These four ancient rocks were all found on Earth...but only one of them actually originated here. The others are pieces of distant worlds. One formed on an asteroid; another, on the Moon; and the third, on Mars. Impacts hurled them into space where they drifted for thousands—even millions—of years before plummeting to Earth as meteorites. Such precious samples carry evidence of the tumultuous history of our Solar System.

Acasta Gneiss
At 4 billion years old, this gneiss is the oldest known rock that formed on Earth. The Earth is about 500 million years older still, but little record of that early time has survived our planet’s geologic activity. In this satellite view of North America, you can see the region of Canada where the gneiss was found.

Shergotty
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. With its giant volcanoes Mars’s Tharsis Plateau is the most likely source of the "young," 180-million-year-old Shergotty meteorite. Few craters mar the region’s lava-covered plains, suggesting that they are geologically young.

MacAlpine Hills 88105
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 this image of the Moon are lunar highlands. Such terrain is probably the source of this meteorite.

Lost City
Cameras operated by the Smithsonian Astrophysical Observatory recorded Lost City's fall in 1970. The photos enabled scientists to reconstruct the meteorite's orbit and determine that it originated in the asteroid belt. We don't know which asteroid the Lost City meteorite came from, but it may have looked similar to the asteroid Ida.