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Volatile loss from exoplanetary atmospheres and its possible implications for the longevity of habitable surface conditions is a topic of vigorous debate currently. The vast majority of the habitable zone terrestrial-like exoplanets known to date orbit low-mass M- and K-dwarf stars and are subject to the conditions drastically different to those of terrestrial planets in the Solar System. In particular, they orbit far closer to their host stars than similar planets around G-dwarfs similar to the Sun. Therefore they receive higher X-ray and UV fluxes, even though luminosities of M- and K-dwarfs are lower than those of heavier stars. Furthermore, due to their slower evolution, M-dwarfs retain high activity on the gigayear timescales. The combination of these two effects has led to claims that most terrestrial planets orbiting M-dwarfs may have their atmospheres stripped from the higher X-ray and UV fluxes of their host stars. Opposing this are researchers who point out that volatile inventories for terrestrial exoplanets are ill-constrained, and hence, they may be able to “weather the storm” of these higher X-ray and UV fluxes. In this article, we focus on exploring volatile loss in the upper atmospheres of terrestrial planets in our solar system and applications to those in exoplanetary systems around stars of different types.
Trends of essential climate variables are often estimated from climate data records to quantify changes in the Earth system. An understanding of the uncertainty in a trend is essential for accurately determining the significance of a trend and attributing its causes. Despite this importance, trend-uncertainty estimates rarely account for all known sources of uncertainty. Common approaches neglect measurement-system instability or neglect the impact of natural variability on trend uncertainty. Such neglect can result in over-confidence in trend estimates. This study addresses trend-uncertainty assessment, particularly the need to account for the combined effects of measurement instability and natural variability on the trend uncertainty. The study presents a novel, unified framework for trend estimation that combines available measurement uncertainty information with empirical modelling of natural climate variability to achieve a more accurate uncertainty estimate. The framework is demonstrated for a time series of global mean sea level observations, obtaining more realistic trend-uncertainty values. The framework is applicable to most other climate data records. Adopting this approach will enhance confidence in climate change analysis through more accurate trend-uncertainty assessment in climate studies.
We present a parametric strong-lensing model for the galaxy cluster MACS J1931.8-2635 (z(l) = 0.35), accompanying the detection of the spectroscopically confirmed SN Eos at z = 5.13. We identify 10 new multiple-image systems in recent VENUS JWST/NIRCam imaging, so that the model is constrained with a total of 19 robust multiple-image systems-nine of which also have a spectroscopic redshift. For the point-like source corresponding to SN Eos, our model predicts a total of five images, with the observed radial image pair having a similar magnification of mu similar or equal to 25-30 and a small time delay of <5 days, in agreement with their simultaneous observation. According to the model, the other three predicted images arrived earlier, with time delays of 3.6 +/- 0.7, 3.4 +/- 0.7, and 53.9 +/- 10.8 yr prior to the two observed images, and with magnifications of 14.5 +/- 2.9, 11.9 +/- 2.4, and 2.2 +/- 0.4, respectively. The absence of detections at the predicted positions, where the host galaxy's images are also visible, confirms the transient nature of the source. SN Eos and its host galaxy are studied in separate articles, and we here focus on the lens model. The final model reaches a very good rms distance between model and observations of 0.'' 44. We present the lens-modeling results, including newly identified systems such as a triply imaged, grand-design spiral galaxy candidate at z similar or equal to 3.6 5 - 0.09 + 0.04 , and discuss the potential of using high-redshift lensed SNe for cosmography.
This paper is a collaborative effort that originated at the International Space Science Institute Workshop on “Physical Links between Weather and Climate in Space and the Lower Atmosphere” held on January 22-26, 2024. Our goals are to survey the role of tides in facilitating the coupling of the lower and upper atmosphere and identify pathways forward that address challenges to our current understanding. To that end, we provide a brief review of the physics of atmospheric tides and the sources of their day-to-day and seasonal variability during quiet geomagnetic conditions. We identify the mechanisms that couple vertically propagating atmospheric tides to variations in thermosphere–ionosphere wind, composition, and plasma. Each process is punctuated with examples showcasing state-of-the-art observations or models, and requirements for scientific progress. A recurrent theme is a thermospheric measurement gap region between 100 and 200 km that precludes direct observations of tidal vertical coupling processes and their day-to-day variability.
We present an analysis of archival JWST NIRSpec IFS and HST imaging observations of the z = 3 Lyman continuum emitter (LCE) candidate LACES104037. We show that a nearby galaxy, denoted LACES104037-S, has a redshift offset from the main galaxy by only similar to 450 km s(-1). Together with the identification of a tidal bridge between the galaxies, this indicates that the galaxies are interacting and most likely in the early stages of a merger. We show that the rest-frame LCE cluster sits similar to 2.7 kpc from the galaxy core in the tidal bridge. It is faint in the nonionizing stellar continuum and shows faint but nonnegligible H alpha and [O III] emission, suggesting that much of the gas surrounding the LCE cluster has been dispersed by feedback in the shallower gravitational potential of the tidal bridge. Comparing the direct LyC escape and the local H alpha emission, we find a total ionizing escape fraction of f(esc)(LyC) =57 +/- 8% from the LCE cluster. We estimate the age of the LCE cluster to less than or similar to 6.5 Myr, indicating that the cluster must have formed in situ in the tidal bridge well after the time of closest interaction. LyC escape from tidal stripping or in situ formed stars in tidal features would depend less on intrinsic galaxy properties than typically observed in low-z LCE surveys and could help explain the higher cosmic escape fraction and enhanced diversity of LCE galaxy properties observed at cosmic noon.
