Rust is an iron oxide, usually red in color and found mostly on iron, while tarnish is a thin layer, often black or gray, that forms on many different metals, says Fulton. When iron or steel is ...

The scientists decided that the planet’s red color more closely matches that of iron oxides containing water, called ferrihydrite. That version of rust typically forms quickly in cool water. Therefore ...

The new explanation for the reddish color – the rusty ... a process that continues today. But iron oxides come in many flavors, and the exact chemistry of Martian rust has been intensely debated ...