Night-Shining Clouds Come Early Over South Pole

The rare types of wispy, blue-white clouds form when water molecules freeze around 'meteor smoke' close to the edge of space.

Night-shining clouds started glowing high above Antarctica earlier than usual this year, observations from a NASA satellite show.

These rare types of wispy blue-white clouds are called noctilucent clouds, or NLCs. They form when water molecules freeze around "meteor smoke" close to the edge of space, typically about 50 to 53 miles (80 and 85 kilometers) above Earth's surface - so high that they can reflect light after the sun sets.

The phenomenon looks spectacular from the ground, but scientists also have watched these night-shining clouds from above with NASA's AIM (Aeronomy of Ice in the Mesosphere) satellite since 2007. Data from AIM indicate that noctilucent clouds started forming around the South Pole on Nov. 20 this year as a tiny spot of electric blue that quickly expanded to cover the entire frozen continent, as this NASA video shows. (Photo Gallery: Reading the Clouds)

AIM's observations over the past few years helped scientists discover a key ingredient in night-shining clouds: "smoke" from meteoroids that bombard Earth's atmosphere. The falling space rocks leave behind a cloud of tiny particles that hovers about 43 to 62 miles (70 to 100 kilometers) above the ground.

Summer is primetime for noctilucent clouds. Because of global wind and humidity patterns, more water molecules are lifted up from the atmosphere during summer. It's also the season when the upper atmosphere is coldest, meaning more water vapor condenses into tiny ice crystals that latch onto the dust particles of disintegrated meteoroids, according to NASA. Accordingly, noctilucent clouds typically flare up over the South Pole from November to February (summer in the Southern Hemisphere), and then shift to the North Pole from May to August.

In all the years that AIM has been observing the clouds, only the 2009 noctilucent season got off to an earlier start in the South Pole, according to NASA. The 2013 season above the North Pole also started quite early (around May 13).

Though night-shining clouds are typically associated with Earth's poles, they have been spotted in recent years at latitudes as low as Colorado and Utah, NASA officials say. Some scientists studying noctilucent clouds think this shift could be an effect of increased methane emissions, since the greenhouse gas is known to boost the abundance of water at the top of Earth's atmosphere.

AIM launched on April 25, 2007. In August 2103, NASA officials announced that the mission was being extended for two years.

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In Photos: Crazy Cloud Patterns In Images: Mysterious Night-Shining Clouds Aurora Photos: Northern Lights Dazzle in Night-Sky Images Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

This story originally appeared on LiveScience's OurAmazingPlanet.

Observations from NASA's AIM spacecraft on Dec. 19, 2013, show noctilucent clouds (NLCs) over the South Pole.

Clouds, stars, and aurora borealis display in the night sky above, and reflected in the glassy surface of Lake McDonald, Montana. As a night sky watcher, I look forward to some amazing opportunities in 2014 to witness dancing aurora. In the meantime though, and as a celebration of the arrival of

this year's winter solstice

here are some spectacular photographs capturing the interactions between our sun and the planet we call home.

Northern lights (aurora borealis) above snow covered mountains at a fjord in the Norwegian arctic. The solar wind from the sun carries charged particles that are drawn by Earth's magnetic fields to the poles. In the high northern and southern hemispheres the solar wind particles collide with molecules and gas atoms in Earth's atmosphere. The interaction emits a glowing light that ripples across the sky.

A 15 second time exposure shows the International Space Station passing above the aurora borealis as viewed From Blackduck Minnesota on the night of June 6, 2013. The Station, with its 250- to 260-mile-high orbit, flies well above the aurora that is caused by the interaction of charged particles and the upper atmosphere at an altitude of 80 to 200 miles.

Northern lights above a bridge and snow covered mountains at a fjord in the Norwegian arctic. During the winter solstice on Saturday, daylight hours will be at a minimum for the year -- providing northern night-sky watchers with a longer opportunity to see the vivid colors of any potential aurora displays.

A person stands on a frozen river along the Dempster Highway in the Yukon of Canada watching a show of aurora borealis.

The night of Oct. 10, 2013, and into the very early hours of Oct. 11, north of Wasilla, Alaska, brought an incredible display of the aurora borealis over many parts of the state. Here they are seen over Willow, Alaska, and reflected on a small pond near Nancy Lake.

In this creative double image, aurora are reflected over lake Prestvannet in Tromsø, Norway.

Northern lights with the moon illuminating the skies and icebergs at the Jokulsarlon Glacial lagoon, Iceland.

Nothern lights dance above the Iowa landscape in this photo from June 2013.

Aurora borealis over Hotel ION in Iceland. Hotel ION is close to mountainous lava fields and Thingvellir National Park. The park is listed as a UNESCO World Heritage Site.