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February 2010
 The
Image of the Month for February shows a microscopic view of some of the
snow which fell on the Campus last month. Dr Chris Stain from CfAM used
the powerful Environmental Scanning Electron Microscope in the Centre to
image the microscopic detail of the recent snow fall. We overcame the main
challenge of stopping the snow melting using a special cryogenic stage to
keep the snow at -140 degrees below zero.
The most striking feature of these images is just how little space is
occupied by the ice crystals. In fact, fresh snow only contains about 8%
water, the rest is air. The images show that there is a wide variety of
shapes and sizes of ice crystals and these interlock to form a lightweight
structure largely filled by air. One common form of ice crystals is the
hexagonal prism. The precise shape depends on the temperature and humidity
conditions at the time of formation. The traditional open branched
snowflake is generally seen in rather cold atmospheres with a high level
of water supersaturation.
CfAM
contributes to the 'Big Freeze' Channel 4
CfAM on
Radio Berkshire Breakfast Show
CfAM on Snow
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