NASA's helicopter on Mars, the four-pound "Ingenuity," failed to get off the ground for its fourth flight Thursday, but NASA said it is safe and will try again Friday.
Previous test flights for the helicopter went well, with Ingenuity rising up 16 feet in the air during the third flight last Sunday then flashing downrange about 50 yards at a speed of 6.6 feet per second.
The second test flight on April 22 and the first flight on April 19 also went as planned.
The cause of Thursday's hiccup was a "watchdog" timer issue that prevented Ingenuity from transitioning to "flight mode."
INGENUITY MARS HELICOPTER CAPTURES PERSEVERANCE ROVER IN UNPRECEDENTED AERIAL SHOT
Flying on Mars is no easy task, as the atmosphere is incredibly thin, about 1% that of Earth's. Nighttime temperatures on the Red Planet can also drop as low as minus 130 degrees, potentially freezing any unprotected electrical systems.
"Mars is hard," MiMi Aung, project manager for Ingenuity Mars Helicopter, said before the test flights. "Our plan is to work whatever the Red Planet throws at us the very same way we handled every challenge we’ve faced over the past six years – together, with tenacity and a lot of hard work, and a little Ingenuity."
Ingenuity originally touched down at an ancient river delta on Mars in mid-February aboard Perseverance before coming out of the rover's belly on April 3.
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Once Ingenuity's test flights are completed, the Perseverance rover will set off in search of past microscopic life.
Ingenuity was built at NASA's Jet Propulsion Laboratory in California and is carrying some wing fabric from the Wright Flyer that made the first ever flight on earth at Kitty Hawk, North Carolina in 1903.
The Associated Press contributed to this report.