Monday, 27 February 2012

Long Distance Storm Chasing - A Plea for Help!

Last spring, Saturn’s gigantic springtime disturbance was characterised for the first time in the infrared, allowing us to measure the vertical temperature structure of a Saturnian storm system.  Our paper (Fletcher et al., 2011, Thermal Structure and Dynamics of Saturn’s Northern Springtime Disturbance, Science, 332, 1413--1417, http://dx.doi.org/10.1126/science.1204774), showed that the thermal infrared imaging yielded some surprises - not least was the dramatic effect that this churning, tropospheric storm system had on the usually calm and quiescent stratosphere (see Saturn image on the far right).  It spawned two warm airmasses, which we termed ‘beacons’ because of their impressive emission at infrared wavelengths.  These heated airmasses were tracked throughout 2011 by Cassini, the Very Large Telescope in Chile, and the Infrared Telescope Facility in Hawai’i.

Today (February 2012), a single large hot airmass remains in Saturn’s stratosphere, but there’s a big question remaining - does this have any impact on the visible cloud tops?  Indeed, one of the big challenges for giant planet science is relating visible changes in albedo and cloud colouration to environmental changes (e.g., changes in temperature, cloud formation or chemistry).  So far, our comparisons with visible light observations have suggested that the effects of the hot stratospheric beacon are completely invisible.  The chart above shows the expected longitude (System III West) of the beacon, and an Excel spreadsheet listing the longitude on each date through the rest of 2012 can be found here:
http://www.atm.ox.ac.uk/user/fletcher/io/saturn/beacon_location_27feb2012.xls  

As Saturn reaches opposition on April 16th 2012, the next few months provides an excellent opportunity to search for any unusual goings-on beneath the hot beacon.  To find the System III Longitude visible from Earth at any time, use the JPL Horizons Ephemeris Generator (with option 14 for the table settings).

Wishing you clear skies and happy storm chasing!

Cheers,
Leigh

Tuesday, 21 February 2012

Becoming a Planetary Scientist

In 2012, I was asked a series of questions about how I became a planetary scientist, and what advice I’d give to school students wanting to get involved in this exciting field.  I’ve reproduced my answers here, just in case it serves to help any visitors to this site!

Job Title: Planetary Scientist

What do you actually do? 
I’m a planetary weather man, studying the physics and chemistry of all the atmospheres in our solar system to better understand the worlds around us.

What did you choose to do once you could leave school, ie at age 16?
Stay on at sixth form college to study A Levels – Maths, Further Maths, Physics, Chemistry, Biology and General Studies

What did you choose to do next?
Went to University:  Emmanuel College Cambridge to study for a BA and MSci in Natural Science, specialising in Physics.

How did you get to where you are now?  
When I left University, I really wanted to study a topic that I felt was close to home, that some day we could reach out and touch with our own hands, see with our own eyes.   Despite an interest in astronomy, I decided against studying the far reaches of our universe and chose instead to explore the planets of our own solar system.  In 2004, the Cassini-Huygens spacecraft was about to arrive at Saturn, and Oxford were looking for research students to help analyse the first data from the ringed world.  I spent my PhD characterising Saturn’s dynamic atmosphere, which then set me on a course to study all of the giant planets in our solar system in a series of short fellowships at NASA’s Jet Propulsion Laboratory and Oxford’s Planetary Physics department.  Today I use a variety of interplanetary spacecraft, orbital telescopes and giant ground-based observatories to learn more about the planets.

Were there other routes you could have taken to get this job?
Planetary science requires you to be a jack of all trades:  being a planetary scientist requires an excellent knowledge of physics, computing, maths and chemistry, so each of these topics would have allowed me to work in this exciting field, provided they’d been studied to degree level.

What do you like best about your job?  
Things can change quickly, and we have to be responsive to that.  If an asteroid strikes Jupiter, or a storm explodes in the atmosphere of Saturn, we have to bring all our experience to try to understand what’s happening.   So the days are never dull, and you rarely do the same thing from one day to the next!  I get to work as part of an international team of scientists, which means I get to travel far and wide to communicate my research and forge new collaborations.  Finally, we find ourselves in a revolution in this subject, with more missions and telescopes in flight than at any point in humankinds history – that means that the potential for new discoveries is enormous, and you never know when you might be the first human to observe a new phenomenon in our solar system.  The old adage is true – when you love what you do, you never work a day in your life!

What would your top tips be to a 16-year old considering working in this field?  
For any scientific subject, it’s essential to get a good grounding in maths and computing, as these topics go hand in hand.  So much of what we do requires the ability to write computer code and solve mathematical problems, that you really can’t escape it!  Without a doubt, you should forge ahead with A-levels, but never forget the bigger picture – there’s so much exciting science happening out there; if you read widely you might just stumble across a topic that really excites you.  That’s what happened to me with planetary exploration.

