Bell, S. K.

Bickel, V. T.

Czaplinski, E. C.

Farrant, B. E.

Harrington, E. M.

Honniball, C. I.

Kring, D. A.

Martinez, S. N.

Rogaski, A.

Sargeant, Hannah

Tolometti, G. D.

English

Open Research Online 

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsDetermining Trafficability of Pyroclastic Deposits andPermanently Shaded Regions of the Moon UsingBoulder TracksConference or Workshop ItemHow to cite:Sargeant, H. M.; Bickel, V. T.; Honniball, C. I.; Martinez, S. N.; Rogaski, A.; Bell, S. K.; Czaplinski, E. C.;Farrant, B. E.; Harrington, E. M.; Tolometti, G. D. and Kring, D. A. (2019). Determining Trafficability of PyroclasticDeposits and Permanently Shaded Regions of the Moon Using Boulder Tracks. In: Lunar ISRU 2019, 15-17 Jul 2019,Columbia, Maryland, United States.For guidance on citations see FAQs.c© [not recorded]Version: Accepted ManuscriptCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukDETERMINING TRAFFICABILITY OF PYROCLASTIC DEPOSITS AND PERMANENTLY SHADED REGIONS OF THE MOON USING BOULDER TRACKS.  H. M. Sargeant1, V. T. Bickel2,3, C. I. Honniball4, S. N. Martinez5, A. Rogaski6, S. K. Bell7, E. C. Czaplinski8, B. E. Farrant7, E. M. Harrington9, G. D. Tolometti9, D. A. Kring10,11. 1The Open University, United Kingdom (Email: hannah.sargeant@open.ac.uk), 2Max Planck Institute for Solar System Research, Germany,3Swiss Federal Institute of Technology, Switzerland, 4University of Hawai’i, Unit-ed States, 5Tulane University, United States, 6South Dakota School of Mines & Technology, United States, 7University of Manchester, United Kingdom, 8University of Arkansas, United States, 9University of Western Ontario, Canada, 10Lunar and Planetary Institute, Universities Space Research Association, United States,11NASA Solar Sys-tem Exploration Research Virtual Institute, United States.   Introduction: Lunar Pyroclastic deposits (LPDs) and Permanently Shaded Regions (PSRs) are areas of the Moon that have significant ISRU potential. LPDs can contain volatile- and ilmenite-rich glasses [1,2], whilst PSRs act as cold traps for stable water ice [3,4]. Although several proposed missions may explore these regions, little is known about trafficability of those terrains. Here we  used boulder tracks to remotely de-termine the bearing capacity of regolith in representa-tive sites within LPDs and PSRs. Lunar boulder tracks: Rockfalls and their associ-ated boulder tracks are abundant on the Moon. They are also classic tools for determining surface proper-ties, having been used during Apollo to evaluate bear-ing capacities at the Apollo 17 landing site.  The key input parameters are boulder and track dimensions, and those of their associated shadows, which can be evalu-ated as a function of slope and boulder shape using Hansen’s formula [5].  Methods: Forty-eight boulder tracks in 10 large LPDs [6] and 13 boulder tracks in 5 PSRs [7] were identified.  A baseline set of boulder tracks in highland and mare regions was also measured. Whilst measure-ments for boulders in LPDs, highland, and mare re-gions can be made directly from NAC imagery, that is not possible in PSRs.  For those regions, NAC images were stretched by enhancing contrast and brightness to identify boulder tracks in shadowed areas. Only areas that experience secondary sunlight, diffusively reflect-ed from crater walls into PSRs, could be used in this study as some secondary source of illumination was required to identify boulders. After suitable images were selected, they were pro-cessed to remove excess noise. Boulder and track di-mensions, and the associated shadows produced, were recorded. All measurements and complementary soil properties from the literature were then input into Han-sen’s formula to estimate bearing capacities.  Results: Qualitative analyses show that boulder tracks formed in LPDs and PSRs have similar mor-phologies to those formed in highland and mare re-gions. Bearing capacity decreases with increasing slope across all location types. Therefore, rover wheels and lander pads will sink more on steeper slopes [5]. LPDs and PSRs are significantly stronger than mare regions in almost all depth ranges of regolith with estimated bearing capacities of 131±21 kNm-2 and 127±29 kNm-2 respectively, compared to 85±12 kNm-2 for mare re-gions (for upper 1 m on 0° inclines). There was insuffi-cient data in the upper 1 m of highland regolith for comparison. It should be noted that this technique is limited by the minimum depth of measured boulder tracks (≳19 cm in LPDs), which is limited by the reso-lution of the available NAC imagery (~0.5 m/pixel).  Combining our results with data obtained from sur-face images of lunar rover tracks, and extrapolating to the upper few cm’s of regolith, suggests that rovers and landers planning to explore LPDs should not sink as far into the regolith there as in highland and mare regions. The nature of the uppermost 28 cm of PSRs (the mini-mum track depth measured in PSRs) remain unclear as a result of special environmental conditions.  Conclusions: This initial study of boulder track analyses suggests the regolith in LPDs and PSRs is significantly stronger than mare regolith at equivalent depths of ≳19 cm and 28 cm respectively. Trafficabil-ity should not be an unusually difficult impediment to ISRU within LPDs, meanwhile the trafficability of rov-ers in PSRs remains uncertain. To further reduce mis-sion risk, the soil strengths calculated here for LPDs and PSRs should be tested in situ.  Acknowledgements: Thank you for the support and funding from USRA-LPI and CLSE. References: [1] McCubbin F. M. et al. (2015) Am. Mineral., 100, 1668–1707. [2] Hawke B. C. et al. (1990) LPS XX, 249–258. [3] Colaprete A. et al. (2010) Science, 330, 463–468. [4] Li S. et al. (2018) PNAS, 115, 8907–8912. [5] Bickel V. T. et al. (2018) JGR (submitted). [6] Gaddis L. R. et al. (2003) Icarus, 161, 262–280. [7] McGovern J.A. et al. (2013) Icarus, 223, 566–581. 

Determining Trafficability of Pyroclastic Deposits and Permanently Shaded Regions of the Moon Using Boulder Tracks

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Determining Trafficability of Pyroclastic Deposits and Permanently Shaded Regions of the Moon Using Boulder Tracks

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