Mars Atmospheric Dust: Behavior and Effect on Rover Solar Cells
Research Associate: Adam Miller
Principal Investigator: Geoffrey Landis
Background on Mars Rover and Mars Atmosphere
The Mars Exploration Rovers (MERs) were a significant undertaking by NASA, sent to the red planet for 4 major reasons: to determine whether life ever arose on Mars, to characterize the climate of Mars, to characterize the geology of Mars, and to prepare for human exploration. However, none of these goals could be achieved without a power source, and since the rovers are roughly 36 million miles away, the options for a constant, renewable power supply are rather limited.
Just like the Mars missions that came before, these current rovers utilize solar cell arrays to collect solar energy. The arrays, consisting of one fixed and five deployable panels, were feared to have to battle both atmospheric opacity and dust accumulating on the arrays. The atmospheric dust on Mars alone was projected to cut the short-wavelength spectrum and reduce cell efficiency directly by up to ten percent from a no-atmosphere situation. Tau, or the opacity of the atmosphere (1 to 0, with 0 being completely clear), was around 0.9 when the rovers initially landed and has decreased over time, becoming less dusty over time. This dust has to travel somewhere, though, and the dust in the atmosphere was expected to slowly settle down on the solar arrays, thereby reducing the solar cell efficiency until the rovers would not generate enough power to function. The initial mission was given a timeline of three months.
However, the negative effects seemed to have been overestimated, since both rovers lost only ~20-25% efficiency due to dust over their first six Martian months, already doubling the initial projected timeline for the rovers. Since the rovers landed, the mission has been renewed five times for a life of over five Earth years. For one, both the settling time of the dust in Mars’s atmosphere is incredibly long and the coverage is incredibly small due to the dust being very fine (each particle is a few microns in diameter).
Also, there have been unexpected “dust events”. While these events sometimes increase the atmospheric tau, there also are times where there is enough wind generated to clear the dust partially, thereby increasing the amount of solar power that the arrays generate. This unexpected phenomenon did not occur with the previous landings on Mars, since the measured wind was too little to help clear off the solar arrays. However, during the Martian summer, when atmospheric activity is at its greatest, the rovers are now receiving some panel-cleaning help in the form of wind.
My Role as a Research Associate
Our time on Mars is not nearly close to being finished. In fact, it wouldn’t be presumptuous to say that this is just the beginning of missions to Mars. The popular type of power generation for many of the past missions, and likely for future missions, is the solar array. To study the effect of dust and the obscuring factor of the Martian atmosphere would be advantageous to the development and planning of future missions to the red planet. I intend on analyzing the solar power data from each Sol (Martian day) to map where and when in the Martian year we can expect these dust clearing events to occur. I plan to explore further the effects of the atmosphere on current and future missions on Mars so that we will have a better understanding of the properties and effects we’ll encounter when we decide to go back and NASA can further optimize our solar power technology. Perhaps even a solar experiment is in my future since I’m housed in a facility that specializes in them, but the program is still too young to determine what my exact course of action is going to be even though I am certain of my subject of research. Aside from that, though, I trust Geoff Landis to make use of me for research and analysis in varied subjects related to the current analysis.