Vision and Voyages for Planetary Science in the Decade 2013-2022 (2011) / Chapter Skim
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4 The Primitive Bodies: Building Blocks of the Solar System
4 The Primitive Bodies: Building Blocks of the Solar System
Pages 87-110
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From page 87... ...
Indeed, ground-based telescopes continue to discover unusual and puzzling objects in the Kuiper belt and elsewhere, and those objects might serve as the targets for future missions. Comet sample return is a major goal of the study of primitive bodies, and one of the ultimate goals is a mission to return cryogenic samples.
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From page 88... ...
The planetary habitats theme also includes the question, What were the primordial sources of organic matter, and where does organic synthesis continue today? -- which is also relevant to the study of primitive bodies, because comets are believed to be a primary source of primordial organic materials.
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From page 89... ...
Specific objectives for continued advancement of studies of primitive bodies in the coming decade include the following: • Understand presolar processes recorded in the materials of primitive bodies; • Study condensation, accretion, and other formative processes in the solar nebula; • Determine the effects and timing of secondary processes on the evolution of primitive bodies; and • Assess the nature and chronology of planetesimal differentiation.
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From page 90... ...
Now, analyses of materials from primitive bodies are revolutionizing this field of research. Studies of microscopic presolar grains in chondritic meteorites, interplanetary dust particles, and comet samples returned by the Stardust mission provide critical constraints for models of the synthesis of elements and isotopes within stars and supernovae.1 Studies to characterize the organic matter in these materials are proceeding apace; they reveal how simple carbon-based molecules formed in interstellar space have been processed into more complex molecules in the solar nebula and in planetesimals.
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From page 91... ...
Future Directions for Investigations and Measurements While previous laboratory work has focused on presolar grains extracted from meteorites by harsh chemical treatments, future efforts will exploit new technologies to locate and analyze presolar grains in situ in the host meteorites, so as to identify less refractory materials. Obtaining presolar grains and organic matter from additional comet sampling missions and from interplanetary dust particles will allow researchers to understand how these materials were distributed in the solar nebula and preserved in solar system solids.
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From page 92... ...
Future Directions for Investigations and Measurements Although progress has been made in assessing whether various kinds of interplanetary dust are derived from comets or asteroids, there remains some uncertainty about the parent objects of some kinds of primitive meteorites. Determining the ages of chondrite components that record specific nebular processes is required to produce a timeline for major events in the solar nebula.
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From page 93... ...
At the other end of the compositional scale, the Kuiper belt is home to the largest number of silicate-ice objects, some of which might have undergone internal heating and differentiation. New age dates have revolutionized the chronology of differentiated silicate bodies, 17,18 while new meteorite recoveries have broadened the range of differentiation styles and conditions experienced by these bodies.
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From page 94... ...
Specific objectives for continued advancement of this field in the coming decade include the following: • Determine the composition, origin, and primordial distribution of volatiles and organic matter in the solar system; HED meteorites; all photomicrographs are taken with crossed nicols. a QUE 97053 • Understand how and when planetesimals were assembled to form planets; and h subophitic texture Constrain the dynamical evolution of laths)
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From page 95... ...
Cometary organic matter and volatile elements have been analyzed in samples returned by the Stardust spacecraft, 26,27,28 and cometary volatiles are now recognized to be heterogeneous as determined by the Deep Impact spacecraft.29 Spectroscopy of recently discovered KBOs has provided some constraints on their surface compositions.30 Comparison of meteoritic and cometary organic matter inventories with the composition of young circumstellar disks has been facilitated by recent Spitzer Space Telescope observations.31 Important Questions Some important questions concerning the composition, origin, and primordial distribution of volatiles and organic matter in the solar system include the following: • What are the chemical routes leading to complex organic molecules in regions of star and planet formation? • What was the proportion of surviving presolar organic matter in the solar nebula, relative to the organic compounds produced locally?
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From page 96... ...
Bodies exhibiting cometary activity have now been recognized within the main asteroid belt and among the Centaur asteroids.36 The structure of the Kuiper belt provides one of the best constraints on the dynamical r earrangement of the giant planets, and some recent KBO studies have revised scenarios for the early orbital history of the solar system.37 The size distribution of main belt asteroids has been matched to that of impactors during the late heavy bombardment about 4 billion years ago, suggesting that the asteroid belt was the source of these impactors.38,39 A different population of impactors is indicated for the outer solar system, judging from the cratering record preserved on Saturn's ice satellites.40
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From page 97... ...
