These nondescript stones really are from Mars! They are part of a meteorite collection at the Naturhistorischen Museum Bern. (Photo courtesy Beda Hofmann.)

The piece at the lower left will be on display at the exhibition, along with a magnified image of the thin slice at the upper left. Both are cut from the Zagami meteorite, which landed in 1962 in a farm near Zagami in Nigeria. A local farmer witnessed the fall from just a few metres away. (Sadly, we have not been able to find his name.) Later analysis of trapped gas within the meteorite showed the same isotope ratios as the Martian atmosphere, thus revealing the Martian origin of the rock. It is presumably part of debris ejected by an earlier meteorite impact on Mars and fortuitously launched into a transfer orbit that would take it to Earth.

In a charming epilogue, another piece of the Zagami meteorite subsequently returned home by spacecraft.