Aging in Lunar Swirls: Segmented Evolution, Evidences and Implications

AGING IN LUNAR SWIRLS: SEGMENTED EVOLUTION, EVIDENCES AND IMPLICATIONS Deepak Dhingra, Department of Earth Sciences, Indian Institute of Technology Kanpur, Kalyanpur, Kanpur, Uttar Pradesh – 208016, India (Email: dee[email protected]m). Introduction: Lunar swirls have conventionally been defined as optically bright, surficial features with a sinuous geometry, which are generally associated with regions of strong magnetic field on the Moon [1]. They occur at wide variety of spatial scales and may extend to several hundred kilometers. Although their origin is debatable, their preservation through solar wind deflection by the associated magnetic field is widely acknowledged [1-9]. The age of lunar swirls, however, represents an important unknown. It has bearing on the understanding of the space weathering process and the origin of lunar swirls.We are investigating the question of the age of lunar swirls through a multipronged approach utilizing morphological and spectral observations from variety of lunar missions [10]. Data and Methods: We are using high spatial resolution data from Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) and Wide Angle Camera (WAC) to document morphological variations in different parts of the swirl region [11]. These observations are supplemented by spectral observations from Moon Mineralogy Mapper (M3) onboard Chandrayaan-1 mission [12]. Early Results: Synergistic utilization of these datasets are enabling us to evaluate the aging process of lunar swirls. Preliminary results suggest that the bright swirls may represent only the most immature segments which are supported by very strong magnetic field in the region and hence are maturing at a slow pace. However, investigation of the nearby region has led to the identification of swirl-like features which are significantly subdued. Do these represent the mature endmember of swirls? Further detailed investigations are underway to characterize these newly identified morphological features (Figure 1). Implications for formation and evolution of swirls: There are interesting implications of our observation of swirl segments with contrasting albedo. It includes potentially a much wider spatial extent of swirls (which would influence the swirl formation models), degradation of the magnetic field strength with respect to time and spatially segmented (disconnected ?) evolution of the swirl. In the latter case, the striking contrast in albedo will increase the uncertainty while determining the age of a lunar swirl. Summary: We report the possible occurrence of a mature endmember of lunar swirls, one which has a much lower albedo in contrast to its brighter counterpart. It is based on the analysis of high resolution imaging data. Further detailed investigations are needed to characterize the observed swirl segments and understand their implications. References: [1] Blewett, D. T. et al. 2011, J. Geophys. Res. (Planets), 116, E02002. [2] Denevi, B. W. et al. 2016, Icarus, 273, 53. [3] Kramer G Y et al. 2011 J. Geophys. Res., 116 E00G18. [4] Bhatt et al. 2023 A&A 674, A82, https://doi.org/10.1051/00046361/202245356 [5] John R. Weirich et al, 2023 PSJ, DOI: 10.3847/PSJ/ace2b8 [6] Garrick-Bethell, I., Head, J. W., & Pieters, C. M. 2011, Icarus, 212, 480 [7] Glotch, T. D., Bandfield, J. L., Lucey, P. G., et al. 2015, Nat. Commun., 6, 6189 [8] Bruck Syal, M., & Schultz, P. H. 2015, Icarus, 257, 194 [9] Kinczyk et al., (2025) PSJ, 6:57, https://doi.org/10.3847/ PSJ/adafa6 [10] Dhingra D., (2024) 12th ELS, Dumfries, UK [11] Robinson, M. S., et al. (2010) Space Sci Rev., 150, 81–124 [12] Pieters, C. M., et al. (2009) Curr. Sci., 96, 500–505. Figure 1 Optically bright swirls may represent only the most immature segments. Sub-mature to mature swirl segments may also exist.