Not for the first time, the Perseverance rover has fallen foul of an errant rock on Mars.
The plucky little machine's weekend sojourn on the red planet's surface was spoiled by a pebble, picked up by a particularly strong gust of wind, which collided with the rover.
This follows another stone mishap in January when the rover's attempts to stow away some core samples were thwarted by "pebble-sized debris" obstructing its robotic arm.
Ironically, the recent gust-lifted pebble assault struck the rover in an instrument designed precisely for measuring wind speed and direction along with other weather phenomena. Perseverance's weather station, called the Mars Environmental Dynamics Analyser (MEDA), contains two wind sensors among other devices to measure humidity, radiation and air temperature.
The wind sensors are roughly 30cm-long devices, encircled by six detectors which can provide accurate measurements of wind speed from any direction.
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Both wind sensors are attached to foldable boom arms to keep them away from the rover itself. This is because the car-sized Perseverance actually affects wind currents when travelling through the thin Martian atmosphere.
Although one of the wind sensors was damaged, MEDA can still evaluate wind speeds, albeit with decreased sensitivity, according to MEDA's principal investigator, José Antonio Rodriguez Manfredi.
"Right now, the sensor is diminished in its capabilities, but it still provides speed and direction magnitudes," Rodriguez Manfredi, who is a scientist at the Spanish Astrobiology Centre in Madrid, tells Space.com.
"The whole team is now re-tuning the retrieval procedure to get more accuracy from the undamaged detector readings."
Rodriguez Manfredi notes that the sensors were designed with redundancy and protection in mind: "But of course, there is a limit to everything."
Such safeguards are particularly difficult for instruments like MEDA, which are intended to be exposed to environmental conditions. But gusts as strong as the one which flung a pebble at Perseverance were not anticipated.
"Neither the predictions nor the experience we had from previous missions foresaw such strong winds, nor so much loose material of that nature," says Rodriguez Manfredi.
It is ironic, Rodriguez Manfredi admits, that the wind sensors were damaged by "precisely by what we went looking for".
But Perseverance perseveres.
The endearing rover continues the mission it began when it landed on the red planet's surface on February 18, 2021.
Let's hope that it's more smooth sailing for Perseverance from here on. But this may not be the only pebble on this very desolate beach.
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