Group leader: Jonathan P. Merrison

Background

Mars seen from Hubble telescope

Mars is covered by fine red dust. It gives the planet its characteristic colour. It is ever present in the atmosphere, dominating the weather and sometimes becoming so thick that it plunges the planet into darkness. Its origin, its physical, chemical and geological properties have all yet to be fully understood.

With the help of simulators, modelling and the development of new instrumentation, researchers can get a deeper understanding of the dusty environment on Mars and help to solve some of mysteries of the planet: was it once like Earth? could it harbour life?

Experimental Facilities

Central to this research has been the development of a unique re-circulating windtunnel housed in an environmental chamber. Here parameters such as: gas pressure, composition, temperature and wind conditions can be controlled to reproduce those found on Mars, importantly special analogue dust can be injected to simulate the Martian aerosol. Experiments or flight instruments can be exposed to the dusty conditions observed on the Martian surface. Physical properties of analogue dust can be studied with a variety of techniques (see: Marslab facilities).

A second environmental chamber can be used for studying other properties of the Martian surface. The atmosphere and temperature can be controlled and monitored using a rest gas analyser. An ultra violet lamp can simulate the hard solar UV radiation, which penetrates the thin Martian atmosphere. Chemical and mineralogical processes can be studied, for example oxidation of Iron II compounds. Transport of heat and water vapour can be measured using modified sensors.

Objectives

By developing better analogues and simulations of the Martian surface it is hoped to improve our understanding of the physical processes at work. This has been shown to be vital in interpreting observations made on Mars as well as pioneering the next generation of experiments to be flown. Specific research projects underway are:

• Aerodynamics (modelling and simulation)
• Electrical Charging (discharging)
• Magnetic Properties Experiments (past and present)
• Dust Adhesion/Cohesion
• Water Transport through the surface layers

These are not just of scientific interest, but can be crucial for securing the safety and performance of instrumentation on the Martian surface, where dust is the most dangerous of the environmental hazards.

Beagle 2 materials testing from wind tunnel

The wind conditions on Mars are variable and make modelling of the aerodynamics at the Martian surface difficult. In combination with windtunnel studies computer models are being developed which can allow wind flow to be predicted. Knowledge of the properties of suspended dust can then allow the behaviour of the suspended dust to be predicted, specifically how it sticks and importantly where it sticks, also how it is transported and effects of erosion.

Dust adhesion/cohesion, atmospheric transport and electrical storms on Mars may all be aspects of the same phenomena: the electrical activity of the suspended dust. Investigations are underway in the Mars simulation laboratory, which can quantify this electrification with the use of Mars analogue dust.

Dust aggregation in the wind tunnel

Dust loading at the surface affects water transport and therefore the possibility of life. Evidence for recent flow of liquid water (Mars Global surveyor) and the probable detection of buried water by neutron scattering has prompted speculation as to the possibility of stable liquid water close to the surface of Mars. In fact at temperatures and pressures common on Mars the presence of liquid water can be stable given high humidity. Deposited dust makes water diffusion extremely slow and can therefore act as a barrier to escaping humidity.

These are just some of the physical aspects of the Martian surface being tackled at the Aarhus Mars Simulation Laboratory. It is hoped that by improving these simulations a better scientific understanding of Mars is obtained and the quality of experiments on the surface is heightened.

Contact person	Research Field
Jonathan P. Merrison, adjunkt	Aerodynamics and dust properties
Haraldur Páll Gunnlaugsson	Mössbauer spectroscopy, magnetic properties
Kjartan Kinch, Ph.D student	Aerodynamic modelling and magnetism