SR388... This is an unnamed frontier world that has yet to be examined by the Federation...

Old Bird

This is where the trouble began...

Chief Hardy

SR388 was a planet that was explored by Samus Aran during Metroid II: Return of Samus and its remake, Metroid: Samus Returns. It was then briefly visited again in the very beginning of Metroid Fusion, before the rest of the game takes place on the Biologic Space Laboratories research station which orbits the planet.

The planet was of great significance, due to the fact that it served as the homeworld of the Metroid species. As such, it was referenced numerous times throughout the series, including in the original Metroid's manual. It was later discovered that the X Parasites were native to the planet as well.

The planet's coordinates are given as 371° / 012° / 02° in the Samus Returns introduction, observable on Samus's Gunship monitor.

Complete Map of SR388 : [3]


MSR Art Gallery 033

The surface of SR388.

The barren surface of SR388 was notable for its rough, rocky and dry terrain (possibly as a result of earthquakes), with a greenish atmosphere that was likely toxic or radioactive for humans, who required special, protective suits in order to explore the planet. Storms and hurricanes were shown to happen on SR388's surface, making its conditions even harsher for life.[1] Underneath SR388's surface was a vast maze of tunnels and lava, where most of the planet's native fauna used to live, with some of them occasionally coming to the surface in search of food.[2]

MSR Chozo Memory 03

The Chozo and their machines exploring the interiors of SR388.

Since the planet was once inhabited by the Chozo, it is safe to assume that they created much of the underground complex. The ancient Chozo's colonies filled portions of the planet's interior, and many had deteriorated into ruins. The race had long since either abandoned SR388 or were wiped out. Many robots and drones left by the ancient civilization were still functioning during Samus' mission on the planet, but most of these synthetic beings had seemingly gone rogue since then and displayed high aggression against her. One of them was the Diggernaut, a gigantic robot used for mining operations that also attacked any intruders. Incidentally, Chozo Statues and weaponry could be found amongst the ruins.

A unique quality to the planet is the presence of Aeion energy. While it is evident that Aeion is found within all native life forms of SR388 and can be collected from their deceased bodies, it is later implied that the energy is initially produced by the planet itself as a form of natural radiation; several Chozo Memories feature rays of golden light (matching those from Aeion) emanating from fissures on the ground deep below the surface of SR388. Aeion energy has several uses, the most notable being fuel for the gauge which powers four mysterious artifact abilities.

In Metroid II: Return of Samus, lava on SR388 blocked off many of the underground caverns and ruins. The planet was described in various sources as being unstable and prone to earthquakes. In the game, these frequent earthquakes occurred and when they did, it usually happened in conjunction with the lava level decreasing, often-times exposing new areas of the planet to be explored. These earthquakes coincided with Samus exterminating a certain amount of Metroids; it is possible these lava level lowering tremors were caused by the Queen Metroid in response to Samus's efforts.

In Metroid: Samus Returns, the lava was changed to a purple hazardous liquid which would be lowered when Metroid DNA was inserted into the Chozo Seals. One of the Chozo Memories and the Official Guide states that the seal was built in order to somehow contain the Metroids within SR388 after the artificial life forms started rebelling against their creators. Much more traditional Lava, as seen in Sector 1 of the BSL, is still present in superheated areas of SR388.

The entirety of Metroid II and Samus Returns took place on SR388.

SR388's solar system Edit

Based on the cutscenes seen in Metroid Fusion and Metroid: Samus Returns, an asteroid belt appears to be in close proximity to SR388, possibly caught in its orbit. In the latter game, the planet's star which illuminates it can be seen in the distance, as well as what appears to be a black hole with a line of matter erupting from both sides. A neighboring planet designated as SR387 is seen in a wire-framed map of this solar system.

After the Metroid species was rendered extinct on the planet by Samus Aran in Metroid II and its remake, the Galactic Federation constructed a massive space station out of an asteroid that orbited near SR388.


SR388 Explosion Starchart

A large explosion engulfed the planet, but the neighboring SR387 was not destroyed.

This facility was used to observe, research and study animals from SR388 and various other planets. Specimens from the now-destroyed Bottle Ship were also brought in; unlike the prior ship, the B.S.L. was seemingly intended peaceful, scientific purposes. Within the station were six sectors; five of these were constructed to emulate specific climates and housed the organisms that best suited each of them. A single sector called SRX would be entirely dedicated to replicating SR388's environment.

Main article: SRX

The sector would be home to not only the animals captured on SR388 by the Biologic's research team, but also the Metroids created within the station's Restricted Laboratory.

Metroid FusionEdit

SR388. A vile planet, former home of the Metroids. After so many years, the remaining creatures on this planet still seemed to be trying to recreate a natural hierarchy, one without Metroids at the top.