What would your top tips be to an 18 year old considering working in this field?
Think carefully about where you’d like to go for your degree, and make sure that the institution provides a good balance between science, maths and computing.  All three are needed to be a successful atmospheric scientist or meteorologist.  It’s all about building up a toolkit of experience, which you can then apply to new problems as they’re presented to you.  So be curious, don’t be satisfied with explanations that are unclear, and experiment for yourself.  Curiosity and the ability to solve problems are the traits that are essential in any independent research scientist, and will be vital as you head to university.

Tell us something about yourself.  
In the summer of 2009, I was having a barbeque on a sunny California day with my wife.  My boss called to say that an Australian amateur astronomer had spotted something rather odd near Jupiter’s south pole.  I raced to the office, where we could remotely use the telescopes in Hawaii to figure out what was going on, and we were in for a massive surprise.  A huge, super-heated plume of aerosols and debris had been lofted into Jupiter’s atmosphere by an asteroidal collision.  Without the data we took that Californian evening, we might never have been able to unravel the mystery of what had happened up there on Jupiter.  It was the chance of a lifetime, a stroke of luck, and provided us with fascinating scientific results for years to come.  It shows just how exciting this field is, and that there are so many surprises and marvels out there for us to explore.

Wednesday, 15 February 2012

Planetary Science Decadal Requirements

1.Maintain capabilities for high spatial-resolution imaging of bright, extended sources within our own solar system (UV, visible, IR) in the post-Hubble era.
a.Jupiter and Saturn will be too bright to image with many JWST filters.  Saturn could be imaged by JWST/NIRCAM at the very longest wavelengths, but imaging of Jupiter would require a highly specialised mode. Jupiter and Saturn can be imaged using JWST/MIRI neutral density filter, provided specific calibration procedures are adopted.  Uranus and Neptune can be observed in both imaging and spectroscopic mode.
b.Provisions should be made in the JWST designs to ensure that outer planets can be observed in both imaging and spectroscopic modes

2.Establish a space-borne telescopic facility for the semi-continuous monitoring of atmospheric dynamics and compositional changes, across a wide range of temporal scales (hours, to weeks, to seasonal variability).
a.Enable a fast response to rapidly evolving phenomena on the gas giants (e.g. asteroidal/cometary impacts, global disturbances).
b.Contextual support for orbiting spacecraft and in situ probes.
c.Imaging and spectroscopic modes across a broad range of frequencies (UV to far-IR) to capture regions of the spectrum inaccessible from the ground.

3.Update ground-based observatories for discovery-class science and support of planned spacecraft missions.
a.Larger primary mirrors (in the 8-10 m range) for IR diffraction-limited resolutions.
b.Investment in new adaptive optics technologies and outfitting existing observatories.
c.Investment in upgraded instrumentation covering mid-IR wavelengths to replace existing technologies, extend wavelength range, improve spatial/spectral resolution.

4.Ongoing support for laboratory studies pertinent to interpretation of outer planet atmospheric measurements.
a.Spectroscopic measurements for species at relevant temperatures and pressures (e.g. high pressures and temperatures for NH3, H2S, H2O for interpretation of Juno microwave spectra).
b.Numerical simulations for general circulation models, radiative models, thermochemical and photochemical models, etc.
c.Geophysical fluid dynamics experiments for simulations of outer planet flow.
d.High-pressure equation of state experiments in the lab for extreme conditions in the centres of the outer planets.
e.Low temperature measurements for the IR opacity of H2-He mixtures pertinent to the ice giants (i.e. below 60 K at pressures around 1 bar).

5.Investment in new technologies for mitigation of extreme environments for visiting spacecraft:
a.High-radiation environment for Jupiter missions (e.g. EJSM, Juno).
b.Extremes of temperature and pressure for entry probe missions, and ablative materials for heat shield manufacture.
c.Efficient solar-panel technologies for the low-light conditions of the outer solar system.
d.Mini-probes to trace the atmospheric circulation and measure composition at multiple locations.
e.Development of new power sources for outer planet missions to mitigate the depleted stockpiles of Plutonium-238 for RTGs.
f.Development of fast IR detectors with increased sensitivity for detection of low fluxes, prevent image smearing and enable rapid mapping.
g.Low-power instrumentation, particularly for ice giant missions.

6.Inclusion of Outer Planet Atmospheric science as a major component in any satellite-focused mission (flybys or orbiters):
a.Jupiter atmospheric science should be made a major consideration for EJSM, with modifications to satellite-focused instruments (particularly in the visible, near-IR and thermal-IR) to produce high-quality atmospheric science.
b.Provision in designs for Titan/Enceladus missions to study Saturn’s atmosphere.
c.Ensuring Uranus and Neptune missions feature the ice giant atmospheres as a primary mission driver.

