It looks as though NASA's InSight Mars lander's days are numbered after the space agency announced that the spacecraft is gradually losing power due to dust building up on its solar panels, already reducing their output by 90 percent.

After touching down on the Red Planet on November 26, 2018, the InSight lander deployed two circular solar arrays with a diameter of 7 ft (2.2 m) each. At first, these generated 5,000 Wh of power each Martian day, but over the last three and a half years dust has accumulated on the panels, cutting power down to a mere 500 Wh per day, and it's getting worse.

Winds have blown dust off the panels as well as on them, and NASA engineers have used InSight's robotic arm to trickle sand on the panels so the wind blew the grains across, turning them into little dust collectors. However, the power levels continue to decline and the coming seasons at the lander's site on Elysium Planitia will deposit enough dust to drop these levels beyond the point of no return by the end of the year.

In response to this, Mission Control has ordered the lander's robotic arm locked into its retirement pose for the last time and power is being diverted to the spacecraft's seismometer, which will continue to record for several months. By September, power levels will have dropped so low that the seismometer will have to be shut down and InSight will only be able to send the occasional image or signal. Sometime in December, the craft will cease to operate.

On the plus side, InSight has already completed its primary mission and during its extended science mission it has sent back new data about Mars, including the detection on May 4, 2022 of a magnitude 5 quake – the most powerful yet detected off Earth.

NASA says that InSight could still get a reprieve if it encounters a dust devil that sufficiently clears its panels, but the low power levels make this an increasingly unlikely scenario.

“We’ve been hoping for a dust cleaning like we saw happen several times to the Spirit and Opportunity rovers,” said Bruce Banerdt, InSight’s principal investigator at NASA’s Jet Propulsion Laboratory in Southern California, which leads the mission. “That’s still possible, but energy is low enough that our focus is making the most of the science we can still collect.”