Connections with Extrasolar Planets Studies of the sizes, orbital distributions, and compositions of the KBO population and of interplanetary dust derived from KBOs, comets, and asteroids provide critical data for interpreting accumulating data on debris disks around stars such as Beta Pictoris and Fomalhaut. Connections with Astrophysics The isotopic compositions of presolar grains in meteorites and interplanetary dust particles provide tests of theoretical models of nucleosynthesis in stars and supernovae, which are of great interest to astrophysics.
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From page 98... ...
Ideally, comet sample return missions should preserve samples at or below 150 K from collection to delivery at the curation facility. While there is no substitute for the science that can be performed in terrestrial laboratories on samples from primitive bodies, significant science at considerably less cost can be performed by in situ investigations.
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From page 99... ...
, and NEO surveys can be found in Chapter 10. Sample Curation and Laboratory Facilities Curation is the critical interface between sample return missions and laboratory research.
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From page 100... ...
To enable a broad range of primitive bodies missions in the near future, technology developments are needed in the following key areas: ASRG and thruster packaging and lifetime, thermal protection systems, remote sampling and coring devices, methods of determining that a sample contains ices and organic matter and preserving it at low temperatures, and electric thrusters mated to advanced power systems. ADVANCING STUDIES OF THE PRIMITIVE BODIES To date there have been no flagship missions to primitive bodies, and none was identified in the 2003 planetary science decadal survey.45 However, in March 2004 the European Space Agency launched Rosetta, a flagship-class mission in which there is modest participation by NASA-sponsored investigators.
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From page 101... ...
Priority New Frontiers missions are the Comet Surface Sample Return and the Trojan Tour and Rendezvous. Comet Surface Sample Return It is widely believed that active comets contain the best-preserved samples of the initial rocky, icy, and organic materials that led to the formation of planets.
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From page 102... ...
Most of these instruments would collect important data during the flybys on the way to the rendezvous. Potential Candidate Missions Beyond 2022 and Related Technology Requirements Future Flagship Mission Candidate The return of cryogenic comet samples is viewed as an essential goal (which would be enabled by a precursor New Frontiers Comet Surface Sample Return mission)
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From page 103... ...
A study carried out by Goddard Space Flight Center (Chiron Orbiter Mission: Mission Concept Study Report to the NRC Planetary Science Decadal Survey, Primitive Bodies Panel; see Appendixes D and G) found that with current propulsion technology it is not feasible, within the New Frontiers program, to place in orbit an adequate science payload (e.g., an imager, ultraviolet and infrared spectrometers, a magnetometer, and a radio science experiment)
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From page 104... ...
Proximity operations around small bodies might allow some science observations, and eventual human landings on small bodies would presumably involve sample returns. Such interaction might present a spectrum of opportunities, including providing inputs into mission design, furnishing flight instruments, characterizing objects through data analysis, and sharing newly developed technologies.
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From page 105... ...
Past and ongoing successes include: • Near Earth Asteroid Rendezvous -- The first mission to orbit and land on an asteroid; • Stardust -- The first mission to return samples of comet dust to Earth; • Deep Impact -- The first mission to investigate the subsurface of a comet and determine the density of a comet nucleus; and • Dawn -- A solar-electric propulsion mission on its way to explore two of the largest asteroids in the main belt, 4 Vesta and 1 Ceres. Investigations of primitive bodies are ideally suited for the Discovery program.
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From page 106... ...
• Landed investigations of Phobos and Deimos -- A major goal of in situ surface science on the m artian moons is to determine their compositions in order to constrain their origins. • Stardust-like sample return missions to other Jupiter-family comets to investigate mineralogical and chemical diversity -- The results of multiple missions would provide fundamental insights into the origin of crystalline materials around stars and the processes of radial transport in circumstellar disks.
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From page 107... ...
a family of bodies that originated in the outer asteroid belt or at a farther distance, and reached the inner solar system to deliver volatiles and organics to the accreting terrestrial planets. Investigation of Phobos and Deimos crosscuts disciplines of planetary science, including the nature of primitive asteroids, formation of the terrestrial planets, and astrobiology.
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From page 108... ...
• Technology development -- Expand technology developments in the following areas that affect the highestranked missions to primitive bodies: ASRG and thruster packaging and lifetime, thermal protection systems, remote sampling and coring devices, methods for determining that a sample contains ices and organic matter and for preserving it at low temperatures, and electric thrusters mated to advanced power systems. Develop a program to bridge the TRL 4-6 development gap for flight instruments to ensure that state-of-the-art instrumentation is available for future missions to primitive bodies.
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From page 109... ...
2005. NMR studies of chemical structural variation of insoluble organic matter .
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From page 110... ...
41st Lunar and Planetary Science Conference, The Woodlands, Texas. LPI Contribution No.
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