NASA’s Viking 1 and Viking 2 landers arrived at Mars in 1975 carrying seismometers intended to study the planet’s geological activity and determine whether it might once have been habitable. Viking 1 deployed its instrument incorrectly, while Viking 2 recorded signals affected by substantial interference, making them difficult to interpret reliably.
Viking 2’s seismometer was mounted directly on the lander. Wind could move the spacecraft and transmit vibrations to the instrument, while the lander’s legs were its only contact with the ground and could also introduce additional interference. As a result, it was difficult to establish whether a recorded signal came from the Martian surface or from the surrounding environment.
Later missions used a different approach. NASA’s InSight lander, which reached Mars in 2018, used a robotic arm to place its seismometer directly on the ground. Between 2018 and 2022, InSight detected 1,319 marsquakes, showing that Mars is more seismically active than previously thought.
Viking 2 captured two suspicious recordings, made on Martian Sol 53 and Sol 80. The first was eventually classified as a gust of wind, while the second remained a possible seismic event. A team of Chinese scientists has now revisited both recordings using knowledge gained from InSight’s observations.
Their analysis found that the Sol 80 signal resembled earthquakes recorded in California as well as marsquakes detected by InSight. The recording was also made during the early hours of the Martian day, when winds are generally weaker, and 20 minutes after a period of light winds. These circumstances make wind interference less likely, according to the researchers.
The signal cannot be identified with certainty. A meteorite impact or another type of event remains possible, and the limitations of Viking 2’s equipment prevent a definitive conclusion. Nevertheless, the researchers suggest that the recording could contain the oldest signal of a Mars earthquake ever captured.
Sources: Xataka.