Sediments Within the Icy North Polar Deposits of Mars Record Recent Impacts and Volcanism

Abstract

The North Polar Layered Deposits (NPLD) of Mars are ice‐rich sedimentary layers that formed under the influence of Mars' modern climate and thus record the recent climatic history of Mars, analogous to terrestrial ice sheets. The 2013–2023 Planetary Science Decadal Survey recommends a lander mission to sample the NPLD for climatic records; however, linking the geologic record to the climatic history will require quantitative dating of the NPLD. In this study we use orbital reflectance spectroscopy to show for the first time that dateable mafic lithics are present throughout the NPLD. We find significant glass as well as diverse crystalline minerals, which suggests that surface processes like impacts and volcanism were active during the late Amazonian and transported sediments from across the planet to the north pole. In situ investigation of the NPLD will thus provide critical quantitative constraints on both the recent geologic and climatic histories of Mars.

New Insights Into Composition Variation of Mars South Polar Layered Deposits From SHARAD Radar Sounder

“…Although forward modeling that considers shergottite or altered basalt as inclusions is consistent with the observed shadow zones, other lossy materials such as perchlorate minerals (Orosei et al., 2018), saline ice (Bierson et al., 2021), smectite clays in the SPLD surface lag material and bedrock (Smith et al., 2021), and mafic minerals within the NPLD (Sinha & Horgan, 2022) cannot be excluded as potential causes of the shadow zones. However, it is unlikely that liquid brine stably exists above the base of the SPLD under the current Martian pressure and temperature conditions (Ojha et al., 2021; Sori & Bramson, 2019).…”

“…The englacial lossy material could be the result of Mars Amazonian volcanism, with erupted volcanic ash being transported through atmospheric circulation, such as global dust storms (Haberle et al., 1982; Hernández‐Bernal et al., 2019). A combination of impact ejecta, dust, and distal volcanic ash is also possible (Horgan et al., 2014; Sinha & Horgan, 2022). The similarity in the distribution of dust content with depth between terrestrial ice cores and our inferred SPLD (see Figure 2 in Delmonte et al.…”

“…The englacial lossy material could be the result of Mars Amazonian volcanism, with erupted volcanic ash being transported through atmospheric circulation, such as global dust storms (Haberle et al, 1982;Hernández-Bernal et al, 2019). A combination of impact ejecta, dust, and distal volcanic ash is also possible (Horgan et al, 2014;Sinha & Horgan, 2022). The similarity in the distribution of dust content with depth between terrestrial ice cores and our inferred SPLD (see Figure 2 in Delmonte et al (2004) and Figures 1 and 2 in Hammer et al (1985)), as well as the significant correlation observed between dust flux and temperature records on Earth (Lambert et al, 2008), suggesting that the heterogeneity of the SPLD, as indicated by the radar shadow zone resulting from inferred presence of lossy material is likely attributable to variations in the local south polar environment.…”