Jupiter Atmospheric Science Goals

In 2009, the US National Science Academies established a committee to develop a planetary science strategy for the coming decade.  Along with an international team of planetary scientists, I helped to write white papers surveying atmospheric science goals for the four giant planets in our solar system.  Given the page-constraints for these white papers, and the huge volume of feedback we received, we decided to provide supplementary material for the Decadal Survey 2013-2023 committee.


The pages below provide a list of outer planet atmospheric science themes and investigations to summarise the white papers. Any comments and suggestions should be directed to me, and the pages will be continually updated as new ideas and topics arise.  The lists aren’t meant to be exhaustive, and are biased towards atmospheric science.

A.Dynamics and Circulation of the Troposphere and Stratosphere

Scientific Aim

Determine the three dimensional structure of Jupiter’s upper troposphere and stratosphere, and the relation between the weather layer and convective overturning in the planet’s interior.  Study temporally-evolving atmospheric phenomena (upheavals, plumes, storms and vortices) over a variety of timescales from hours to years.  Characterise the strength of vertical coupling in the atmosphere down to the troposphere. 

Investigations

1.Determine zonal and meridional wind speeds with ~2 m/s accuracy, eddy momentum fluxes and the redistribution of energy and momentum within the troposphere. 

a.Dayside imaging with ~15 km/pixel resolution.  Imaging should include repeated coverage of the same regions at ~2 hour intervals for cloud tracking (necessary to obtain winds, divergence and vorticity).  Wavelengths should include visible and/or near-IR continuum as well as one or more methane absorption band (e.g., 889 nm and other).  Imaging strategy must characterize behaviour over a range of timescales, including short (1-3 days), medium (~1 month), and long (~1 year) timescale variability.  Global or near-global daily coverage for periods of weeks-to-months. [EJSM]

b.Global nadir thermal mapping in the 7-250 micron spectral range to obtain 80-700 mbar (troposphere) and 0.5-20 mbar (stratosphere) thermal winds (via temperatures).  Spatial resolution of 100 km/pixel.

2.Determine the global three-dimensional temperature structure and horizontal gradients to derive thermodynamic quantities related to the atmospheric circulation (thermal wind shear, potential vorticity, altitude of the radiative-convective boundary and tropopause, etc.). 

a.Global nadir thermal mapping in the 7-250 micron spectral range to obtain 80-700 mbar (troposphere) and 0.5-20 mbar (stratosphere) temperatures.  Spatial resolution of 100 km/pixel.  Limb viewing geometry to achieve 10-20 km altitude resolution at a wide range of latitudes

b.Repeated radio occultations closely spaced in latitude and time, retrieving pressure as a function of altitude and relating this to zonal winds. [EJSM]

c.Stellar and solar occultations in the near-IR and UV to determine the vertical temperature structure of the upper stratosphere. [EJSM]

d.Sub-mm spectroscopy to determine 3D temperatures from selected atmospheric species between 400 mbars to 1 µbar. [EJSM]

3.Direct determination of atmospheric winds above the cloud tops at 5-10 m/s accuracy. 

a.Sub-mm spectroscopy to obtain Doppler broadening of molecular lines at a wide range of latitudes and times to derive 5-300 mbar temperatures and wind speeds with high vertical resolution (10-20 km).   [EJSM]

4.Determine the composition, colouring-agents, vertical structure and temperatures within discrete atmospheric features (plumes, vortices, storms, including the Great Red Spot and the turbulent upwelling cells to the northwest) over a wide range of wavelengths and on multiple timescales (days to years).

a.Spectroscopic determination of composition from UV, near-IR, thermal-IR at regular intervals to study changes in the physiochemical characteristics of dynamical features. [EJSM, Juno]

b.Multi-wavelength visible imaging to determine vertical cloud structure and wind field;

c.Thermal observations to study temperature structure.  Observations should be repeated at monthly intervals to track the evolution of features.

d.Far-IR spectroscopy in the 15-250 micron region to determine the ratio of ortho/para hydrogen as a quasi-conserved tracer of vertical mixing.

