Research Projects
Highly depleted Alkali metals in Jupiter’s deep atmosphere
Astrophysical Journal Letters paper
Water and ammonia vapors are known to be the major sources of spectral absorption at pressure levels observed by the microwave radiometer (MWR) on Juno. However, the brightness temperatures and limb darkening observed by the MWR at its longest-wavelength channel of 50 cm (600 MHz) in the first nine perijove passes indicate the existence of an additional source of opacity in the deep atmosphere of Jupiter (pressures beyond 100 bar). The absorption properties of ammonia and water vapor, and their relative abundances in Jupiter’s atmosphere, do not provide sufficient opacity in the deep atmosphere to explain the 600 MHz channel observation. Here we show that free electrons due to the ionization of alkali metals, i.e., sodium and potassium, with subsolar metallicity, [M/H] [log-based 10 relative concentration to solar] in the range of [M/H] = −2 to [M/H] = −5, can provide the missing source of opacity in the deep atmosphere. If the alkali metals are not the source of additional opacity in the MWR data, then their metallicity at 1000 bars can only be even lower. This upper bound of −2 on the metallicity of the alkali metals contrasts with the other heavy elements—C, N, S, Ar, Kr, and Xe—that are all enriched relative to their solar abundances, having a metallicity of approximately +0.5.
Probing Dust and Water Vapor in Martian atmosphere
Bhattacharya et al. 2023, Remote Sensing
Airborne dust plays an active role in determining the thermal structure and chemical composition of the present-day atmosphere of Mars and possibly the planet’s climate evolution over time through radiative–convective and cloud microphysics processes. Thus, accurate measurements of the distribution and variability of dust are required. Observations from the Mars Global Surveyor/Thermal Emission Spectrometer Mars Mars Reconnaissance Orbiter/Mars Climate Sounder and Mars Express/Fourier Transform Spectrometer and the Curiosity Rover have limited capability to measure dust. We show that spacecraft occultation of the Martian atmosphere at far-infrared frequencies between 1 and 10 THz can provide the needed global and temporal data on atmospheric dust by providing co-located measurements of temperature and dust opacity from the top of the atmosphere all the way down to the surface. In addition, spacecraft occultation by a small-satellite constellation could provide global measurements of the development of dust storms.
Thermochemical Equilibrium in Jupiter’s Deep Atmosphere: The role of Anions
The Juno Microwave Radiometer has allowed observation of Jupiter’s atmosphere down to previously inaccessible depths, although the complexity of the atmospheric dynamics has complicated analysis. The longest-wavelength channel (600 MHz) is sensitive to pressure levels of hundreds of bars, and has observed opacity sources other than the known gaseous and cloud components, likely caused by thermally ionized free electrons from alkali metal vapor. We extend previous analysis of limb darkening at these wavelengths, using radiative transfer and thermal equilibrium modeling, by considering the effect of anions in the deep Jovian atmosphere, which act as a sink for free electrons and will thus decrease opacity for a given alkali metal abundance. We show that MWR observations are consistent with a sodium and potassium abundance on the order of 0.1× solar around the 1-kilobar level, higher than previously estimated but still substantially depleted compared to other heavy elements, a value that would be within the range of observed alkali metal abundances on giant exoplanets; alternatively, MWR observations may be consistent with 3× solar sodium abundance, but only if potassium is even more strongly depleted. Such depletion may be the result of either chemical processes yet deeper in the atmosphere, such as in the silicate clouds, or of a long-lived stable layer shallower than the alkali salt clouds.
Mars CubeSat Satellite Constellation for Radio Science Experiments
A space mission design project focused on providing daily near-global observations of Mars’ neutral atmosphere and ionospheric medium. Radio occultation is a powerful method of probing atmospheric temperature profiles, and capture local scale stability and mixing processes. We leverage the engineering advances in small spacecraft to provide a mission concept of Mars radio occultation observation network (MaROON). The project has been selected for presentation at AIAA SciTech 2025.
TREX: Temporarily-Captured Orbiter Rendezvous Explorer
A mission concept focused on rendezvous and remote sensing of Temporarily Captured Object (TCO) in Earth’s orbit. Stepping into the shoes of Project Scientist, and Instrument Lead, I worked with an interdisciplinary team as a part of Cornell SmallSat Mission Design School. Watch this space for more updates.
Juno Microwave Radiometer Observations of Extreme Electron Precipitation Events
[Manuscript under review in JGR: Space Physics] Pre-print available on ESS Open Archive
Jupiter’s auroral ionosphere is characterized by high electron density due to energetic particle precipitation near the polar regions resulting in a plasma environment that exhibits reflection and absorption at microwave frequencies. Juno Microwave Radiometer (MWR) observations have detected cold brightness temperatures over the auroral oval in Jupiter’s northern hemisphere. These features are found to be prominent at 600 MHz to 5 GHz frequency channels, showing a temporal variation in brightness temperature over a time span less than a minute encompassing length scale of MWR polar footprint e.g. 0.1 RJ. We analyze Juno MWR observations of the northern aurora, and simulate the electron densities corresponding up to 10 MeV energetic particle precipitation events inferred from the JEDI and UVS instruments. The plasma environment of Jupiter’s northern aurora is investigated using microwave opacity models to characterize the nature of reflection and absorption required to explain the MWR observations.