AMBITION, the Comet Nucleus Cryogenic Sample Return mission for ESA Voyage 2050 program
Authors: Filacchione Gianrico , Bockelée-Morvan Dominique ,   AMBITION Team
Published: October 2020

Since the 1980s, ESA has played a leading role in cometary space science with Giotto and the Rosetta/Philae missions to comets 1P/Halley and 67P/Churyumov-Gerasimenko, respectively. These missions have greatly improved our knowledge of comets and placed Europe in an ideal position for the preparation of future cometary missions. After a cometary flyby mission (Giotto) and an orbiter (Rosetta) with a nucleus lander (Philae), and the selection of F-class Comet Interceptor ESA mission, the next major step in cometary science would be a cryogenic sample return mission as studied in the AMBITION proposal [1] which was submitted to ESA in the context of the future Voyage 2050 program. Despite the success of previous missions, a number of high priority scientific questions are still debated within the cometary community:The best approach to answer these questions is to return a pristine and volatile rich cometary sample to Earth. Such a sample, preserved at cryogenic temperature, will be transferred to a state-of-the-art curation facility, where it will be investigated in great detail.In this scenario part of the sample will be studied by means of different analytical techniques in laboratory-controlled conditions while the remaining sample will be stored at cryogenic temperature for future investigations. Laboratory analyses of the returned sample can achieve much higher precision and resolution measurements as compared to in-situ measurements.The AMBITION study has considered different mission targets (see Figure 1), including Centaurs, Jupiter family comets and its extinct members, returning Oort cloud comets, dynamically new comets, main belt comets and interstellar comets as possible candidates. Among them, Jupiter family comets are the ones which offer the best characteristics, in terms of orbital parameters, evolutionary history, composition and activity, to be to be selected for an L-class cryogenic sample return mission. The other targets could be explored by more consolidated (orbiters, landers) small and medium class missions.The selection, collection and storage of the sample at controlled cryogenic temperature and pressure during the return flight, Earth re-entry and landing phases will require significant technological advancement to guarantee maintenance of the optimal environmental conditions for the collected sample. Several options are identified for pristine sample collection from the cometary nucleus, including subsurface corers able to extract carrots up to 3 m depth as well as grabbers and manipulator arms to collect ice-rich, semi-buried boulders from the surface.The AMBITION mission is the &#8220;Holy Grail&#8221; in the field of cometary exploration and Solar System formation. For its implementation it will need a strong commitment from the scientific community, industrial partners, ESA and national space agencies.Figure 1: Approximate mission classes for different mission and comet types, in increasing complexity from left to right, and covering varying evolution stages of comets from the four possible reservoirs (Kuiper Belt, the Oort cloud, the Main Belt, and other planetary systems). Shading indicates approximate cost from yellow (F-class) through orange (M-class) to red (L-class or multiagency flagship missions). Hatched boxes indicate that such a combination is unfeasible, mostly due to excessive &#8710;v requirements. Past and planned missions are shown. From [1].&#160;[1] Bockel&#233;e-Morvan, D. et al., AMBITION, Comet Nucleus Cryogenic Sample Return (2019), eprint, 2019arXiv190711081B&#160;