Samus Aran's cybernetic suit is said to have an Infrared Ray Scope in the manual for Metroid II: Return of Samus. This predates the introduction and use of her X-Ray Scope, and may be the basis for the Thermal Visor.
Despite the description saying Samus can see in the dark, it does not allow her to see in total darkness. Some dark areas in the Metroid games are completely unviewable, including a pitch-black section of Phase 7's Chozo ruins in Return of Samus itself. It is possible this was meant to be an upgrade in the game that was later scrapped. Alternatively, it could simply be providing a canon explanation for how Samus can see in most underground caves and tunnels without any apparent source of illumination.
No mention of such an item has been made in any further Metroid or related media.
Manual[]
INFRARED RAY SCOPE
"Allows Samus to see, even in the dark."
Virtual Console Manual[]
Infrared Scope
"An infrared scope that ensures perfect vision even in the dark."
| Heads-Up Display |
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| Targeting Reticule | Threat Assessment | Radar | Map | Energy Meter | Phazon level | "Heart Monitor" Translator Module | Screen-Shot Tool | "Low battery warning" | Sight Window | Scan Point | Infrared Ray Scope Charge Meter | Missile Counter | Ammo Gauge | Visor Select | Command Icon | Hover Gauge | Aeion Gauge | Bookmark/Map Pin | Nav point | Points bonus |