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

arrive at Earth, often generated by coronal mass ejections (CME’s), and the detailed forecasting of these
events is the subject of the NSF-funded Center for Integrated Space weather Modeling (CISM).
Understanding the interactions at all planets aids our understanding of physical processes at Earth. Solar
system objects furthermore provide our only opportunity to make in situ measurements of plasma
processes. Such processes are important in all areas of astrophysics; 94 solar system plasma observations
thus play a role in shaping our ideas about hosts of other cosmic systems.
In addition to the global magnetospheres, “space weathering” is the collection of physical
processes that erode and chemically modify surfaces directly exposed to the space environment, either the
solar wind or a planetary magnetosphere. Understanding space-weathering effects is critical to the correct
interpretation of surface observations from remote-sensing and in situ studies. Space weathering
exposure results in a thin patina of material that covers and sometimes obscures the endogenic surface
materials that are often the principal interest of remote-sensing observations. Space weathering also
encompasses surface-removal processes such as sputtering by energetic particles, micrometeoroid erosion
and photon-stimulated desorption; a less well-recognized (but potentially important) process is electronstimulated
desorption. These processes may be more important for planetary rings than they are for icy
satellites, where they can result in relatively short lifetimes for dusty rings such as those at Jupiter and
Uranus. The chemical products of space weathering could also affect subsurface processes on small
satellites. Finally, irradiation can affect the electrostatic and magnetic environment of airless bodies
through the build-up of static charge. The effect of the build-up of charged dust on the Mars rover solar
panels is well known; whether or not such effects are important on small icy satellite surfaces or in ring
systems is unknown.
Important Questions
Some important questions concerning solar wind and magnetic field interactions with planets
include the following:
• How do magnetospheres interact with the solar wind?
• How is surface material modified exogenically (e.g., processes such as magnetospheric
interactions and impacts) versus being pristine or relatively unmodified?
Future Directions for Investigations and Measurements
For all planetary magnetospheres from Earth to the outer solar system, in situ measurements of
local magnetic fields and plasma environments should be combined with remote observations of the
global magnetosphere. Local measurements should include both fields and particles to clearly determine
the local density, currents, and large scale flows. Global measurements may be a combination of auroral
imaging and spectroscopy (Earth-orbital ultraviolet and/or groundbased infrared measurements),
observations of nonthermal radio emissions, and measurements of energetic neutral atoms. In situ
measurements require missions to the planets. Remote observations can be provided from Earth or other
vantage points, for example, a spacecraft en route to Neptune or Uranus could observe Jupiter and Saturn.
In all cases, however sufficient time coverage is essential for complete context. Space weathering
processes are interdisciplinary and “universal” in nature, requiring grounding in laboratory and theoretical
studies, as well as simulation facilities.
PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION
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