Even though we know that it is a vast, vacant lot full of orange rocks, we seem to be hellbent on going to Mars. One of the schemes for exploring more of the Martian surface before the first deluded colonists get there is to use drones. They would have to be very light and have a large wingspan to fly in the wispy Martian atmosphere, which is the equivalent of Earth’s somewhere above 100,000 feet, but it helps that things on Mars weigh only three-eighths of what they do on Earth. On Mars, a drone with a wing area of 10 square feet and an indicated airspeed of 20 knots could weigh 10 Earth pounds or more — easy work for the structure’s team. More of a challenge would be achieving an indicated speed of 20 knots in the first place; the true airspeed would have to be around 200 knots. The problem is that at a given indicated airspeed, the power required is proportional to the true airspeed; that’s why it takes more fuel to indicate 150 knots at 10,000 feet than at 5,000. Air particles are hitting the airplane with the same force, but in a given period of time more of them hit it.