Darkness
The film has a markedly dark and gray-toned color palette, emphasizing the vast abyss of space, and reflecting the dark circumstances that the crew of the Nostromo finds themselves in. They are both literally and figuratively "in the dark" throughout the film. Hallways are shadowy and elusive. Power circuits blow, cloaking entire levels of the ship in darkness. The darkness of the film emphasizes the hidden nature of the evil lurking onboard. An unseeable enemy is all the more terrifying, as it could be anywhere at any time. Additionally, the creature itself is black when it is fully mature, which adds to its horror factor. Darkness emphasizes the film's depiction of the horrifying unknown.
Claustrophobia & Enclosed Spaces
In addition to the use of darkness, the constant enclosure in small spaces enhances the suspenseful and terrifying mood of the film. Ridley Scott brilliantly invents scenarios that capitalize on the horrors of enclosure and claustrophobia. During Dallas' trip into the air vents to try and trap the alien, the camera makes angles that give the impression of enclosing the audience, just as Dallas feel cramped and enclosed. In the famous jump cut, in which Dallas is attacked by the alien, Dallas is trying to get oriented in the small space, but struggles. The viewer is brought along on his terrifying journey through the space. We do not watch the horror take place from far away, but experience the same surprise that Dallas does when the alien suddenly emerges in the small space. When Brett dies, he is also somewhat enclosed; even though he is in a large part of the ship, he is apprehended by the alien in close quarters. Later, Parker wants to kill the alien and save Lambert, but he cannot do so without killing Lambert because they are in such a small space. Indeed, the entire scenario is a claustrophobic one. The crew members cannot leave the ship, and though it is large, it becomes a kind of inescapable prison once the alien comes aboard.
The Alien
The most notable image of the film, perhaps, is the alien itself, which is notably grotesque and disturbing. You see it in every stage of its development, and throughout it appears horrifying, neither animal nor human nor plant, something closer to a demon or a monster. When it first erupts from Kane's chest in a bloody mess, it is unthinkably disgusting, like a small eyeless snake with fangs. Adding to the horrifying shape of the alien itself is its unceremonious birth through Kane's body. It is truly disgusting, and Ridley Scott intended for it to be so, basing his design for the creature on art by a Swiss surrealist, H.R. Giger, as well as on images of deep sea creatures, spiders, and other grotesque animal inspirations. The result is truly monstrous. In its adult state, the alien remains eyeless, and has a small mouth within a larger mouth which protrudes forward and can easily kill its prey. It also has a preternaturally long head, threatening posture, and walks on two legs. Its black skin allows it to hide in the dark, even remaining unnoticed on the escape vessel.
Ripley in her Underwear
One of the most iconic images from the movie is Ripley, played by Sigourney Weaver, stripping down to nothing but a tee-shirt and her underwear on the escape vessel. The moment is a strange combination of sexy and scary, as she soon realizes that she is not alone—the alien has followed her on. Her state of undress is an unexpectedly sexy moment in an otherwise grotesque and unsexy film. Having only worn space suits and genderless uniforms, Ripley finally believes she is safe enough to take off her clothes; who can blame her, she thinks she is alone in space with a cat. However, the ultimate predator lies in wait. Ripley's nakedness combined with her unawareness of her own vulnerability renders her all the more endangered, representing her nakedness not just literally, but also in terms of safety. Ripley's state of undress positions her not only as a straightforward victim of the evil creature, but also—in true horror movie fashion—an unknowing victim of a more sexually-tinged evil as well; not only is she in danger of being attacked, but also of being spied on.
