Morbius living on Altair-IV’s surface with his teenage daughter, Altaira. Although Altair-IV holds mysteries and dangers, Morbius and Altaira have survived on its surface with little physiological difficulty, thanks in part to Morbius’s now-iconic assistant, Robby the Robot.

Exploring less welcoming worlds

Books about exoplanet colonization seemed to take a turn after the dawn of the space age. Perhaps inspired by the newfound evidence that nearby planets, particularly Mars , were unable to support human life, writers began envisioning worlds that posed significant habitability challenges.

Two notable entries in this category, Marion Zimmer Bradley’s Darkover Landfall (1972) and Anne McCaffrey’s Dragonsdawn (1988), were written as prequels to much more sprawling sci-fi series. In Dragonsdawn, 6000 human settlers land on McCaffrey’s signature planet, Pern, to start a new civilization away from the warfare and technological overdevelopment that devastated their home system. At first Pern, with its breathable atmosphere and lush ecosystem, seems like paradise. However, vicious spores called Thread, which destroy any organic matter that they touch, threaten the colony’s survival.

Darkover Landfall depicts an even more difficult path to colonization. Bradley’s characters also set out to find a new home, but they accidentally crash-land on a brutal, windswept planet orbiting a red giant star. As the castaways debate over whether to repair the ship or try to make the planet their home, they realize that the harsh ecosystem is not their only obstacle. The remnants of an ancient alien civilization are evaluating the newcomers, and they aren’t sure they like what they see.

Polish author Stanisław Lem created an even stranger exoworld in his classic novel Solaris (1961). We quickly learn from the protagonist, a scientist named Kelvin, that according to the laws of gravity the planet Solaris should have long ago spun out of its orbit. It should not be stable, and yet it is. Solaris’s orbit seems to be held steady by the “gravity-controlling colloid” that covers the planet like an ocean.

Kelvin, along with the other scientists at the Solaris research station, is tasked with studying this strange ocean to determine if it is a life-form. However, new visitors soon arrive at the station: physical beings who look and act like people from the scientists’ pasts. Kelvin slowly comes to believe that Solaris’s ocean is responsible for the creation of these visitors—and that the scientists may be able to communicate with the ocean through a psychic link.

Stranger than fiction

Real-life astronomers haven’t detected a planet as mysterious as Solaris, but they have spotted an unexpectedly diverse set of worlds that may be capable of supporting life. Kepler-442b rotates so slowly that there are probably weeks or months between sunrise and sunset. Proxima Centauri b likely gets bombarded by stellar winds 2000 times as strong as the ones reaching Earth. Kepler-452b was nicknamed “Earth’s cousin” because of the high probability that its surface is composed of silicate rocks, but it has twice the surface gravity of Earth, and its high density means that it could be covered with active volcanoes.

The 2013 short-story collection A Kepler’s Dozen (Hadrosaur Press), edited by NASA’s Steve Howell and astronomer and author David Lee Summers , uses real worlds discovered by the Kepler telescope as inspiration for 13 tales of life on exoplanets. “Our goal,” the editors write, “was to bring together science fiction writers and scientists involved in the quest for exoplanets to imagine what these real places might be like.”

Notably, many of the Kepler’s Dozen tales are set on exoplanets outside the habitable zone, making the collection distinct from the “new Earth” tradition of exoplanet fiction. Kepler-42d, a tidally locked planet with one side of perpetual daylight and another side of eternal night, inspires Mike Brotherton’s “Middle Ground,” which imagines how advanced life-forms might have evolved to thrive under those conditions. The characters in Laura Givens’s story “Turtle Soup” have been genetically modified to live on Kepler-36b, a small, hot planet that scientists believe might be covered in oceans. Howell’s own story, the lively “A Mango and Two Peanuts,” is set in the Kepler-37 system, which has three small planets circling their star in 40 days or less.

Although the collection suffers somewhat from unevenness, the stories represent a glimpse of where science fiction might go if real exoplanets are taken as inspiration. With notable exceptions like Solaris, most science fiction imagines worlds that are fairly amenable to human life. Perhaps sci-fi writers’ imaginations will get fired up as they examine the inherent questions raised by the discoveries of real-life worlds. Imagining how humans might rise to the steep challenges of investigating and landing on those new worlds, and considering what kind of life we might find when we arrive there, could inspire truly innovative works of science fiction.