Reevaluation of Viking 2 seismic signals suggests activity on Mars

In 1976, the Viking 1 and 2 missions took seismometers to Mars, with the goal of studying the planet's seismic activity. However, the results were inconclusive: the Viking 1 seismometer did not deploy correctly, and Viking 2 recorded only two ambiguous events. The Viking mission had as its main focus the search for life on Mars, but seismology was crucial for understanding the planet's internal structure and tectonic activity. This would help reconstruct the geological history that shaped Mars' habitability ^2,3.

Recently, a study reevaluated these seismic events from Viking 2 in light of the data collected by the InSight lander, which operated on Mars between 2018 and 2022. The researchers showed that one of the events recorded by Viking 2 may have been a true marsquake, originating from the same region where InSight detected nearly 1,000 marsquakes decades later. This suggests that the region was active both during the Viking era and almost 50 years later ^1,2,3.

The Viking 2 seismometer was mounted on the lander deck, which picked up a lot of wind noise. This made it difficult to distinguish between true marsquakes and environmental noise. On the other hand, the InSight seismometer was placed directly on the ground, which allowed it to detect more than 1,300 seismic events. The new analysis indicates that one of the Viking 2 events may have been a marsquake, reinforcing the idea that the region has continuous seismic activity ^1,2,3.

The study also revealed that the seismic signals from Viking 2 decay more rapidly than typical marsquakes detected by InSight. This suggests heterogeneity in Mars' attenuation structure. Additionally, the origin of the signals could be a meteorite impact, although this cannot be confirmed ¹.

These findings integrate Viking observations into a modern framework of Martian seismicity, showing how old data can gain new scientific implications when reexamined based on subsequent missions ¹.