Vision and Voyages for Planetary Science in the - Solar System ...

In the previous decadal survey, CCSR was not advocated because of the immaturity of critical
technology. To enable a CCSR mission that can be carried out at acceptable cost and risk certain critical
technologies must be perfected.
The Applied Physics Laboratory undertook a study at the committee’s request to identify the
technological issues that need to be addressed in order to facilitate a CCSR mission (Appendix G). The
report concluded that it should be possible to obtain a stratigraphy-preserving core sample at least 25 cm
deep and 3 cm across using a touch and go approach which does not require an actual landing on, or
anchoring to, the comet’s surface. Also studied were potential approaches to “sample verification,” the
goal of which is to guarantee that the sample contains at least 20% ice and accompanying volatile
organics. A key element of the study was to consider methods of encapsulating the sample and to assess
the relative difficulty/cost of maintaining the sample at 90 K, 125 K or 200 K from collection to delivery
to a terrestrial laboratory. The study concluded that a practical thermal design is feasible with the storage
temperature required to preserve water ice during the expected long cruise phase being about 125 K. In
this case the integrity of more volatile ices such as hydrogen cyanide and carbon dioxide would be
compromised, unless a temperature of no more than 90 K was maintained. The study indicates that
achieving this lower temperature would have significant impacts on the complexity and cost of the
mission. On the other hand, relaxing the minimum temperature limit to 200 K appears to be unnecessary
to reduce cost.
The report concluded with a technology development roadmap outlining seven important
questions that need to be addressed to make CCSR a practical mission in the decade of the 2020s.
A Cryogenic Comet Sample Return mission is of great importance to the study of primitive
bodies. However, this mission cannot be achieved without substantial technology development. NASA
will have to conduct technology development and demonstration in this coming decade in order to make it
possible for the next decade.
Priority New Frontiers-class Missions
Competitively selected missions provide the optimum avenue for fostering innovation and new
ideas and for making flight opportunities available to a wider spectrum of investigators. Successful New
Frontiers concepts will have focused objectives and well-integrated science and flight teams, aspects
which lead to reduced cost and lower risk of cost growth. An experienced PI can assure that these goals
are achieved while maximizing science return. Important examples of 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. A Comet Surface Sample Return (CSSR)
mission is of the highest priority to the primitive bodies community. A study of this mission,
commissioned by NASA and published in 2008, served as a concept study for this decadal survey. The
objective of the CSSR mission is to collect at least 100 grams of surface material and return it for analysis
to Earth. 42
The Stardust mission returned the first samples from a known primitive body and the analysis of
these samples has profoundly changed our understanding of the formation of comets. The materials
collected by Stardust indicate that comets contain significant amounts of inner solar system materials
including chondrules and refractory inclusions. It appears that comets are made of materials that formed
across the full expanse of the solar nebula and thus are bodies that are far more important preservers of
early solar system history than previously believed. Stardust collected hundreds of particles but most of
them were small and the high-speed capture process degraded organics, submicron grains and the surface
layers of larger grains.
PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION
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