—Samus Aran

The events of Metroid Fusion mainly take place on the previously mentioned Biologic Space Laboratories research station orbiting the planet. SR388 is only briefly visited by Samus in the game's cutscene introduction when she accompanies the Biologic's research team to protect them from hostile life forms as they collect samples and specimens.

It is during this visit that Samus becomes infected with an X Parasite, leading to the events of Metroid Fusion where an outbreak would spread out in the B.S.L. station. Samus was ultimately forced to change the station's orbit and crash it into SR388 in order to eradicate the X on both the station and their native world.[3] The former home of the Chozo and Metroids were thus destroyed in a massive explosion.

Official dataEdit

Development RoomEdit

SR388 map

Map of SR388, Metroid II instruction manual

"In the 'Metroid' manga, it describes that "The Chozo developed the Metroids in order to exterminate the X living on SR-388", but I think it was previously established that "there is a high probability that the Metroid destroyed the civilization on SR-388." I think it was the X that really destroyed SR-388."

Yoshio Sakamoto: "I think SR-388's civilization was destroyed and the Chozo left for Zebes after the Metroids were released into the wild (became feral). The Galactic Federation, not knowing the reason why the Metroids were developed, requested Samus to clean them up ("Metroid II"). The result of Samus exterminating the Metroids was that the propagation of the X could permit the SR-388 ecosystem to be destroyed ("Metroid Fusion")." [4] (Samus Returns)Edit

"This desolate landscape looks empty at first glance, but there is a dark and dangerous world waiting for you just below the surface."
A lost world
"The underground labyrinth of SR388 is filled with peril at each turn. From vicious flora to killer creatures, each step you take may be your last. As you explore the dark tunnels, you may notice the remains of an ancient civilization. Could this long-lost culture be connected to the Metroids that now infest its ruins?"
DEADLY ALIEN CREATURES — (blinking light)
"The deadly Metroids that inhabit SR388 are rapidly growing in number. Worse yet, they are evolving, becoming increasingly more powerful by the minute. This vicious species must be wiped out before they destroy the entire galaxy."
DANGER IN THE DARKNESS — (blinking light)
"Countless explorers have been lost in the twisted underground tunnels of SR388. Luckily, you will be equipped with enhanced tools to help you safely navigate the treacherous caverns."
ANCIENT ARTIFACTS — (blinking light)
"Besides the equipment you start with, there are many strange items you can find throughout SR388 to assist you."

Life forms and robotsEdit

There were a variety of animals on the planet, the most well-known being Metroids who were at the top of the food chain. Originally, the X Parasite was the most prolific of SR388's fauna and had reached a point where they endangered all other life on the planet. When the Chozo that colonized the planet became aware of the X's existence and evaluated their potential threat outside of SR388, they genetically engineered the Metroids to be the perfect predator of X Parasites. However, the civilization came to an end when their creations began molting into larger, more powerful forms that could no longer be controlled by their creators.

Despite this, the Metroids seemingly kept acting out their primary function of hunting down X Parasites, reducing the latter's numbers to an extreme scarcity. This helped SR388's other native life and flora to expand, though they would have to deal with occasional attacks from Metroids.

Living among the planet's wildlife were also a large amount of active mechanical constructs and robots left behind by the Chozo.

Mt hero2

Earliest known visual depiction of the planet in the Nintendo Comics System story, The Coming of a Hero.

Mfend a

Biologic Space Laboratories research station

Mfend d

Destruction of SR388.

Native Inhabitants:




  • Chozo (prior to the events of any game in the Metroid series)
  • Proteus Ridley (Samus Returns only)

Chozo Robots:

With the extinction of Metroids in SR388 by Samus Aran, the X Parasite population was able to re-surge on the planet, destroying much of its wildlife.

Additional floraEdit



Metroid: Other M

BSL soldiers

Metroid Fusion

Baby birth MOM commercial

TV Commercial :60 Spot

Note: This article lists locations by their names in Samus Returns. These areas use a different naming scheme in official walkthroughs of Return of Samus in Nintendo Power, which lists them as Phase 1 through Phase 9. Note that Phase 5 and Phase 6 were combined into Area 4, and Phase 8 was divided into Area 6 and Area 7.


The Surface area of SR388, where Samus' Gunship lands, and the first Alpha Metroid is fought.

Area 1Edit

Area 1 contains 4 Alpha Metroids.

Area 2Edit

Area 2 contains 6 Alpha Metroids and 2 Gamma Metroids in Return of Samus; 7 Alpha Metroids and 1 Gamma Metroid in Samus Returns; and the optional boss Arachnus in both games.

Area 3Edit

Area 3 contains 2 Alpha Metroids and 8 Gamma Metroids.

Area 4Edit

Area 4 contains 1 Alpha Metroid and 2 Gamma Metroids in Return of Samus; 1 Alpha Metroid, 2 Gamma Metroids, and 1 Zeta Metroid in Samus Returns.

