A Lunar Sample Return Mission to : A Proposal for ESA’s NEXT Mission I. A. Crawford1 and K. Geelen2 1School of Earth Sciences, Birkbeck College London, Malet Street, London, WC1E 7HX, UK 2Mission Systems Team, Astrium Ltd., Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2AS [email protected], [email protected]

(1) Introduction (3) Mission architecture We propose a lunar sample return mission, targeting the ‘young’ basaltic lava flows in northern Oceanus Procellarum, The mission architecture will be based on a Soyuz-Fregat launch (Fig. 2) as a suitable project for ESA’s recently announced Next Exploration Science and Technology (NEXT) mission. to GTO, and transfer from Earth to a 100 km lunar orbit using chemical Northern Oceanus Procellarum consists of a patchwork of discrete lava flows with different compositions and propulsion on a Carrier Spacecraft. From lunar orbit, the lander will estimated ages ranging from about 3.5 to 1.2 Gyr (Fig. 1; Wilhelms,1987; Hiesinger et al., 2003). This is a far greater separate from the Carrier Spacecraft and descend using a dedicated range of ages than any samples collected by the missions (which occupy the narrow age range 3.8 to 3.1 chemical propulsion stage (Fig. 3(a)). A lunar sample(s) (mass 0.5-1 kg) Gyr). Collecting samples from one or more of these different lava flows, and returning them to Earth for radiometric will be obtained with a robotic arm and placed in a Lunar Ascent Vehicle dating, would yield at least three major scientific benefits (Crawford et al., 2007): (LAV; Fig. 3(b)). The mode of sampling will be assessed during the (1) By obtaining reliable radiometric dates for ‘young’ surfaces with known crater densities it will be possible to Phase-A study, but we currently envisage a sieved and/or cored sample of greatly improve the calibration of the lunar cratering rate for the last three billion years (see Stöffler et al. (2006) and containing a number of cm-sized ‘rocklets’ suitable for dating and NRC (2007) for reviews of the scientific importance of such an improved calibration). Briefly, the post 3Ga lunar mineralogical and geochemical analyses (a ~30cm core sample would also cratering rate is poorly calibrated (as a result of Apollo not having visited younger surfaces), but this is the cratering provide stratigraphic information about the regolith and implanted rate that is used, with assumptions, to date cratered surfaces elsewhere in the Solar System (most notably the surface of volatiles). Mars). Thus, better constraining the lunar cratering rate would be of importance to planetary science generally, not After sample acquisition, the LAV will take off from the lander leaving merely in the context of lunar geology. behind the sample mechanism, landing stage, and some scientific (2) Geochemical studies of these would yield information on the magmatic history of the , and thus lunar instruments (Fig. 4). Once in lunar orbit, the sample container will be Fig. 2. LSR will be launched by a Soyuz- mantle evolution, over this relatively recent time period, extending our understanding of lunar thermal evolution to ejected, captured by the Carrier Spacecraft and transferred into the Earth Re-Entry Vehicle. The Carrier Spacecraft will capture the sample and use Fregat rocket, such as this one which more recent times than is possible using the Apollo sample collection. launched Venus Express in 2005. the same propulsion system as used for the outward journey to return to (3) It will help provide ‘ground truth’ for the next generation of lunar remote-sensing instruments by providing direct Earth. access to a region of the Moon for which samples have not yet been returned. This architecture allows for a lander of 665 kg (including 437 kg of propellant), LAV of 145 kg (including 62 kg of propellant), and a Carrier Spacecraft of 1988 kg (including 1417 kg of propellant for the two transfers); it will also directly demonstrate technology for the Mars (2) Additional in situ surface science Sample Return (MSR) mission. During the Phase-A study, a trade-off will In addition, because the descent payload will also be able be performed between using electric propulsion and chemical propulsion (a) to emplace geophysical and geochemical instruments at for the Carrier, which might result in significant mass savings; the (b) the landing site, there will be additional scientific possibility of sampling multiple lava flows by surface ‘hopping’ will also benefits: be investigated in the Phase-A study. (i) geochemical (e.g. XRF) characterisation of the landing site and the collected sample(s); Fig. 3. CAD drawings of (a) the Ascent Vehicle and (b) the Lander (Astrium). (ii) seismic studies of an area outside the Apollo network and measurement of the thickness of the sampled lava Acknowledgements We thank all those colleagues who have contributed to developing the science case for this flow; and mission proposal, especially: M. Anand, A. Ball, R. Burgess, A. Coates, A. Coradini, H. Hiesinger, K. Joy, P. Lognonné, T. Spohn, D. Talboys, M. Wieczorek, and L. Wilson. We (iii) measurement of the lunar heatflow in a region of also thank A. Povoleri for help with mission analysis, and Elie Allouis for generating the special interest owing to its location within the artwork. Procellarum KREEP Terrain with its anomalous References Crawford, I.A., Fagents, S.A., Joy, K.H., “Full Moon Exploration: Exploring the Basaltic concentration of heat-producing radioactive elements Lava Flows of Oceanus Procellarum – Valuable (Non-Polar) Lunar Science Facilitated by a (Jolliff et al., 2000; Wieczorek and Phillips, 2000). 250 km Return to the Moon,” Astron. Geophys., 48, 3.18-3.21, (2007). Hiesinger, H., et al., “Ages and Stratigraphy of Mare Basalts in Oceanus Procellarum, Mare It is envisaged that up to 10 kg will be available for such Nubium, , and ,” J. Geophys. Res., 108 (E7), 1-27, (2003). additional instruments. Jolliff, B.L., “Major Lunar Crustal Terranes: Surface Expressions and Crust-Mantle Fig. 1. Ages of lava flows in Oceanus Procellarum, as Origins,” J. Geophys. Res. 105(E2): 4197-4216, (2000). mapped by Hiesinger et al. (2003). Sample return from Stöffler et al., “Cratering History and Lunar Chronology,” Rev. Min. & Geochem., 60, 519- one or more of these lava flows would verify these ages, 596, (2006) with the benefits described in the text (Image courtesy of NRC, The Scientific Context for Exploration of the Moon: Final Report, National Research Dr. H. Hiesinger; © AGU). Council, Washington DC, (2007). Fig. 4. The Ascent Vehicle takes off from the lunar Wieczorek, M. A and Phillips, R. J., “The Procellarum KREEP Terrain: Implications for surface (Astrium). Mare Volcanism and Lunar Evolution,” J. Geophys. Res., 105(E8), 20417, (2000). Wilhelms DE The Geologic History of the Moon USGS Prof Paper 1348 (1987)