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Plasma Experiment celebrates its anniversary on board ISS
On 27th January 2010 the 25th series of experiments studying complex plasmas will start on board
the international space station ISS. Physicists from the Max-Planck-Institute for extraterrestrial
Physics in Garching, Germany, will use them to study fundamental structure forming processes to better
understand what happens in liquids and solids.
Figure 1: Cosmonaut Oleg Kotov with the PK-3 Plus laboratory in MIM-2, the new Russian docking and
research module, after installation of the experiment apparatus (front, in the black barrel) and the
control computer (behind the cosmonaut).
(Credit: Image courtesy of RKK-Energia).
Figure 2: Phase separation (droplet formation) in a binary complex plasma on board the ISS.
That matter exists in three states is widely known: as solid, liquid or gas. Our Universe, however, is
dominated by a fourth state of matter: plasma. This forms, if a gas is heated to very high temperatures,
so that its molecules dissociate in ions and free electrons. A plasma is regarded as the most disorganised
state of matter. Researchers at the Max-Planck-Institute for extraterrestrial Physics, however, have found
that under certain conditions plasmas can become liquid or may even crystallise. These are called "complex
plasmas" and allow new insights into the physics of liquids and solids. Plasma physicists use them to study
melting and crystallisation, motion of lattice defects in crystals, or liquid effects and other processes by
looking at single atoms.
Complex plasmas consist of tiny particles (about one thousandth of a millimetre) that are suspended in a
plasma and carry a highly negative electric charge. Due to the strong interaction between the particles,
they can form regular structures, either liquid or solid. Since Earth´s gravitational field interferes with
these processes, experiments with complex plasmas are carried out in space.
Research on complex plasmas with the PKE-Nefedov laboratory in 2001 was the first science project on board
the international space station ISS and the most successful one during the first years. Its successor PK-3
Plus has already been running for four years and provides again unique results. The new series of experiments,
carried out from 27th to 29th January is already the 25th mission to study complex plasmas in the absence of
gravity. Moreover, PK-3 Plus has now been installed permanently in the new ISS module MIM-2, and will be its
first scientific experiment.
One of the experiments in the PK-3 Plus laboratory will deal with "binary" complex plasmas: if two kinds
of particles with different sizes are suspended in a homogeneous plasma, one could expect them to mix due
to mutual repulsion. Previous experiments on board the ISS, however, have shown a clear phase separation of
the two particles clouds (see figure 2).
"This phenomenon is well known from many different systems, such as molecular liquids or colloidal suspensions,
and has been studied for a long time," says Hubertus Thomas, MPE-scientist and coordinator of the PK-3 Plus
experiments. "In complex plasmas, for the first time we can now study these processes looking at the movement
of individual particles and we hope that our latest experiments will lead to new insights into the physics of
The study of complex plasmas is interdisciplinary, fundamental research. As in other fundamental research
before, however, this work initiated a new approach in applied research: the results and experience gained
with the plasma experiments on board the ISS and in the lab led to a new medical field, the so-called plasma
medicine. Currently a clinical trial is carried out to study how plasmas can be employed for contact-free
sterilisation of wounds, hand disinfection in clinical environments or treatment of gingivitis.
The continuous research on board the ISS for many years has only been possible with the bilateral agreements
with Russia. The MPE partner institute in Moscow, the Joint Institute for High Temperatures of the Russian
Academy of Sciences, has been one of the key contributors to this success story by securing the necessary
resources and logistics on the Russian side for implementing research on complex plasmas on board the ISS.
The German contribution, the construction and testing of a space-qualified laboratory for plasma crystal
research, was funded by the space agency of the German Aerospace Centre with support from the Federal
Ministry of Economics and Technology.
Joint Institute for High Temperatures in Moskau:
(in Russian language)
Minor Investigation Modul 2 (MIM-2) on board ISS:
Plasma Medicine Research Group at MPE:
Further Press Releases:
DLR Presse-Information (in German language)
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Dr. Hubertus Thomas
Max Planck Institute for extraterrestrial Physics
Phone: +49 89 30000-3838
Dr. Hannelore Hämmerle
Max Planck Institute for Astrophysics
and Max Planck Institute for extraterrestrial Physics
Phone: +49 89 30000-3980