Recent Impact Craters on Mars

Cutaway of the martian interior. A primary target of future seismic missions is to determine the size of the core.

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The detailed structure of the Martian interior places essential constraints on the formation, evolution, and dynamics of Mars. Impact events are key sources of seismic waves for interrogating internal structure in future geophysical missions. Recent, fresh craters formed by ongoing impacts are detectable in high-resolution orbital images of the Martian surface, providing an extremely accurate epicenter and estimate of source size for seismic recordings of the impact, enabling calibration of Martian seismic velocities and retrieval of internal structure from future missions, particularly InSight. Thus, current impacts are an invaluable source of information for constraining the deep Martian interior.

We are investigating impact-produced seismic activity using a detailed characterization of crater morphometry and cluster dispersion for ~400 recent impact events. This analysis includes obtaining diameters, depths, and shapes of craters and dispersion properties of crater clusters associated with recent impact events. These parameters are being obtained through examination of PDS-available images from the Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE). The resulting crater catalog and associated crater characteristics is being used to model the expected seismic response of Mars to each impact event. A primary goal of these investigations is to provide direct constraints for the detectability of seismic waves generated by impact events on Mars.

Theoretical model of the martian interior (Vp, Vs, density) from Sohl and Spohn, 1997.

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The seismic modeling of observed crater properties is occuring in 3 stages: 1) crater characteristics and end-member models of target properties are used to scale the amount of impact energy translated from the bolide into seismic energy within Mars. 2) The size and locations of contemporaneous multiple impact craters and singular impacts is used to construct source time functions for each impact. 3) The resulting sources are then be convolved with Green’s functions produced for elastic models of attenuation and surface material properties. The resulting seismic amplitudes will then be used to evaluate the detectability at distance of an impact for various body and surface wave phases and also for developing techniques to recover Martian internal structure from a single 3-component seismometer. These results are directly relevant to what will be observed by future seismic missions, and place constraints on the types of seismic energy and amplitudes that can be observed from new impacts by the InSight geophysical mission.

Relevant Papers:

Ruedas, T., Schmerr, N., Gómez Pérez, N., (2009), Seismological investigations of Mars' deep interior, NASA Decadal Whitepaper Proposals. (pdf)

This research is supported by the NASA Mars Fundamental Research Program Grant #NNX14AQ92G.

© Nicholas Schmerr 2014