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Space·2 min read

Viking 2 Data May Hold the Oldest Marsquake Ever Recorded

Fifty years after NASA's Viking 2 landed, Chinese researchers say a long-dismissed signal from Sol 80 could be the earliest recording of a marsquake.

Viking 2 lander on the surface of Mars with its legs resting on rocky red terrain under a dusty sky.
Image: xataka.com
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A team of Chinese scientists says a signal recorded by NASA's Viking 2 lander half a century ago may be the oldest known recording of a marsquake. The data had been set aside for decades because it was too noisy to trust.

NASA sent Viking 1 and Viking 2 to Mars in 1975 to look for signs of life. Both carried a seismometer to help judge whether the planet is or once was habitable. Viking 1 deployed its instrument badly, and Viking 2's picked up too much interference to confirm any quakes, so the records were largely forgotten.

Why Viking 2 was so noisy

Viking 2's seismometer was mounted directly on the lander. The wind moved the craft, much like a sail, and passed those vibrations to the instrument. It was impossible to tell whether a signal came from the ground or from the air. The lander's legs were its only contact with the surface, adding more room for distortion along the way.

NASA fixed this with InSight, launched in 2018. A robotic arm placed its seismometer directly on the ground, cutting wind interference. Between 2018 and 2022, InSight detected 1,319 marsquakes, showing Mars is more seismically active than expected.

The Sol 80 signal

Viking 2 made two suspicious recordings, on Sol 53 and Sol 80 (Martian days are called sols). The first was classified as a gust of wind. The second had long been seen as a quake candidate, but doubts over interference kept it unresolved.

Applying what InSight taught them, the authors of the new study re-examined it. They found the Sol 80 signal closely resembles both California earthquakes and InSight's marsquakes. It was also recorded in the early hours, when winds tend to be weaker, and about 20 minutes after a period of light wind, which makes wind interference unlikely.

Certainty is out of reach. The recording could still come from another event, such as a meteorite impact. Even so, the work shows that old planetary data can yield new results when read with modern knowledge.

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Tags:marsviking 2nasamarsquakeinsightseismology

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