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40. Wild Winds Made Gorgeous Mars Gorges: The ice cap of Mars's north pole was sculpted over millions of years.
39. Microbes Are the Key to a Happy Gut: Each person's unique ecosystem of gut microbes plays a vital role in good health.
38. Sinkhole Eats Guatemala City: Well, it didn't devour the entire city, but it did take down a clothing factory.
37. CIA Doctors Did Forbidden Research: A report states that doctors went too far with prisoners after the 9/11 attacks.
36. Astronomers Catch an Asteroid Smashup: An X-shaped tail provides direct evidence of a space collision.
35. Haitian Quake Signals Future Shocks: Is the Caribbean in for more serious shakes?
34. Our Jumbled Ancestor (pictured): With a braincase and limb bones that don't look like they're from the same species, this fossil poses an evolutionary riddle.
33. Science Saves the Chilean Miners: The dramatic rescue was a triumph of engineering and psychology.
32. Sleep Switch Found in the Brain: The chemical trigger that lets us nod off may not work on the whole brain at once.
31. Autism: One Label, Many Diseases. A study of more than 1,000 autistic children reveals daunting diversity in their genetic variations.