Figure 12. Boulder Range-Frequency Distribution (BRFD,top) and Boulder Size-Range Distribution (BSRD, bottom) for the unnamed martian crater (Fig. 11), and the two lunar craters: Camelot, and South Ray (Watkins et al., 2019). Data for the unnamed crater are cutoff at 3R to minimize contamination from nearby craters. The data for Camelot and South Ray crater were originally expressed in crater radii from the crater rim (Watkins et al., 2019), and they are re-plotted here in radii from the crater center.
The comparison of BSRDs and BRFDs around these craters show several intriguing similarities and disparities in the boulder populations. The unnamed martian crater shows the expected radial decrease in boulder abundance, and maximum boulder size for impact ejecta. However, compared to craters of similar size on the moon, there is a substantial lack of boulders with diameters above ~4 m. In addition, the ejected boulders lack a prominent peak in frequency near the rim (as seen in Camelot) and diminish in abundance near 3 R (unlike South Ray). Further investigation would be required to determine if these differences are attributable to the differing erosional processes, regolith thicknesses, or target lithologies, as well as how these results can inform the relative rates of boulder degradation vs. crater relaxation inferred for these boulder halo craters (Levy et al., 2018). However, such an investigation would be readily enabled by MBARS, and could greatly expand the number of craters with fully characterized ejecta populations.

6. Conclusions

MBARS is an accessible, open source tool for planetary scientists to locate and measure boulders in HiRISE images accurately and rapidly. We demonstrate that this tool, when applied in conjunction with supplemental manual analyses, provides a reliable technique to automatically assess large boulder populations with minimal manual effort. We show this in four key ways:
1) MBARS can accurately measure the height and width of the Viking landers, demonstrating accuracy of these methods on objects of known size.
2) Manual boulder measurements taken for other purposes and surveys can be used to calibrate the automated results, reducing the need for new, redundant analyses.
3) MBARS is capable of measuring boulders (and landers) to the same or greater degree of accuracy with previously published methods of automated boulder measurements.
4) Comparison of MBARS analyses around a small crater compare well with prior analyses of similarly sized lunar craters.
Variations in boulder distributions can be distinctive of specific geologic processes including impacts, mass wasting, and glacial processes. We hope that MBARS can be used as an essential tool going forward in many surface investigations of these processes. It is built to function on high resolution images of the martian surface but can be adapted to work on other bodies where sufficiently high-resolution data is available. This methodology enables many avenues of scientific investigation into impact, erosional, and glacial processes, which can now be pursued more rapidly and at broader scope than is viable with manual analysis alone.

Acknowledgements

Current support for this research comes from NASA’s MDAP program, grant #80NSSC21K1093D. D. Hood has been funded throughout the project by the Louisiana Space Grant Graduate Student Research Assistantship awarded to D. Hood (NNX15AH82H) and NASA’s Mars Data Analysis Program to S. Karunatillake and D. Hood (80NSSC18K1375‐MDAP). The authors also thank Elizabeth McKinnie, and J. Patrick Brothers for their boulder delineations used as part of this work. The authors thank NASA, JPL, and the University of Arizona for supporting access to HiRISE images.

Data and Software Availability Statement

Data in support of this publication are located on the Texas Data Repository “Supporting Data for: ‘The Martian Boulder Automatic Recognition System, MBARS”’ DOI: 10.18738/T8/EFPJWY .The code to operate MBARS, along with operating instructions and other information is available at https://github.com/dhood14/MBARS .

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