Acid Rain is a substance that is formed when pollution from an unprotected source enters a planet's water cycle, and in turn, acts as rain that falls from the sky, corroding metal products and acting as a hazard to humans. Acid Rain is featured in Metroid Prime 3: Corruption with extremely exaggerated volatile power.
The Pirate Homeworld is the only area that is plagued by the rain, due to the Space Pirate's constant pollution that ruins their environment. However, they do take action of the hazard, as they have installed drains that lead to an underground piping network that leads out of the facility. Every ground personnel at the Homeworld has also been equipped with a Hazard Shield, a device that protects its wearer from the harmful affects of Acid Rain and other substances. In a gameplay point of view, the Acid Rain's energy-draining qualities are extremely hazardous. When exposed to, Samus' energy drains at the same rate as it is refilled while exposed to Phazon in the PED Suit. However, after staying in the rain for an extended period of time, Samus will immediately be killed with the corrosive power of the rain. Additionally, Acid Rain is reported in Crateria on Zebes. This rain does not cause damage to Samus, most likely due to a lower acidity.
Acid rain also appears on Crateria, the surface of the planet Zebes. It is probably much less acidic than Pirate Homeworld's rain considering that it is unable to damage even Samus's weakest Power Suit. Acid rain is a possible factor contributing to the desert-like surface of Zebes.
Rain is visible on Crateria as Zero Suit Samus crash lands back on Planet Zebes in Zero Mission, if this is the same acid rain, then it is so neutral that it can't directly damage Samus's Zero Suit or face.
- The Acid Rain that falls during the fight with Gandrayda does conveniently less damage to Samus. This is most likely due to the boss fight taking place outside in an uncontrolled area.
- Interestingly, Demolition Troopers are not harmed by the rain as well as the Scritter enemy.
- Acid rain occurs on Earth and other planets in the Solar System (notably Venus). Though relatively neutral, Earth's acid rain is still able to severely damage forest ecosystems. This mirrors Crateria's acid rain.
- "Acid rain is prevalent on the Pirate Homeworld, where the constant pollution has ruined the environment. The caustic effects of the rain are incredibly volatile and will severely damage your suit. Exposure to the rain for any extended period of time will prove fatal. Avoid all contact with the rain." — Logbook "Acid Rain" (Metroid Prime 3: Corruption)
- "Drain releases acid rain into a piping network in the floor to be pumped out of the facility." —Scan Data-Courtyard Passage (Metroid Prime 3: Corruption)
- "Crateria is the surface area of Planet Zebes. It is under constant deluge of acid rain" Super Metroid Instruction Booklet, Pg 18