• On the clear, moonless night on May 20, 2012, Wayne Jaeschke recorded a Martian phenomenon that he was sure couldn't be real: an unexplained cloud moving the Mars atmosphere. And now, two and a half years later, professional scientists who have studied it still aren't sure what it is, according to their report out in Nature today.
  • Oddly, the rotating plume could only be seen as it crested the northern horizon (never the southern horizon.) By all reckoning, it was high enough in Mars's atmosphere that it should have been dispersed by solar wind—but it persisted for over 10 days.
  • Luckily (thanks to a bit of auspicious, improbable timing) we may have an answer soon. MAVEN, the atmospheric NASA probe that Jakosky heads, has only just reached Mars last September—and is currently orbiting the planet and collecting its first round of data.

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