First flight on Mars

Until we discover otherwise, the first ever known powered flight on Mars has just happened.

The helicopter that went to Mars with the latest rover just had a test flight, going about three metres into the air, hovering and then landing safely. Having an aircraft on Mars is going to have a huge impact on our exploration of the planet.

This is not the equivalent of flying a drone here on Earth. There are two huge, additional challenges.

Mars' atmosphere is much thinner than what our drones fly in on Earth.

With radio signals taking many minutes to get from Mars to Earth and just as long to go the other way, there is no way we can remotely control the vehicle.

Although here on Earth jet aircraft can reach the edge of space, helicopters are confined to low altitudes. It is possible to coax the most advanced helicopters to heights of around eight kilometres, but the highest they can hover is about three kilometres.

The atmospheric pressure on the surface of Mars is about the same as we find here on Earth at an altitude of around 25 kilometres. Our earthly helicopters would not get off the ground on Mars.

The problem is getting enough lift. This is the force that gets an aircraft off the ground and keeps it in the air.

The amount of lift depends on the density of the air, the area of the wing surface and how fast that wing surface is moving. Can we not just "flap our wings" faster? Unfortunately that won't work.

When the ends of the blades of the propeller get close to the speed of sound, they stop producing lift. So the only real solution is to go for as much wing area as possible, so that the propeller blades don't have to move as fast.

The other thing we can do is cut the weight of the aircraft to a bare minimum, and this includes the weight of our larger propeller blades. Luckily there are advanced construction materials available that provide strength while being lightweight.

Thanks to great efforts by NASA, that helicopter weighs in at less than two kilograms, is ready to go. The cameras and other electronics on the helicopter are small and very lightweight.

The first spacecraft that landed on Mars were immobile. They just observed their surroundings, so the fact that signals took many minutes to get between Earth and Mars was not a huge problem. Things changed when the rovers landed on the Red Planet.

The solution to the time-delay problems involved first, driving slowly, which was necessary on rough, unpredictable terrain; the main thing was to make the vehicles smart.

They would have to make all the decisions necessary for driving safely, relying on operators on Earth to merely point out what to drive to.

Robot helicopters bring up a whole range of new issues. They fly faster, so they have to "think" faster. It is true there are few things to hit while flying, but Mars can be a windy place, so conditions can be turbulent.

With nobody around to put things right when something happens at take-off or landing, the aircraft has to be smart enough to identify all the hazards a human pilot has to, and to respond to them.

For example there are frequent "dust devils" on Mars: small tornadoes of whirling dust that extend well up into the atmosphere. It would not be good to fly a fragile, small, light aircraft into one of them.

These first flights can be planned to avoid or minimize these threats, but eventually vehicles carrying out long, autonomous exploratory flights will have to be smart enough to avoid such hazards.

This flying Martian explorer is the first of its kind, but certainly won't be the last. The ability to explore Mars by flying around, studying the atmosphere and maybe landing for a closer look at places of particular interest will revolutionize our knowledge of our neighbour world, and make it all much safer for those first human explorers.

• Mars is still high in the southwest after dark.
• Jupiter and Saturn lie low in the southeast before dawn.
• The Moon will reach Last Quarter on the 3rd.

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