Planetary surfaces

Abstract:

Plain Language Summary: Earth absorbs energy emitted by the Sun, radiating some of that as heat back into space. The energy exchange between Earth and space drives weather and climate. Scientists measure and track this energy using satellite instruments that can identify which parts of Earth's surface and atmosphere emit specific portions of the overall heat radiated into space. But these instruments are complicated and expensive, and until now, no one has built a sensor that can look at and separate all of Earth's heat emissions in a systematic way. The Polar Radiant Energy in the Far‐InfraRed Experiment (PREFIRE) has developed a novel instrument that combines simple, miniaturized heat sensors with specially shaped optics and microelectronics to provide such measurements to further our understanding of the planet's weather and climate. Furthermore, implementation of the sensors has been done within a cost‐capped mission profile that encourages development of a sustainable sensor system for Earth monitoring. This manuscript describes the instrument design, including its components and their characteristics, the system and its functionality, its trade‐offs, cost limitations, and testing and performance information. PREFIRE began operating two of these instruments in space in 2024, in order to start quantifying the heat exchange processes in Earth's polar regions.

Abstract:

Venus is home to thousands of volcanoes, with a wide range of volumes and sizes. Its surface is relatively young, with a temperature of approximately 735 K and an atmosphere of 92 bar. Past and possible ongoing volcanic outgassing is expected to provide a source to the sustenance of this massive atmosphere, dominated by CO2 and SO2. The lower atmosphere can be investigated in the near-infrared transparency windows on the nightside, such as the 2.3μm thermal emission window, which provides a chance of detection of species with volcanic origin, such as water vapor. The Planetary Spectrum Generator was used to simulate the nightside 2.3μm thermal emission window of Venus. We simulated the effect of a volcanic gas plume rising to a ceiling altitude, for species such as H2O, CO, OCS, HF and SO2. The sensitivity of the radiance spectrum at different wavelengths was explored as an attempt to qualitatively access detection for future measurements of both ground-based and space-instrumentation. We conclude from our qualitative analysis that for the H2O, CO and OCS plumes simulated there is potential to achieve a detection in the future, given a minimum required signal-to-noise ratio of 50. For SO2 and HF plumes, a higher signal-to-noise ratio would be needed.

Abstract:

High-resolution spectroscopy (HRS) of exoplanet atmospheres has successfully detected many chemical species and is quickly moving toward detailed characterization of the chemical abundances and dynamics. HRS is highly sensitive to the line shape and position; thus, it can detect three-dimensional (3D) effects such as winds, rotation, and spatial variation of atmospheric conditions. At the same time, retrieval frameworks are increasingly deployed to constrain chemical abundances, pressure–temperature (P–T) structures, orbital parameters, and rotational broadening. To explore the multidimensional parameter space, we need computationally fast models, which are consequently mostly one-dimensional (1D). However, this approach risks introducing interpretation bias since the planet’s true nature is 3D. We investigate the robustness of this methodology at high spectral resolution by running 1D retrievals on simulated observations in emission within an observational framework using 3D global circulation models of the quintessential HJ WASP-76 b. We find that the retrieval broadly recovers conditions present in the atmosphere, but that the retrieved P–T and chemical profiles are not a homogeneous average of all spatial and phase-dependent information. Instead, they are most sensitive to spatial regions with large thermal gradients, which do not necessarily coincide with the strongest emitting regions. Our results further suggest that the choice of parameterization for the P–T and chemical profiles, as well as Doppler offsets among opacity sources, impact the retrieval results. These factors should be carefully considered in future retrieval analyses.

Abstract:

The presence of cryovolcanic activity in the form of geyser-like plumes at Jupiter’s moon Europa is a much-debated topic. As an active plume could allow direct sampling by a passing spacecraft of a potentially habitable interior environment, the detection and analysis of ongoing plume activity would be of the highest scientific value. In the past decade, several studies have interpreted different remote and in situ observations as providing evidence for large gaseous plumes at different locations on Europa. However, definitive proof is elusive, and visible imaging data taken during spacecraft flybys do not reveal clear indications of ongoing activity. After arrival at Jupiter in 2030, the NASA Europa Clipper spacecraft will systematically search for and constrain plume activity at Europa utilizing a variety of investigations and methods during, before, and after close flybys. Given the lack of a confirmed plume detection to date, the Europa Clipper science team has adopted a global plume search strategy, not focusing on any specific geographical area or any specific type of observation. This global search strategy assigns enhanced value to data obtained early in the mission, which allows time for further observations and characterization of any observed plume at later times. Here we describe the current state of knowledge on plume activity, the Europa Clipper search strategy, and the role of various instruments on the Europa Clipper payload in this search.

Abstract:

Activity in small bodies, defined here as the episodic or continuous release of material, was long thought to be exclusively a behavior of comets, but it has since been discovered in some centaurs, main-belt asteroids, and near-Earth asteroids. To date, however, no activity has been discovered on Jovian trojan asteroids, the target of NASA’s Lucy Discovery Program mission. Although Lucy was originally conceived without studies of or searches for trojan activity, it was realized in 2016–2017 that the spacecraft and scientific payload aboard Lucy could provide unique and meaningful constraints or detections on activity in these trojans. Here we describe how the Lucy mission will search for such activity using (i) its terminal tracking navigation camera to search for wide-field coma scattered light, (ii) its Lucy Long Range Reconnaissance Imager narrow-angle camera to also search for scattered light from any coma or jets, and (iii) its Multispectral Visible Imaging Camera imager to search for CN emission (a common activity tracer species in comets). Sensitivity estimates for each of those measurements are discussed below.