Getting a Handle on How Much Cosmic Dust Hits Earth


Does Earth have a dust build-up problem?

Estimates vary of how much cosmic dust and meteorites enter Earth’s atmosphere each day, but range anywhere from 5 to 300 metric tons, with estimates made from satellite data and extrapolations of meteorite falls. Thing is, no one really knows for sure and so far there hasn’t been any real coordinated efforts to find out. But a new project proposal called Cosmic Dust in the Terrestrial Atmosphere (CODITA) would provide more accurate estimates of how much material hits Earth, as well as how it might affect the atmosphere.

“We have a conundrum – estimates of how much dust comes in vary by a factor of a hundred,” said John Plane from University of Leeds in the UK. “The aim of CODITA is to resolve this huge discrepancy.”

Even though we consider space to be empty, if all the material between the Sun and Jupiter were compressed together it would form a moon 25 km across.

So how much of this stuff – leftovers from the formation of the planets, debris from comets and asteroid collisions, etc. — encounters Earth? Satellite observations suggest that 100-300 metric tons of cosmic dust enter the atmosphere each day. This figure comes from the rate of accumulation in polar ice cores and deep-sea sediments of rare elements linked to cosmic dust, such as iridium and osmium.

But other measurements – which includes meteor radar observations, laser observations and measurements by high altitude aircraft — indicate that the input could be as low as 5 metric ton per day.

Knowing the difference could have a big influence on our understanding of things like climate change and, noctilucent clouds, as well as ozone and ocean chemistry.

“If the dust input is around 200 tons per day, then the particles are being transported down through the middle atmosphere considerably faster than generally believed,” said Plane. “If the 5-tonne figure is correct, we will need to revise substantially our understanding of how dust evolves in the Solar System and is transported from the middle atmosphere to the surface.”

When dust particles approach the Earth they enter the atmosphere at very high speeds, anything from 38,000 to 248,000 km/hour, depending on whether they are orbiting in the same direction or the opposite to the Earth’s motion around the Sun. The particles undergo very rapid heating through collisions with air molecules, reaching temperatures well in excess of 1,600 degrees Celsius. Particles with diameters greater than about 2 millimeters produce visible “shooting stars,” but most of the mass of dust particles entering the atmosphere is estimated to be much smaller than this, so can be detected only using specialized meteor radars.

The metals injected into the atmosphere from evaporating dust particles are involved in a diverse range of phenomena linked to climate change.

“Cosmic dust is associated with the formation of ‘noctilucent’ clouds – the highest clouds in the Earth’s atmosphere. The dust particles provide a surface for the cloud’s ice crystals to form. These clouds develop during summer in the polar regions and they appear to be an indicator of climate change,’ said Plane. “The metals from the dust also affect ozone chemistry in the stratosphere. The amount of dust present will be important for any geo-engineering initiatives to increase sulphate aerosol to offset global warming. Cosmic dust also fertilises the ocean with iron, which has potential climate feedbacks because marine phytoplankton emit climate-related gases.”

The CODITA team will also use laboratory facilities to tackle some of the least well-understood aspects of the problem

“In the lab, we’ll be looking at the nature of cosmic dust evaporation, as well as the formation of meteoric smoke particles, which play a role in ice nucleation and the freezing of polar stratospheric clouds,” said Plane. “The results will be incorporated into a chemistry-climate model of the whole atmosphere. This will make it possible, for the first time, to model the effects of cosmic dust consistently from the outer Solar System to the Earth’s surface.”

CODITA has received a EUR 2.5 million grant from the European Research Council to investigate the dust input over the next 5 years. The international team, led by Plane, is made up of over 20 scientists in the UK, the US and Germany. Plane presented information about the project at the National Astronomy meeting in the UK this week.

Source: Jodrell Bank Centre for Astrophysics

A Noctilucent Masterpiece


Night-shining “noctilucent” clouds create a magical glow in the night skies over Reykjavíc, Iceland in this beautiful photo by Örvar Atli Þorgeirsson, taken on August 6. In the foreground is “The Sun Voyager” (Sólfar), an iconic steel sculpture located on the city waterfront representing a Viking ship.

Örvar did not set out to photograph this rare atmospheric phenomenon but had instead intended to shoot aurora triggered by recent solar outbursts.

“The forecast on the 6th of August was predicting extreme aurora activity,” Örvar says in his Flickr description. “Even though it was very early August and the night would not get fully dark I went out as the aurora can be seen in deep twilight conditions. I saw the aurora for 1 – 2 minutes that night. I did not get a good picture of it though. Instead we witnessed this even rarer phenomenon called noctilucent clouds.”

Noctilucent clouds are extremely high-level clouds made located in the mesosphere, around 76 to 85 kilometers (47 to 53 miles) high… nearly at the very edge of space. (Most commercial airplanes fly between 6 and 7 miles high.) They are high enough to reflect sunlight coming from beyond the horizon long after night has fallen over the land below. They usually appear as a wispy web of blue, white, purple and orange tendrils stretched across the sky.

