Duncan Jones’s Moon rises high in the sky, but twinkles somewhat faintly. It borrows heavily from Stanley Kubrick’s 2001: A Space Odyssey, Ridley Scott’s Alien and Blade Runner, and Andrei Tarkovsky’s Solaris. It’s a variation on common themes, but themes that may not be common enough. And, compared to the others, Moon is exceptionally modest and accessible. It distills ruminations from the great sci-fi megillahs and boils them down to simple human drama.

In the not-too-distant future, Earth’s “clean” energy is mined on the lunar surface. The mines require only one overseer, who’s secluded on our satellite for three years; communications to and from Earth must be prerecorded, so his only face-to-face companion is a mobile computer called GERTY (voiced by Kevin Spacey), whose operating system is half-HAL-9000 and half-WALL-E. Sam Bell (Sam Rockwell) is finishing up his three-year contract as the movie opens. Homesick, he’s grown a grizzly beard and is surly with his programmed pal; he takes solace in videos from his family, and in making a paper model of his home town. But his reminisces get the best of him: He sees a mirage of his wife (Dominique McElligott) while driving in his lunar rover, and accidentally crashes into a giant thrasher. We then see Sam awakened by GERTY back on the station and forbidden to leave; but Sam seems to have an intuition, goes out to the thrasher, and discovers himself to be in the wreckage, as well.

If this passage seems a little hard to follow, it’s because there are now two Sams perambulating about the base. (If you don’t want to know why, you may not want to read on.) GERTY is invariably shady when the Sams question him about this, and, at first, the Sams can’t get much out of each other; they behave like one of the more unfortunate pairings forged through Craigslist. The “new” Sam thinks they’re both clones, and the old one concedes that their lives, memories, and destinies are all a sham; like the crew of the Nostromo in Alien, they are secondary to corporate directives. Eventually, they seek ways to return “home”—that is, to Earth—before a repair crew arrives at the base and discovers them both there. The Sams question their humanity and authenticity, but mature before our eyes. Like the vivacious replicants in Blade Runner, old Sam seems to be reaching his expiration date; new Sam starts out brutal and impatient, but learns to respect his fellow self.

Moon runs the old what-is-it-to-be-human jag, but does so at full gallop. Fancy bouts of pontification are disposed of without detriment to the movie; the screenwriter, Nathan Parker, keeps the dialogue ever fluid and never dripping with significance. Unlike cousin HAL, GERTY—by way of Spacey’s smarmy-smooth diction—is ultimately humane, but this revelation is never lingered on. The ambiguous little smiley faces that GERTY expresses himself with are enough to make the complexity of his “humanness” clear. But, despite such touches, which make this a shimmering crescent-moon of a picture, Jones’s conception hasn’t entirely waxed.

Moon was released a few weeks short of the 40th anniversary of the Apollo 11 landing, but its enthusiasm for space travel seems to have been jettisoned at takeoff. To my thinking, this broad pessimism is a tad regrettable; fortunately, it is not Jones’s focus. His eyes are more earthbound—toward people (or their equivalents), not planets. While there’s certainly nothing wrong with that viewpoint, it does make the movie seem limited in scope: Even when a feeling for cosmic wanderlust is absent, the cold beauty of outer space can be expressed no more vividly than on a wide silver screen. Someone once remarked to me that certain things are beautiful only when one is sad; in Moon, the loneliness and sorrow could be measured in light-years, but Gary Shaw’s cinematography looks clinical and cramped. It’s always adequate, and sometimes pretty, but never quite worthy of either the heavens above or Rockwell’s mere mortal below. Jones appears to be more of a humanist than Kubrick, but Kubrick’s command of the medium is, as yet, far greater than Jones’s. This shortcoming may seem superficial, but it has the potential to make Moon seem smaller than it is—and easily eclipsed.

But, despite some pictorial deficiencies, Jones’s direction is strong when the situation becomes tense, and his unusually judicious cutting (the film is only one hour and 37 minutes long) unleashes the fertile ideas poetically but efficiently; Moon’s lack of wonder may also be its lack of ponderousness. (In most movies of this sort, such as parts of Danny Boyle’s Sunshine, wonder and ponderousness are entangled.) Jones’s ideas speak for themselves, and so do his actors—and the fact that there are so few of them makes Moon’s ability to hold our attention even more remarkable.

Like Michael Cera, Rockwell is an actor whose nervousness makes him likable and worth rooting for. But Rockwell’s tweakier than Cera. Both actors emote melancholy proficiently, but Cera’s (at this stage of his career) is always easily resolved. Rockwell’s antsiness is never resolved; his characters—such as the coked-up paranoiac in Confessions of a Dangerous Mind, or half-wit brother of Robert Ford in the mythic Assassination of Jesse James, or impotent historian-activist in Frost/Nixon—never seem quite capable of taking care of themselves, and this makes one genuinely uneasy for him. Sam is no heroic Buzz Lightyear stationed on Moon; he’s scuzzy like the space truckers feasted on by Alien. But Rockwell gets to have it both ways, and pulls it off. He’s both the sickly, weary clone who’s collapsing like an addict in withdrawal and the fresh replacement who jogs, gets into fights, and needs Aviators when extracted from his synthetic womb. He’s playing the same man at different stages of a short life: It’s a compressed Benjamin Button stint, but achieved without the luxury of computerized makeup.

As A.O. Scott cleverly surmises, Jones “is no doubt tired of reading that his father is David Bowie,” but one can’t help but compare the introverted, fastidious elegance of Moon with the intergalactic intrigue of Ziggy Stardust. Both have their place. But Moon suggests “There Will Come Soft Rains,” Ray Bradbury’s Martian chronicle that told of domestic machinery going about its tasks long after an A-bomb wiped out those it had served. Bowie makes you want to visit outer space; Jones makes you happy you’re stuck on Earth.