Viking Marsquakes 1976—Seismic Archaeology

Abstract

AbstractTo date, three Mars landers carried seismometers: Viking 1 and 2 in 1976 (Viking 1 seismometer failed) and InSight in 2018. In 574 Sols (one Sol is one solar day on Mars), Viking detected one possible marsquake on Sol 80 and one discounted marsquake on Sol 53. Both events were recorded in Event Mode, a two‐channel (amplitude and frequency at 1 Hz) compression technique. In contrast, in 1440 Sols, InSight confirmed 1319 full waveform marsquakes. InSight's technology and capability were significantly better than Viking's, with wind and lander noise being significant for both missions. This project developed three evaluation tools: (a) Comparison and re‐evaluation of Viking Sol 80 and 53 with Viking wind data, (b) a recovered Viking tool to convert InSight waveforms to the Viking compressed Event Mode format, and (c) a new analysis tool to convert Viking compressed Event Mode approximate “reconstruction” to time series similar to InSight format. Evaluation using these tools allows answering the question “What would the Viking Seismology Team has concluded given the new information from InSight and the evaluation tools developed for this project?” Findings from these analyses confirm that both Viking Sol 80 and Sol 53 were marsquakes. The plausible conclusion that Sol 80 was a marsquake also provides potential information for estimating the crustal thickness in Utopia Planitia. Combining data and analysis from only two Mars landers containing working seismometers, landing 42 years apart, is planetary seismic archaeology.