7.Ensure mission support structures are maintained and improved for future missions:
a.Upgrades to the Deep Space Network so that data is no longer lost on a regular basis. 
b.Increased support for early-career scientists to provide exposure to mission operations and planning during an active mission (e.g. Cassini).

Neptune Atmospheric Science Goals

A.  Formation, Evolution and Internal Structure of Neptune

1.Determine the elemental enrichment of Neptune to constrain formation theories.
a.In situ sampling of Neptune to at least the 10 bar level to determine vertical profiles of CH4, NH3 and H2S clouds in the upper troposphere, etc.  Well-mixed regions of NH3 and H2O are expected to exist at pressures of several hundred kbars, inaccessible with present probe technology and microwave radiometry.
b.In situ sampling to 40 bars to determine the chemistry of NH3, H2S and NH4SH below the condensation cloud levels.
c.In situ sampling or microwave radiometry to 100 bars to investigate the aqueous chemistry in the H2O cloud.
d.In situ determination of isotopic ratios (12C/13C, D/H, 14N/15N, 18O/16O)
e.In situ measurement of Noble gases (He, Ne, Ar, Kr, Xe, etc.)
f.Detection and upper limits on disequilibrium species (PH3, AsH3, GeH4) to constrain enrichment from in situ sampling or high-sensitivity spectroscopy in the 4-5 micron region.
g.Radio wavelengths (1-100 cm) to probe the composition beneath 100 bars.

2.Measure the internal structure and mass distribution profile of Neptune
a.Measurement of high-order gravitational and magnetic field moments to understand the vertical distribution of rock, ice and gas from the core of the planet through to its outer layers.  Repeat for a range of latitudes and longitudes.  Requires an orbiter at close proximity.
b.Laboratory simulations of ices representative of the interior structure of Neptune.

3.Precise determination of Neptune’ self-luminosity and internal energy.
a.Spectroscopic measurements of the emission of thermal energy across the electromagnetic spectrum to determine the energy balance, and search for variability since Voyager 2.
b.Global mapping of thermal emission to determine the locations of maximal radiative cooling (e.g. the importance of high latitude polar emission).

4.Determine the nature and location of the magnetic field generation region
a.Measure high-order moments of the planetary magnetic field at a wide range of latitudes and longitudes to determine the location of the dynamo (potentially at 70% of the planetary radius).
b.UV and IR imaging of auroral regions to map the spatial variability of energy deposition, modulated by the magnetic field.

B.  Circulation and Dynamics of the Troposphere and Stratosphere

1.Determine the spatial distribution of tracers for atmospheric motion
a.High spectral resolution microwave and IR studies of CO, CH4, NH3, H2S, and H2O distributions to constrain planet-wide circulation systems.
b.Far-IR spectroscopy to map the spatial distribution of the ortho/para-H2 ratio as a tracer for vertical mixing in the troposphere and stratosphere.  Regular monitoring of this ratio to determine how vertical mixing rates vary with time.
c.Near-IR and visible measurements of cloud opacity and structures, used to trace strong convective updrafts and redistribution of material.

2.Investigate the implications of seasonal forcings experienced by Neptune (165 year orbital period) for comparison with Saturn
a.Study asymmetries in cloud and aerosol properties as tracers of vertical mixing and convective instabilities using near-IR and UV spatio-spectral imaging.  Repeat observations on 2-5 year timescales to search for seasonal changes.
b.Global thermal mapping in the mid and far-IR to determine the response of the temperature field to the seasonal forcings, and establish radiative time constants for the atmosphere.
c.Radio occultations and solar/stellar occultations for high vertical-resolution studies of the temperature field. Repeat at multiple latitudes to determine asymmetries in vertically-propagating wave activity and implications for atmospheric stability.
d.High latitude observations in UV, visible, near-IR and thermal to study polar vortices and zonal organisation.  Temporal monitoring of Neptune’s south polar hotspot as the degree of insolation varies over time.

3.Determine the zonal and meridional circulation of Neptune, and the depth of the belt/zone structures and jet streams, and the reason for Neptune having the fastest equatorial winds in the solar system:
a.Track visible cloud features on timescales of hours to measure zonal wind speeds at the cloud tops, dayside imaging at 200 km spatial resolution.
b.Monitor discrete cloud features over daily-weekly timescales to study meridional motions.
c.Search near-IR wavelengths to find contrasts for cloud tracking at multiple atmospheric levels (e.g. will 5 um studies reveal contrasts at depth as they have for Jupiter and Saturn?)
d.Determine the zonal organisation of Neptune near the poles to understand whether polar vortex phenomena are common to all of the outer planets (i.e. does Neptune exhibit polar vortices?)
e.Thermal measurements of the vertical temperature structure to determine the vertical windshear, and hence extrapolate cloud-tracked winds to lower pressures in the stratosphere.
f.Meridional variability in the temperature field to look for spatial variations in the emission of internal energy left over from formation.
g.Search for perturbations to magnetic and gravity field measurements to identify temperature and density contrasts in the deep interior, to study the depth of the zonal wind field and the relation to interior convection.

