These mysterious, electric glowing clouds are beautiful to watch, but scientists believe they could be dangerous to our planet.
They were 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. There is no doubt any more. The clouds at the edge of space are spreading.
There are those who think that these mysterious clouds are a result of recent climate changes, or something else...
The clouds are called noctilucent or "night-shining" clouds (NLCs) and they are a relatively new phenomenon.
"They were first seen in 1885" about two years after the powerful eruption of Krakatoa hurled plumes of volcanic ash as much as 80 km high
in Earth's atmosphere," says Gary Thomas, a professor at the University of Colorado who studies NLCs.
When the ash from the volcano settled and the vivid sunsets of Krakatoa faded, the noctilucent clouds were still there.
"It's puzzling," says Thomas. "Noctilucent clouds have not only persisted, but also spread." A century ago the clouds were confined to
latitudes above 50o; you had to go to places like Scandinavia, Russia and Britain to see them.
In recent years they have been sighted as far south as Utah and Colorado.
"Although NLCs look like they're in space," continues Thomas, "they're really inside Earth's atmosphere, in a layer called the mesosphere ranging from
50 to 85 km high."
The mesosphere is not only very cold (-125 C), but also very dry--"one hundred million times dryer than air from the Sahara desert."
Nevertheless, NLCs are made of water. The clouds consist of tiny ice crystals about the size of particles in cigarette smoke.
How ice crystals form in the arid mesosphere is the essential mystery of noctilucent clouds.
Noctilucent clouds, Kuresoo bog, Soomaa National Park, Estonia. Credit: Martin Koitmäe
No observations of anything resembling noctilucent clouds before 1885 has ever been found.
Why are they getting more numerous? Why are these clouds getting brighter and why are they appearing at lower latitudes?
"That's a real concern and question," said James Russell, an atmospheric scientist at Hampton University and the principal
investigator of an ongoing NASA satellite mission to study the clouds.
Are the clouds a result of global warming? Could we human be responsible for their sudden appearance?
Noctilucent clouds over Finland. The orange hues near the horizon are ordinary sunset colors, notes Gary Thomas. NLCs, on
the other hand, are usually "luminous blue-white or sometimes just pale white," he says. Image credit Pekka Parviainen.
"The prevailing theory and most plausible explanation is that CO2 buildup, at 50 miles above the surface, would cause the temperature decrease,"
Russell said. He cautioned, however, that temperature observations remain inconclusive.
Noctilucent clouds photographed by the crew of the ISS. Credit: NASA
The global changes that appear to be reshaping noctilucent cloud distribution could be much more complex, said Vincent Wickwar,
an atmospheric scientist at Utah State University whose team was first to report a mid-latitude noctilucent cloud in 2002.
Temperature does not explain their observations from around 42 degrees latitude.
"To get the noctilucent clouds you need temperatures that are about 20 degrees Kelvin colder than what we see on average up
there," Wickwar said. "We may have effects from CO2 or methane but it would only be a degree or a fraction of a degree."
For now scientists are left with more questions exist than firm answers.
"I suspect, as many of us feel, that it is global change, but I fear we don't understand it," Wickwar said. "It's not as simple as a temperature change."
Something Mysteriously Warms Antarctica Ice
Very rapid climate changes take place on Antarctica.
"Something" mysteriously warms Antarctica Ice and it's a dangerous process.
The huge 18-mile-long crack that was discovered at the end of last year, is still growing and it remains unclear what is causing the sudden change in temperature.
Antarctica is getting warmer and the melting of ice is adding to global sea level rise.
Geological Rift That Baffles Scientists Is Still Expanding
This huge rift can be clearly seen from space.
Geologists are truly surprised at how fast it developed, when a 60 meter long rift opened up in Ethiopia.
It occurred in the course of a few days, in 2005 and the rift is still expanding.
Fastest Wind Ever Coming From A Disk Around Stellar-Mass Black Hole Discovered
This record breaking wind is moving about 20 million miles per hour - about 3% the speed of light and may be carrying away much more material
than the black hole is actually capturing.
This is nearly ten times faster than had ever been seen from a stellar-mass black hole, and matches some of the fastest winds g
enerated by supermassive black holes, objects millions or billions of times more massive.
Extremely Distant And Exotic Quasar
It is an exotic and distant object, which has a velocity of recession of approximately 270,000 kilometers per second (!) or - 91 percent of the
velocity of light itself.
The results show that this quasar, known as Q1442+101, is among exotic objects receding from the Milky Way at tremendous velocities of thousands
and occasionally even hundreds of thousands of kilometers per second!
Very Puzzling Appearance And Trajectory Of Fireballs
In the middle of the night on February 13th, something disturbed the animal population of rural Portal, Georgia.
Cows started mooing anxiously and local dogs howled at the sky. The cause of the commotion was a rock from space.
Unusual Pulsar Or Alien Signals?
The pulse timing of this object is considered unusual.
What kind of phenomenon is related to this object?
It is the first time this kind of phenomenon has been observed by astronomers.
The "Cloaked" Star Was Difficult To Find
An object obscured by dust, and buried in a two-star system enshrouded by dense gas, is not easy to find.
A "cloaked" star was discovered after it ate a little of its neighbor. The meal must have given the star a bit of indigestion, because it
"burped" with a blast of high-energy radiation, which gave it away.
Black Gaps In The Sky Puzzle Astronomers
Very dark isolated interstellar clouds of very cold gas like black gaps have puzzled astronomers for more than a century.
Looking at the sky in the direction of the constellation Sagittarius, it is clear that there are extremely dark,
opaque knots of gas and dust especially in the region toward the center of our Milky Way.
Invader From Another Galaxy
This alien intruder from another galaxy is in many ways different from other exoplanets observed by astronomers.
Located about 2000 light-years from Earth in the southern constellation of Fornax (the Furnace), the Jupiter-like planet orbits a dying star of
extragalactic origin and risks to be engulfed by it.