Encyclopedia Britannica Editor
Flying a helicopter on Mars, the first powered flight on another planet, is such a feat of engineering that it would be difficult to isolate one facet of the project as the main challenge. The atmosphere on Mars is much less dense than that of Earth. The atmospheric pressure at the Martian surface is less than 1% that on Earth’s surface, so even though the Ingenuity helicopter is very light, weighing only 1.8 kg (4 lb), the blades have to be much longer (about 1.2 metres [4 ft] across) and spin much faster (about 2,400 rpm) than such a helicopter on Earth. Once the Perseverance rover lowered Ingenuity to the Martian surface, the helicopter had to survive the cold Martian night (about -90 C [-130 F]) on its own. Because radio signals take several minutes to travel between Mars and Earth, Ingenuity cannot be flown from Earth by an operator but must be able to operate autonomously and respond on its own to changing conditions on Mars.