Opening New Frontiers in Space Choices for the Next New Frontiers Announcement of Opportunity (2008) / Chapter Skim
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2 New Frontiers Mission Options
2 New Frontiers Mission Options
Pages 15-57
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From page 15... ...
To date there have been two New Frontiers missions selectedthe New Horizons mission to Pluto and the Kuiper Belt and the Juno mission to orbit Jupiter. Three missions remain from the original decadal survey list of potential New Frontiers missions: • South Pole-Aitken Basin Sample Return, • Venus In Situ Explorer, and • Comet Surface Sample Return.
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From page 16... ...
No science prioritization is implied by their order. South Pole-Aitken Basin Sample Return The South Pole-Aitken Basin Sample Return mission, as described in the decadal survey, is an inner-solarsystem mission to study basin-forming processes and impact chronology by returning samples from the deepest, most heavily crateredand, hence inferred to be the oldestimpact structure preserved on the Moon (Figure 2.1)
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From page 17... ...
It is possible, for example, to conduct far more sophisticated analysis of Apollo samples today than it was when they were first returned to Earth. Background A South Pole-Aitken Basin Sample Return mission would directly address the following crosscutting themes and key questions identified in the decadal survey (numbering is taken from the decadal survey)
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From page 18... ...
One model for the evolution of the outer solar system postulates that the eccentricities of Jupiter and Saturn were pumped up as they passed through 2:1 orbit:orbit resonances, sweeping resonances through the main belt and dislodging main belt asteroids. These asteroids then produced cataclysms on all terrestrial planets and satellites, including the Moon. See R
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From page 19... ...
Conclusions The committee concludes that the South Pole-Aitken Basin Sample Return mission remains a very scientifically important mission that should be considered for the New Frontiers Program. Although the committee is concerned that NASA should not be too specific in defining how New Frontiers missions should be conducted, it has concluded that in this case, given the maturity of the science questions and the precise design of the mission as stated in the decadal survey, studying new samples from the Moon is a reasonable and irreducible requirement of the mission.
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From page 20... ...
Venus Express mission has greatly expanded knowledge of the upper atmosphere and exosphere of Venus, and has contributed to understanding of regions of the atmosphere nearer to the planet's surface. However, characterization of the noble-gas and isotopic signatures of the well-mixed lower atmosphere would greatly expand understanding of the formation and evolution of the atmosphere of Venus, illuminate important elements of the current climate, including the drivers for the Venus greenhouse effect, and potentially provide insight on the early tectonic evolution of the planet.
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From page 21... ...
How do the processes that shape the contemporary character of planetary bodies operate and interact? As noted in the decadal survey, a New Frontiers VISE mission should address a number of the following objectives, which were not prioritized: Science mission objectives for VISE are as follows: • etermine the composition of Venus's atmosphere, including trace gas species and light stable D isotopes; • Accurately measure noble gas isotopic abundance in the atmosphere; • Provide descent, surface, and ascent meteorological data; • Measure zonal cloud-level winds over several Earth days; • Obtain near-infrared descent images of the surface from 10-km altitude to the surface; • Accurately measure elemental abundances and mineralogy of a core from the surface; and • Evaluate the texture of surface materials to constrain weathering environment.
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From page 22... ...
11The committee has reproduced only the top three VEXAG goals but notes that the VEXAG committee has produced a valuable document that can be used as a reference on Venus science objectives. This document, Venus Exploration Goals, Objectives, Investigations, and Priorities: 2007, is available at http://www.lpi.usra.edu/vexag/vexag_goals_2007.pdf.
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From page 23... ...
However, most of the science objectives from the decadal survey require in situ measurements that are beyond the capabilities of an orbital mission such as Venus Express. 12 Conclusions The committee concludes that a VISE mission remains a very scientifically important mission that should be considered for the New Frontiers Program.
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From page 24... ...
For instance, Soviet-era Venus missions not only successfully reached the surface, but also operated there for up to an hour, proving that surface missions are possible. In the decadal survey, the VISE mission concept was discussed in terms of what it could contribute to a future flagship-class Venus sample return mission.
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a mission may not fit within the fiscal limits and programmatic timescale of the New Frontiers Program. The science yield from a warm sample return mission will have to be strongly defended by proposers.
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Stardust data also indicate that comets may resemble asteroids more than scientists previously believed.15 Finally, comets have been discovered in the asteroid belt. Unlike other comets previously studied, these mainbelt comets appear to have formed in the much warmer inner solar system where they are found today and might, therefore, contain ice that is quite different in chemical and isotopic composition from that in other comets.
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From page 27... ...
Finally, the committee notes that proposers for warm comet sample return missions must demonstrate that significant progress toward the goals of the decadal survey will be achieved by noncryogenic sample return. Network Science Network Science missions to study the interiors of Mercury, Venus, and the Moon, with geophysics measurements as a primary objective, would address fundamental science questions.
