On 15 October 1997, NASA’s Cassini orbiter embarked on an epic, seven-year voyage to the Saturnian system. Hitching a ride was ESA’s Huygens probe, destined for Saturn’s largest moon, Titan. The final chapter of the interplanetary trek for Huygens began on 25 December 2004 when it deployed from the orbiter for a 21-day solo cruise toward the haze-shrouded moon. Plunging into Titan’s atmosphere, on 14 January 2005, the probe survived the hazardous 2 hour 27 minute descent to touch down safely on Titan’s frozen surface. Larger image — ESA
Understanding Titan’s planetary boundary layer (PBL) — the lowest region of the atmosphere influenced by surface conditions — remains challenging due to Titan’s thick atmosphere and limited observations.
Previous modeling studies have also produced inconsistent estimates of surface temperature, a critical determinant of PBL behavior, often without clear explanations grounded in surface energy balance.
In this study, we develop a theoretical framework and apply a three-dimensional dry general circulation model (GCM) to investigate how surface thermal inertia influences surface energy balance and temperature variability across diurnal and seasonal timescales. At diurnal timescales, lower thermal inertia surfaces exhibit larger temperature swings and enhanced sensible heat fluxes due to inefficient subsurface heat conduction.
In contrast, at seasonal timescales, surface temperature variations show weak sensitivity to thermal inertia, as atmospheric damping tends to dominate over subsurface conduction. The PBL depth ranges from a few hundred meters to 1,000 m on diurnal timescales, while seasonal maxima reach 2,000–3,000 m, supporting the interpretation from a previous study that the Huygens probe captured the two PBL structures.
Simulated seasonal winds at the Huygens landing site successfully reproduce key observed features, including near-surface retrograde winds and meridional wind reversals within the lowest few kilometers, consistent with Titan’s cross-equatorial Hadley circulation.
Simulations at the planned Dragonfly landing site predict shallower thermal PBLs with broadly similar wind patterns. This work establishes a physically grounded framework for understanding Titan’s surface temperature and boundary layer variability, and offers a unified explanation of Titan’s PBL behavior that provides improved guidance for future missions.
Sooman Han, Juan M. Lora
Comments: 25 pages, 11 figures Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph) Cite as: arXiv:2506.23477 [astro-ph.EP] (or arXiv:2506.23477v1 [astro-ph.EP] for this version) https://doi.org/10.48550/arXiv.2506.23477 Focus to learn more Submission history From: Sooman Han [v1] Mon, 30 Jun 2025 02:46:00 UTC (6,806 KB) https://arxiv.org/abs/2506.23477 Astrobiology,
Time series of relative FWHM measurements for all NETS stars with multiple nights of data collected prior to August 2021. We observe a sharp decrease in FWHM in August 2021 for all Solar-type stars, and we interpret this as a break in the RV time series necessitating the definition of a new NEID RV era prior to this date. A sharp FWHM change is also observed for HD 95735, an M-dwarf, but this change does not follow that of the other stars, suggesting a chromatic dependence. Though the ∆FWHM time series for HD 170657 and HD 201091 stand out from the other Solartype stars, these variations reflect changing stellar activity levels rather than an instrumental effect. — astro-ph.EP
The NEID Earth Twin Survey (NETS) has been delivering a rich set of precise radial velocity (RV) measurements for 41 bright, nearby main sequence stars.
Here, we describe the status of the survey after three years on sky and we present the full set of RV measurements and accompanying stellar activity indicators. We discuss intermediate survey diagnostics, including calibration of the known RV zero point offset introduced following the Contreras fire in 2022 and the identification of an undiagnosed and previously unknown zero point offset in 2021.
An analysis of our data set using RVSearch demonstrates that for these target stars, NEID is independently sensitive to nearly all known planets with periods shorter than the NETS observing baseline. We also highlight a number of newly detected RV signals, which present exciting opportunities for future investigations.
