At 3.96 billion years old, this gneiss is the oldest-known Earth rock. The Earth is 500 million years older still, but no record of that early time has survived our planet's geologic activity. This specimen was discovered in the Northwest Territories of Canada. We know Shergotty came from Mars because it contains gas whose composition matches that of Mars's atmosphere as measured by the U.S. Viking spacecraft. An impact trapped the gas in the rock and flung it into space.
Few craters mar the region's lava-covered plains, suggesting that they are geologically young.
This specimen was discovered in Bihar, India, in 1865. A meteoroid impact ejected this rock from the Moon 300,000 years ago. It is similar to rocks collected in the lunar highlands by Apollo astronauts. The light-colored, densely cratered regions you see in images of the Moon are lunar highlands. Such terrain is probably the source of this meteorite.