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From page 28... ...
Geophysical network science would address how small bodies differentiate and how the bulk composition of Mercury is related to the composition of the terrestrial planets." 20 For the Moon, the decadal survey said that "seismic data would resolve the internal structure, permitting a much-improved estimate of bulk composition."21 For Venus, the decadal survey recommended "geophysical network science (seismic, heat flow) to determine internal structure, distribution of heat-producing elements, lateral and vertical heterogeneity of crust and mantle, and the possible existence of an iron-rich core.
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From page 29... ...
Key investigations that address evolution of the crust, mantle, and core include the following: • Determination of the horizontal and vertical variations in internal structures, • Determination of the compositional variations and evolution of crusts and mantles, • Determination of the major heat-loss mechanisms and resulting changes in tectonic and volcanic styles, and • Determination of the major characteristics of iron-rich metallic cores (size and the nature of liquid and solid components) .27 In the decadal survey section titled "A Long-Term Exploration Strategy for the Inner Planets," the Inner Planets Panel recommended a focus on "essential network science" involving "the establishment of multiple surface stations operating concurrently on a planet."28 In addition, the decadal survey identified geophysical network science as providing scientific return in three categories: highly significant scientific return, very useful scientific return, and supporting scientific return:29 23New Frontiers in the Solar System, p.
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3. Characterize magnetic fields and relationships to surface, atmosphere, and the interplanetary medium. Future: What fate awaits Earth's environment and those of the other terrestrial planets?
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In light of the decadal survey's recognition of the importance of network science on all the terrestrial planets and the Moon, the committee recommends that Network Science missions to the Moon, Venus, and Mercury be considered as candidate missions for the New Frontiers announcement of opportunity in addition to a Mars mission. The scientific objectives of a Network Science mission should be drawn from a subset of the objectives (not in priority order)
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From page 32... ...
• Determine the mineralogic composition of the surface and its thermophysical properties. Trojan/Centaur Reconnaissance The decadal survey's Primitive Bodies Panel recommended "reconnaissance of the Trojans and Centaurs," 32 and the decadal survey listed this as a deferred medium-class mission.33 A variety of developments since the decadal survey, when combined with the strong initial rationale, elevate this mission concept to one for consideration.
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From page 33... ...
The Centaur flyby would provide insights into the nature of the Kuiper Belt, the nature and origin of short-period comets and their parent bodies, and activity in distant comets." 36 The decadal survey identified a number of crosscutting science themes that have been addressed by the New Horizons mission and could be addressed by a Trojan/Centaur Reconnaissance mission. As listed in the decadal survey, these include:37 The First Billion Years of Solar System History 1.
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34 OPENING NEW FRONTIERS IN SPACE FIGURE 2.6 NASA close-up image of Saturn moon Phoebe by the Cassini spacecraft. Phoebe is roughly spherical and has a diameter of 220 kilometers.
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The Primitive Bodies Panel of the decadal survey identified the following high-level science questions as significant for being addressed by the Trojan/Centaur Reconnaissance mission, dividing these into paradigm-altering, pivotal, and foundation-building observations for each of two themes, "Building Blocks of the Solar System" and "Organic Matter in the Solar System: Materials for the Origin of Life": 38 Paradigm Altering • What is the nature of the KBOs (Kuiper Belt objects)
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solar system evolution will elucidate these physical and dynamical processes through time. The Primitive Bodies Panel further listed the following specific questions deserving of investigation: 39 • here in the solar system are the primitive bodies found, and what range of sizes, compositions, W and other physical characteristics do they represent?
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Coupled with the idea that large-planet migration might perturb Kuiper Belt objects into Centaur-like orbits, this mission is necessary to fully inventory the primitive bodies of our solar system and understand their origins. Mission-Specific Recommendations Coupling new science emerging in the past several years with the decadal survey, the Trojan/Centaur Reconnaissance mission originally described in the decadal survey should be modified so that NASA informs potential proposers of the kind of science questions that should be answered and does not prescribe how the mission should actually be accomplished.
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From page 38... ...
The decadal survey's Primitive Bodies Panel recommended an Asteroid Rover/Sample Return mission as its fourth-ranked mission priority;42 however, the mission was ultimately deferred from consideration by the decadal survey.43 A variety of developments since the decadal survey, when combined with the strong initial rationale, prompted the committee to elevate this mission concept to one for consideration. The primary motivations for an asteroid sample return mission is the desire to both acquire samples with known geologic context and to return materials that are either unlikely to survive passage to Earth (e.g., friable, volatile-rich material)
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The Primitive Bodies Panel of the decadal survey identified the following high-level science questions for which an Asteroid Rover/Sample Return mission could provide breakthrough advances or significantly address, dividing these into paradigm-altering, pivotal, and foundation-building observations: 46 Paradigm Altering • What are the compositions and origins of the organic and volatile materials in primitive bodies? • How is organic matter distributed throughout the solar system?
