Study of lunar dust storms and Mars aurorae could influence spacecraft design

(Edmonton) The Canadian Space Agency has funded a University of Alberta-led project to study the effects of solar winds on Earth’s moon and on Mars. The results are anticipated to influence design of spacecraft for robotic and human exploration.

“We have limited data regarding the environments in which equipment and astronauts must function and how these environments respond to solar activity,” says Clare Watt, a research associate with the project. “There is small room for error in these high-cost missions, especially when there are lives at stake.”

The Cluster for Lunar and Planetary Sciences project is a multiple university undertaking led by Department of Physics professor Robert Rankin. The three-year, $450,000 award is split evenly between the University of Alberta and the University of Waterloo. The University of Toronto also has a piece, while the University of Calgary is part of the group in an advisory capacity.

“Researchers will combine state-of-the-art simulation models of our solar system in order to study the solar wind and its interaction with rocky planetary surfaces such as our moon and Mars,” says Watt. She adds that the Clusters project also allows for collaboration between scientists who study the atmosphere around planetary bodies and scientists who study the surfaces.

Watt leads a part of the project that looks specifically at the effect of solar winds on the moon. For example, solar winds intensify the static electric charge of dust storms on the moon. “You don’t want to land in one,” she says. “Lunar dust is not like the dust we have here on Earth. It’s very fine and difficult to shield against. It’s electrically charged, so it’s attracted to the metal [on landing craft and the electronics in them] and could create short circuits.”

Another University of Alberta group, led by professor Ian Mann, will concentrate on Martian aurorae. Discovered in 2005, aurora activity on Mars is little understood. Watt says, “Martian aurorae can provide key information about how the solar wind interacts with the Martian surface, and will provide valuable insight into how the atmosphere and surface have been eroded through thousands of years of solar wind weathering.”
Besides the possible technological applications, the Clusters project will allow students to hone computer modeling skills using recent exploratory data from NASA and the European Space Agency. Students working with mature software that simulates the larger scale will be customizing it in light of new data. Students working on the smaller scale – the “up close” data from Mars and our moon – will be building new simulation models from scratch. “There are a lot of new skills involved,” says Watt. “They will have to be creative to envision the environments on the moon and on Mars.”

Q & A with Clare Watt

The surface of the moon

What more do we need to know about the surface of the moon to land and operate craft there?

The environment near the surface of the Moon is entirely unlike that on Earth: there is next to no atmosphere and no substantial magnetic field. There is therefore nothing to protect the lunar surface from the bombardment of the solar wind – a gas of charged particles travelling at hundreds of kilometres a second that is constantly emitted from the Sun’s surface.

The constant pounding of the solar wind creates static charges over the surface of the moon and the resulting electric fields vary strongly between the sunlit face and the dark side of the moon. The Moon’s surface is covered in dust from the cumulative effect of asteroid impacts over millennia, and thanks to the action of the solar wind, these dust particles can become charged themselves. The charged dust particles are controlled by the surface electric fields and can rise up to 100km above the surface, creating dust clouds which appear to be most prevalent close to the day-night terminator.

It is thought that charged dust is responsible for lunar horizon glow phenomena observed by astronauts of the Apollo 17 mission, but the physics of lunar dust transport is not yet understood. Charged, fine-particle dust is a significant technological hazard for the sophisticated instruments used on landing vehicles and which control astronaut spacesuits. Apollo astronaut Gene Cernan noted that “Dust is probably one of our greatest inhibitors to a nominal operation on the Moon.” The research undertaken in the Cluster will seek to make predictions of the charged dust environment on the Moon to guide the design of new, safer hardware for use in lunar missions.

The acquisition of new detailed observations of lunar dust is the key objective of the proposed NASA Lunar Atmosphere and Dust Environment Explorer, due for launch in 2013.

The aurorae of Mars

What do we know about the aurorae of Mars and how will that knowledge help in designing landing craft?

The two essential components for the terrestrial aurora are (1) a magnetic field to guide high energy particles down into the atmosphere, and (2) a thick enough atmosphere to create visible light as a result of the particles hitting it. Unlike terrestrial aurorae, which form an extended ring around our magnetic poles, Martian aurorae occur in very concentrated regions near crustal magnetic field remnants, all that remains of an ancient magnetic dynamo.

It was thought that the core of Mars was molten and that Mars once had a North Pole and a South Pole. For some reason, whatever created that magnetic field turned off. Based on remote/orbital observations by Mars Express and Mars Global Surveyor, there is evidence in the crust, a detectable magnetic field. The rocks have a memory of those magnetic fields, and it seems they don’t change; they’re embedded.

Martian aurorae were first confirmed using measurements from Mars Express in 2005 (Bertaux et al., Nature, 435, 2005). Further analysis of Mars Express data have since revealed several occurrences of Martian aurorae, and the race is now on to find physical models which can explain how aurorae form on a planet which has a different magnetic field structure and atmospheric composition from the Earth.

We need to know the atmospheric composition so we would know what light would be emitted when ions and atoms get excited and create an aurora. It will probably be in the ultraviolet range and therefore invisible.
At this stage, the study of Martian aurorae is part of the international effort to explore our fascinating neighbour and find out how its planetary evolution has differed from ours. The lack of a significant dipole magnetic field on Mars means that it is constantly pounded by the solar wind, much like our moon. Martian aurorae can provide key information about how the solar wind interacts with the Martian surface, and will provide valuable insight into how the atmosphere and surface have been eroded through thousands of years of solar wind weathering. For example, we know that Mars had water. How did Mars lost that water? Could it have been erosion by solar wind?