Summary

• LV-223 & LV-426 reveal Engineers' actions through xenomorph history in franchise.
• Unique atmospheres & life differentiate LV-223's jungle vs. LV-426's barren land.
• LV-223 & LV-426's ties explained through history, xenomorphs, and terraforming efforts.

In the Alien franchise, two moons play a vital role in the history of the xenomorphs and the most important happenings of the films and the world: LV-223 and LV-426. In Alien (1979), the crew of the Nostromo visits LV-426 to discover a xenomorph, and it almost kills them. Many years before that in the prequel, Prometheus (2012), the crew of the Prometheus landed on LV-223 and discovered the Engineers and the structure they created there. LV-223 and LV-426 are two of the three known moons of the gas giant Calpamos in the Zeta2 Reticuli system.

While the two moons may have originally featured similar climates, by the time they appear in the films, LV-223 is covered by a lush jungle filled with endemic life, most likely due to the Engineers' actions there. LV-426 is almost barren, featuring a rocky, mountainous terrain with no known native life. The characters revisit these moons throughout the franchise, but they appear most in Alien and Prometheus. Thanks to information from movies, comics, novels, short films, and all sources canon to the franchise, there's a lot of information available to compare and contrast.

LV-223: History & Description

The Moon From Prometheus

LV-223 features an atmosphere almost identical to Earth but with a much higher concentration of carbon dioxide (3.7%), making it toxic for humans to breathe. The weather there is described as being very harsh, with complex weather changes and natural silica storms. Endemic life includes monkey-like creatures, deacon sharks, and mutated factions of ants. However, these life forms may have arisen from the interference of the Engineers and may not actually be native. It's unknown when the history of LV-223 begins, but the Engineers first settled the planet before any of the Alien films take place.

In 2179, xenomorphs arrived on LV-223 with the Onager.

The ancient aliens built an outpost on LV-223, most likely a military base designed to make biological weapons, before an incident compromised their operation and wiped them out. Captain Janek (Idris Elba) asserts this idea in Prometheus. In 2179, xenomorphs arrived on LV-223 with the Onager, the ship piloted by Hadley's Hope settlers when they tried to escape the xenomorph infestation on LV-426. These xenomorphs remained trapped until 2219, when the Geryon, a ship in Prometheus: Fire and Stone, came to the moon in search of the missing USCSS Prometheus.

LV-426: History & Description

The Moon From The First Alien Movies

LV-426's atmosphere consists mainly of nitrogen and carbon dioxide, with smaller quantities of oxygen, methane, and ammonia. Its smaller size yet slightly decreased gravity in comparison to Earth suggests that it is composed of very dense materials, while basalt, rhyolite, and microgranite lava flows indicate a history of volcanic activity, though no ongoing volcanic or tectonic activity remains in any of the Alien franchise. The moon remains constantly racked by strong winds, though the small size makes it impossible for large, dangerous storms to form.

The Differences Between LV-223 & LV-426

The Atmosphere Is The Main Difference Between The Two

The most significant difference between LV-223 and LV-426 is that LV-223 has an almost Earth-like atmosphere, while LV-426 is a barren wasteland when the crews find it. However, Weyland-Yutani terraformed LV-426 in an attempt to make the two moons more similar. Interestingly, it seems that LV-223 was supposed to be LV-426 when Prometheus was in development, but Ridley Scott ended up changing it to a different moon.

It also appears that after the terrifying events that happened on LV-426, surviving colonists escaped that moon on a mining ship and ended up on LV-223, which is how the two moons actually tie in together if they truly are neighbors.

How LV-223 & LV-426 Are The Same

The Moons Appear To Have Been The Same Before The Terraforming

The two moons are close to the same size. Both LV-223 and LV-426 are located around Gas Giants. The two moons are close to 1/7 the diameter of them. This means that they are both around 1,200 kms, which means the Gas Giants are around 8,400 kms. As a result, both moons are easily much smaller than Earth. They are also extremely dangerous, as both ended up with xenomorphs living on them, although they likely were brought there by outside forces, whether Weyland or by accidental means

According to the Fire and Stone comics, the two moons are neighbors.

Some questions about the two moons make little sense, however. According to the Fire and Stone comics, the two moons are neighbors, but this was never part of the movies. With that in mind, if this is canon, and they are neighbors, the two should have similar atmospheres, making it seem like both were terraformed, just many years apart, one by the Engineers and one by Weyland-Yutani.

How These Moons Play Into The Alien Franchise

Alien, Aliens, & Prometheus

LV-426 is the first moon appearing in the Alien franchise, as the crew of the Nostromo is lured to its surface by a mysterious distress call in Alien (1979). The crew then discovers the xenomorph eggs when the face-hugger attacks Kane (John Hurt). Nostromo's crew finds a derelict ship on the moon's surface, later discovered to belong to the Engineers. In Alien, the crew finds the space jockey in the ship's control room, but no other signs of life within the massive structure until they come upon a bay filled with xenomorph eggs.

a human settlement was formed on LV-426, and the moon was renamed Acheron.

After the events of Alien and before the events of Aliens (1986), a human settlement was formed on LV-426, and the moon was renamed Acheron by its early inhabitants. The main colonist base on Acheron, called Hadley's Hope, housed 158 people before the xenomorphs killed all of them.

However, the moon in Prometheus is LV-223. This moon is where the archaeologists and scientists, accompanied by mercenaries and mechanics, went to learn more about the universe's beginning. When they arrive, they find mountains and canyons and discover the Alien Temples on the moon. It is here that David steals one of the ampules to study and uses the black liquid in it to release the aliens. It isn't until the comic books that the two moons are connected as being neighbors, though he movies never mention that.