InSight mission to Mars, why not clean the solar panels?

► What is the InSight mission and what has it taught us?

Arrived on Mars in November 2018, the American InSight probe was to study the interior of the red planet. Getting to know this neighbor better, which was formed 4.5 billion years ago, allows us to learn more about the processes at the origin of the rocky planets of the solar system: Mars, but also the Earth, Mercury and Venus. For this, the probe carries a seismometer provided by the French National Center for Space Studies (CNES), among other scientific instruments. It has detected more than 1,300 earthquakes, including the strongest of magnitude 5 in early May 2022.

→ REREAD. The InSight probe will explore the bowels of Mars

On the science side, the mission notably made it possible to confirm that the core of Mars is indeed liquid, and to determine that the Martian crust is less dense than envisaged. The data collected will also be used to study the climate of Mars and its former magnetic field, which is now “extinct”.

► Why is the mission coming to an end?

The probe is powered by solar panels, like most small Martian machines (1). But while the latter provided power equivalent to two hours of operation of an electric furnace at the start of the mission, they only provide the equivalent of ten minutes today. “The atmosphere of Mars is permanently dusty, and over time this dust, finer than talc and slightly magnetic, sticks to the solar panels”, describes François Forget, planetary scientist and director of research at the CNRS. The latter therefore receive less light and produce less energy.

The American NASA decided this week to begin end-of-mission operations. A decision that has earned him many letters of incomprehension. The non-essential instruments should be shut down at the end of May, then the seismometer will shut down at the end of the summer. Finally, around December, all communication with the robot will cease for lack of energy. The probe was already well past its expected lifespan, with a two-year primary mission. For scientists, these last two years were therefore a “bonus”.

► Can’t we dust the solar panels?

Such a clean-up operation was indeed thought of before the departure of the mission, but ultimately ruled out. Adding a brush to InSight’s backpack or developing repellent solar panels would have increased costs, even though current manufacturing has perfectly fulfilled the scientific objectives. But preventing the deposit on the panels would have required significant development because Martian dust sticks much more than terrestrial dust.

The engineers have also tried to use the small motors of the deployment of the solar panels to “shake” them, without effect. In May 2021, they had also taken coarse sand from the Martian soil with the robot’s arm, to let it flow on the panels and take the dust with it. A delicate operation for a very slight improvement. Why not put a real dustpan at arm’s length? “Too complicated, and the risk of damaging the solar cells without success is too great”, believes Philippe Caïs, research engineer at the Bordeaux astrophysics laboratory and technical manager of an instrument of the Martian robot Perseverance.

“Previous Martian probes, Spirit and Opportunity, had benefited from gusts, sort of mini-tornadoes, which had stripped their solar panelsrecalls François Forget. It was not impossible that InSight benefits from the same natural cleaning. » Alas, the probe is not in the same area of ​​the planet and the saving winds seem less common.


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