WHY CAN’T ROBOTS ON MARS CLEAN THEMSELVES?

Dust has always been a problem when exploring Mars. The thin atmosphere kicks up the planet’s fine dust, which then settles on solar panels. This steadily reduces the sunlight reaching the panels, until power drops too low for the spacecraft to function.

The Spirit and Opportunity rovers avoided this fate as the wind periodically blew the dust away. Not every spacecraft is so lucky. NASA’s most recent victim was the InSight lander, which lost contact with Earth on 15 December 2022 after four years on the surface.

So why not just include a ‘windscreen wiper’ to brush away the dust? One of the biggest issues is weight. The mass you can send to another planet is a limit set by the power of your rocket. Every gram counts and adding a cleaning system would mean leaving something else out. So far, the trade-off hasn’t been worth it.

Some missions have used existing hardware to try cleaning the panels instead. Using the solar panels’ positioning motors to shake the dust loose have met with little success, but InSight did manage to clear some dust using its robotic arm. Counterintuitively, it poured more sand onto the panels. This ran straight off, but not before sending up a bunch of dust already on the spacecraft. The procedure was done during the windiest part of the day, so the lifted material was blown away.

Perseverance and Curiosity bypassed the problem entirely by using radio thermal generators (RTGs) rather than solar panels. These convert the heat given off by a radioactive material, in this case plutonium, into electricity. However, plutonium is hazardous, and more dense than lead. As this makes the craft heavy, plutonium and other radioactive materials are only used for power-hungry missions like the two rovers.