MessageToEagle.com - Northern sky watchers first noticed these strange clouds in 1885 about two years after the eruption of Krakatoa.
The question is: did they even exist prior to 1885?
It seems very unlikely that experienced astronomers and meteorologists would have overlooked such remarkable phenomena
as noctilucent clouds.
Krakatoa was one of the greatest volcanic eruptions that has ever taken place.
It catapulted
enough water and particles into the mesosphere such that —two years after the event, noctilucent clouds formed."
"After various volcanic eruptions, increased twilight phenomena were observed over many
years and there is enough data providing good insight into the twilight and night sky variability,
but only in terms of regular and irregular color phenomena in the sky."
However, no noctilucent clouds can be identified from the descriptions in these reports before 1885.
Eventually, Krakatoa’s ash settled and the sunsets faded, but strangely the noctilucent clouds didn’t vanish.
They’re still present today, stronger than ever. Researchers aren’t sure what role Krakatoa’s ash played in those early sightings.
Some scientists have already suggested noctilucent clouds may be regarded as indicators of
global change in the physical structure of the mesosphere during recent decades, a process that is on going.
Click on image to enlarge
Noctilucent clouds. Photo Credits: nlcnet.co.uk/
Previously only seen over almost exclusively in Earth's polar regions, but they are now also visible in
the skies over the United States and Europe and else where.
Now scientists can at least to shed some light on their mysterious origin.
A new ScienceCast video explains how "meteor smoke" seeds noctilucent clouds
A key ingredient for the mysterious clouds comes from outer space, they say.
"We've detected bits of 'meteor smoke' imbedded in noctilucent clouds," reports James Russell of Hampton
University, principal investigator of NASA's AIM mission to study the phenomenon.
"This discovery supports the theory that meteor dust is the nucleating agent around which NLCs form."
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Noctilucent clouds, Kuresoo bog, Soomaa National Park, Estonia.
"Using AIM's Solar Occultation for Ice Experiment (SOFIE), we found that about 3% of each ice crystal
in a noctilucent cloud is meteoritic," says Mark Hervig of the company GATS, Inc, led the team that
found the extraterrestrial connection.
The inner solar system is littered with meteoroids of all shapes and sizes. When meteoroids hit our
atmosphere and burn up, they leave behind a haze of tiny particles suspended 70 km to 100 km above Earth's surface.
The process called "nucleation" happens all the time in the lower atmosphere. In ordinary clouds, airborne
specks of dust and even living microbes can serve as nucleation sites. Tiny ice crystals, drops of water, and snowflakes
grow around these particles, falling to Earth if and when they become heavy enough.
A graphic prepared by Prof. James Russell of Hampton University shows how methane, a greenhouse gas, boosts
the abundance of water at the top of Earth's atmosphere. This water freezes around "meteor smoke" to form icy noctilucent clouds.
Image credits: Hampton University
Nucleating agents are especially important in the ethereal realm of NLCs. The clouds form at the edge
of space where the air pressure is little more than vacuum.
The small size of the ice crystals explains the clouds' blue color. Small particles tend to scatter
short wavelengths of light (blue) more strongly than long wavelengths (red). So when a beam of sunlight
hits an NLC, blue is the color that gets scattered down to Earth.
So, it's no coincidence that NLCs form 83 km high, squarely inside the meteor smoke zone.
James Russell believes that our climate is changing.
One of the greenhouse gases that has become more abundant in Earth's atmosphere since the 19th century is
methane coming from landfills, natural gas and petroleum systems, agricultural activities, and coal mining.
It turns out that methane boosts NLCs.
"When methane makes its way into the upper atmosphere, it is oxidized by a complex series
of reactions to form water vapor. This extra water vapor is then available to grow ice crystals for NLCs,"
Russell explains.
Meteor smoke explains much about NLCs, but a key mystery remains:
Why are these strange clouds brightening and spreading?
(references: Thomas, G. E., Global change in the mesospher-lower thermosphere region: Has it already arrived?;
NASA, Bulletin of the American Meteorological Society)
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MessageToEagle.com - Northern sky watchers first noticed these strange clouds in 1885 about two years after the eruption of Krakatoa.
>
The universe is changing and stars are changing as well, even if they appear static and predictable every night.
Wolf-Rayet stars remain a fascinating subject of research for astronomers even if the first of them were discovered more than 140 years ago.
In the summer of 1867, French astronomers Charles Wolf and Georges Rayet observed for the first time three strange
objects during a visual spectroscopic study of stars in the constellation Cygnus at the Observatoire de Paris, France.
During a light storm we expect to see flashes in the sky and evil-looking clouds.
What we certainly do not expect to see are objects hiding inside these clouds.
When you look at these videos and images, it appears as if there is a solid object in the middle of the clouds...
The clouds are called noctilucent or "night-shining" clouds (NLCs) and they are a relatively new phenomenon.
Previously, they were only seen over almost exclusively in Earth's polar regions, but they are now
also visible in the skies over the United States and Europe and else where. There is no doubt any more. The clouds at the edge of space are spreading.
As we have previously mentioned, noctilucent clouds are back, but their origin is still unknown.
There is no doubt that noctilucent clouds have been spreading in the recent years.
You don't need to go to the poles to admire these beautiful, mysterious electric clouds.
Some days ago, these beautiful, "night-shining" clouds spilled over the Canadian border into
the lower United States as far south as Denver, Colorado.
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The results have potential implications for future global climate.
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