Heat Shield Rock

Heat Shield Rock is a basketball-sized iron–nickel meteorite found on the Meridiani Planum plain of Mars by NASA's Opportunity rover in January 2005. It got its name because it was found by chance near the rover's own discarded heat shield; the Meteoritical Society formally named it the “Meridiani Planum meteorite” in October 2005. It was the first meteorite found on another planet and the third found on another body in the Solar System.

To survive largely undeformed, it must have hit Mars at less than about 1.5 kilometres per second, which gives a clue to how dense the Martian atmosphere was when it fell. Its lack of rust also says something about surface conditions, though when it fell is not known.

Mars's past: Its impact speed and lack of rust give clues to the history of the Martian atmosphere and surface conditions. Planetary science: Meteorites found on other planets help study how meteorites are spread through the Solar System and how planetary surfaces weather. History of space exploration: As the first meteorite found on another planet, it has a special place in the history of space exploration.

It has a hardness of 4–5.5 on the Mohs scale. A fingernail cannot scratch it, but a steel knife can. Its specific gravity is 7–8 g/cm³.

Its surface shows regmaglypts, the thumbprint-like pits typical of meteorites that have passed through an atmosphere. It first stood out because its infrared spectrum looked surprisingly like a reflection of the sky. It is 93% iron and 7% nickel, very like IAB iron meteorites on Earth.

On the “street to diamond” value ladder it sits on step 6 of nine: Fine ornamental and collector stone. Heat Shield Rock lies on Mars, so it is not a collector's item; its value is purely scientific. As the first meteorite found on another planet it has historic importance, and it tells us about the past of Mars's atmosphere and surface.