Researchers led by Wanbo Xiao reexamined two ambiguous seismic signals from NASA’s Viking 2 lander on Mars and suggest one may have been a marsquake from 1976, according to reporting published by Phys.org on Oct. 21, 2026. A marsquake is a quake on Mars. cite_ids: [
Phys.org reports that Xiao’s team compared the Viking 2 signals with seismic data from NASA’s InSight lander, the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport lander, which operated on the Martian surface from 2018 to 2022. Its seismometer sat directly on the ground. It recorded nearly 1,000 marsquakes in the same region where the possible Viking 2 marsquake originated, along with more than 1,300 seismic events. The study suggests that region was seismically active both in the Viking era and nearly 50 years later, during InSight’s mission. cite_ids: [
Both Viking landers reached Mars in 1976. Viking 1’s seismometer failed to deploy properly after landing, leaving Viking 2’s two ambiguous events as that mission’s only seismic record. cite_ids: [
Viking 2’s seismometer sat on the lander’s deck rather than on the ground, so it recorded wind noise. As a result, it remains uncertain whether either ambiguous event was a true marsquake or wind-related noise. A seismometer is an instrument that measures ground motion. cite_ids: [
Xiao and co-authors published the findings in AGU Advances in 2026 as Fifty Years Later: Revisiting Viking 2 Seismic Signals Through InSight, with DOI 10.1029/2026av002319. Eos, hosted by the American Geophysical Union, provided the story to Phys.org. cite_ids: [
Viking was primarily a mission to search for life on Mars, and the source ties that question to the planet’s geological evolution, internal structure, tectonic activity, and habitability history. Seismic waves help reveal a planet’s interior. Scientists placed seismometers on the Apollo moon missions, where the detectors succeeded, while the Viking results on Mars were less clear. cite_ids: [
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