5 Most Incredible Discoveries of the Week

An amazing find by a sharp-eyed astronomer and a bizarre discovery about the pooping habits of dogs are on this week's list:

• For 2nd Time Ever, We Saw an Asteroid Before It Hit Us: While working a solo shift on New Year's Eve, an Arizona astronomer spotted a car-sized asteroid en route to Earth. There are a few amazing things about this: 1) It's only the second time ever that an asteroid has been spotted before impact, and 2) The previous one was spotted by the same guy.
• Dogs Use Earth's Magnetic Field to Poop: There's a reason why dogs position themselves just so before doing their business, say scientists. Rover and friends just might be getting in sync with the Earth's magnetic field—and in a very specific way.
• Ancient Obelisk's True Purpose Revealed: Researchers using 3D modeling and data from NASA think they've discovered the true purpose of the Obelisk of Montecitorio—upending a theory that has stood for decades. The 71-foot-tall ancient Egyptian obelisk was brought to Rome by Emperor Augustus, but it seems he was paying homage to Apollo, not himself.
• Ancient Diamonds Aren't Exactly Diamonds: Back in 2007, a team of researchers said they'd found 4.3-billion-year-old diamonds inside zircon crystals taken from Australia's Jack Hills. But those researchers had used a grinding paste made of synthetic diamonds to polish the zircons in preparation for lab tests, and that apparently led to a big mistake.
• China's 'Great Wall' Wasn't Its First Great Wall: As NPR tells it, archaeologist Gary Feinman was "simply walking around eastern China's Shandong province" on a hunt for pottery shards when he found something much, well, greater: a rammed earth wall that reached as high as 15 feet in places. Then he decided to map it, and things got really interesting.

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