Area 5Edit

Area 5 contains 4 Gamma Metroids and the only 3 Zeta Metroids in Return of Samus; 1 Alpha Metroid, 4 Gamma Metroids, and 2 Zeta Metroids in Samus Returns.

Area 6Edit

Area 6 contains 1 Alpha Metroid and 1 Omega Metroid in Return of Samus; 1 Zeta Metroid, 1 Omega Metroid, and the Diggernaut boss in Samus Returns.

Area 7Edit

Area 7 contains 3 Omega Metroids.

Area 8Edit

Area 8 is the final area of SR388, containing the Queen Metroid itself, 8 Larva Metroids, and the baby, which Samus brings back to Ceres Space Colony.



Metroid II Commercial.

  • SR388 is the last of four planets to be destroyed, even if not her intention, by Samus Aran, the others being Dark Aether, Phaaze and Zebes. It and Dark Aether are also the only two planets that she deliberately destroyed.
  • As mentioned before, artificial beings created by the Chozo can be found among the latter's ruins on SR388, many of which have weapons installed on them and attack on sight. It is possible the Chozo created them to keep the native wildlife at bay or more specifically, to use against the dangerous X Parasites and X infected creatures.
  • Ever since the discovery of the Metroids and Chozo ruins on SR388, it was believed that the life-sucking organisms were responsible for the supposed annihilation of the Chozo inhabitants of the planet. However, when the existence of the X Parasites was uncovered, the initial theory had been put into doubt and the X were equally considered to be the main culprit. Samus Returns eventually confirmed it was the Metroids that killed or drove the Chozo off the planet.
  • During Metroid II and Samus Returns, SR388 seemed to have a relatively low population of wildlife. The X Parasites were seemingly responsible for this, as stated by Yoshio Sakamoto and the Metroid manga. This would also explain why, in Metroid Fusion, the BSL Station's SRX (a sector that perfectly replicates the planet) contained very few of SR388's wildlife seen in the earlier games; after the extinction of Metroids, the X undoubtedly resurfaced in large numbers and steadily reduced the fauna on the planet even further (if not completely), making Galactic Federation researchers' task of collecting varied specimens a difficult one.
  • The planet's name is pronounced differently between games. Fusion renders the last two numbers as an "88" (eighty-eight) while Other M makes them distinct digits as "8-8" (eight-eight). During the countdown sequence in Fusion, the computer voice pronounces it as "SR-three-eighty-eight". The narrator in the overview trailer for Metroid: Samus Returns also pronounces it as "Eighty-eight".
SR388 Samus Returns

Metroid: Samus Returns

  • A Galactic Federation Ripper specimen was known as "SR-478", a planet in the Nintendo Comics System was called RX 338, and the Pirate Homeworld is also identified in unused Logbook entries as "SN-883", all with very similar names to SR388. Several GF Database files identified in scans have similar names, such as BY-550.
  • Despite the Space Pirates being absent in the original Metroid II, the Space Pirates are known to be aware of SR388's significance, as well as having visited the planet; a scanned tank in the Metroid Processing room in Metroid Prime 3: Corruption states a specimen from SR388 had been moved. In addition, the presence of Metroid Eggs (matching those seen on SR388) within their facilities in Prime 3 and Federation Force heavily insinuates that they acquired these from the Metroid homeworld. In the remake Metroid: Samus Returns, Proteus Ridley arrives on SR388 to acquire the last Metroid, making it the first observable instance of Pirates setting foot on the planet; the same game's intro also states that they deliberately timed their attack on the Research Vessel Marina to coincide with their discovery of the Metroid in order to steal it, indicating they knew about the species' existence on the planet.
  • In the 2014 strategy game Planetary Annihilation, the name "SR-388" was included as one of the possible names a generated planet could have in the System Editor mode.
  • An interview with several of the staff from the original Metroid state that SR388 came from a motorcycle engine, SR400: " those days, while it was called 400cc, you didn't have any choice but 388cc, but it was written like that for the time being, and that's how it came out!" [5]

The atmospheric limit.

  • In Return of Samus, Samus can attempt to ascend into a high altitude on the planet's surface via her Space Jump or Spider Ball, but she will take heavy damage upon reaching a certain limit. This limit is denoted by a line, above which is greyed-out, clouded space. On her return to her Gunship, the harmful atmosphere appears much higher than it initially did, which allows Samus to climb over a cliff to reach her Gunship. The atmosphere is blocked off by clouds in Samus Returns, observable if Samus visits the Surface with the Space Jump or during the Proteus Ridley battle.


Samus Returns SR388

SR388 in Samus Returns.

  1. ^ Metroid: Samus Returns - Proteus Ridley Battle
  2. ^ Metroid: Samus Returns - Post-Credits Cutscene
  3. ^ Question 31 of the "Metroid FAQ", Metroid Zero Mission Official Site


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