NASA Mars helicopter heard humming through planet's thin air

Cape Canaveral: First came the amazing pictures, then the video. Now NASA is sharing sounds of its little helicopter humming through the thin Martian air.

NASA’s Jet Propulsion Laboratory in California released this first-ever audio Friday, just before Ingenuity made its fifth test flight, a short one-way trip to a new airfield. During the fourth flight a week earlier, the low hum from the helicopter blades spinning at more than 2,500 revolutions per minute is barely audible. It almost sounds like a low-pitched, faraway mosquito or other flying insect.