Hard rain

Every year about this time, when the night skies are clear, and when standing still under the stars for half an hour doesn't call for a parka, I like to go outside and take in the show. It's pretty simple astronomy: orient to a few constellations, vaguely familiar from the same splendid viewing last year; check out Joe Rao's latest almanac of the Moon and planets (see "The Sky in September," page 65); and, with any luck, "catch a falling star."

Most meteors are nothing fancy: a fleeting streak, often not very bright. A friend to say, "Hey, look!" is nice, because if you glance in the wrong direction, it's gone. But if rocks from the sky seem a small thing, no more consequential than the fireflies of July and August, take a look at the Moon. Turn to page 46 for the gallery of lunar photographs that accompany G. Jeffrey Taylor's article, "Moonstruck." Make a mental note of the chaotic surface. And the next time you're looking at the real Moon, imagine that you're a time traveler, gazing at the Earth as it appeared, say, four billion years ago.

It's easy to forget that the Moon records the history of our own cosmic neighborhood. The Earth, too, was once subjected to an inconceivably violent rain of rock--and without water or an atmosphere, our planet, too, might still look like the wasted battlefield of an epic war. The story of meteorites, as Donald Goldsmith tells it in his "Bolts from Beyond" (page 28), is a tumultuous one, but it is also a story with great scientific promise: a few dozen meteorites have been identified from the Moon, Mars, and the asteroid Vesta, serendipitous gifts from the cosmos that carry vital clues about our planetary origins.

To most people, though, the most noteworthy meteorite of the Earth's past was the one that killed the dinosaurs. That, too, was probably a lucky accident--for us. It's hard to imagine how we mammals could have so thoroughly covered the Earth had the killer asteroid not knocked off some big reptiles and opened up some turf. In his article "Terrible Lizards of the Sea" (page 36), Richard Ellis describes one of the more successful families of prehistoric creatures with large teeth that ever roamed--or at least swam--the Earth: the mosasaurs. Mosasaurs had flourished for a long time, 25 million years, and there is no reason to think they were on their way out when they were abruptly extinguished. We may owe our very existence to a big, fast-moving rock.

This month the newly renovated Arthur Ross Hall of Meteorites reopens at the American Museum of Natural History. Anyone fortunate enough to visit will find plenty more reasons there, as our columnist Neil deGrasse Tyson ("Universe," page 18) puts it, to "keep looking up."

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