The origins of planets

German students’ space station experiment seeks to prove planet-formation theory

William J. Holstein
14 January 2019

3 min read

Scientists have long sought to understand the origins of the planets. One theory suggests that lightning strikes cause dust particles in space to become ‘sticky’ and cling to each other. In the gravity-free environment of the International Space Station, the theory is being put to the test.

In the beginning there was gas, and the gas was everywhere. No planets. Nothing solid.

So what force caused that gas to begin forming into planets?

Scientists speculate that more than 4.5 billion years ago, intense lightning strikes hitting clouds of dust and gas caused dust particles to become ‘sticky’ and cling to each other. These clumps then clung to other clumps, growing until they formed asteroids and, eventually, planets. These submillimeter to millimeter spherical bits of dust, called chondrules, have been found in meteorites, lending weight to the theory.

Earth’s strong gravity makes it impossible to perfectly replicate the near-weightless conditions required for chondrule formation. Therefore, Frank Brenker and Björn Winkler, professors at Goethe University Frankfurt, assembled a team of students and technicians, as well as programmers from Hackerspace, to develop an experiment for the weightless conditions available on the International Space Station (ISS).


Competition for space and research time on the ISS, as well as weight in the payloads of rockets that deliver materials to the station, is intense. The students discovered a national competition administered by Johannes Weppler, Überflieger Program Manager at German Aerospace Center (Deutsches Zentrum für Luft und Raumfahrt e.V, or DLR). Of the 24 entries into the Überflieger competition, the Goethe University Frankfurt experiment – named EXCISS, for Experimental Chondrule Formation at the ISS – was among three chosen to make the trip.

“I am very optimistic that the experiment will work as planned,” Weppler said, explaining why he selected EXCISS to receive a coveted spot.

The experiment took place in late 2018, conducted by German astronaut and ISS Commander Alexander Gerst.


Constructing a device small enough to meet the ISS size and weight restrictions while replicating the conditions that existed before planets formed was an enormous challenge. The experiment had to fit in a Nanolab, a 10 by 10 by 15 centimeter (about 4 by 4 by 6 inch) receptacle specifically made to fit into the experimental bays on the ISS.

Scientists speculate that more than 4.5 billion years ago, intense lightning strikes hitting clouds of dust and gas caused dust particles to fuse, growing until they formed asteroids and then planets. (Image © Stocktrek / Getty Images)

The experiment is designed to bombard the gassy dust inside the Nanolab with a variety of energy levels.

“We can adjust the energy of the lightning strikes anywhere from 3 to 30 joules by changing the charging voltage of our capacitors,” said Dominik Spahr, one of the doctoral students who developed the experiment and build the equipment for it.


Finding a way to capture data from the experiment for analysis requires some fancy footwork. A high-powered video camera with a microscope optic records the behavior of the dust particles during and between the lightning events. But the camera itself had to be protected from the energy surges, accomplished with protective shields that include ferrite beads.

The video camera, which also takes still pictures, is connected to an electronic lab notebook, which automatically captures the data. Because the ISS is connected wirelessly to Earth, daily results are communicated to the Science Cloud, a cloud computing-based platform. Team members can access each day’s results on the platform and make needed adjustments before the next day’s tests.

An experiment in the weightless conditions on the International Space Station will test the theory of how chondrules were formed. (Image © 3DSculptor / Getty Images)

Detecting changes in the dust particles and identifying chondrules, if any, can only be done after the Nanolab returns to Earth. “We will analyze the dust particles using different techniques, including electron microscopes,” said Tamara Koch, the lead doctoral student on the EXCISS project. “We will compare our dust particles with the results of experiments conducted on Earth and with natural chondrules found in meteorites. This will take at least a few months.”


The project represents a coming of age for Germany and the overall European space effort.

“Of course, the U.S. and Russia are the two dominant and most visible powers in space,” Weppler said. “Nevertheless, Germany aims at playing a major role as well.”

Therefore, he said, Germany is the second biggest financial contributor to the European Space Agency, and the DLR is conducting many projects with international partners. Weppler, an avid Star Trek fan, welcomes the chance to encourage young people to think big about space.

The American television series’ tagline was “to boldly go where no man has gone before.” That philosophy clearly had an impact on Weppler.

“My love for Star Trek has been and continues to be a big inspiration for me,” he said. “This experiment is about one of the core ideas of Star Trek: the exploration of space. These are the first European students to have their own experiment on the ISS. What could be more fitting than ‘boldly going where no European student has gone before?’” ◆

Hear the Goethe University team talk about the project:

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