5.Investigate the depth of the zonal wind field and the coupling of the jet stream pattern with convection within the deep interior.

a.Dayside imaging with ~15 km/pixel resolution.  Multi-spectral imaging in the visible and 4-5 micron range to determine shears on the zonal wind fields and the vertical structure of vortices and plumes between 2-3 bar and the 0.5-1.0 bar levels.  [EJSM]

b.Global nadir thermal mapping in the 7-250 micron spectral range to obtain 80-700 mbar (troposphere).  Require spatial resolutions of 300-600 km to permit potential vorticity derivations along with the wind-field, particularly in association with discrete atmospheric features and the belt/zone structure.

c.Determine the spatial distribution of lightning activity with visible imaging of lightning flashes on the nightside of Jupiter, combined with imaging of discrete thunderstorms on the dayside.

d.UHF radio occultations for sensing the deep troposphere to 50-100 bar.

e.Microwave remote sensing to detect compositional contrasts within the deep troposphere (100 bar), for relation to the zonal wind field. [Juno]

f.Doppler tracking of multiple entry probes penetrating below the 20 bar level of the Galileo probe to determine the deep wind field in multiple locations. [Probes]

g.Study perturbations to the gravitational field moments for evidence of deep zonal winds.

6.Study the high-latitude zonal organisation all the way to the poles to test similarities with Saturn’s hot polar vortices

a.Visible, near-IR and thermal-IR mapping of polar regions (partially accomplished by Juno) under various emission angle and lighting conditions. [Juno, EJSM]

b.Compositional studies of  polar vortex (haze material, hydrocarbons, exotic chemistry related to aurorae). [Juno]

c.Numerical modeling to study zonal flow at high latitudes and implications for deep atmospheric motion.

B.Tropospheric Chemistry and Composition

Scientific Aim

Determine the spatial distribution of volatiles (NH3, H2S, H2O) in the troposphere and the relation to atmospheric circulation and cloud condensation; and determine the distribution of disequilibrium species in the upper troposphere (PH3, AsH3, GeH4, CO and para-H2) and their redistribution by atmospheric flow.  The distribution of water vapour humidity will be used to determine the importance of moist convection in shaping the tropospheric structure. Each of these species will be used (a) as quasi-conservative tracers of the atmospheric motion (vertical and horizontal); and (b) to study the thermochemistry and photochemistry of the troposphere and stratosphere.

Investigations

1.Measure the global distribution of water vapour humidity in the 2-8 bar region, at a spatial resolution of 100 km, to determine the importance of moist convection and resolve differences in belt/zone meteorology.  

a.Imaging spectroscopy in the near-IR (4.8-5.2 microns) with a spectral resolution R>400.

b.In situ sampling by multiple entry probes.

2.Measure the global distribution of gaseous ammonia throughout the troposphere to study the effects of cloud formation and tropospheric photochemistry at 100 – 200 km spatial resolution.

a.Near-IR studies (1.0-5.2 microns) with 100 km spatial resolution below the cloud tops (2-6 bar). 

b.Thermal spectroscopy in the 8-12 micron region to determine the 100-400 mbar distribution with a 200 km spatial resolution. 

d.UV spectroscopy in the 160-230 nm region to determine the NH3 distribution in the photochemical depletion region (pressures less than 400 mbar).

e.In situ sampling by multiple entry probes.

3.Determine the vertical distribution of radio/microwave opacity sources (NH3, H2S and H2O) to depths of 1 to 100 bars.   [Juno]

a.Passive microwave radiometry at 1-5 cm wavelength to probe to the 100-bar level.  [Juno]

b.Radio science with modulated 3.6 cm (X-band) and 0.94 cm (Ka-band) source to probe to the 1-bar level (EJSM).

c.In situ sampling of the atmosphere below the cloud tops. [Probes]

4.Determine the spatial distribution and power of lightning in the troposphere.

a. Visible imaging of lightning flashes on the nightside of Jupiter, combined with imaging of discrete thunderstorms on the dayside.

