Dust in the works

Here on Earth, if we find our car covered with dust we brush or wash it off. If the vehicle is a robot explorer on the planet Mars, the issue becomes enormously more complicated.

Those of us living in dusty environments, or who have worked in them, have experienced how much of a problem sand and dust can be, and it's not just cosmetic.

Sand in the works is a bad thing. It clogs things up and when it gets between moving surfaces, such as wheel bearings, it sticks in the lubricant and turns smooth bearings into grinding machines.

In the desert, the situation is even worse, because the sand is fine, dry and is always blowing around.

The first astronauts to land on the Moon ran into problems with dust. Over billions of years of vacuum and wide temperature changes, it had become very fine, and very dry.

The result is that any disturbance got it electro-statically charged, so it stuck to space suits and equipment and got into everything. Their space suits were white to reflect the Sun's heat. The dust was dark grey and coating the suits degraded their effectiveness at doing this.

The dust got into the machinery of the vehicles and other devices taken to the Moon to help the astronauts explore. When the astronauts got back into the lunar lander, the dust came off the suits and got everywhere. It smelled of burned gunpowder.

Human astronauts can brush it off. It's harder for robot explorers.

Mars has a far denser atmosphere than the Moon, but it is still less than one percent of the density of our world's atmosphere at sea level, and moreover it is very, very dry.

There is, however, enough atmosphere to provide winds strong enough to blow the dust around. In fact there is so much dust in the Martian atmosphere the sky does not look blue; it looks pink.

There are dust devils and sandstorms, sometimes big enough to hide large areas of the planet's surface. Moreover, continually being blown around makes the particles get finer and finer, and, in the dryness, they become electro-statically charged.

The result is that, as in the case of lunar dust, the Martian dust sticks to everything, and the blowing around of the dust by the winds ensures it gets everywhere. The selfies the Mars rovers send back show them getting more and more dusty.

Most of the rovers so far have been powered by solar cells, which convert sunlight into electricity. The solar cell arrays are flat panels that are almost horizontal, so that during the Martian days (called "sols") they are always catching the sunlight.

So they are almost ideal dust catchers. However, wind can blow dust off as well as drop it on, and occasionally positioning the rover so that the wind blows off most of the dust brings the electrical output back up.

If the spacecraft is an immobile lander the situation is more difficult. Over time one might expect the dust cover to sort of average out, with wind blowing as much off as it blows on.

However, this does not rule out occasional severe dust coverings where the weather is uncooperative, which is the situation NASA's Insight Mars Lander is faced with at the moment.

Luckily NASA came come up with an ingenious solution. The operators of the rover commanded it to scoop up some gritty soil from the ground beneath the rover.

Then, when the wind was blowing hard enough in the right direction, the grit was slowly released so the wind blew it over the surface of the solar panels, scouring off a lot of the dust and immediately bringing up their electrical power output.

Engineers are working on better ways to deal with dust accumulations on critical parts of the equipment. The solution I like best is to have an astronaut around who can go outside with a brush.

While there on the Red Planet, he or she could do a few other things too, such as explore, and exploit any new opportunities on the spot.

• Jupiter and Saturn lie low in the southeast before dawn.
• Mars is getting lost in the sunset glow.
• The Moon will reach First Quarter on the 17th.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.