ESA - Robotic Exploration of Mars - Taking ExoMars for a ride

ExoMars Dosing Station Credit: ESA – A. Pacros

The ExoMars Dosing Station will be responsible for distributing soil samples for analysis once the Rover carrying the Analytical Laboratory arrives on Mars in early 2019. To do this, it relies on gravity to help the samples fall into the right places.

However, the gravity on Mars is just one-third of its strength on Earth. So it has to be tested under Martian rather than terrestrial gravity. Where can this be found on Earth? In an aircraft that follows a special flight path.

Getting ready to fly to Martian gravity levels Credit: ESA – A. Pacros

Europe’s ‘Zero-G’ Airbus usually simulates the weightless conditions in orbit but, by adjusting its flight path, it can replicate the gravities of other planets.

It is rather like the temporary feeling of lightness experienced on a roller coaster as it plunges down a slope.

By repeatedly following a particular curving trajectory, the Airbus recently gave the ExoMars team a total of about 20 minutes of Martian gravity.

The Dosing Station was placed inside a vacuum chamber with a cooling system to recreate the pressure and temperature of the Martian environment.

“It was a very special experience. It was a bit like already being on Mars,” says Anne Pacros, the ESA system engineer who participated in these tests.

Analogue Martian samples Credit: ESA – A. Pacros

Cross-contamination Credit: ESA – A. Pacros

Making the best use of every single collected grain of Martian soil will be critical for the ExoMars Rover. The team prepared nine types of rock similar to those they expect to find on Mars, such as lava and sandstone, and a special mixture called salten skov, comparable with its red dust.

Each sample was crushed to a fine powder and loaded into the experiment. During each run about half a gram of a sample was poured from the dosing station into a carousel of glass tubes.

The team was testing how much of each sample clings to the dosing station. To avoid cross-contamination, the dosing station shakes itself after each application. On Earth, this process cleans off 99% of the dust.

The question that the ExoMars team want answered is: does the dosing station behave the same in Martian conditions? According to the first post-flight measures and video recordings, the behaviour of the powders is very different compared to tests conducted on ground. There seems to be a reduced sample flow with some powder sticking in the feeding tubes.

A look into the Dosing Station Credit: ESA – A. Pacros

The team is now conducting more in-depth analysis in order to decide whether the set-up needs to be modified and retested.

“This was an important test. We want to know exactly how much powder we lose on the way from the moment the ExoMars drill collects the sample until it reaches the analytical instruments inside the Rover,” says Pacros. “That way, we can make the best possible use of the samples.”