5.Measure the 3D distribution of disequilibrium species in the upper troposphere, at 100-km spatial resolution, particularly in response to temporal evolution of discrete atmospheric features.

a.Near-IR imaging spectroscopy to measure PH3, CO, AsH3 and GeH4 in the 0.1-4.0 bar region (spectral resolutions R > 500 required to resolve lines of H2O, NH3 and PH3; R>1000 for AsH3, GeH4 and CO).  Both regional high-resolution hyperspectral maps, and lower resolution global contextual maps are required. 

b.Thermal spectroscopy at 200 km spatial resolution in the 8-12 micron range to determine the distribution of PH3 in the 0.1-0.8 bar region. 

c.UV spectroscopy in the 160-230 nm region to determine the PH3 distribution at altitudes higher than p<400 mbar. 

d.Far-IR spectroscopy/imaging (15-250 microns) to determine the ortho/para-H2 ratio (an important input for potential vorticity calculations).

e.In situ sampling at multiple locations to provide ground-truth for remote sensing.

C.Clouds, Aerosols and Hazes in the Troposphere and Stratosphere

Scientific Aim

Determine the cloud and haze inventory of Jupiter’s atmosphere, and the relation between cloud colours/opacity and the tropospheric circulation.  Investigate the production mechanisms for tropospheric and stratospheric hazes (including auroral-induced chemistry and photochemistry).  Determine the reason for the cloud colours, particularly in regards colour changes coincident with other thermophysical atmospheric changes.

Investigations

1.Determine the global properties of Jupiter’s clouds, hazes and aerosols (composition, single scattering albedoes, column abundances, topography of upper cloud layers, particles size distributions, IR opacities).   

a.Global mapping from the far-UV to the thermal-IR using a variety of emission angles and phase angles (at 100-km resolution), including high resolution (15-km) feature tracks and latitudinal (center to limb) scans.

b.VIS-NIR mapping at 100 km resolution of the clouds composition and particle size distribution, both globally and regionally on the dayside and nightside.   Multiple phase angle coverage to constrain scattering properties.

c.Multi-spectral imaging at visible/near-IR wavelengths using strong and weak CH4 absorptions to investigate the vertical cloud structure to a spatial resolution of 30 km/pixel. 

c.Thermal spectroscopy/imaging in the troposphere to study the physiochemical environment in which clouds and aerosols form, 200-km spatial resolution.

d.UV imaging to study the distribution and densities of high altitude UV-absorbent hazes.

e.In situ sampling of aerosols above and below the cloud-tops.

2.Monitor changes to cloud properties related to variations to the atmospheric state (temperature, composition) and relate this the convective motion below the cloud-layers, both during discrete events, such as cloud upheavals, and during normal activity (e.g., photochemical reddening). 

a.Quasi-regular observations of discrete clouds features (localized storms, polar vortices, giant anticyclones) with visible imaging and spectral coverage.

b.Near—IR observations (1.0-5.2 microns) at a range of phase angles to determine changes to scattering properties.

c.Continuous monitoring from dedicated facilities (ground-based or space-based).

3.Determine the chemical pathways responsible for the creation of stratospheric hazes, particularly at high latitudes. 

a.UVIS studies of the absorbing/scattering properties of high altitude hazes. 

b.Near-IR occultation observations (limb viewing) to search for trace species that may be contributing to the hazes. 

c.Thermal-IR spectroscopy of hydrocarbons at high spectral resolutions to determine vertical distribution. 

d.In situ sampling of stratospheric aerosols by multiple entry probes.

D.Wave Motion, Eddies and Vertical Coupling

Scientific Aim

Investigate the nature of wave propagation (horizontal and vertical) in the neutral and charged atmosphere as a fundamental constraint on geophysical fluid dynamics.  Determine the extent of energy, momentum and material transport by wave motion (small-scale gravity waves, larger-scale Rossby waves, QQO), and the coupling between different vertical regions of the atmosphere.

