Phobos Sample Return: Next Approach

The Martian moons still remain a mystery after numerous studies by Mars orbiting spacecraft. Their study cover three major topics related to (1) Solar system in general (formation and evolution, origin of planetary satellites, origin and evolution of life); (2) small bodies (captured asteroid, or remnants of Mars formation, or reaccreted Mars ejecta); (3) Mars (formation and evolution of Mars; Mars ejecta at the satellites). As reviewed by Galimov [2010] most of the above questions require the sample return from the Martian moon, while some (e.g. the characterization of the organic matter) could be also answered by in situ experiments. There is the possibility to obtain the sample of Mars material by sampling Phobos: following to Chappaz et al. [2012] a 200-g sample could contain 10-7 g of Mars surface material launched during the past 1 mln years, or 5*10-5 g of Mars material launched during the past 10 mln years, or 5*1010 individual particles from Mars, quantities suitable for accurate laboratory analyses. The studies of Phobos have been of high priority in the Russian program on planetary research for many years. Phobos-88 mission consisted of two spacecraft (Phobos-1, Phobos-2) and aimed the approach to Phobos at 50 m and remote studies, and also the release of small landers (long-living stations DAS). This mission implemented the program incompletely. It was returned information about the Martian environment and atmosphere. The next profect Phobos Sample Return (Phobos-Grunt) initially planned in early 2000 has been delayed several times owing to budget difficulties; the spacecraft failed to leave NEO in 2011. The recovery of the science goals of this mission and the delivery of the samples of Phobos to Earth remain of highest priority for Russian scientific community. The next Phobos SR mission named Boomerang was postponed following the ExoMars cooperation, but is considered the next in the line of planetary exploration, suitable for launch around 2022. A possible scenario of the Boomerang mission includes the approach to Deimos prior to the landing of Phobos. The needed excess ΔV w.r.t. simple scenario (elliptical orbit à near-Phobos orbit) amounts to 0.67 km s-1 (1.6 vs 0.93 km s-1). The Boomerang mission basically repeats the Phobos-SR (2011) architecture, where the transfer-orbiting spacecraft lands on the Phobos surface and a small return vehicle launches the return capsule to Earth. We consider the Boomerang mission as an important step in Mars exploration and a direct precursor of Mars Sample Return. The following elements of the Boomerang mission might be directly employed, or serve as the prototypes for the Mars Sample return in future: Return vehicle, Earth descent module, Transfer-orbital spacecraft. We urge the development of this project for its high science value and recognize its elements as potential national contribution to an international Mars Sample Return project. Galimov E.M., Phobos sample return mission: scientific substantiation, Solar System Res., v.44, No.1, pp5-14, 2010. Chappaz L., H.J. Melosh, M. Vaguero, and K.C. Howell, Material transfer from the surface of Mars to Phobos and Deimos, 43rd Lunar and planetary Science Conference, paper 1422, 2012.