“These clouds where extremely beautiful to look at and reminded me of the aurora but where much more stationary and had this beautiful blue color.”

–  Örvar Atli Þorgeirsson

Noctilucent clouds are mainly visible at latitudes between 50º – 70º north and south during the months of June and July. This means Reykjavíc, located right in the middle, can get great views. (Of course it helps to have a talented photographer like Örvar to capture them so nicely!)

Oddly enough noctilucent clouds are a relatively recent phenomenon, only having been recorded for about 120 years. They have been connected with space shuttle passages through the upper atmosphere, and it’s even been suggested that they may be associated with the 1908 Tunguska impact.

Read more about noctilucent clouds here.

Image © Örvar Atli Þorgeirsson. All rights reserved. Used with permission.


Jason Major is a graphic designer, photo enthusiast and space blogger. Visit his website Lights in the Dark and follow him on Twitter @JPMajor or on Facebook for the most up-to-date astronomy news and images!

Stunning Noctilucent Clouds Shine Brightly in the UK


Mysterious “night shining” or Noctilucent Clouds are beautiful to behold, and here are some gorgeous examples what skywatchers in the UK have been experiencing. Stu Atkinson took this stunning panoramic view from Kendal Castle. (Click image for access to a larger version). NLCs are usually seen during the summertime, appearing at sunset. They are thin, wavy ice clouds that form at very high altitudes and reflect sunlight long after the Sun has dropped below the horizon. Scientists don’t know exactly why they form, and they seem to be appearing more and more in recent times.

See more below.

Science writer Will Gater also had a great view of NLCs this morning. Click the image to see his animation, or see more of his images and animations at his website post.

NLCs seen over the UK on July 1, 2011. Click to see animation. Credit: Will Gater
Another view of Noctilucent Clouds from Kendal Castle in the UK on July 1, 2011. Credit: Stu Atkinson

See more from Stu Atkinson at his Cumbrian Sky website.

Noctilucent Clouds and A Bright Northern Star


Noctilucent Clouds are finally here! Well, at least they were for me at about 3:00am on the 29th of June.

I have heard that there have been some sightings, but for me, this mornings display heralds the new NLC season – a month later than usual?

Conditions were amazingly warm, and the night was still and magical as I looked northwards from my home in West Berkshire UK. I couldn’t help but notice a burning bright star almost due North and quite low, Capella in the constellation of Auriga! This is when I spotted the first faint wisps of noctilucent cloud.

Capella isn’t always in the North, but it is this time of year and it usually makes a guest appearance during morning noctilucent cloud displays.

Noctilucent clouds are very rare and tenuous clouds on the edge of space and occur at altitudes of around 76 to 85 kilometers (47 to 53 miles).

They are only seen when conditions are just right (still not fully understood) after sunset or before sunrise. They are illuminated by the sun, which is still way below the horizon from the observers location. Due to their very delicate nature, noctilucent clouds can only be seen at these times. More info on what NLC’s are, can be found here

Will you see any NLC’s?

Noctilucent clouds over Saimaa. Credit: Wikipedia

Coming Soon – Night Shining Noctilucent Clouds


Soon you may see an eerie spectacle on clear summer nights if you are located at latitudes between 50° and 70° north and south of the equator: Noctilucent Clouds.

These ghostly apparitions are a delight to see and are quite rare. It is incredibly difficult to predict exactly when they will appear, but we do know they should begin to appear soon.

The season for Noctilucent Clouds (Noctilucent = Latin for “Night Shining”) starts early June and continues into late July. They are seen just after dusk, or before dawn and an apparition can last around an hour.

These mysterious clouds, with their bizarre tenuous wispy shapes reminiscent of ripples in sand or the changing surface of a pool of water, spread like a glowing web across the northern sky. Colours can range from brilliant whites, with tinges of blue, pink and orange.

Formed by tiny ice crystals, they are the highest clouds in the Earth’s atmosphere, located in the mesosphere at altitudes of around 76 to 85 kilometers (47 to 53 miles) almost at the edge of space.

They are normally too faint to be seen, and are visible only when illuminated by sunlight from below the horizon, while the lower layers of the atmosphere are in the Earth’s shadow. Noctilucent clouds are not fully understood and are a recently discovered meteorological phenomenon, only being recorded for about 120 years.

Noctilucent clouds can only form under very restrictive conditions, and their occurrence can be used as a guide to changes in the upper atmosphere. Since their relatively recent classification, the occurrence of noctilucent clouds appears to be increasing in frequency, brightness and extent.

There is evidence that the relatively recent appearance of noctilucent clouds and their gradual increase, may be linked to climate change. Another recent theory is that some of these bright displays come from particulates and water vapour in the atmosphere left over from Space Shuttle launches.