Investigations

1.Study coupling between the troposphere and the middle-atmosphere (stratosphere and mesosphere) by vertical wave propagation and eddies, and the temporal evolution of such wave phenomena. 

a.Repeated radio occultations closely spaced in space and time (e.g,. at the same latitude +/-10 degrees, once every 2 weeks) to determine pressure, density and temperature profiles perturbed by the waves (particularly the spatial distribution of molecules due to the QQO).   [EJSM]

b.High resolution determinations of the vertical temperature structure between 1 microbar and 400 mbars from sub-mm sounding of molecular lineshapes.  Limb observations in the thermal-IR to determine stratospheric temperature oscillations (20 km resolution). 

c.Near-IR stellar and solar occultations to obtain high resolution stratospheric temperatures. 

d.Three-dimensional distribution of stratospheric constituents (hydrocarbons, hazes) from spectroscopic observations (UV, near-IR, thermal-IR). 

e.Regular thermal-IR observations (yearly) of the tropospheric and stratospheric temperature fields to study the quasi-quadrennial oscillation (QQO)

2.Measure the horizontal distribution of zonal wave activity in the troposphere and stratosphere, and the relation to deep internal convection.  

a.Visible dayside imaging of wave activity in the cloud tops at spatial resolutions greater than 30 km/pixel.  Multiple high-resolution snapshots of cloud features, images of cloud structure on a timescale of hours, days months, and years. [EJSM, ground-based]

b.Regular monitoring of atmospheric dynamics from a dedicated platform (ground-based or space-based).

c.Thermal-IR imaging (15-250 microns)  of upper tropospheric temperatures at regular (2 week) intervals to study propagation of slowly moving thermal waves.  7-14 micron imaging to study variability of stratospheric emission and relation to thermal wave activity. 

c.Near-IR imaging of multiple altitude levels to determine vertical structure of horizontally propagating waves.  Observations of dayside (0.4-5.2 micron range) or nightside (2.5-5.2 micron range), including coverage of equatorial regions and polar vortices.

3.Determine the relationship between vertically propagating waves and heating mechanisms (the “energy crisis”) for the ionophere and thermosphere. 

a.Repeated radio occultations closely spaced in latitude and time (e.g,. at the same latitude +/-10 degrees, once every 2 weeks) to determine pressure, density and temperature profiles in the upper atmosphere and search for wave perturbations.

4.Detect and characterize the internal modes/waves of Jupiter. 

a.Doppler-spectro-imaging of Jupiter to determine oscillation modes of the planet.  [EJSM]

E.Stratospheric Composition and Photochemistry

Scientific Aim

Study the unique chemistry (hydrocarbon pathways, haze production mechanisms) in the stratosphere, and the contribution of exogenic materials from infalling exogenic material (asteroidal/cometary impacts; micrometeorites, connection to the interplanetary environment).

Investigations

1.Determine the three dimensional structure, temperature and circulation of the stratosphere. 

a.Multiple radio science occultations for vertical temperature, pressure and neutral density profiles.

b.Sub-mm spectroscopic measurements of temperatures (from HCN, H2O and CH4) and Doppler winds (zonal wind fields in the stratosphere),

c.Near-IR stellar and solar occultations for high vertical resolution temperature sounding over a wide range of latitudes in the upper stratospher.

d.Thermal mapping using stratospheric emission features at regularly spaced intervals (every 1-2 weeks) to study the temporal evolution of zonal waves and vertical wave structures.

e.Visible/UV/near-IR observations of particulates/hazes in the stratosphere to determine meridional advection of material. 

f.Global mapping of hydrocarbons (UV, near-IR and thermal spectroscopy) to determine stratospheric circulation.

