Researchers Develop Model for Simulating the Interaction of
Ice is everywhere. Learning more about how water molecules
in ice behave can help scientists analyze many processes such as how glaciers
move and how lightning occurs.
Over the years, scientists have developed a number of models
to simulate the interaction of water molecules. Some of these models have been
simple and easy to work with but have not produced accurate results. More
accurate models have been complicated and hard to work with.
A team of chemists, physicists, and materials scientists at the
University of Washingtonwith collaborators from the University of North
Carolina, Pacific Northwest National Lab, the Supercomputer Computations
Research Institute, and Los Alamos National Labset out to find a better
way. They started with everything we know about how water molecules interact
and built a simulation model from the bottom up. This model can simulate how
water molecules interact under different conditionsfor example, as ice
crystals or as liquid water. This new simulation model is simple, and its
results are promising.
According to Fernando Vila, one of the investigators on this
KDI project, "Now we are starting to use the model for real things. We are
currently studying the behavior of water molecules interacting on the surface
of ice and are just starting to get results."
When we think about ice, what comes to mind most often are
familiar imagesicicles hanging from the gutter or ice cubes in the
freezer. Ice also plays a key role in a number of important phenomena such as
lightning. Lightning occurs when ice particles in clouds collide, charge, and
separate, creating a buildup of static electricity that is then discharged as
The new model will be able to simulate this process that
results in lightning. The additional information generated by the model about
how ice particles behave in cloudsespecially, about the transfer of
charge from one ice particle to anothershould help meteorologists predict
The new model also can teach us about space and about the
origins of life on Earth. The water ice that we have on Earth is different from
the water ice found in space. Because it is very cold in space and there is no
air, instead of regular ice, you have what is called amorphous solid
water. It is not in crystal form, like the ice we know. According to Vila,
"Since it is very difficult to generate this kind of ice in the lab, we are
trying to understand it using simulations. This new model is perfect for that
since it can simulate very different phases of water."
These kinds of ice found in space are interesting because
they probably form the surface of Jupiter's moon Europa and because they coat
interstellar dust particles. Such particles likely serve as catalysts for the
formation of organic molecules in space.
For life to develop, you need at least some organic
molecules. There are several hypothesis of how the molecules came to be on
Earththey were either formed here or they came from space loaded in
comets. If they came from space, then how were they formed out there? One
possibility that scientists are starting to check is that the molecules were
formed as a result of reactions on the surface of these dust particles.
Ice also has an important role in the global energy balance.
Most climate, weather, and biological processes on Earth are fueled by the
intake of light (i.e., energy) that comes from the sun. The global energy
balance is determined by how much of that light is retained and how much is
reflected into space.
Two of the most important factors affecting the global
energy balance are the amount of ice on the surface of the Earth and the
Earth's cloud cover. Ice on the ground and water vapor in clouds are mostly
white and are very reflective. The creation of more clouds and glaciers
increases the amount of light that is reflected into space. Fewer clouds and
glaciers increase the amount of energy that is retained. Therefore, the balance
of energy depends crucially on the chemical and physical processes that create
or destroy both clouds and glaciers.
This balance of energy is regulated by feedback processes:
the more energy you let in, the higher the temperature and the more clouds you
have. The clouds then start reflecting more energy out into space, which causes
the temperature to drop. At the same time, the greenhouse effect tends to raise
These feedback processes are complicated. The new model can
simulate all the reactions that occur in its different phases. Simulations of
these complex chemical reactions can be done in a matter of minutes!
As Vila explained, "All these chemical and physical
processes have energy requirements. Knowing exactly how much energy is required
allows you to create models that help predict both weather and climate. What we
want to do is to provide accurate energy values for as many processes as
possible, in that way helping create the best possible global models."
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