Fundamental Science Achieved with a Single Probe in Each Giant Planet AtmosphereMandt, Kathleen E.; Simon, Amy A.; Mousis, Olivier; Atkinson, David H.; Hofstadter, Mark
doi: 10.1007/s11214-024-01083-0pmid: N/A
Recent observations of Jupiter’s atmosphere showing unexpected depletion of ammonia below the ammonia cloud-forming region has brought up the question of whether a single point measurement below the cloud decks in a giant planet atmosphere can provide sufficient information to answer fundamental science questions. We outline here the science questions that can only be answered by in situ observations in the giant planet atmospheres, many of which are location invariant. These questions are identified in the recent planetary science decadal survey as high priority for answering over the next decade. We evaluate the implications of the ammonia observations at Jupiter for the specific measurements needed and demonstrate that they do not invalidate single point measurements made to answer these questions.
Geologic Constraints on the Formation and Evolution of Saturn’s Mid-Sized MoonsRhoden, Alyssa Rose; Ferguson, Sierra N.; Bottke, William; Castillo-Rogez, Julie C.; Martin, Emily; Bland, Michael; Kirchoff, Michelle; Zannoni, Marco; Rambaux, Nicolas; Salmon, Julien
doi: 10.1007/s11214-024-01084-zpmid: 39036784
Saturn’s mid-sized icy moons have complex relationships with Saturn’s interior, the rings, and with each other, which can be expressed in their shapes, interiors, and geology. Observations of their physical states can, thus, provide important constraints on the ages and formation mechanism(s) of the moons, which in turn informs our understanding of the formation and evolution of Saturn and its rings. Here, we describe the cratering records of the mid-sized moons and the value and limitations of their use for constraining the histories of the moons. We also discuss observational constraints on the interior structures of the moons and geologically-derived inferences on their thermal budgets through time. Overall, the geologic records of the moons (with the exception of Mimas) include evidence of epochs of high heat flows, short- and long-lived subsurface oceans, extensional tectonics, and considerable cratering. Curiously, Mimas presents no clear evidence of an ocean within its surface geology, but its rotation and orbit indicate a present-day ocean. While the moons need not be primordial to produce the observed levels of interior evolution and geologic activity, there is likely a minimum age associated with their development that has yet to be determined. Uncertainties in the populations impacting the moons makes it challenging to further constrain their formation timeframes using craters, whereas the characteristics of their cores and other geologic inferences of their thermal evolutions may help narrow down their potential histories. Disruptive collisions may have also played an important role in the formation and evolution of Saturn’s mid-sized moons, and even the rings of Saturn, although more sophisticated modeling is needed to determine the collision conditions that produce rings and moons that fit the observational constraints. Overall, the existence and physical characteristics of Saturn’s mid-sized moons provide critical benchmarks for the development of formation theories.
Strong Gravitational Lensing as a Probe of Dark MatterVegetti, S.; Birrer, S.; Despali, G.; Fassnacht, C. D.; Gilman, D.; Hezaveh, Y.; Perreault Levasseur, L.; McKean, J. P.; Powell, D. M.; O’Riordan, C. M.; Vernardos, G.
doi: 10.1007/s11214-024-01087-wpmid: N/A
Dark matter structures within strong gravitational lens galaxies and along their lines of sight leave a gravitational imprint on the multiple images of lensed sources. Strong gravitational lensing provides, therefore, a key test of different dark matter models. In this article, we describe how galaxy-scale strong gravitational lensing observations are sensitive to the physical nature of dark matter. We provide an historical perspective of the field, and review its current status. We discuss the challenges and advances in terms of data, treatment of systematic errors and theoretical predictions, that will enable one to deliver a stringent and robust test of different dark matter models in the next decade. With the advent of the next generation of sky surveys, the number of known strong gravitational lens systems is expected to increase by several orders of magnitude. Coupled with high-resolution follow-up observations, these data will provide a key opportunity to constrain the properties of dark matter with strong gravitational lensing.
Time-Delay Cosmography: Measuring the Hubble Constant and Other Cosmological Parameters with Strong Gravitational LensingBirrer, S.; Millon, M.; Sluse, D.; Shajib, A. J.; Courbin, F.; Erickson, S.; Koopmans, L. V. E.; Suyu, S. H.; Treu, T.
doi: 10.1007/s11214-024-01079-wpmid: 38899030
Multiply lensed images of a same source experience a relative time delay in the arrival of photons due to the path length difference and the different gravitational potentials the photons travel through. This effect can be used to measure absolute distances and the Hubble constant (H0\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$H_{0}$\end{document}) and is known as time-delay cosmography. The method is independent of the local distance ladder and early-universe physics and provides a precise and competitive measurement of H0\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$H_{0}$\end{document}. With upcoming observatories, time-delay cosmography can provide a 1% precision measurement of H0\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$H_{0}$\end{document} and can decisively shed light on the current reported ‘Hubble tension’. This manuscript details the general methodology developed over the past decades in time-delay cosmography, discusses recent advances and results, and, foremost, provides a foundation and outlook for the next decade in providing accurate and ever more precise measurements with increased sample size and improved observational techniques.
