Recent Lunar missions and new scientific results in multiple disciplines have shown that working and operating in the complex lunar environment and exploiting the Moon as a platform for scientific research and further exploration poses major challenges. Underlying these challenges are fundamental scientific unknowns regarding the Moon's surface, its environment, the effects of this environment and the availability of potential resources. The European Lunar Lander is a mission proposed by the European Space Agency to prepare for future exploration. The mission provides an opportunity to address some of these key unknowns and provide information of importance for future exploration activities.Areas of particular interest for investigation on the Lunar Lander include the integrated plasma, dust, charge and radiation environment and its effects, the properties of lunar dust and its physical effects on systems and physiological effects on humans, the availability, distribution and potential application of in situ resources for future exploration. A model payload has then been derived, taking these objectives to account and considering potential payloads proposed through a request for information, and the mission's boundary conditions. While exploration preparation has driven the definition there is a significant synergy with investigations associated with fundamental scientific questions. This paper discusses the scientific objectives for the ESA Lunar Lander Mission, which emphasise human exploration preparatory science and introduces the model scientific payload considered as part of the on-going mission studies, in advance of a formal instrument selection.

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A 3D thermal model that includes a discrete subsurface exponential density profile, surface shadowing and scattering effects has been developed to simulate surface and subsurface temperatures across the Moon. Comparisons of the modelled surface temperatures with the Lunar Reconnaissance Orbiter's Diviner Lunar Radiometer Experiment ("Diviner") measured temperatures show significant improvements in model accuracy from the inclusion of shadowing and scattering effects, with model errors reduced from ~10 K to ~2 K for mid-latitude craters. The 3D thermal model is used to investigate ice stability at potential landing sites near the lunar south pole, studied for Roscosmos' 'Luna Resource' (Luna 27) lander mission on which the ESA PROSPECT payload is planned to fly. Water ice is assumed to be stable for long periods of time (> 1 Gyr) if temperatures remain below 112 K over diurnal and seasonal cycles. Simulations suggest ice can be stable at the surface in regions near to potential landing sites in permanently shaded regions and can be stable below the surface in partly shaded regions such as pole-facing slopes. The simulated minimum constant subsurface temperature (where the seasonal temperature cycle is attenuated) typically occurs at a depth of ~50 cm and therefore the minimum depth where ice can be stable is 0 ≤ ≲ 50 .

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