NASA's Mars helicopter "smart" failed to take off in its fourth flight

NASA's Mars helicopter, Wit, was due to make its boldest flight attempt yet Thursday local time, but it failed to take off.

Wit made history on April 19 when it completed its first controlled powered flight over another planet, flying at an altitude of 10 feet. Since then, Wit has completed two more flights, each going higher and farther.

The Wit is in good shape after completing its last round trip of about 330 feet. On Thursday, it had planned an even more adventurous flight: completing 117 seconds at a record speed of 3.5 meters per second and reaching an altitude of 16 feet, traveling about 436 feet south and photographing the Martian surface along the way. At that point, Wit will hover to take more pictures, then turn around and fly back to the starting point for a landing. But on Thursday, the Wit's rotor blades didn't make it fly at all.

NASA engineers are evaluating the data, and it's not clear what caused the flight to fail. One potential cause could be an earlier software glitch, which first appeared during a high-speed spin test before Wit's maiden flight. The test failed because Wit's flight computer could not switch from "pre-flight" mode to "flight" mode. However, NASA engineers fixed the problem in a matter of days with a quick software rewrite.