4.Measure the albedo of Neptune to constrain energy budget calculations
a.Visible and near-IR measurements of the planet’s albedo with a wide range of solar phase angles and incidence angles.

5.Observe the frequency, morphology and stability of discrete convective events (storms, plumes, turbulence) to understand the nature of small-scale convection
a.Determine the three-dimensional structure of discrete cloud-features (which are known to be ephemeral in nature) using multi-wavelength imaging from the UV to the IR.
b.Compare the optical properties of the bright, reflective material seen in the near-IR with the surrounding atmosphere to constrain  the composition and the mechanisms generating the cloud features.
c.Determine the stability of the cloud features, and the processes maintaining/dissipating the discrete activity.

6.Determine the spatial distribution of discrete cloud activity to study the underlying mechanisms and their seasonal variability
a.Long term multi-wavelength imaging of the regions of discrete cloud activity to study changes in cloud and aerosol altitudes, atmospheric temperature and composition.
b.Numerical simulations to reproduce the seasonal variations in the brightness of these features in response to the changing stability of the atmosphere.
c.Continuum radio imaging to determine the NH3, H2S, and H2O distributions at depth, for use as a proxy for cloud locations.
d.In situ sampling of regions of discrete cloud activity, versus regions of more sluggish motion, to study the thermophysical differences in atmospheric properties between the different regions.
e.In situ sampling to 40 bars to determine the chemistry of NH3, H2S and NH4SH below the condensation cloud levels.
f.In situ sampling or microwave radiometry to 100 bars to investigate the aqueous chemistry in the H2O cloud.


C.  Composition of the Troposphere and Stratosphere

1.Determine the spatial distribution of volatiles in the upper troposphere
a.Far-IR and mid-IR spectroscopy to determine the vertical distribution of NH3.
b.Microwave radiometry and radio occultation studies for the vertical NH3 and H2S profiles, but this will not probe the well-mixed region for bulk N/H and S/H content.
c.Place constraints on the spatial distribution of H2S, NH3, and H2O from radio, microwave and sub-mm observations.
d.In situ sampling of Neptune to at least the 10 bar level to determine vertical profiles of CH4, NH3 and H2S clouds in the upper troposphere;  to 40 bars to determine the chemistry of NH3, H2S and NH4SH below the condensation cloud levels; and radiometry to 100 bars to investigate the aqueous chemistry in the H2O cloud.

2.Study the inventory and optical properties of cloud and hazes
a.In situ sampling of aerosol and haze layers to determine optical properties, vertical distribution, size, shape, number density and optical depth. 
b.Pressures approaching 40 bars are needed for NH3, H2S and NH4SH cloud chemistry.
c.Pressures approaching 100 bars are required to constrain H2O clouds and aqueous chemistry in the liquid-water cloud.
d.Reflection spectroscopy of the clouds and hazes at multiple phase angles and solar incidence angles to determine optical properties (size, scattering properties, composition) of the aerosols.

3.Measure the spatial distribution of stratospheric hydrocarbons and hazes to constrain photochemical models for Neptune
a.Mid-IR imaging and spectroscopy to search for meridional gradients (asymmetries) in the stratospheric composition.
b.Monitor the hydrocarbon distributions on yearly intervals to search for seasonal variability.
c.Determine the composition of Neptune hazes using solar/stellar occultations at UV and IR wavelengths, or in situ sampling.

4.Detect and map the distribution of trace species and disequilibrium species horizontally, vertically and with time
a.High sensitivity near and thermal-IR spectroscopy to place upper limits on the abundance of PH3, AsH3 and GeH4, which are disequilibrium species on Jupiter and Saturn.
b.Map the spatial distribution of CO using sub-mm spectroscopic maps of the troposphere.
c.High-resolution IR and submillimeter spectroscopy to search for previously undetected species in the troposphere and stratosphere.


D. Upper Atmosphere Circulation and Aurora

1.Confirm the presence and longevity of Neptune aurora
a.No direct detection of aurora from the ground, only detection from Voyager 2.  Require better observations of the morphology of the aurora, in the IR (from the ground, possibly using adaptive optics) and in the UV.

2.Monitor the morphology of Neptune aurora with time to constrain models of the ionosphere and magnetosphere of the planet
a.Acquire regular maps of the polar regions of Neptune, in both the UV and the near-IR (H3+ emission).
b.Compare aurora at north and south pole to understand seasonal differences and constrain the unique morphology of the magnetic field.

3.Determine the importance of vertically propagating waves on the heating of the mesosphere and thermosphere
a.Radio occultations, solar/stellar occultations and sub-mm sounding to determine the vertical temperature structure at multiple latitudes to search for evidence of wave activity.
b.Constrain the general circulation of the upper atmosphere and its latitudinal redistribution of energy and tracers.


