Carol A. Raymond

Coronal mass ejections (CMEs) are enormous bursts of plasma and magnetic field from the Sun that propagate explosively through the Solar System. CMEs are the primary drivers of the most severe space-weather events, posing major radiation hazards for human exploration beyond Earth’s magnetosphere, including missions to the Moon and Mars. During Europa Clipper’s cruise between Earth and Mars, its Plasma Instrument for Magnetic Sounding (PIMS) recorded unusual solar-wind conditions later identified as the wake of a complex CME. Data from an unprecedented network of 17 spacecraft across the inner Solar System revealed a hidden Earth-directed component that propagated asymmetrically and could not have been predicted without off-Sun-Earth-line observations. This component also affected Europa Clipper and Mars, demonstrating how a missed forecast of this kind could endanger a crewed mission. These findings highlight the need for multipoint observations, including planetary missions in cruise, to improve space-weather forecasting, mission planning, and operations.

Sample return missions are among the most difficult tasks for robotic spacecraft in exploring our solar system. However, the samples they return to Earth have significantly high value for the planetary science community. Thus far, we have only acquired samples from the Moon, three asteroids, a comet’s tail, and the solar wind at the Earth–Sun Lagrange Points. The National Academy’s most recent decadal survey of planetary science at NASA emphasized the value of samples returned to Earth for analysis and called for NASA to prioritize samples returned from Mars, the Moon’s South Pole, a Jupiter-family comet, and Ceres. Currently available rockets and propulsion technology impose severe, and possibly insurmountable, limits to where we can send robot explorers and return samples within a reasonable timescale. Now, the advent of large new rockets offers the potential for very high C₃ (characteristic energy) Earth escape trajectories. Parallel developments in Nuclear Propulsion yield much higher I_SP than chemical propulsion and can operate far away from the Sun. Our novel trajectory modeling results and mission architecture analysis show that, by combining these technologies, sample return from across the solar system becomes feasible within the career lifetime of a planetary scientist.

Sample return missions are the most difficult tasks we ask robotic spacecraft to undertake in exploring our solar system, but we do so because of the high value returned samples have for the planetary science community. Thus far, we have only acquired samples from: the Moon, three asteroids, a comet’s tail, and the solar wind at the Earth-Sun Lagrange Points. The National Academy’s most recent decadal survey of planetary science in NASA — Origins, Worlds, Life (OWL) — emphasized the value of samples returned to Earth for analysis and called for NASA to prioritize samples returned from Mars, the Moon’ South Pole, a Jupiter-family comet, and Ceres. Currently available rockets and propulsion technology impose severe, and possibly insurmountable, limits to where we can send robot explorers and return samples within a reasonable timescale. Now, the advent of large new rockets offers the potential for very high C3 Earth escape trajectories. Parallel developments in Nuclear Propulsion yield much higher ISP than chemical propulsion and can operate far away from the Sun. Our novel trajectory and mission architecture analysis shows that, combining these technologies, sample return from all across the solar system starts to become feasible within the career lifetime of a planetary scientist.

Asteroid (16) Psyche is the largest likely metal‐rich asteroid in the Solar System and the target of the NASA Psyche mission. The mission aims to determine whether the asteroid is the core of a differentiated planetesimal that lost its mantle via a giant impact. To prepare for spacecraft observations of the asteroid, we combine impact and geodynamic models to predict the magnetization, composition, and interior structure of a mantle‐stripped core with the mass and density of Psyche. We show that Psyche‐like bodies can form from a single giant impact, with a hit‐and‐run collision being the most likely scenario. After the impact, Psyche's materials could have become magnetized while cooling in a dynamo field generated by its advecting core and/or in the magnetic field of the solar nebula. The former is diagnostic of Psyche being a mantle‐stripped core and is favored if Psyche's primordial sulfur content and current metal content are 10 wt.% and 50 wt.%, respectively. A sulfur content 10 wt.% delays core solidification long enough for kamacite in the asteroid's exterior to cool through the Curie temperature while the dynamo is still active. Formation of Psyche analogs with 50 wt.% metal content requires highly energetic impacts that more favorably occur after nebular‐gas dissipation. Therefore, if the Psyche spacecraft's Magnetometer, Gamma‐Ray Neutron Spectrometer, and Gravity and Topography Investigations respectively measure strong ( ) magnetization, sulfur‐rich surface provinces compatible with a bulk primordial sulfur content 10 wt.%, and metal content 50 wt.%, Psyche most likely formed as a mantle‐stripped core.

The close approach of asteroid (99942) Apophis in 2029 offers a rare opportunity to observe the reaction of a small, suspected rubble-pile body to planetary tidal forces, providing insight into its surface and interior properties and contributing valuable knowledge for planetary defense. The California Institute of Technology (Caltech) is pioneering a mission to rendezvous with Apophis before and escort it through its Earth closest approach (ECA). The mission consists of a Mothership and two radar-equipped CubeSats. Mission science objectives include observing potential resurfacing due to ECA and studying the asteroid’s interior using low-frequency radar, producing three-dimensional maps of Apophis’s internal composition and porosity and providing unprecedented insight into the interiors of rubble piles. Here, we compile and summarize Apophis modeling and data, focusing on knowns, unknowns, current science knowledge gaps, and how Caltech’s mission can fill those gaps. We discuss current knowledge regarding the surface dynamics and interior structure of rubble-pile asteroids, implications for asteroid formation and evolution, predicted responses to Earth encounters via numerical modeling, and how these predictions inform mission requirements. We outline how Caltech’s mission aligns with the landscape of other Apophis missions, such as OSIRIS-APEX and RAMSES, and how its unique bistatic radar data set complements the data returned by other missions.

