Presentation #515.02 in the session Mars Surface (iPosters).
Seismic waves generated by meteoroid impacts have been used to study the interior of the Moon, but never before on Mars. When combined with orbital imaging of newly formed craters, impact-generated seismic events can provide an independently determined and exactly measured source location and event energy, invaluable for constraining internal structure. The InSight mission seismometers have been listening for impacts at Mars for four Earth years. We will report on our recent successes in these areas, including the seismic detection of multiple nearby small impacts (Garcia et al., 2022). These were recognized by their unique dispersive arrivals of acoustic waves resulting from the impact, which propagated through a near-surface atmospheric waveguide and were converted to ground movement. We demonstrate this propagation and transmission using both numerical and analytical tools. Impact locations were calculated from the polarization and arrival times of the seismic and acoustic waves, and subsequently confirmed via orbital imaging. The analysis of the dispersed seismo-acoustic signal associated with these impacts may also help constrain the martian atmospheric and shallow subsurface structure.
Seismic methods of detecting impacts can also supplement and improve on previous methods of using orbital imaging to find new craters, which have resulted in a comprehensive published catalog of >1,200 new impact sites on Mars (Daubar et al., 2022). When these different datasets are scaled to appropriate search areas and periods of time of observation, the resulting current impact rate appears to be higher than previously measured or predicted. Possible explanations will be discussed.
This work exemplifies the high science return of coordinated orbital and landed mission assets. Our results demonstrate the value of seismology in understanding planetary interiors and impact cratering processes throughout the Solar System, as well as the population of small bodies in the inner Solar System.