Uranus 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.  Formation, Evolution and Internal Structure of Uranus

1.Determine the elemental enrichment of Uranus to constrain formation theories.
a.In situ sampling of Uranus to at least the 10 bar level to determine vertical profiles of CH4, NH3 and H2S clouds in the upper troposphere, etc.  Well-mixed regions of NH3 and H2O are expected to exist at pressures of several hundred kbars, inaccessible with present probe technology and microwave radiometry.
b.In situ sampling to 40 bars to determine the chemistry of NH3, H2S and NH4SH below the condensation cloud levels.
c.In situ sampling or microwave radiometry to 100 bars to investigate the aqueous chemistry in the H2O cloud.
d.In situ determination of isotopic ratios (12C/13C, D/H, 14N/15N, 18O/16O)
e.In situ measurement of Noble gases (He, Ne, Ar, Kr, Xe, etc.)
f.Detection and upper limits on disequilibrium species (PH3, AsH3, GeH4) to constrain enrichment from in situ sampling or high-sensitivity spectroscopy in the 4-5 micron region.

2.Measure the internal structure and mass distribution profile of Uranus
a.Measurement of high-order gravitational and magnetic field moments to understand the vertical distribution of rock, ice and gas from the core of the planet through to its outer layers.  Repeat for a range of latitudes and longitudes.  Requires an orbiter at close proximity.
b.Laboratory simulations of ices representative of the interior structure of Uranus.

3.Precise determination of Uranus’ self-luminosity and internal energy.
a.Spectroscopic measurements of the emission of thermal energy across the electromagnetic spectrum to determine whether the internal heat source is consistent with zero.
b.Global mapping of thermal emission to determine the locations of maximal radiative cooling.

4.Determine the nature and location of the magnetic field generation region
a.Measure high-order moments of the planetary magnetic field at a wide range of latitudes and longitudes to determine the location of the dynamo (potentially at 70% of the planetary radius).
b.UV and IR imaging of auroral regions to map the spatial variability of energy deposition, modulated by the magnetic field.

B.  Circulation and Dynamics of the Troposphere and Stratosphere

1.Determine the spatial distribution of tracers for atmospheric motion
a.High spectral resolution microwave and IR studies of CO, CH4, NH3, H2S, and H2O distributions to constrain planet-wide circulation systems.
b.Far-IR spectroscopy to map the spatial distribution of the ortho/para-H2 ratio as a tracer for vertical mixing in the troposphere and stratosphere.  Regular monitoring of this ratio to determine how vertical mixing rates vary with time.
c.Near-IR and visible measurements of cloud opacity and structures, used to trace strong convective updrafts and redistribution of material.

2.Investigate the implications for the extremes of seasonal forcings experienced by the Uranian atmosphere
a.Study asymmetries in cloud and aerosol properties as tracers of vertical mixing and convective instabilities using near-IR and UV spatio-spectral imaging.
b.Global thermal mapping in the mid and far-IR to determine the response of the temperature field to the seasonal forcings, and establish radiative time constants for the atmosphere.
c.Radio occultations and solar/stellar occultations for high vertical-resolution studies of the temperature field. Repeat at multiple latitudes to determine asymmetries in vertically-propagating wave activity and implications for atmospheric stability.

3.Determine the zonal and meridional circulation of Uranus, and the depth of the belt/zone structures and jet streams:
a.Track visible cloud features on timescales of hours to measure zonal wind speeds at the cloud tops, dayside imaging at 200 km spatial resolution.
b.Monitor discrete cloud features over daily-weekly timescales to study meridional motions.
c.Search near-IR wavelengths to find contrasts for cloud tracking at multiple atmospheric levels (e.g. will 5 um studies reveal contrasts at depth as they have for Jupiter and Saturn?)
d.Determine the zonal organisation of Uranus near the poles to understand whether polar vortex phenomena are common to all of the outer planets (i.e. does Uranus exhibit polar vortices?)
e.Thermal measurements of the vertical temperature structure to determine the vertical windshear, and hence extrapolate cloud-tracked winds to lower pressures in the stratosphere.
f.Meridional variability in the temperature field to look for spatial variations in the emission of internal energy left over from formation.
g.Search for perturbations to magnetic and gravity field measurements to identify temperature and density contrasts in the deep interior, to study the depth of the zonal wind field and the relation to interior convection.

4.Measure the albedo of Uranus to constrain energy budget calculations
a.Visible and near-IR measurements of the planet’s albedo with a wide range of solar phase angles and incidence angles.