How can you see them? Over the next couple of months look north during dusk and dawn and try and spot this mysterious and elusive phenomenon. They are best seen when the sun is between 6 and 16 degrees below the horizon, and seem to occur more frequently in the Northern hemisphere than the Southern.

Good luck!

Noctilucent clouds over Blair, Nebraska, USA. Credit: Mike Hollingshead

Mysterious Noctilucent Clouds As Seen from Space


Mysterious “night shining” or noctilucent clouds are beautiful to behold, and are usually seen during the summertime, appearing at sunset. They are thin, wavy ice clouds that form at very high altitudes and reflect sunlight long after the Sun has dropped below the horizon. Scientists don’t know exactly why they form, but continue to observe them – both from Earth and from space. These images were taken by the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite.

Also called polar mesospheric clouds, they are puzzling scientists with their recent dramatic changes. They used to be considered rare, but now the clouds are growing brighter, are seen more frequently, are visible at lower and lower latitudes than ever before, and — as these satellite image reveal — they are now even appearing during the day.

Noctilucent clouds over Kendal Castle, England in June 2010. Credit: Stuart Atkinson

Noctilucent clouds form in an upper layer of the Earth‘s atmosphere called the mesosphere during the Northern Hemisphere’s summer – at an altitude of 80 km (50 miles). They can start forming as early as May, and extend through August. They can also be seen in high latitudes during the summer months in the Southern Hemisphere.

What could the observed changes mean? Some scientists believe they are a good gauge of even the tiniest changes in the atmosphere, as they are extremely sensitive to changes in atmospheric water vapor and temperature. The clouds form only when temperatures drop below -130 degrees Celsius (-200 Fahrenheit), when the scant amount of water high in the atmosphere freezes into ice clouds.

Scientist Matthew DeLand of Science Systems and Applications Inc. and NASA’s Goddard Space Flight Center has been monitoring polar mesospheric clouds with instruments that were actually designed to study ozone, including the OMI, which provides more detailed and frequent observations than previous instruments. This gives DeLand a way to refine his previous measurements of a long-term trend towards more and brighter noctilucent clouds linked to rising greenhouse gases.

These images at the top of this article show OMI measurements of polar mesospheric clouds on July 10, 2007. The clouds, detectable because they are the only things that reflect light in this part of the atmosphere, are shown in white and pink. The Aura satellite travels in a polar orbit, circling from south to north as the Earth turns beneath it. As a result, the satellite gets several opportunities to image the poles every day. This series of images shows the clouds over six consecutive orbits between 7:16 and 15:52 Universal Time. Throughout the day, a wide area of polar mesospheric clouds developed over northern Greenland and Canada, peaking around 10:30 UTC (the third orbit).

Another instrument observing these clouds is the Solar Backscatter Ultraviolet (SBUV) instruments, which have flown on seven different satellites over the past 32 years, and that wealth of data is showing how the clouds change throughout the day.

DeLand now has an index to help correct the SBUV measurement trends to account for the time of day. The correction allows him to develop a more accurate view of the long-term trend. Even with the corrections, the trend indicates that the atmosphere has been responding to increased greenhouse gases over the past 30 years.

The fact that polar mesospheric clouds are getting brighter suggests that the mesosphere is getting colder and more humid, says DeLand. Increasing greenhouse gases in the atmosphere could account for both phenomena.

Sources: NASA Earth Observatory, twice

It’s Noctilucent Cloud Season!


It’s summer (well, OK, technically next week it is summer) but it’s the time of year that northern latitudes can see the beautiful, awe inspiring atmospheric phenomena called Noctilucent Clouds, or night shining clouds. They aren’t like regular cumulus or cirrus clouds, but are mysterious and unique high atmosphere cloud formations thought to be composed of small ice-coated particles. How they form and why is not well understood, and usually the best time to see them is at twilight when the high altitude clouds are backlit by the sun. But Stu Atkinson in England sent in these great images of NLC’s, which he took in the wee hours of the morning (he woke up at 1:30 am) from the stunning location of Kendal Castle. He’s got more at his website, Cumbrian Sky.

Noctilucent clouds in Lancashire taken by Mark Purvis in 2009.

This image was sent in by UT reader Mark Purvis, who wrote, “This is an image I took in Beacon point in Lancashire. It was taken on the 21st July 2009 at 23:30(ish) with an Olympus E-400.”

Another look at Noctilucent clouds over Kendal Castle, England. Credit: Stuart Atkinson

If you have taken some images of NLC’s send them to Nancy and we’ll post them.

For more NLC images, see’s gallery.

Here’s a link to some NLC pictures (plus a Comet McNaught photo) taken in Germany, also taken in the early morning hours, about 2:30 am local time.

Check out this link for a NLC FAQ.

And here’s some observing tips from Look west 30 to 60 minutes after sunset when the Sun has dipped 6 degrees to 16 degrees below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud. High-northern latitudes are favored.

Thanks again to Stu for sending us his images.