December 24, 2013
Electric Blue Clouds Cover Antarctica
[ Watch the Video: ScienceCasts: Electric-Blue Clouds Appear Over Antarctica ]
Lee Rannals for redOrbit.com - Your Universe Online
Noctilucent clouds (NLCs) are the Earth’s highest clouds, forming at the edge of space, 51 miles above the Earth’s surface. From a plane, the clouds appear as slivers of light streaking across the sky, because sunlight hitting the ice crystals that make up the clouds gives them a unique glow.
The clouds have been blanketing Antarctica since November 20th, when NASA says a tiny puff of electric-blue quickly expanded to overlie nearly the entire continent. The space agency’s AIM spacecraft is monitoring these clouds as they work around the continent.
"The clouds appeared over the south pole earlier than usual this year," stated AIM science team member Cora Randall of the Laboratory for Atmospheric and Space Physics in Colorado said in a statement. "Since AIM was launched, only the 2009 season got an earlier start.
NASA said some experts initially believed NLCs were a side-effect of the Krakatoa volcano eruption that took place in the middle of the 19th century, followed by the spread of volcanic ash throughout the atmosphere.
It is currently summer time in the south pole, which means these clouds are at their peak. This season brings proper wind patterns and flow of humidity to the atmosphere and the greatest number of water molecules, which mix with “meteor smoke” at the edge of space. Summer is also the time when the upper atmosphere is coldest, allowing the ice crystals to form the clouds.
The clouds can be seen at both the North and South Pole, but NASA said NCLs have intensified and spread over the years and can sometimes be seen as low as states like Colorado and Utah. Researchers believe this could be a sign of climate change because of the greenhouse gases that have become more abundant in Earth’s atmosphere since the 19th century.
AIM has helped to show that meteors play a role in the clouds’ formation. Specks of debris from disintegrating meteors act as nucleating points where water molecules can gather and crystallize.
"When methane makes its way into the upper atmosphere, it is oxidized by a complex series of reactions to form water vapor," stated Hampton University Professor James Russell, the principal investigator of AIM. "This extra water vapor is then available to grow ice crystals for NLCs."
Since AIM launched, it has helped make numerous discoveries about NLCs and the way these clouds are affected by long-distance teleconnections in the atmosphere. NASA said that it has extended the AIM mission for another two years, giving scientists even more time with this instrument to understand one of Earth’s more-mysterious cloud species.