<p>Oxia Planum (OP), located at the transition between the ancient terrain of Arabia Terra and the low lying basin of Chryse Planitia, will be the landing site for the ESA-Roscosmos ExoMars Programme&#8217;s 2022 mission [1]. The descent module and landing platform, Kazachock, will transport the Rosalind Franklin Rover to search for signs of past and present life on Mars, and investigate the geochemical environment in the shallow subsurface over a 211-sol nominal mission.</p><p>OP forms a shallow basin, open to the north, characterized by clay-bearing bedrock, and episodic geological activity spans from the ~mid-Noachian to ~early Amazonian in age [2,3,4]. Building a thorough understanding of Oxia Planum prior to operations will provide testable hypotheses that facilitate interpretation of results, and hence provide an effective approach to address the mission&#8217;s science objectives. To this end, we have run a detailed group mapping campaign at HiRISE-scale using the Multi-Mission Geographic Information System (MMGIS) [5], co-registered HRSC [6], CaSSIS and HiRISE mosaics [7], and 116 1km<sup>2</sup> quads covering the 1-sigma landing ellipse envelope. Complementary CTX-scale mapping covers the wider area around the landing site and is described elsewhere [8].</p><p>Throughout 2020, 84 mapping volunteers associated with the mission&#8217;s Rover Science Operations Working Group followed a pre-formulated programme of training, familiarisation and mapping. With the mapping phase complete, a small sub-team are focused on map reconciliation phase, comprising data cleaning and science decision making. The process will culminate in map finalisation and submission for publication, and use in activities to plan rover science activities.</p><p>This campaign yields important advances for overall science readiness of the ExoMars 2022 mission:</p><ul><li>Team experience working, communicating and learning together, valuable for operations.</li> <li>Building team knowledge of the landing site, and the main scientific interpretations.</li> <li>Curated datasets and software available for team use in ongoing planning.</li> </ul><p>High-resolution map data representing our geologic understanding of Oxia Planum. This is an input to ongoing RSOWG work to construct the mission strategic plan, which provides science traceability from mission objectives to rover activities.</p><p><strong>Acknowledgments:</strong> We thank Fred Calef and Tariq Soliman at JPL for their support regarding MMGIS.</p><p><strong>References:</strong> [1] Vago, J. L. et al., (2017) Astrobiology 17 (6&#8211;7), 471&#8211;510. [2] Carter, J. et al., (2013) J. Geophys. Res. 118 (4), 831&#8211;858. [3] Quantin-Nataf, C. et al., (2021) Astrobiol. 21 (3),&#160; doi:10.1089/ast.2019.2191. [4] Fawdon P. et al., (2019) LPSC50 #2132. [5] Calef, F. J. et al., (2019) in 4th Planet. Data Work., Vol. 2151. [6] Gwinner, K. et al., (2016) Planet. Space Sci. 126, 93&#8211;138. [7] Volat, M. et al., (2020), EPSC, #564. [8] Hauber, E. et al. (2021), LPSC52.</p>
Oxia Planum is the selected landing site for the ExoMars Rosalind Franklin (RF) Mission, launching in 2028. The science objectives of the mission are to search for signs of life and to characterize the geochemical environment in the subsurface as a function of depth. RF will accomplish this with its ‘Pasteur’ suite of scientific instruments, and a drilling and sampling subsystem to retrieve samples for analysis from as deep as 2 m [1].In preparation for this mission ESA, though the Rover Science Operations Working Group (RSOWG), has conducted a program of high resolution morphostratigraphic mapping and analysis to understand the geological significance of the landing site, to provide context for in-situ sample analysis and to serve as an input into strategic planning for rover operations. This effort: (i) has defined and described the geography of Oxia Planum as a framework for its exploration [2], (ii) has produced a geological map of the landing site [3], and (iii) in our ongoing work, is building a set of geological hypotheses that the RF rover can test during its nominal mission (in 2030-2031).Figure. 