2.Measure the 3D distribution of stratospheric hydrocarbons at 100 km resolution and their relation to stratospheric circulation and photochemistry. 

a.UVS FUV spectroscopy in the 70-200 nm range to study the 1-1000 microbar distributions of methane, acetylene and ethane. 

b.UV occultation studies to detect minor stratospheric hydrocarbons in absorption.

c.Near-IR retrievals of stratospheric composition.

d.Thermal spectroscopy in the 7-14 micron region samples 1 mbar methane, ethane and acetylene distributions (R>2000).  Higher spectral resolutions would permit searches for previously unidentified higher-order hydrocarbons, important constrains on photochemical models.

3.Measure the distribution of stratospheric water and other minor species of exogenic origin.

a.High spectral resolution sub-mm sounding of H2O lines in the 100-3000 GHz range.  

b.Sub-mm measurements of stratospheric CO2, CO, HCN, CS left over from asteroidal/cometary impacts and/or micrometeorite bombardment.  [EJSM]

c.Far-IR spectroscopy (spectral resolutions in excess of R>400) in the 30-80 micron range for stratospheric emission lines or water.  Simultaneous derivations of atmospheric temperature given measurements of the line width. 

d.High spectral resolution (R>2000) thermal spectroscopy for HCN in 13-14 micron region.

4.Assess the seasonal insolation response in the stratosphere over decadal timescales.

a.Thermal mapping of the stratospheric emission over monthly timescales.

b.Sub-mm sounding of the same latitudes under similar observing conditions but separated by 6-12 months. [EJSM]

c.Radio occultation studies of the same latitudes 6-12 months apart to study long term evolution of the stratospheric temperature structure in response to seasonal variations.

F.Circulation and Composition of the Upper Atmosphere/Aurora

Scientific Aim

Determine the three-dimensional structure of the Jovian aurora and their variability with time, and the extent of coupling between the neutral atmosphere and the charged particle environment of the magnetodisc.  Comparisons with magnetosphere/plasma studies could reveal relationships between ionospheric structure and source regions within the magnetosphere. 

Investigations

1.Three-dimensional morphology and mechanisms for energy transport within the Jovian aurora.

a.Near-IR imaging of H3+ emission in the 2-5 micron range at regular intervals to determine the changes of shape of the auroral oval in response to solar wind variability.  High resolution scans of polar latitudes (70-90 degrees in both hemispheres). [Juno, EJSM]

b.UV spectro-imaging studies of the polar H2 glow, morphology and the composition of the polar vortices (aerosols, exotic chemicals) in the 70-200 nm range to determine the relation between the polar vortices and auroral energy deposition. UV spectra to assess the latitudinal morphology of H2 emissions (from nadir viewing) to derive information on neutral wind.

c.UV occultation studies for hydrocarbons seen in absorption over the poles at micro-bar altitudes.  Derive neutral density altitude profiles from solar and stellar occultations.

d.High resolution limb studies to determine the vertical distribution of the Jovian aurora, and the nature of energy deposition processes.

f.Detection of molecular species at high altitudes: (H2O18, CH3OH, H2CO, HC3N, ….) up to the 1 µbar level.

2.Temporal Variability of Ionospheric total electron densities and Ionization processes.

a.Determine the variability of the distribution of ionic species, total electron density vertical profiles, lateral electron density content in the charged upper atmosphere via radio occultations (multiple frequencies) at multiple latitudes, regularly spaced in time to obtain an adequate sampling.  .

b.UV imaging of the H2 glow to study the H2 bulge.

c.Measure electron distribution from energy as low as possible to identify primary and secondary ionospheric photoelectrons.

3.Determine the atmospheric circulation of the ionosphere and thermosphere. 

a.Measure the thermospheric winds, both zonally and meridionally, and determine the importance of wave acceleration and ion drag at these altitudes. 

b.Measure the spatial distribution of ionic species and other tracers of the general circulation of the thermosphere using H3+ emission in the near-IR.

c.UV spectral-spatial images to assess the latitudinal morphology of H2 emissions (from nadir viewing) to derive information on neutral wind.

d.Radio occultation studies to determine the importance of vertically-propagating waves for thermospheric heating and the electron density of the ionosphere.

e.Sub-mm measurements of molecular lines to determine atmospheric temperatures, neutral density profiles and 3D distribition of atmospheric species between 1 microbar and 400 mbars.