Atmospheric Helium Abundances in the Giant PlanetsNettelmann, Nadine; Cano Amoros, Marina; Tosi, Nicola; Helled, Ravit; Fortney, Jonathan J.
doi: 10.1007/s11214-024-01090-1pmid: N/A
Noble gases are accreted to the giant planets as part of the gas component of the planet-forming disk. While heavier noble gases can separate from the evolution of the hydrogen-rich gas, helium is thought to remain at the protosolar H/He ratio Yproto∼0.27\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$Y_{\mathrm{proto}}\sim 0.27$\end{document}–0.28. However, spacecraft observations revealed a depletion in helium in the atmospheres of Jupiter, Saturn, and Uranus. For the gas giants, this is commonly seen as indication of H/He phase separation at greater depths. Here, we apply predictions of the H/He phase diagram and three H/He-EOS to compute the atmospheric helium mass abundance Yatm\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$Y_{\mathrm{atm}}$\end{document} as a result of H/He phase separation. We obtain a strong depletion Yatm<0.1\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$Y_{\mathrm{atm}}<0.1$\end{document} for the ice giants if they are adiabatic. Introducing a thermal boundary layer at the Z-poor/Z-rich compositional transition with a temperature increase of up to a few 1000 K, we obtain a weak depletion in Uranus as observed. Our results suggest dissimilar internal structures between Uranus and Neptune. An accurate in-situ determination of their atmospheric He/H ratio would help to constrain their internal structures. This is even more true for Saturn, where we find that any considered H/He phase diagram and H/He-EOS would be consistent with any observed value. However, some H/He-EOS and phase diagram combinations applied to both Jupiter and Saturn require an outer stably-stratified layer at least in one of them.
Candidate Landing Sites for the Emirates Lunar Mission (ELM) Rashid-1 RoverFlahaut, J.; Els, S. G.; Joulaud, M.; Wöhler, C.; Breton, S.; Füri, E.; AlMaeeni, S.; Almarzooqi, H.; ,
doi: 10.1007/s11214-024-01086-xpmid: N/A
Launched in December 2022 onboard the Hakuto-R lunar lander, the Mohammed Bin Rashid Space Centre (MBRSC) Emirates Lunar Mission (ELM) Rashid-1 rover experienced an unsuccessful landing on the lunar surface on April 25th, 2023. The mission’s prime landing site was Atlas crater, a 87 km diameter floor-fractured crater emplaced within the lunar highlands in the northeastern quadrant of the Moon. This paper describes the landing site selection procedure for the ELM Rashid-1 rover, from technical requirements that led to the selection of four broad areas of interest, to the placement of candidate landing ellipses based primarily on slope analysis and science interest. The rock abundance and presence of boulders were analyzed to verify the suitability of the target location for landing. Geological context as well as high resolution imagery and topography are presented for the four selected landing sites: Atlas crater (prime), Sinus Iridum, Oceanus Procellarum, and Lacus Somniorum (back-ups). Terrain characteristics and key science questions to be addressed at these locations are discussed, emphasizing the high scientific value of these locations for future lunar missions.
Microlensing Near Macro-CausticsWeisenbach, Luke; Anguita, Timo; Miralda-Escudé, Jordi; Oguri, Masamune; Saha, Prasenjit; Schechter, Paul L.
doi: 10.1007/s11214-024-01088-9pmid: N/A
Microlensing near macro-caustics is a complex phenomenon in which swarms of micro-images produced by micro-caustics form on both sides of a macro-critical curve. Recent discoveries of highly magnified images of individual stars in massive galaxy cluster lenses, predicted to be formed by these micro-image swarms, have stimulated studies on this topic. In this article, we explore microlensing near macro-caustics using both simulations and analytic calculations. We show that the mean total magnification of the micro-image swarms follows that of an extended source in the absence of microlensing. Micro-caustics join into a connected network in a region around the macro-critical line of a width proportional to the surface density of microlenses; within this region, the increase of the mean magnification toward the macro-caustic is driven by the increase of the number of micro-images rather than individual magnifications of micro-images. The maximum achievable magnification in micro-caustic crossings decreases with the mass fraction in microlenses. We conclude with a review of applications of this microlensing phenomenon, including limits to the fraction of dark matter in compact objects, and searches of Population III stars and dark matter subhalos. We argue that the discovered highly magnified stars at cosmological distances already imply that less than ∼ 10% of the dark matter may be in the form of compact objects with mass above ∼10−6M⊙\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$\sim 10^{-6}~M_{\odot }$\end{document}.