The rate of discovery of new NEAs and the success of D-S 1 and NEAR-Shoemaker, suggest that sample return from NEAs is now technically feasible. Here we present a summary of a recent workshop on the topic

Allen, C.

Britt, D.

Brownlee, D.E.

Chapman, C.R.

Cheng, A.F.

Clark, B.C.

Drake, B.G.

Franchi, I.G.

Gorevan, S.

Kochan, H.

Lewis, J.S.

Lindstrom, M.M.

Nishiizumi, K.

Pieters, C.M.

Race, M.S.

Scheeres, D.J.

Scott, E.R.D.

Sears, D.W.G.

Yano, H.

English

Open Research Online (The Open University)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsNear-Earth asteroid sample return missionsConference or Workshop ItemHow to cite:Sears, D.W.G.; Allen, C.; Britt, D.; Brownlee, D.E.; Cheng, A.F.; Chapman, C.R.; Clark, B.C.; Drake, B.G.;Franchi, I.G.; Gorevan, S.; Kochan, H.; Lewis, J.S.; Lindstrom, M.M.; Nishiizumi, K.; Pieters, C.M.; Race, M.S.;Scheeres, D.J.; Scott, E.R.D. and Yano, H. (2001). Near-Earth asteroid sample return missions. In: 32nd Lunar andPlanetary Science Conference, 12-16 Mar 2001, Houston, Texas, USA.For guidance on citations see FAQs.c© [not recorded]Version: [not recorded]Link(s) to article on publisher’s website:http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1891.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.uk  NEAR-EARTH ASTEROID SAMPLE RETURN MISSIONS.  D. W. G.  Sears1, C. Allen2, D. Britt3, D. E. Brownlee4, A. F. Cheng5, C. R. Chapman6, B. C. Clark7, B. G. Drake2, I. A. Franchi8, S. Gorevan9, H. Kochan10, J. S. Lewis11, M. M. Lindstrom2, K. Nishiizumi12, C. M. Pieters13, M. S. Race14, D. J. Scheeres15, E. R. D. Scott16, H. Yano17,  1Center for Space and Planetary Science, Univ. of Arkansas, Fayetteville, AR 72701 (dsears@uark.edu), 2Johnson Space Center, Houston, 3Univ. Tennessee, Knoxville, 4Washington Univ., Seattle, 5John Hopkins Univ. Laurel, 6Southwest Research Institute, Boulder, 7Lockheed Martin Astronautics, Denver, 8Open Univ., Milton Keynes, U.K., 9Honeybee Robotics, New York, 10German Aerospace Center, Köln, Germany, 11Univ. of Arizona, Tucson, 12Univ. of California, Berkeley, 13Brown Univ., Providence, 14SETI Inst., Mountain View, 15Univ. of Michi-gan, Ann Arbor, 16Univ. of Hawai'i, Honolulu, 17Inst. of Space and Astronautical Science, Kanagawa, Japan   Introduction  The exponential increase in the rate of discovery of near-Earth asteroids (NEA), the success of Deep Space 1 (in particular solar electric propulsion and autonomous navigation - notwithstanding encoun-ter difficulties), the success of NEAR-Shoemaker, and the pending ISASs MUSES-C asteroid sample return mission, Stardust and the upcoming Contour, Deep Impact and other small body missions, suggest that sample return from near-Earth asteroids is now techni-cally feasible [1].  Deep Space 1 and MUSES-C mis-sions are technology missions, but it is now possible to consider NEA sample return for scientific purposes.  A recent workshop in Houston considered NEA sample return from a variety of viewpoints [2].  Here we pre-sent our summary of the workshop.  The Scientific Case for Sample Return:  Aster-oids and the comets are an integral and uniquely impor-tant part of our solar system. Not only do they provide insights into the nature of primordial solar system ma-terial − the material from which the Sun and planets formed − but their impact onto planetary surfaces is one of the most important geological and biological forces for change. They are also a potential natural resource and target for human exploration and devel-opment of space.  The NASA report Mission to the Solar System:  A Mission and Technology Roadmap advocates sample return from small solar system ob-jects and the NASA Space Science Enterprise Strate-gic Plan lists eleven goals of which seven can be uniquely addressed by NEA sample return. • Primitive asteroids are relics of the formation of the Solar System and contain evidence for processes during planet formation.  Many primitive asteroids are probably too weak to supply meteorite samples and atmospheric selection effects are clearly major.  Spec-tral data suggest that NEAs are representative frag-ments of main belt asteroids. • These asteroids may contain pre-solar grains that help us understand stellar evolution and the relation-ship between stars and planet formation. • Some asteroids should contain organic compounds that can shed light on the origin of molecules necessary for life on Earth. • By understanding the chemical processes that pre-ceded life on Earth, we can better understand possibili-ties of life on other planets. • Asteroids capture solar wind and solar energetic particles, so studies of their surface materials will con-tain a record of solar activity for bodies of known re-cent orbital history. • The samples (and the data from the encounters) will help us to design devices to deflect potentially hazardous objects and predict the effects should they reach Earth's atmosphere. • Robotic missions to NEA will be pathfinders for human missions that might use asteroid resources to facilitate human exploration and the development of space.  We have cosmic dust and meteorite samples, the latter probably come from asteroids although the match between specific types of asteroids and meteorites is not firmly established.   The Main Belt asteroids and the NEAs show similar spectral class distributions, suggesting that the NEAs fairly represent the main belt, even though some NEAs may be cometary in origin.  However, meteorites and cosmic dust are cosmic jet-sam, and, as with terrestrial geology, we need to visit the outcrops.  In situ measurements are necessary for global geo-physical and geochemical studies, but sample return is essential for a meaningful examination of the surface materials.  Sample return has the advantage over in situ methods of an unlimited range of techniques, vastly superior precision, the ability to archive samples for future investigation as instrumentation is developed, and they permit flexible responses to surprise results.  Isotopic analysis for dating and characterizing samples requires extensive preparation that can only be done in terrestrial laboratories.  