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Current projects
Last update: October 2016

My core focus is on atmospheric gas and cloud composition, especially as tracers of atmospheric chemistry, climate, evolution, and origins.

I study planetary atmospheres using a wide range of techniques and facilities: remote sensing with ground-based and space telescopes like Keck and Hubble, the mass spectrometers on the Galileo Probe and Curiosity Mars Rover, and sensors on spacecraft missions like Cassini.

An older page lists projects and science themes from back in 2014.


G550, G485, G320, G470

Juno has begun its scientific measurements of Jupiter's atmosphere and interior. One thing that Juno needs is wide-field imaging---because Juno's highly eccentric orbit takes it close over the cloud tops, where it will not be able to see what surrounds its small instrument footprints.

I have been selected to lead a 49-orbit HST/WFC3 program (with STScI funding) to provide regional and global map context for the Juno perijove (close-approach) passes. Data will begin pouring in November 2016, and continue through the end of the Juno mission in 2018. As part of this program, we will measure Jupiter's wind field---and its short-term variability---at the time of Juno's main atmospheric investigation (November 2016 through January 2017).


G540, G527, G485

The Outer Planet Atmospheres Legacy program (OPAL) is a unique, solar system-focused example of the trend toward large programs at premier observatories. I am the UC Berkeley lead of this program, whose PI is Amy Simon at NASA Goddard.

OPAL maps each planet for two consecutive rotations, every year, using the Wide Field Camera 3 (WFC3) on Hubble. So far OPAL data have ruled out a convective origin for 2014 cloud activity on Uranus, discovered a new dark vortex on Neptune in 2015, and found evidence of new and rare atmospheric waves on Jupiter in 2015 and 2016. A 2016 follow-up study of Neptune's dark vortex is funded by STScI (PI Wong).



SAM on Curiosity measured accurate ratios of isotopes and molecules in Mars' atmosphere, producing some interesting surprises. A higher than expected argon/nitrogen ratio presents an intriguing puzzle when compared with Mars meteorite data: how could this gas ratio have changed so much over only a few million years? Methane and oxygen have been observed by MSL (ChemCam and SAM) to vary over the martian year, but this too is completely unexpected. The atmosphere of Mars is more compositionally dynamic than we thought! MSL research is performed as a NASA-funded collarboration with Prof. Sushil Atreya at the University of Michigan.


G512, G480, G485

Cloud features, in a series of images over time, trace the horizontal flow in the atmospheres of the giant planets. We extract velocities using ACCIV, an algorithm coded by Xylar Asay-Davis, which was called the best available method for measuring velocities by Andy Ingersoll in 2015. The ACCIV method, which stands for Advection-Corrected Correlation Image Velocimetry, is an iterative technique that is able to find correlations over longer intervals, by using crude initial velocity fields to correct for distortions in the cloud field caused by complex flow. ACCIV excels on Jupiter and Saturn, where usable albedo contrasts are everywhere. But on Uranus and Neptune, the best results come from manual tracking of discrete features. Dynamical studies on Jupiter and Saturn are NASA- and STScI-funded collaborations with Amy Simon (NASA Goddard) and Prof. Philip Marcus.


G526, G470, G320

The remote-sensing projects described above all rely on sunlight scattered from particles in the planets' atmospheres. But on Jupiter, we have also been studying thermal infrared and radio wavelength light, heat energy that is radiatively escaping from the planet.

Observations with the VLA show intricately detailed bright and dark patterns at different wavelengths, revealing spatial variation in the amount of ammonia gas present. Ammonia acts as a tracer of vertical motions, so the brightness patterns correspond to upwelling and downwelling due to convection, waves, jets, and turbulence. Juno's microwave radiometer will use a similar approach, but at a unique vantage point inside Jupiter's radiation belts. VLA science is performed as a collarboration with Prof. Imke de Pater.

High-resolution spectrometers, operating in the 5-μm region of the thermal infrared spectrum, are also able to sense variations in ammonia concentration. We use facilities at the NASA IRTF and Keck telescopes to measure individual molecular line shapes, revealing water vapor, phosphine, and cloud distributions as well as ammonia. High-resolution spectroscopic studies are performed as a collarboration with Gordon Bjoraker at NASA Goddard, funded by NASA.