Over the course of NASA’s Dawn Discovery mission, the onboard framing camera mapped Ceres across a wide wavelength spectrum at varying polar science orbits and altitudes. With increasing resolution, the uniqueness of the 92 km wide, young Occator crater became evident. Its central cryovolcanic dome, Cerealia Tholus, and especially the associated bright carbonate and ammonium chloride deposits—named Cerealia Facula and the thinner, more dispersed Vinalia Faculae—are the surface expressions of a deep brine reservoir beneath Occator. Understandably, this made this crater the target for future sample return mission studies. The planning and preparation for this kind of mission require the characterization of potential landing sites based on the most accurate topography and orthorectified image data. In this work, we demonstrate the capabilities of the freely available and open-source USGS Integrated Software for Imagers and Spectrometers (ISIS 3) and Ames Stereo Pipeline (ASP 2.7) in creating high-quality image data products as well as stereophotogrammetric (SPG) and multi-view shape-from-shading (SfS) digital terrain models (DTMs) of the aforementioned spectroscopically challenging features. The main data products of our work are four new DTMs, including one SPG and one SfS DTM based on High-Altitude Mapping Orbit (HAMO) (CSH/CXJ) and one SPG and one SfS DTM based on Low-Altitude Mapping Orbit (LAMO) (CSL/CXL), along with selected Extended Mission Orbit 7 (XMO7) framing camera (FC) data. The SPG and SfS DTMs were calculated to a GSD of 1 and 0.5 px, corresponding to 136 m (HAMO SPG), 68 m (HAMO SfS), 34 m (LAMO SPG), and 17 m (LAMO SfS). Finally, we show that the SPG and SfS approaches we used yield consistent results even in the presence of high albedo differences and highlight how our new DTMs differ from those previously created and published by the German Aerospace Center (DLR) and the Jet Propulsion Laboratory (JPL).

The role played by transient impact-induced endogenous brines in the formation of geomorphic features has been proposed on airless worlds such as Europa, Vesta, and Ceres, as well as on worlds with thin atmospheres such as Mars. After liquefaction, the hypothesized brines flow in a debris-flow-like process, incising curvilinear gullies and constructing lobate deposits within newly formed craters. Here we investigate what parameters (if any) could enable liquid to be transiently present for a sufficient time (∼tens of minutes) under postimpact transient atmospheric pressures (10⁻⁴–10⁻⁵ torr) to form curvilinear gullies and lobate deposits, as have been seen on Vesta and more tentatively Ceres. We report that water likely vacuum-freezes too quickly, while NaCl brine enables flow longevity. We also find that frozen lid formation facilitates longer liquid lifetimes, as with lava in terrestrial lava tubes and model predictions for cryovolcanic flows on Europa. This work provides additional contributions to the growing body of literature that investigates the role of transient brines in sculpting the surfaces of airless worlds.

Spacecraft magnetic fields are very complex in nature, and they must be understood and minimized, as they can mask or even mimic signals of interest. Current approaches simulate the 3D nature of the magnetic field and then visualize it in 2D images. However, limited 2D views hide much of the information in the complex spacecraft magnetic field. We describe a prototype system that allows for both an interactive 3D web experience as well as an immersive virtual reality (VR) experience to view and manipulate the 3D spacecraft magnetic field, allowing engineers and scientists to trace field lines, real-time in 3D. A preliminary user study validates the usefulness of the tool and guides further development.

Striking exposures of Na‐carbonate‐bearing bright materials are found in Ahuna Mons and the central landforms of Occator and other impact craters on Ceres; however, most bright materials on its surface occur as excavated material on the rims and walls of impact craters. The source of the widespread excavated Na‐carbonate is uncertain. We map the distribution and extent of rim/wall Na‐carbonate with Dawn's Visible and Infrared Imaging Spectrometer and Dawn Framing Camera. We find a strong spatial correlation between domes and shallow subsurface Na‐carbonate deposits, suggesting that they form by the same or related processes. Using Monte Carlo impact models, we constrain the timing of emplacement of the shallow subsurface Na‐carbonate to be within the last ∼1 Ga and probably within the last few hundred Ma. We examine the likelihood that the Na‐carbonate was mobilized from Ceres' deep interior and the plausibility of brine upwelling or solid‐state processes. We demonstrate that a combination of processes, including diapirism driven by Rayleigh‐Taylor instabilities and solid‐state deformation due to differential loading, could mobilize Na‐carbonate‐bearing ices to the shallow subsurface without requiring the recent presence of brines.

Some icy moons and small bodies in the solar system are believed to host subsurface liquid water oceans. The interaction of these saline, electrically conductive oceans with time-varying external magnetic fields generates induced magnetic fields. Magnetometry observations of these induced fields in turn enable the detection and characterization of these oceans. We present a framework for characterizing the interiors of icy moons using multifrequency induction and Bayesian inference applied to magnetometry measurements anticipated from the upcoming Europa Clipper mission. Using simulated data from the Europa Clipper Magnetometer, our approach can accurately retrieve a wide range of plausible internal structures for Europa. In particular, the ocean conductivity is recovered to within ±50% for all internal structure scenarios considered, and the ocean thickness can be retrieved to within ±25 km for five out of seven scenarios. Characterization of the ice shell thickness to ±50% is possible for six of seven scenarios. Our recovery of the ice shell thickness is highly contingent on accurate modeling of magnetic fields arising from the interaction of Europa with the ambient magnetospheric plasma, while the ocean thickness is more modestly affected and the ocean conductivity retrieval is largely unchanged. Furthermore, we find that the addition of a priori constraints (e.g., static gravity measurements) can yield improved ocean characterization compared to magnetometry alone, suggesting that multi-instrument techniques can play a key role in revealing the interiors of Europa and other ocean worlds.