The achievement of powered flight on another world is one of the great spaceflight feats of the last decade. Since its first brief hop on April 19, 2021, the Mars Ingenuity helicopter has subsequently made an additional 27 flights, traveling nearly 7 km across the surface of the red planet and scouting ahead of NASA’s Perseverance rover. It has wildly exceeded the expectations and hopes of its scientists and engineers.

But recently, the small, automated helicopter has had problems with dust accumulating on its solar panels, NASA says. This dust reduces the ability of the vehicle to recharge its six lithium-ion batteries. And just as the helicopter needs all of the solar energy it can get, the northern hemisphere of Mars is approaching the dead of winter, which comes in a little more than two months.

Due to these battery issues, the helicopter’s team of flight controllers at NASA’s Jet Propulsion Laboratory lost contact with the helicopter on May 3. They had been closely monitoring the health of their tiny spacecraft, particularly the charge state of its batteries. After losing contact, the engineers figured that the Ingenuity‘s field-programmable gate array—essentially, its flight computer—entered into shutdown mode due to a lack of power. In such a situation, virtually all of the helicopter’s on-board electronics turned off to protect them from the cold nighttime temperatures, more than 100° Fahrenheit below freezing. This included the internal clock.

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With this working hypothesis, the engineers on Earth took an extraordinary step to save their plucky helicopter. Ingenuity landed on Mars in February 2021 as a small component on the much larger Perseverance rover, which it uses as a bridge to communicate back to Earth. After it shut down earlier this month, the engineers figured that when the Sun rose and Ingenuity‘s batteries started to charge, it would try to communicate with the nearby rover. Only, because its internal clock had reset, when Ingenuity tried to call Perseverance, the rover wouldn’t be listening.

Read more: Arstechnica