Night Shining Noctilucent Clouds

Noctilucent clouds were first thought to be reported between 1849 - 1852 by Thomas Romney Robinson, a director at the Armagh Observatory, N. Ireland at that time. Robinson reported seeing "luminous clouds, not auoral" in May 1850, but scientists today cannot determine for sure that these were noctilucent clouds because Robinson had died by the time the next report of noctilucent clouds was made. May is also just outside of the NLC season.

The next reports were made 3 years after the massive Krakatoa volcano explosion, and Robinson was dead, so the reports cannot be compared accurately.

Noctilucent Clouds by Nick Bramhall, on Flickr

The enormous Krakatoa eruption of 1883 destroyed the Indonesian Island and the effects were felt and seen worldwide, with violent tsunamis, earthquakes and tidal patterns. The weather patterns were chaotic for years afterwards, darkening the sky worldwide and causing beautiful optical effects, blue moons and blood red sunsets.

Noctilucent clouds were reported in 1885 and at first it was thought that the volcanic ash from Krakatoa created these clouds for the first time. We know now that this isn't the case, as you will see if you read on!

Krakatoa eruption Lithograph, Wikimedia Commons

The Sun was shining on the sea,
Shining with all his might,
He did his very best to make
The billows smooth and bright-
And this was odd, because it was
The middle of the night.

From Through the Looking Glass and What Alice Found There
by Lewis Carroll (1872)

Noctilucent Clouds by couleewinds, on Flickr

For clouds to form, they need water vapour and a nuclei, like dust particles, to collect or seed onto. The big mystery with noctilucent clouds is that they form in the mesosphere, which is a hundred times drier than deserts on Earth. So why is there water (in the form of ice crystals) in the mesosphere? And what is the dust that the ice crystals are collecting on?

The two most common theories are that:
1. The ice particles and dust come from rockets as they pass through the world's atmosphere. However, rockets have only been launched since the 1950s and noctilucent clouds have been seen since the mid to late 1800's. A good article from NASA about this theory can be read here: Study Finds Space Shuttle Exhaust Creates Night-Shining Clouds

2. The ice particles could possibly come from an increase in methane from industrial farming or from an increase of carbon dioxide with the rise of the industrial age since the Victorian era. It isn't clear yet if the dust particles, which act as seeds for the ice particles, come from the Earth or is being blown into our atmosphere from outer space. This great article from the New Scientist elaborates more on this theory: Mysterious glowing clouds targeted by NASA

Road to somewhere by jkymis72, on Flickr

Until recently it has been difficult for scientists to measure and monitor noctilucent clouds, weather balloons don't reach as high as the mesosphere and satellites were too high. In 2007 NASA launched a satellite called AIM, which stands for Aeronomy of Ice in the Mesosphere. This satellite is now monitoring the mesosphere and noctilucent clouds to determine exactly why they occur and why we are seeing more of them. Find out what the AIM satellite has been discovering here: NASA's AIM Satellite and Models are Unlocking the Secrets of Mysterious "Night-Shining" Clouds

So are the increased sightings of noctilucent clouds due to a steady increase of pollution? Are these beautiful clouds something not to admire, but to be worried about? Another theory is that these clouds actually may help against global warming; if they continue to grow they would form a protective barrier - like a band aid over the world! Who knows...?

In Summer 2010 an amateur scientist, John Rowlands, with the support of the BBC, conducted an NLC experiment asking people all over the UK to send in their photos and observations of noctiliucent clouds for a research project. Rowlands wants to research the frequency and brighteness of when and where NLCs appear and there is a Facebook page for people to contrubute their findings. Click here to see John Rowlands Facebook page - there are some amazing photos!

BBC: Noctilucent cloud experiment

Noctilucent clouds by Jeppe Salvesen, on Flickr