Monday, 16 April 2007

Martian Cleaning Service

On April, 12th 2007, I assisted at the Cosmocaixa to a conference by Steve Squyres, of the Ithace University (NY) and responsible of the Spirit and Opportunity NASA's Mars Rovers. The title of the conference was "The exploration of the Victoria Crater: The definitive probe of water in Mars". The context of the presentation was the Cosmocaixa exhibition "Mars-Earth: compared anatomy". Finally, the presentation wasn't very tecnical at all because it was addressed to the general public. However, aided with very impressive images, he described the past and present mission events and he explained very interesting things related to the engineering and operation of such type of mission. Practically all this information is in the Marsrovers JPL webpage.

One of the most interesting things he explained was related with the solar panels design and operation. It is well know that the mars surface is covered by dust that is transported by the atmosphere and deposited everywhere. Thus, as the time passes the solar pannels are gradually covered by dust. Of course, it reduces the available electrical power. At the end, the dust can cover totally the panels disabling the power supply. During the design, after the trade off of different mechanisms to clean the dust, they decided to compensate the efficiency reduction of the panels with a bigger surface. Thus, they used panels as big as possible. As a consequence, the panels should work until dust made it unusable. The designed life was estimated to be from few months to one year. But the good health of the rovers aimed a mission extension until they fail. But, as known, dust was covering everything. The following image shows this dust deposition.

And the mars winter arrived, the available sunlight was reduced and the efficiency of the solar pannels decreased by the dust... and the unexpected happened! Despite of the low pressure of the Mars atmosphere, the same meteorization phenomena that happens in the Earth as a result of the interaction of the atmosphere and the surface are present in Mars. The wind moves the dust and erode and model the surface producing sand and more dust. Thus, the same dust devils that appear in the Earth desserts are also present there. The following animation was captured by the Spirit Rover (5.7 M!).

More dust devils animations can be found in this link.

After the past of some dust devils in March, 2005, the dust on the rover was cleaned! The following pictures show the Spirit color calibration pattern and the solar pannels before and after.

And after the rover was prepared for at least another two year of power supply!