A meteorite found last year in the Sahara Desert is likely the first recognized piece of ancient Martian crust, a new study reports. The Mars meteorite NWA 7533 is 4.4 billion years old and contains evidence of long-ago asteroid strikes, suggesting that the rock came from the Red Planet's ancient and cratered southern highlands, researchers said... Humayun and his colleagues subjected NWA (short for northwest Africa, where the rock was found) 7533 to a series of analyses. The researchers determined the meteorite's age, for example, by determining that crystals within it called zircons formed about 4.4 billion years ago... The...