4.Search for evidence of non-thermal loss mechanisms for atmospheric species at high altitudes. 

5.Auroral footprints from satelliltes, structure inside aurora.

G.Internal Structure of Jupiter

Scientific Aim

Determine the internal structure of Jupiter, the nature of hydrogen and helium under extreme conditions in the interior, and the size and mass of Jupiter’s core.

Investigations

1.  Determine oscillation modes of Jupiter to study wave propagation within the bulk of the atmosphere.

a.Doppler spectro-imager to measure of frequencies of the global acoustic modes of the planet in the range 0.3 to 3 mHz. Radial velocity maps of the whole surface of Jupiter monitored continuously for months (1 frame/mn).

2.  Study phase transitions of molecular and metallic hydrogen within the deep interior.

a.Far-IR spectroscopy to determine the abundance of tropospheric He

3.  Constrain the size, mass and composition of Jupiter’s core and degree of homogenization with the extended atmosphere

a.Close in mapping of higher order gravitational moments and magnetic field moments. [Juno]

b.Determine oscillation modes of Jupiter.

c.Measure bulk composition of Jupiter (see below).

4.  Determine the depth of the magnetic field generation.

5.  Determine the sources of energy contributing to the self-luminosity of Jupiter and the cooling history of the planet

a.Compute energy balance by considering absorbed and emitted power over the 1-10000 cm-1 spectral range, requires thermal and near-IR spectroscopic mapping of the entire globe.

b.Study of the nature of hydrogen and helium under extreme conditions of high pressures and temperatures, and model the gravitational separation of the two.

H.Bulk Composition of Jupiter and Formation Mechanisms

Scientific Aim

Characterise the abundance of heavy elements in the Jupiter atmosphere (particularly nitrogen and oxygen) to understand the evolution of the gas giant and the extensive satellite system (including Ganymede and Europa).

Investigations

1.Determination of the elemental enrichments in He, C, N, O, S, P, As and Ge.

a.Near-IR high spectral resolution observations (R>1000) to determine bulk abundances of NH3, CH4, H2O, PH3, AsH3, GeH4 in the upper troposphere (1-6 bar). [EJSM, Juno]

b.Mid-IR and far-IR spectroscopy (7-1000 microns) to determine distributions of PH3, CH4, NH3 in the upper troposphere (0.1-0.8 bar).  Use the collision-induced continuum, in tandem with radio science occultations of the same latitudes, to confirm the abundance of helium in Jupiter. [EJSM]

c.Microwave remote sensing for O, N, S [Juno]

d.In situ sampling via multiple entry probes.

2.Determine isotopic ratios.

a.CH3D/CH4 measurements from near-IR spectroscopy in the 4-5 um region with spectral resolutions exceeding 1000.

b.Thermal-IR spectroscopy between 7-9 microns to study the D/H ratio in the stratosphere (1 mbar).

c.Determine 18O/16O ratio using high resolution spectroscopy or in situ sampling.

e.High spectral resolution 10 micron spectroscopy to determine the 15N/14N ratio in the upper troposphere, 7-8 micron spectroscopy to determine 13C/12C ratio.

3.  Determine the abundances of the Noble gases below the cloud-tops.

a.  In situ sampling with multiple entry probes.

4.  Determine the frequency of asteroidal/cometary impacts with Jupiter, and the long-term consequences of the chemistry associated with these collisions

a.Track the redistribution of material from collisions with UV, visible and infrared imaging.

b. High-resolution spectroscopy to identify exotic molecules within the impact debris introduced by the collisions.

5.Study enrichment of the atmosphere from exogenic sources.

a.Sub-mm investigations of HCN, CS, CO, CO2 in the stratosphere (see above.

b.Far-IR spectroscopy between 30-80 microns to determine the abundance and spatial distribution of stratospheric water.