LRO Targeting of the South Pole-Aitken Basin for the Extended Science Mission

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The recent Decadal Survey for Planetary Science [1] reconfirmed the high scientific priority of sample return from the Moon’s South Pole-Aitken basin (SPA). Well-defined stratigraphic relationships make it the oldest recognizable impact basin on the Moon. Its great size means that the chronology of rocks in a large region of the Moon were reset by the event, which would have produced an enormous impact-melt complex within the basin and widespread ejecta deposits. Although many large impacts have occurred within SPA basin since its formation, including smaller basins such as Apollo, Ingenii, Poincaré, and Schrödinger, and large craters such as Leibnitz, Von Karman, and Oppenheimer, impact ejecta models indicate that much of the material in the present-day basin should reflect the major resetting of ages caused by the SPA event. Sample return from SPA remains a high priority in the Decadal mainly because determining the chronology of the SPA basin can address the onset and duration of the lunar cataclysm [2]. Accordingly, targeting of potential landing sites within SPA for science analysis and landing-site safety assessments (i.e., geometric stereo) is a high priority for the Lunar Reconnaissance Orbiter Cameras (LROC).

As part of the ESMD phase of LRO’s mission, NASA designated nine Constellation sites within and associated with SPA as high-priority targets [3,4]. As such, these sites have been intensely covered with Narrow Angle Camera (NAC) imaging, including images suitable for derivation of geometric stereo [5-7]. These sites include the SPA Interior and Rim sites, Apollo Basin, Mare Ingenii, Van de Graaff, and Schrödinger. In addition to these, sites at Aitken Crater, the South Pole, and Malapert Massif lie on or near the SPA topographic rim. These sites encompass numerous high-priority science objectives as articulated in the NRC SCEM Report [8]. Sites and their coordinates are listed in the table below.

MoonRise, one of the finalists in the most recent New Frontiers competition, submitted targets for geometric stereo NAC coverage during its Phase A Concept Study. MoonRise mainly sought to target sites near the deep interior of SPA in areas of plains deposits and where the mafic geochemical signature is enhanced. The rationale was to seek SPA impact melt materials in the ejecta deposits of large craters that produced the plains deposits, as well as fragments of volcanic rocks (mare and cryptomare) in the regolith. Other key geometric stereo targets in SPA include the areas near Th anomalies near Oresme V and Birkeland Craters, and areas of unusual topography and structures.

As LRO plans for an extended science mission, its elliptical orbit is ideal for southern hemisphere imaging. Requests from the scientific community for geometric stereo imaging in support of a future SPA sample return mission for scientific and landing-site safety assessments are encouraged.

Table: SPA sites with multiple geometric stereo NAC pairs

Refs: [1] NRC (2011) Vision and Voyages. Nat’l Acad. Press, Wash., DC. [2] Tera F. et al. (1973) Lun. Plan. Sci. 4, 723-725. [3] Gruener J. et al. (2009) LRO Targeting Workshop, Tempe. [4] Lawrence S. et al. (2010) LEAG, Sep. 14-16, Wash., DC. [5] Tran T. et al. (2010) Joint Spec. Symp. ISPRS Tech. Comm. IV & AutoCarto, ASPRS/CaGIS 2010 Fall Spec. Conf., Orlando. [6] Archinal B. et al. (2011) Lunar Planet. Sci. Conf. 42, #2316. [7] Burns K. et al. (2012) this conference. [8] NRC (2007) Scientific Context for Exploration of the Moon. Nat’’l Acad. Press, Wash., DC