Powered flight is impossible in Mars's thin atmosphere
The old claim turned out to be wrong and was rejected by evidence.
TaughtMars's atmosphere is only about 1% as dense as Earth's, far too thin for wings or rotors to get a grip. A helicopter or airplane could never generate enough lift to fly there. Mars is explored by rovers on the ground, and always will be.
NowOn 19 April 2021, NASA's Ingenuity helicopter lifted off, hovered, and landed on Mars: the first powered, controlled flight by an aircraft on another world. It went on to fly 72 times over nearly three years, far outlasting its planned five flights.
What actually happened
The thin air is a real obstacle, and Ingenuity beat it with brute engineering: rotor blades over a metre long, spinning at around 2,500 rpm, roughly five times faster than a helicopter on Earth, on a craft built to weigh under two kilograms. Mars's lower gravity helped, but the flight was still on the edge of what physics allows.
What began as a 30-day technology demonstration became a scout for the Perseverance rover, proving that aerial exploration of Mars is not just possible but useful. The flat statement, that powered flight can't happen in Mars's atmosphere, was retired on the first hover.
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Who was taught this
Still standard through 2021, so anyone who finished school between 1950 and 2021 learned the earlier version.