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

1. What is the nature of Enceladus’s cryovolcanic activity, including conditions at the plume
source, the nature of the energy source, delivery mechanisms to the surface, and mass loss rates?
2. What is the internal structure and chemistry (particularly organic chemistry) of Enceladus,
including the presence and chemistry of a global or regional subsurface ocean?
3. What is the nature of Enceladus’s geological history, including tectonism, viscous
modification of the surface, and other resurfacing mechanisms?
4. How does Enceladus interact with the rest of the saturnian system?
5. What is the nature of the surfaces and interiors of Rhea, Dione, and Tethys?
6. Surface characterization for future landing sites.
The committee commissioned a broad study of possible mission architectures including flybys, simple
and flagship-class orbiters, landers, and plume sample return missions, and concluded that a simple
orbiter would provide compelling science (Appendix G). A follow-up detailed study (Appendix G) found
that the above science goals could be addressed well using a simple orbiter with a payload consisting of a
medium-angle camera, thermal mapper, magnetometer, mass spectrometer, dust analyzer, and radio
science. Sophisticated use of leveraged flybys of Saturn’s mid-sized moons before Enceladus orbit
insertion reduced delta-V requirements, and thus mass and cost, compared to previous studies. 78 The
mission requires plutonium for power, in the form of ASRGs, but requires little other new technology
development. However, planetary protection is an issue for Enceladus because of the possibility of
contamination of the probable liquid water subsurface environment, and mission costs could increase
somewhat if it proves necessary to sterilize the spacecraft to meet planetary protection guidelines.
Ice Giant Orbiters
The exploration of the uranian satellites could potentially be accomplished by the Uranus Orbiter
and Probe mission discussed in Chapter 7. The proposed satellite tour (Appendix G), which includes two
targeted flybys of each of the five major satellites, would help to fill a major gap in understanding of
planetary satellites, because the sides opposite to those seen by Voyager 2 would be illuminated, flybys
would be closer than those of Voyager (for instance potentially enabling magnetic sounding of satellite
interiors), and because of instrumentation improvements relative to Voyager. Neptune orbiter and flyby
missions (Appendices D and G) could potentially address many Triton science goals.
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