5.Observe the frequency, morphology and stability of discrete convective events (storms, plumes, turbulence) to understand the nature of small-scale convection
a.Determine the three-dimensional structure of discrete cloud-features (which are known to be ephemeral in nature) using multi-wavelength imaging from the UV to the IR.
b.Compare the optical properties of the bright, reflective material seen in the near-IR with the surrounding atmosphere to constrain  the composition and the mechanisms generating the cloud features.
c.Determine the stability of the cloud features, and the processes maintaining/dissipating the discrete activity.

6.Determine the spatial distribution of discrete cloud activity to study the underlying mechanisms and their seasonal variability
a.Long term multi-wavelength imaging of the two bright collars on yearly-timescales to understand why discrete cloud activity seems largely confined to these two bands at 45N and 45S.
b.Numerical simulations to reproduce the seasonal variations in the brightness of these features in response to the changing stability of the atmosphere.
c.Continuum radio imaging to determine the NH3, H2S, and H2O distributions at depth, for use as a proxy for cloud locations.
d.In situ sampling of regions of discrete cloud activity, versus regions of more sluggish motion, to study the thermophysical differences in atmospheric properties between the different regions.
c.In situ sampling to 40 bars to determine the chemistry of NH3, H2S and NH4SH below the condensation cloud levels.
e.In situ sampling or microwave radiometry to 100 bars to investigate the aqueous chemistry in the H2O cloud.

7.Search for the origin of spatial variability in stratospheric emission, and relate this to the general circulation and wave activity in the stratosphere
a.Mid-IR spatially resolved mapping of stratospheric emission to search for discrete structures of thermal wave activity in the stratosphere.
b.Radio occultation profiles at multiple latitudes and longitudes to search for variations in the vertical temperature structure.


C.  Composition of the Troposphere and Stratosphere

1.Determine the spatial distribution of volatiles in the upper troposphere
a.Far-IR and mid-IR spectroscopy to determine the vertical distribution of NH3.
b.Microwave radiometry and radio occultation studies for the vertical NH3 and H2S profiles, but this will not probe the well-mixed region for bulk N/H and S/H content.
c.Place constraints on the spatial distribution of H2S, NH3, and H2O from radio, microwave and sub-mm observations.

2.Study the inventory and optical properties of cloud and hazes
a.In situ sampling of aerosol and haze layers to determine optical properties, vertical distribution, size, shape, number density and optical depth. 
b.Pressures approaching 40 bars are needed for NH3, H2S and NH4SH cloud chemistry.
c.Pressures approaching 100 bars are required to constrain H2O clouds and aqueous chemistry in the liquid-water cloud.
d.Reflection spectroscopy of the clouds and hazes at multiple phase angles and solar incidence angles to determine optical properties (size, scattering properties, composition) of the aerosols.

3.Measure the spatial distribution of stratospheric hydrocarbons and hazes to constrain photochemical models for Uranus
a.Mid-IR imaging and spectroscopy to search for meridional gradients (asymmetries) in the stratospheric composition.
b.Monitor the hydrocarbon distributions on yearly intervals to search for seasonal variability.
c.Determine the composition of Uranus hazes using solar/stellar occultations at UV and IR wavelengths, or in situ sampling.

4.Detect and map the distribution of trace species and disequilibrium species horizontally, vertically and with time
a.High sensitivity near and thermal-IR spectroscopy to place upper limits on the abundance of PH3, AsH3 and GeH4, which are disequilibrium species on Jupiter and Saturn.
b.Map the spatial distribution of CO using sub-mm spectroscopic maps of the troposphere.
c.High-resolution IR and submillimeter spectroscopy to search for previously undetected species in the troposphere and stratosphere.


D. Upper Atmosphere Circulation and Aurora

1.Confirm the presence and longevity of Uranus aurora
a.No direct detection of aurora from the ground, only detection from Voyager 2.  Require better observations of the morphology of the aurora, in the IR (from the ground, possibly using adaptive optics) and in the UV.

2.Monitor the morphology of Uranus aurora with time to constrain models of the ionosphere and magnetosphere of the planet
a.Acquire regular maps of the polar regions of Uranus, in both the UV and the near-IR (H3+ emission).
b.Compare aurora at north and south pole to understand seasonal differences and constrain the unique morphology of the magnetic field.

3.Determine the importance of vertically propagating waves on the heating of the mesosphere and thermosphere
a.Radio occultations, solar/stellar occultations and sub-mm sounding to determine the vertical temperature structure at multiple latitudes to search for evidence of wave activity.
b.Constrain the general circulation of the upper atmosphere and its latitudinal redistribution of energy and tracers.

Saturn 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

1.Continuous monitoring of wind patterns for studies over a variety of time scales (from hours to seasons)
a.Dayside visible and near-IR imaging with 30 km resolution to determine the 2D horizontal wind patterns (zonal and meridional) and their changes with time, particularly in response to thermophysical changes within discrete features (storms, etc.).
b.Thermal-IR mapping to measure temperatures and thermal windshear gradients.  Repeat on a weekly/monthly timescale to monitor how the thermal field changes in response to localised dynamics and seasonal changes.
c.Sub-mm sounding of molecular lineshapes to directly determine wind speeds in the mesosphere, stratosphere and upper troposphere.
d.Combine wind fields and thermal fields to measure potential vorticity globally and over a range of timescales to study the seasonal variability.

