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xcept for a handful of manned missions to the moon, people have seen celestial bodies only from afar. But sometimes, bits of those far-off space rocks crash onto Earth. We call these rogue bits of space rubble meteorites. And they offer rare, handheld samples of the materials that make up distant places in the solar system. Some meteorites are bits of asteroids or comets. Others are pieces of debris that were blasted off the moon or Mars by asteroid or comet impacts. Still others may have come from planets that no longer exist. Some 44 metric tons (nearly 50 U.S. tons) of space rock are thought to hit Earth each day. Almost all of it burns up in the atmosphere. Still, tens of thousands of meteorites larger than marbles are thought to land on Earth each year. They can be hard to find, though, amongst all the other rocky bits on our planet. That’s why some scientists search for them in the flat, white terrain of Antarctica. Many meteorites consist of rock leftover from the early solar system. (Due to Earth’s plate tectonics, much of the rock on our own planet is much younger.) That means meteorites can offer clues about our solar system’s history. They can also hint at whether other places in our solar system have hosted the right conditions for life in the past. Earth isn’t the only planet that gets pelted with space rocks. Mercury, for instance, may be coated in diamond, thanks to meteorites bombarding its surface. The solar system is a pretty violent place. So while it might be cool to find more meteorites lying around, it’s probably best that our atmosphere shields us from most rocks raining down from space.