Figure 6-73 A Piece of Mars on Earth Mars’s thin atmosphere does little to protect it from impacts. Some of the debris ejected from impact craters there apparently traveled to Earth. (a) An SNC meteorite recovered in Antarctica. The 4.1-billion-year-old meteorite, designated ALH84001, shows strong evidence of having been exposed to liquid water on Mars, perhaps for hundreds of years. (b) Possible fossil remains of primitive bacterial life on Mars, although theories of nonbiological origins have also been presented.