2.Determine the rotation rate of Saturn (the length of the day) to determine the stability of the zonal jet streams and the belt/zone structure
a.Long-term monitoring of the Saturn Kilometric radiation to establish the causes of variability.
b.Measurement of the shape of the gravitational field.
c.Numerical modelling to determine the rotation rates from stability arguments.

3.Determine the depth of the zonal wind patterns on Saturn
a.Microwave remote sensing and gravitational field mapping to search for evidence of deep zonal wind patterns below the cloud tops.
b.Multiple entry probes/mini probes to track the atmospheric motions to 20 bar or deeper.
c.5-micron imaging of discrete cloud features (cold spots) to measure the wind field at the 2-4 bar level.

4.Study the importance of moist convection of multiple condensibles in shaping the observed cloud-top meteorology
a.Determine the spatial distribution of H2O and NH3 below the cloud tops using entry probes, microwave remote sensing or radio occultation studies.
b.Measure the spatial distribution and power of lightning.

5.Monitor time-varying phenomena in Saturn’s troposphere over a range of timescales
a.Rapid responses required for emergent features such as large storms, equatorial outbreaks of cloud activity, or other rapidly evolving features.  Monitor on hourly timescales across a broad spectral range.
b.Long-term monitoring of the semi-annual oscillation of the temperature field and modulation of composition as a result of wave activity (monthly-yearly timescales).
c.Monitor the ephemeral nature of slowly moving thermal waves in thermal-IR mapping over weekly timescales.
d.Establish the stability of features such as the ribbon wave, string of pearls, north polar hexagon and polar cyclonic vortices via continual visible and IR monitoring as the seasons change.

6.Study the structure and composition of Saturn’s polar vortices
a.High inclination orbits to provide nadir-views for thermal mapping, near-IR mapping and visible imaging of the poles.
b.Track the expected disappearance of the southern hemisphere polar stratospheric warm hood (70-90S) and the emergence of a similar structure in the spring hemisphere.
c.Determine the factors responsible for the stability of the north polar hexagon, and the reason for absence/ephemeral nature of polygonal waves in the southern hemisphere.


B.  Tropospheric Composition and Chemistry

1.Identify seasonal variations in the upper tropospheric distribution of NH3 and disequilibrium species (PH3, AsH3, GeH4), and track these changes with time.
a.Mid-IR and far-IR mapping (100 km spatial resolution) of the global distribution of PH3 and NH3, with regular repeats (yearly) to track the evolution of asymmetries.  Tie asymmetries to aerosols to study photochemical shielding.
b.Near-IR high spectral resolution mapping (100 km resolution) of PH3, AsH3, GeH4 and NH3 (yearly repetition) to study asymmetries at deeper levels (1-3 bar), and relate these to photochemistry and vertical eddy mixing.
c.Far-IR mapping of ortho/para hydrogen fractions with yearly repetition to study the relation between para-H2 conversion and aerosols.

2.Search for and map previously unidentified species in the troposphere
a.High far-IR and sub-mm spectral resolution mapping of HCN, CS, etc.
b.Constrain isotopic ratios 12C/13C and 14N/15N (among others) within the troposphere.

3.Study the atmospheric composition below the cloud tops
a.Microwave remote sensing to constrain the abundances of NH3, H2S and H2O below the condensation levels.
b.Multiple entry probes for in situ measurement of the tropospheric composition.




C.  Clouds, Aerosols and Hazes on Saturn

1.Map the spatial distribution of clouds and hazes in the troposphere and stratosphere to monitor how this evolves seasonally
a.Near-IR mapping over monthly timescales on both the dayside (1-4 microns) and nightside (4-5 microns) to determine the aerosol properties (vertical structure, absorption, scattering properties, composition, optical depth) and their evolution with time.
b.Microwave remote sensing of the vertical cloud structure (NH3, H2S and H2O clouds) and how these evolve with time.
c.Visible, near-IR and UV mapping of high-latitude polar hazes and the relation to auroral activity.

2.Determine the vertical structure, shape and composition of the cloud and aerosol particles
a.Multiple entry probes to sample the clouds and hazes in situ, to determine their composition and the vertical density distribution.
b.The vertical altitudes of cloud tracers will be vital in determining the altitudes for the cloud-tracked zonal jet system.

3.Study the relation between cloud and haze distributions and discrete atmospheric phenomena
a.Track the changes in cloud properties in relation to thermophysical changes to the temperature and composition (e.g. the episodic emergence of cloud activity at the equator, or convective storms).
b.Correlate the spatial distribution of lightning with the emergence of convective cloud activity.


