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Rare luminous clouds get early start this year

These 'Noctilucent' clouds are rarely glimpsed from Earth - but Hadfield captured an image of the 'glowing' cloud formation from the Space Station. 'Noctilucent Cloud - rare super high altitude cloud, barely visible from Earth, seen at dawn in the mesosphere from ISS,' he Tweeted.

Noctilucent clouds are a rarity that form higher than any other type of cloud, and only when conditions are just right. This year, the 'right' conditions are happening earlier than they ever have before, and scientists believe climate change may be to blame.

Noctilucent clouds form when ice crystals collect on dust in the upper atmosphere. There's always a small amount of water vapour in the upper atmosphere, but the air is so thin at that height that, as Dr. Tony Phillips, of Science@NASA, says: "The odds of two water molecules meeting is slim, and of sticking together slimmer still."

[ Related: NASA scientists reveal extraterrestrial origin of rare clouds ]

The dust was the key to these clouds forming, but the source of the dust was a mystery. It was NASA's AIM satellite that gave us the answer: meteor smoke. The ice crystals were collecting on tiny particles of smoke left behind when meteors burn up in the upper atmosphere.

Still, the early start to this year's 'noctilucent cloud season' is a puzzler, because ever since people first reported seeing these clouds in the late 1800s, scientists have tracked a basic trend where they formed more often during solar minimums and less often during solar maximums. With 2013 expected to be the peak of the latest solar cycle, this should have meant a shorter and later-starting 'season', but the clouds started popping up as of May 13th, a week earlier than expected and possibly earlier than ever before.

Not only that, but these clouds, which were normally only seen very far north, have been spotted much further south in recent years, and scientists believe the reason may be more water vapour in the upper atmosphere caused by an increase in the amount of methane being released into the atmosphere, and due to more water vapour being drawn into the atmosphere because of warmer temperatures brought on by climate change.

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Piecing together the answers to riddles like these is challenging, but each discovery leads us to new insights on how our atmosphere and climate work. Seeing these pretty, iridescent clouds in the sky on a regular basis would certainly provide a nice show, but given the other consequences of climate change, the show wouldn't be worth the price of admission.

(Image and video courtesy: NASA)

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