What Are Tholins? The Mysterious Substance That Turned Ultima Thule Red

Posted on Categories Discover Magazine

On New Year’s Day, NASA’s New Horizons probe streaked by a tiny world dubbed MU69, or Ultima Thule, the farthest object humankind has studied up close. With most of the data still on the spacecraft waiting to be transmitted, scientists are still getting to know this distant body. We know that it’s composed of two chunks of rock loosely stuck together. We know that it doesn’t have moons or rings that New Horizons might have careened into on its close pass. And we know Ultima Thule is red.

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