Ferric oxide
Ferric oxide (Fe2O3), commonly known as rust, was a compound made up of high levels of corroded iron particles.

When the landing party from  searched the colony on Terra Nova for any sign on the whereabout of the colonists, Sub-commander T'Pol stated that there was no sign of weapons fire, only rust. ()

In 2371, the crew of  detected this compound in open space while traversing the Delta Quadrant. Its detection raised the question, from Captain Janeway, "how could iron rust in space without oxygen?"

Unable to determine an answer, they decided to follow the "trail of rust" to determine its source, which led them to the  of complex hydrocarbons in the rust, notably benzene, ethylene, and acetylene, the components of gasoline. Once located, the source was discovered to be a 1936 Ford truck, formerly belonging to an Ohio farmer. ()

When presented with the idea of traveling back to the 20th century aboard the , Leonard McCoy asked James T. Kirk if he was "really going to try this time travel in this rustbucket?" ()

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de:Eisenoxid
Chemical compounds