Next week, Elon Musk is slated to make a big announcement about SpaceX’s most ambitious goal to date: the colonization of Mars. Musk has never shied away from the science fictional aspects of his ventures, and it’s a very safe assumption that genre works have played some role in his outlook on the world.

Colonization in particular has been a long-standing part of science fiction, whether it’s an explicit goal of the story or not. There’s countless stories about brave settlers setting down on worlds unknown, to help firm up humanity’s foothold in the universe. Indeed, the SpaceX founder has said on more than one occasion that he wants to make sure that humanity has a backup plan in case of a catastrophic accident.

So, let’s take a look at what science fiction has said about colonizing other worlds.

The Red Planet

Science fiction authors have had their eyes on the red planet for centuries as a colonial destination, long before we knew that living there would be a difficult proposition. Works by early authors such as Edgar Rice Burrough, C.L. Moore, Leigh Brackett, and Ray Bradbury all imagined human settlements on Mars akin to the wild west.

Recently though, there have been a number of books that imagine the terraforming of Mars in great, realistic detail. The best example would be Kim Stanley Robinson’s famous Mars trilogy, which includes Red Mars, Green Mars, and Blue Mars. Starting with a team of colonists, he charts the rise of an inhabited Mars over the course of centuries, and explores the social and political consequences of such a world and its relationship with humanity’s home planet. It’s also worth checking out his book 2312, which features a solar system with many terraformed and inhabitable worlds.

Another good recent example is James S.A. Corey’s Expanse series. While the series isn’t explicitly about colonizing the solar system, that does figures in prominently, as the planet becomes a major political player in this future, inhabited solar system. Corey does go beyond our Solar System as well: the fourth book in the series, Cibola Burn, takes the story out to a distant, habitable world, where a group of settlers attempt to start a colony on what turns out to be a highly dangerous planet.

However, the most realistic depiction that I’ve ever seen about Mars being colonized comes not from a book about colonization, but the third installment of Linda Nagata’s Red trilogy, Going Dark. This military science fiction series explores the growing chasm between a wealthy superclass (called Dragons) and the regular humans of Earth. By the end of the series, Nagata portrays an infant Martian colonization effort as a foolhardy errand put on by a select few as a way to escape the problems of Earth.

It’s easy to see why Mars is such an attractive option for SF authors: in terms of cosmic distance, the planet is just a short hop away from Earth — meaning that it’s a relatively easy trip back and forth in case anything goes terribly wrong, but far enough away that you don’t have to worry about direct interference from home. Mars has some of the resources you need for a colony, such as water and a rudimentary atmosphere, which the Moon doesn’t have. Plus, you won’t die instantly on the surface from pressure, like on Venus.

What about outside of our Solar System?

Mars and the other planets of our Solar System certainly aren’t the only examples of places where humanity has set down a flag in the science fiction world. With the recent revelations that planets such as Proxima b could potentially be habitable, the thought of humanity spreading to the stars seems a little more plausible (provided you get around the distance issue).

Possibly the best example (and one of my all-time personal favorites) of interplanetary colonization is a novel called Coyote and its sequels, by Allen M. Steele. Steele wraps a lot into this book: the United States becomes an oppressive regime, and a group of dissidents steal a starship to colonize a moon known as Coyote. Over the course of the series, Steele looks as the challenges of settling a colony on an alien world with alien biology, as well as the politics involved in recreating a society away from Earth. Another great book from him is Arkwright, which portrays how humans could set up an interstellar ship and colonize a distant planet.

These challenges are mirrored in Karen Traviss’ fantastic five-book The Wess’Har Wars. Traviss looks at the complications of settling a colony down on a world that’s already inhabited by several alien civilizations, and the massive fallout that can occur when it’s done wrong. She also focuses heavily on the environmental impact, as humanity’s track record with keeping the Earth in livable shape isn’t exactly the most stellar.

While we’re looking at the challenges of settling a colony on another distant world, we need to throw Kim Stanley Robinson’s latest novel, Aurora, on the pile. While this book is mainly a realistic take on how humanity can travel to other planets, Robinson takes a hard look at what settling on a new world might look like when such a ship would arrive: incredibly difficult.

Colonization carries with it some difficult subject matter as well, which is the focus of Ursula K. Le Guin’s Hugo Award-winning novella, The Word for World Is Forest. In it, a human colony landed and enslaved a local population of peaceful aliens known as the Athsheans. After a human commander named Davidson rapes and kills the wife of Selver, one of the slaves, the Athsheans rise up in a revolt that ultimately forces the humans to abandon the planet, but not before introducing violence to their culture.

Colonization stories have some deeper, complicated roots within science fiction. Typically, these stories are about expanding humanity’s presence into space, either for a foothold to safeguard against extinction, or simply for economic opportunity. While these themes are present in solar system colonies, these stories typically have an additional set of ethics baked into their core: how do you co-exist with another species that has evolved on that world?

Indeed, we have an entire subgenre of these types of stories already: invasion novels, where Earth comes under attack by a civilization looking to set up shop on Earth, ranging from H.G. Wells’ War of the Worlds, all the way up to Cixin Liu’s The Three Body Problem. This has already been an ethical issue within NASA, as spacecraft and probes could potentially contaminate other surfaces in our Solar System.

While Mars isn’t necessarily inhabited by an alien civilization yet, Elon Musk is certainly aiming to make that happen within the next decades. Hopefully, SpaceX’s settlers will carry along some copies of these books to read when they arrive.