European Space Agency (ESA) astronaut André Kuipers is running experiments on the International Space Station (ISS) to help scientists improve their understanding of conditions deep inside the Earth.
1,864 miles (3,000 km) under our feet, Earth's mantle can best be described as a semi-solid fluid under a thin outer crust. The highly viscous layers vary with temperature, pressure and depth.
Understanding how the mantle flows is a major interest for geophysics as it could help explain earthquakes or volcanic eruptions. Computers can model it, but how can scientists be sure they are correct?
The deepest that humans have ever drilled is just over 7.5 miles (12 km), so investigating the mantle directly is out of reach for the immediate future. So instead of probing Earth's depths directly, six European teams led by the University of Cottbus in Germany attempted to recreate aspects of mantle flow in a laboratory.
But how can gravity be simulated without Earth's gravity itself influencing the results? By sending an experiment to the International Space Station, of course!
Indeed, the ESA sponsored the development of an experiment that mimics the geometry of a planet. Dubbed Geoflow, it contains two revolving concentric spheres with a liquid between them. The inner sphere represents Earth's core, with the outer sphere acting as the crust. The liquid, of course, is the mantle.
Free from the influence of Earth's gravity, a high-voltage electrical field creates artificial gravity for the experiment.
As the spheres rotate slowly and a temperature difference is created between the shells, movement in the liquid is closely monitored. The temperatures can be controlled down to a tenth of a degree.
Astronaut André Kuipers has observed plumes of hotter liquid rising towards the outer shell - as predicted by computer simulations. Mushroom-like plumes in fluids exposed to strong temperature differences might explain the Hawaiian line of volcanoes in the South Pacific.
A better understanding of our planet is not the only advantage of deploying Geoflow. For example, the results could also benefit industry by improving spherical gyroscopes, bearings and centrifugal pumps.