D.  Stratospheric Composition and Photochemistry

1.Map the seasonal variations in hydrocarbon distributions (and hence photochemical rates) throughout the stratosphere, and the impact of dynamical redistribution of this material.
a.Mid-IR high-resolution spectroscopic mapping of ethane, acetylene and higher order hydrocarbons.  Regular repeats (~yearly) of full maps to track seasonal evolution.
b.Near-IR observations of stratospheric hydrocarbons,
c.UV mapping of high-altitude hydrocarbons, yearly repetition to track evolution.
d.Couple photochemical models with dynamical models to understand the spatial distribution of these hydrocarbons.

2.Determine the spatial distribution of stratospheric material from exogenic sources (e.g. HCN, OCS, CO, H2O)
a.Study the influx rates of material both from the rings and the interplanetary environment, and the spatial modulation of this material by the magnetic field.

3.Study the possibility of stratospheric warmings at high latitudes and their associated phenomena.


E.  Upper Atmospheric Processes and Interaction with the External Environment

1.Determine the general circulation of the mesosphere and thermosphere and the existence of zonal jets at these high altitudes
a.Radio occultation and limb-sounding studies of high altitudes to determine the vertical temperature structure.  Use multiple latitudes and repeat with a sufficient spatial sampling to track changes to the circulation with time.
b.Sub-mm sounding of molecular lineshapes to determine windspeeds in the mesosphere.
c.Compositional measurements via solar/stellar occultations for high-altitude hydrocarbons, hazes, etc., for use as tracers of the circulation.  Map these distributions as they vary with time (monthly timescales).

2.Study the influence of vertically propagating waves on the heating mechanisms for the thermosphere and ionosphere
a.Vertical temperature profiles (radio occultations, stellar/solar occultations, sub-mm sounding) to detect and characterise vertically propagating waves.
b.Determine how auroral energy is redistributed with latitude throughout the ionosphere.

3.Study the three dimensional structure and morphology of the Saturnian aurora, and their influence on the upper neural atmosphere
a.Determine the chemical and haze composition of the polar atmosphere, and how this differs from mid-latitudes.
b.Map the temperature of the upper atmosphere to determine the influence of auroral energy deposition versus radiative heating.  Repeat periodically to search for evolution of the thermal field in response to e.g. solar wind activity.
c.Determine the altitude distribution of auroral energy deposition.
d.Map the H3+ emission and H2 glow in the near-IR and UV, respectively, and repeat over multiple timescales (days to years) to study the evolution of the aurora with season.

4.Determine the influence of the rings on atmospheric properties
a.Map the thermal structure of the troposphere and stratosphere over seasonal timescales to study the influence of ring shadowing on temperatures and radiative cooling.
b.Map clouds, aerosols and gaseous composition to determine the influence of ring shadowing on tropospheric chemistry and dynamics.
c.Map the presence of stratospheric oxygen species to understand the direct connection between ring material and the composition of the middle-atmosphere.


F.  Formation, Evolution and Internal Structure of Saturn

1.Determine the bulk composition of Saturn below the cloud-tops to place constraints on the mass of rocky/icy material accreted during formation:
a.In situ sampling at multiple locations to determine the relative enrichments in heavy elements (C, O, N, S, P, As, Ge, etc.) over the solar composition.
b.High spectral resolution near-IR observations to determine the tropospheric abundance of PH3, AsH3, GeH4, CH3D, 13CH4, 15NH3 etc.
c.In situ measurements of isotopic ratios (12C/13C, D/H, 14N/15N, 18O/16O)
d.In situ measurement of Noble gases (He, Ne, Ar, Kr, Xe, etc.)
e.Mid-IR determination of 12C/13C and 14N/15N ratios from 7-14 micron region with high spectral resolutions.
f.Microwave remote sensing of the 1-100 bar region of Saturn’s troposphere to determine the deep abundances of volatiles (NH3, H2S and H2O) below their condensation altitudes.
g.Radio occultation studies (possibly UHF) to probe the vertical distribtution of NH3, H2S and H2O in the upper troposphere.

2.Determine the basic shape of Saturn and the deep zonal jet profile.
a.Measure high order gravitational and magnetic field moments to determine the planet’s shape.
b.Use microwave remote sensing and gravitational field measurements to search for evidence of zonal winds at depth.

3.Investigate the rate of influx of material from exogenic sources, and the impacts of such influx on planetary accretion models.
a.Determine the rate at which Saturn suffers impacts from micrometeorites and asteroidal/cometary collisions.
b.Study the relation ship between the magnetic field and materials from Saturn’s rings, to determine how and where the rings can modify the atmospheric composition (e.g. stratospheric oxygen-bearing species).


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 ┬Ábar. [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 ┬Ábar 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.