1: The (a) location and (b) context of Oxia Planum, inc. the availability of CaSSIS data which has been critical to developing our regional understanding. (c) The geological map of the Oxia Planum landing site summarizing the major unit groups (see Figure 2).Oxia Planum (Figure 1) preserves a record of the diverse geological process that formed and modified the landscape of western Arabia Terra throughout Mars’ geological history. Noachian Terrains contain extensive phyllosilicate–bearing materials in an environment of widespread aqueous alteration [4-7]. These deposits were subsequently added to (and modified by) fluvial activity and burial beneath regional layered terrain in the early Hesperian. They experienced further burial and erosion throughout the Amazonian [8-11]. Consequently, exploring the cross–section of strata exposed in Oxia Planum informs us about the paleoenvironmental conditions across a significant part of martian geological history (symbolized in Figure. 2). Furthermore, as Oxia is topographically open to the north, the processes recorded there probably reflect those occurring along the dichotomy boundary across the wider Chryse/Arabia region [4, 11- 15].We present: (1) The high-resolution geological map of the landing site in Oxia Planum [3] and the data used to create it [2]. (2) An overview of hypotheses relevant to key events in Oxia Planum's geological history. (3) A discussion of how future RF observations will impact these questions and our wider understanding of Mars.Figure 2: A summary of our current working hypotheses for the history of Oxia Planum visualized as an East to West schematic cross-section through the Oxia Basin. This connects the major geological units (Figure 1) to outstanding questions, the answer to which will tell us more about the overall geological evolution of Mars.Acknowledgments: We thank the CaSSIS and HiRISE teams for ongoing data collection in support of the RF rover mission. PF thanks UK Space Agency (ST/W002736/1) and the ExoMars Science Knowledge Program (SKP) for funding.References: [1] Vago et al. (2017) Astrobiology 17 (6–7), 471–510. [2] Fawdon, et al. (2021) J. Maps, 17:2, 621-637. [3] Fawdon et al. (2024) J. Maps 20(1). [4] Carter J. et al. (2015) Icarus 248, 373-382. [5] Quantin et al. (2021) Astrobiology 21:3, 345-366. [6] Mandon et al. (2021) Astrobiology 21:4, 464-480. [7] Brossier et al. (2022) Icarus 386. [8] McNeil et al. (2023) in LPSC 54 Abs.#1252. [9] Fawdon et al. (2022) JGR-Plan. 127, e2021JE007045. [10] Davis et al. (2023) EPSL 601, 117904. [11] Woodley et al. (2023) J. Maps, [12] Frueh et al. (2023) LPSC 54 Abs.#1440. [13] McNeil et al. 2022 JGR-Plan. 127, e2022JE007246. [14] Molina et al. (2017) Icarus 293 27-44. [15] Tornabene et al. (2023) LPSC 54 Abs.#2727
Abstract We conducted a detailed photogeological analysis of the northern portion of the South Pole‐Aitken (SPA) basin (10–60°S, 125–175°W) and compiled a geological map (1:500,000 scale) of this region. Our new absolute model age for the Apollo basin, 3.98 + 0.04/−0.06 Ga, provides a lower age limit for the formation of the SPA basin. Some of the plains units in the study area were formed by distal ejecta from remote craters and basins. The characteristic concentrations of FeO and TiO 2 of other plains are indicative of their volcanic origin. The oldest volcanic materials occur near the center of the SPA basin and have an Early Imbrian age of ~3.80 + 0.02/−0.02 Ga. Late Imbrian volcanic activity occurred in and around the Apollo basin. In total, the volcanic plains cover ~8% of the map area and cannot account for the extensive SPA iron signature. The sources of the signature are the oldest materials on the SPA floor (FeO ~11–14.5 wt%). In contrast, the ejecta composing the SPA rim are significantly poorer in FeO (<7.5 wt%). The signature could be related to the differentiation of the SPA impact melt. However, the spatial segregation of the ancient iron‐rich and iron‐poor materials suggests that the SPA iron signature predated the basin. Thus, the signature might be explained by a pre‐SPA lunar crust that was stratified with respect to the iron concentrations, so that the SPA impact excavated the upper, iron‐poorer portion of the crust to form the SPA rim and exposed the deeper, iron‐richer portion on the floor of the basin.
