Editor’s Note: This week we’ll be writing updates on selected events at the 56th Division for Planetary Sciences (DPS) meeting happening in Boise, Idaho, and online. The usual posting schedule for AAS Nova will resume on October 14th.
Table of Contents:
- The Open-Source Science Initiative at NASA (J.L. Galache)
- Digging Deep: Unveiling Vertical Mixing and the Core Mass of Giant Exoplanets with JWST (David Sing)
- Tracing the Heating of the Solar System Through Geochemical Signatures (Katherine de Kleer)
The Open-Source Science Initiative at NASA (J.L. Galache)
J.L. Galache (Agile Decision Sciences, NASA HQ) opened the session with a brief primer on open-science initiatives at NASA. Essentially, open science is the act of making your data, software, and publications freely accessible to all. Open science benefits the planetary science community by lowering barriers to entry and enhancing reproducibility of research. (Of course, open science also benefits you because your freely accessible data and publications will be cited more often!) NASA approaches open-science implementation through funding (sunpy and astropy have received funding from NASA, among many other recognizable names in science software), training, and policy. Current policy states that data and software should be made available at the time the research is published, and publications should be made available through a pre-print server (e.g., arXiv) if not being published in an open-access journal. Among the existing training options is Open Science 101, an online training module through which 1,900 people have already been accredited.
Digging Deep: Unveiling Vertical Mixing and the Core Mass of Giant Exoplanets with JWST (David Sing)
David Sing (Johns Hopkins University), winner of the 2024 Alexander Prize for outstanding contributions that have significantly advanced our knowledge of planetary systems, described the journey to understanding exoplanet atmospheres and interiors from Hubble to JWST. Sing focused on the transit method, which has enabled the discovery of thousands of planets beyond our solar system and increasingly allows scientists to probe the atmospheres of those worlds.
With Hubble, scientists were able to test their models of photochemical equilibrium in exoplanet atmospheres, which predicted broad compositional trends with planet temperature. Hubble observations confirmed the basic picture of the chemical composition of hot Jupiters while also revealing complexities like clouds and hazes, which make it difficult to extract chemical abundances from spectra, and the presence of disequilibrium chemistry, which required extra attention from modelers.

The mass–metallicity relationship for solar system planets (black points) and exoplanets (colored points). Click to enlarge. [From slide by David Sing]
Sing also described the important results from JWST observations of two other exoplanets, HAT-P-18b and WASP-107b. These are both cool/warm gas giants that are expected to have methane in their atmospheres. HAT-P-18b showed no sign of methane in its atmosphere — since the molecule is expected to exist, does this mean it’s being destroyed by photochemistry or by mixing into the deep, hot atmosphere of the planet?
Observations of WASP-107b provided more clues: in addition to CO2 and water, JWST observations of WASP-107b showed at last a hint of methane. However, there was about a thousand times less methane than expected given the planet’s temperature. By modeling both vertical mixing and photochemistry, Sing’s team showed that the methane depletion was due to mixing. Going further with these data, they used interior structure modeling to estimate the mass of the core at 11.5 Earth masses — consistent with predictions of the core accretion model.
Up next is the exoplanet grand tour spectroscopic survey, which will observe 25 exoplanets during 125 hours of JWST time. Stay tuned for news from this survey — the first data are being collected roughly 24 hours after this talk!
Tracing the Heating of the Solar System Through Geochemical Signatures (Katherine de Kleer)
Katherine de Kleer (California Institute of Technology), winner of the 2024 Harold C. Urey prize for outstanding achievements in planetary science by an early-career scientist, described recent work on the history of heating in the solar system. De Kleer and collaborators use the Atacama Large Millimeter/submillimeter Array (ALMA) to understand where, when, and how objects in the solar system were heated and how that drives the chemical evolution of and geological activity on those objects today.
Let’s take things all the way back to the early days of the solar system: in the beginning, there was aluminum-26, a once-abundant, radioactive form of aluminum that heated the infant solar system. Heating from aluminum-26 melted early planetesimals and caused them to differentiate, separating into distinct compositional layers. Some of these planetesimals clumped together to form what are today the planets in our solar system, while others collided, leaving their remains scattered through the solar system as asteroids. The fragments of planetesimals in the asteroid belt can tell us about differentiation and, thus, heating in the protoplanetary disk that birthed our solar system.
Using ALMA, de Kleer observed the thermal emission from large main-belt asteroids — with an incredible resolution of 30 kilometers — and modeled the observations. The data show high emissivity (indicative of large metal content) but low polarization (indicative of scattering due to metal inclusions). This suggests that rather than having metal tied up in minerals, the metal in these asteroids likely exists in the form of numerous metallic chunks.While heating is still ongoing in the solar system today, radiogenic heating — heating from the decay of radioactive material — is not as important as it once was. Now, small bodies are largely heated through tidal heating. The most dramatic example of the effects of tidal heating is Jupiter’s moon Io — the most volcanically active body in the solar system. Tidal heating melts Io’s rocky interior, which then gushes through the moon’s 400 active volcanoes to its surface.

Many views of the infrared glow of Io and its many volcanoes. Wavelength increases toward the bottom. Click to enlarge. [Slide by Katherine de Kleer]
Scientists have studied volcanic activity on Io for forty years, but the moon has been active much, much longer. If Io has been trapped in a resonance with fellow moons Europa and Ganymede for billions of years, as research suggests, it must have lost the equivalent of its entire mantle contents many times over, churning through and reprocessing this mantle material repeatedly. Another way of looking at Io’s evolution over time is through its atmosphere. Sulfur — an abundant component of Io — is lost to space from the moon’s upper atmosphere. Because different isotopes of sulfur have different masses, lighter isotopes are held less tightly to the moon and are preferentially removed from the atmosphere. By measuring the ratio of different isotopes of sulfur, de Kleer showed that Io has lost 94–99% of its available sulfur, supporting the picture of a dramatically, dynamically heated and evolving world.