The Apollo program is an ex-cellent case study of the impact which sample return can have on our understanding.  A geologist exploring a new region on Earth maps, chooses sample areas, collects samples, returns them to the laboratory for sophisticated analysis. The asteroid equivalent is to obtain reflectivity spectra, select interesting asteroids, Lunar and Planetary Science XXXII (2001) 1891.pdfNEA Sample Return Missions:  D. W. Sears et al.  collect samples, return them to the laboratory for so-phisticated analysis. It is a time-tested strategy.  New Insights into the Nature of Asteroid Sur-faces and Implications for Sample return:  The NEAR-Shoemaker mission to Eros has yielded an abundance of data that will take many years to assimi-late and understand.  Cratering has been important, but boulders are much more abundant than expected.  There is abundant regolith although bedrock might be exposed in places, and there are long lineations that suggest Eros is a coherent object rather than a rubble pile.  X-ray data suggest an LL chondrite composition, at least for the surface, although sulfur appears de-pleted.  The NEAR-Shoemaker studies of Eros show that we cannot understand meteorite-asteroid links and the chemical and physical properties of asteroids with-out returned samples from the surfaces of such NEA.  New Experience in Maneuvering Spacecraft in the Vicinity of Small Asteroids:  Our experience with NEAR-Shoemaker demonstrates a high degree of con-fidence in the new techniques required to maneuver spacecraft around asteroids.  Theoretical treatments for a variety of maneuvers around small asteroids have been developed, including: close stable orbits, low-altitude flyovers, landing trajectories and hovering, stated in order of increasing difficulty.  Asteroid shape, size, density, and rotation state are crucial parameters that must be known to implement these operations, thus these data must be available before detailed maneuvers can begin.  Additionally, the design of the entire space-craft and mission can be simplified if constraints on these asteroid parameters can be estimated early in the mission development phase.  Sample Collection Devices, Sample Contain-ment and Planetary Protection Issues:  A number of sample collection devices have been flown on previous missions, trowels/claws, drillers/corers, percussive devices, penetrators, and passive surfaces.  MUSES-C uses a cone to collect ejecta from an artificial impact during its touch-and-go sequence onto the asteroid sur-face, taking advantage of its microgravity condition.  Asteroids present new difficulties and new opportuni-ties.  Their small size, high rotation rates and irregular shape and the abundance of dust make landing diffi-cult, but at the same time their microgravity on surface makes hovering feasible.  Honeybee Robotics and Lockheed-Martin Astronautics are developing devices that can sample without landing.  There has been considerable progress in designing sample containment devices to prevent contamination of the asteroid by terrestrial organisms, the transfer of organisms to Earth or the contamination of one asteroid sample with another.  Planetary protection issues have been well-addressed by NRC subcommittees, high-risk asteroids identified, and laboratory procedures for han-dling returned samples are well-defined.  Although well-developed, these procedures require that such issues are addressed from the outset of mission plan-ning.  Experience with terrestrial ecosystems demon-strates that natural transfer is not equivalent to anthro-pogenic transfer; for example radiation doses experi-enced by meteorites during transfer may be high enough to destroy living material while this would not be true for samples returned by missions.  Human Exploration and Development of Space and Implications for Resource Utilization:  NEAs represent an attractive target for human exploration of space and could be a useful way to test Mars-bound spacecraft.  The missions would be of shorter duration (one year vs. three years), simpler (no gravity well or atmosphere), launch windows numerous, and lower energy requirements than for a missions to Mars.  The increasing numbers of NEAs means that their accessibility as natural resources has improved.  Re-turned samples will enable a better evaluation of the objects as resources and their possible use as propel-lants, life-support fluids, or structures.  Impact Hazard Mitigation:  The impact hazard is receiving increasing attention from scientific com-munities and governments and is one reason for the increased rate of detection of new NEAs.  Many meth-ods have been proposed for deflecting a potential im-pactor (deep, shallow or standoff nuclear explosions, lasers and others), but the optimal method depends knowing the chemical and mineralogical composition and mass and physical properties of the asteroid, which at the moment cannot be predicted with the required accuracy.  Recommendations from the NEA Sample Re-turn Workshop:  There was a widespread acknowl-edgement that we need data on orbits, spectral class, spin state and size for NEA, and that ∆v should be re-ported in compilations, so that interested astronomers could prioritize asteroids.  There was a strong sense that there should be international collaboration, and that we should be thinking in terms of programs that address the numerous scientific goals rather than a sin-gle mission. Such a program could obtain in-situ data with consistent instruments and to collect samples from asteroids of all major spectral types within a decade or so.  References:  [1]  Sears D. W. G. et al. (2000) A multiple near-Earth asteroid sample return mission called Hera.  Meteorit. and Planet. Sci. 35, A145.  [2]  Near Earth Asteroid Sample Return Workshop, De-cember 11-12, 2000, Lunar and Planetary Institute, Houston, Texas, LPI Contribution 1073. Lunar and Planetary Science XXXII (2001) 1891.pdf

Near-Earth asteroid sample return missions

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Near-Earth asteroid sample return missions

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