Kuiper Belt Objects (KBOs)

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Imaging and spectroscopy observations can be used to:

• determine diameters and albedos for a large sample of KBOs;
• search for evidence of collisionally–induced changes in albedo;
• make near–simultaneous measurements to mitigate rotational.

Spectroscopy will directly constrain surface composition (H₂O, CH₄, CH₃OH) and volatile inventories of known KBOs, and provide the first spectra of many of these objects at 2.5–5 microns. The ice/water hydration band at 3.1 microns is easily within the reach of JWST's NIRSpec instrument in the vast majority of KBOs. Such results will directly address the dynamical (and chemical) history of the solar system and test formation theories. The observations will also elucidate the role that giant planet migration has played in the evolution of the solar system. Radiometry of KBOs will enable better characterization of their albedos and hence the size distribution within the Kuiper Belt.

Dwarf Planets

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Imaging and spectroscopy observations can be used to:

• determine the physical state of the ices and the composition of the organics;
• make detailed studies of the composition to determine what molecules are present on their surfaces (and in their atmospheres), and map the distribution of the constituents vs. longitude.
• provide the first detection of the low-temperature phase of solid N2, and determine whether N2 is present at all on Eris (where there is only indirect evidence for it).
• determine the thermal state of the surface using thermal light-curves for the brighter objects, and to measure the mid-IR thermal emission for the first time for the fainter objects with the JWST MIRI instrument.

Comets

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JWST observations can provide:

• near-infrared spectroscopy with R = 1000 of cometary comae;
• mid infrared spectroscopy of cometary dust grains;
• the first spectroscopic studies of the new class of icy comets in the main asteroid belt.

JWST will enable studies of the chemical composition of cometary ice and dust with unprecedented sensitivity. Spectroscopy will measure abundances of H₂O, CO₂, CO, and CH₃OH in the comae of faint comets and also constrain the ratio of ortho and para H₂O to reveal formation temperatures. This set of observations is a critical ingredient in understanding planetary system formation and evolution, when combined with synergistic JWST observations of circumstellar disks. Additionally, the study of icy comets in the asteroid belt may reveal the source objects that were responsible for the delivery of water to the Earth.

Planets and Moons

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Mars

JWST observations can:

• provide time-resolved near-infrared spectroscopy to study the variability of atmospheric species including CO2, CO, and H2O and constrain radiative and absorptive properties of airborn dust, enabling photochemical and dynamical modeling of the Martian climate;
• provide direct near-infrared detection to assess magnitude and scale of diurnal, seasonal, and interannual volatile transport, and discriminate surface and atmospheric ices and clouds;
• enable constraints to be placed on potential methane outbursts.

Jupiter and Saturn

JWST observations can:

• provide mid infrared medium resolution spectroscopy and IFU data to study the rich atmosphere compositions;
• fully explore infrared diagnostics such as phosphine and methane flourescence, which link to vertical dynamics and thermal structure of the upper atmosphere;
• provide a global context on large-scale weather patterns for high-resolution studies from complementary planetary missions (e.g., Juno and Cassini).

Uranus and Neptune

JWST observations can:

• image clouds structures;
• provide high sensitivity maps of chemical species at high latitudes;
• perform spectral characterization of H3+, CO in flourescence, detailed mapping within the 5 micron window, search for minor species, and measure isotopic ratios of major elements;
• provide mid infrared observations to measure temporal variations in temperature, resolve sources of underlying driving dynamics, and disentangle causes of rotation modulation.

Icy Moons

JWST observations can:

• complement and extend planetary missions such as Cassini.
• perform long-time baseline observations of both atmospheric and surface changes.
• provide near-IR spectrometry for Titan with a six-times greater spectral resolution than Cassini to determine types of organic species present on the surface — the higher spectral resolution over mid-latitude regions will reveal whether surface changes or secular atmospheric changes are in evidence over a decade timescale.