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Developments Since the Decadal Survey In the past several years a number of developments have strengthened the case for asteroid sample return. The most important of these is the complete analyses of the data on 433 Eros (Figure 2.8)
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Eros is approximately 33 by 13 by 13 kilometers in size, whereas Itokawa is much smaller, at 535 by 294 by 209 meters. SOURCE: Eros image courtesy of NASA, Itokawa image courtesy of JAXA (Japan Aerospace Exploration Agency)
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From page 42... ...
This recognition of the diversity of organics in meteorite samples, coupled with the detection of main-belt comets that appear to have formed in the much warmer inner solar system, strengthens the importance of this mission. Mission-Specific Recommendations The committee recommends that although the Asteroid Rover/Sample Return mission should be included as a candidate mission for the New Frontiers Program, the mission objectives should be changed to reflect new
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From page 43... ...
Such a mission should have the following science objectives, which are not prioritized: • Map the surface texture, spectral properties (e.g., color, albedo) , and geochemistry of the surface of an asteroid at sufficient spatial resolution to resolve geologic features (e.g., craters, fractures, lithologic units)
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From page 44... ...
Background The decadal survey identified top-level, crosscutting science themes that are relevant to the study of Io. 54 Although the survey did not specifically address how these crosscutting themes and key questions would be addressed by an Io Observer mission, it is possible to map such a mission against many of the themes, such as those reprinted below.
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What are the active interior processes and their relations to tidal heating, heat flow, and global patterns of volcanism and tectonism? Heat flow and tidal heating Global volcanism and tectonism Secular variations of magnetic field 2.
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How do conditions in the protoplanetary nebula influence the compositions, orbits, and sizes of the resulting satellites? Characterization of magnetic fields in satellites 2.
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From page 47... ...
The assumption that this mission could achieve the stated goals within the New Frontiers cost category rests partially on an assumption that heritage from the Europa Geophysical Explorer would allow significantly reduced costs. Although the Europa Geophysical Explorer was not pursued, significant studies of the Jupiter radiation environment were performed as part of the Jupiter Icy Moons Orbiter program, and some radiation-hardened electronics have been developed in the interim.
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Juno will also provide magnetic field data when it reaches Jupiter in 2015. But the lack of dedicated, targetable observations makes any approach to understanding the system extremely piecemeal.
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From page 49... ...
The mission should address some of the following science questions, which are not listed in order of priority. The committee, however, acknowledges that there are more objectives here than can be included in a single New Frontiers mission and leaves it to potential competitors to choose their science goals and defend their choices.
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Ganymede's geologic activity and magnetic field are probably powered by tidal heating. The decadal survey states that "Ganymede's differentiated interior and actively convecting core (required to generate its magnetic field)
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What are the active interior processes and their relations to tidal heating, heat flow, and global patterns of volcanism and tectonism? Secular variations of magnetic field 61New Frontiers in the Solar System, p.
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From page 52... ...
What are the active interior processes and their relations to tidal heating, heat flow, and global patterns of volcanism and tectonism? Interior structure Heat flow and tidal heating Global volcanism and tectonism • Questions on which a Ganymede Orbiter can offer a significant advance A
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-- Geology/modification 5. What does the magnetic field of Ganymede tell us about its thermal evolution, and is Ganymede unique?
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Moon Interior Structure. Establish internal structure of icy moons including presence and proper ties of putative conducting layers, measurement of higher harmonics and secular variations of Ganymede's magnetic field and set limits on intrinsic magnetic fields for Europa and Callisto • Objective B
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From page 55... ...
A Ganymede orbiter was identified as a potential medium-class mission in the decadal survey, which stated: "No detailed studies are yet available, and the assumption that this mission could achieve the stated goals within this cost category rests partially on assuming that the lesser radiation environment and heritage from the Europa Geophysical Explorer mission would allow significantly reduced costs."65 The development of the Juno mission and the more recent NASA Science Definition Team investigation of the flagship-class Jupiter System Observer could produce a mission that ultimately would achieve orbit around Ganymede, characterizing its surface in detail as well as its gravity and magnetic fields, thereby accomplishing a multitude of science objectives. However, the committee is concerned whether a spacecraft orbiting Ganymede would be feasible under New Frontiers budgetary constraints, given the results of NASA's billion-dollar-box study in 2007.
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From page 56... ...
These objectives, which are not prioritized, include: • Understand Ganymede's intrinsic and induced magnetic fields and how they are generated, and characterize their interaction with Jupiter's magnetic field. • Determine Ganymede's internal structure, especially the depths to and sizes or thicknesses of the probable metallic core and deep liquid water ocean, and the implications for current and past tidal heating and the evolution of the Galilean satellite system as well as ocean chemistry.
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From page 57... ...
However, NASA should limit its choices to the eight specific candidate missions unless a highly compelling argument can be made for an outside proposal.
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