Arvind F. Gupta, Evan Fitzmaurice, Suvrath Mahadevan, Paul Robertson, Jacob K. Luhn, Jason T. Wright, Sarah E. Logsdon, Daniel M. Krolikowski, Leonardo A. Paredes, Chad F. Bender, Mark R. Giovinazzi, Andrea S. Lin, Cullen H. Blake, Caleb I. Cañas, Eric B. Ford, Samuel P. Halverson, Shubham Kanodia, Michael W. McElwain, Joe P. Ninan, Jayadev Rajagopal, Arpita Roy, Christian Schwab, Guðmundur Stefánsson, Ryan C. Terrien
Comments: Submitted to the Astronomical Journal. 27 Pages, 12 Figures (including 5 Figure sets which are included in the source files) Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR) Cite as: arXiv:2506.23704 [astro-ph.EP](or arXiv:2506.23704v1 [astro-ph.EP] for this version) https://doi.org/10.48550/arXiv.2506.23704 Focus to learn more Submission history From: Arvind Gupta [v1] Mon, 30 Jun 2025 10:27:04 UTC (14,846 KB) https://arxiv.org/abs/2506.23704 Astrobiology,
The federal government has further reduced the profit rates on National Savings Schemes.
According to the Central Directorate of National Savings (CDNS), profit rate on Defence Saving Certificates has been decreased by 15 basis points (bps), from 11.91 per cent to 11.76 per cent.
The profit rate on Special Saving Certificates has been significantly reduced by 30bps, bringing it down from 10.90 per cent to 10.60 per cent.
For Islamic Saving Account, the profit rate has been reduced by 59bps, setting the current rate at 9.75 per cent.
The profit on the Shuhada Family Welfare Account has been reduced by 24bps, and the profit on Regular Income Certificates has also been reduced by 20bps.
Earlier in May, the CDNS had reduced rates of return on several National Savings Schemes, with cuts up to 100bps.
The Savings Account rate dropped by 100bps to 9.5 per cent from 10.50 per cent, according to Topline Securities.
Defence Saving Certificates returns fell by 21bps to 11.91 per cent from 12.12 per cent, while Bahbood Savings Certificates declined by 24bps to 13.44 per cent from 13.68 per cent.
Rates for Pensioners Benefit Account and Shuhda Family Welfare Account were also lowered by 24bps each, now standing at 13.44 per cent.
Similarly, Regular Income Certificates returns decreased by 18bps to 11.52 per cent from 11.70 per cent.
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To understand where the measured flux from the planet is coming from we need to capture both reflected and thermal components of the light from the planet. This requires broad wavelength coverage from <0.5 to >1 micron. Predicted planetary reflected signal vs. thermal emission for archetypal planets (letters correspond to planet properties shown in the inset plot) identified by Mayorga et al. (2019). Top: the total planetary flux as measured in flux units. Bottom: the percent contribution of reflected light to the total flux as a function of wavelength (R 300). Colored bands in the top panel show the photometric (hashed) and spectroscopic (solid) coverage from current and future facilities over this wavelength range. Figure courtesy of L. C. Mayorga. — astro-ph.EP
The primary scientific objective of this Habitable Worlds Observatory (HWO) Science Case Development Document (SCDD) is to measure planetary rotation rates of transiting exoplanets to determine the structure, composition, circulation, and aerosol properties of their planetary atmospheres.
For this analysis, HWO would obtain spectroscopic phase curves for planets with orbital periods of 5 – 20+ days, to assess tidal locking radius assumptions. Extending phase curve studies out to longer orbital periods than accessible with current and near-future telescopes will enable detailed investigation of atmospheric structure, composition, and circulation for planets that are much cooler than the more highly irradiated planets accessible with JWST phase curve observations (i.e., Teq < 500 K for HWO versus 1400 K <= Teq <= 2600 K for JWST).
Broad wavelength coverage extending from the UV to the NIR would capture both reflected light and thermal emission, enabling HWO to conduct comprehensive characterization of planetary atmospheres. UV observations would probe high altitudes, thereby providing valuable insights into atmospheric (dis)equilibrium, aerosol properties, and the effects of photochemical processes on atmospheric composition.
We also discuss the role of polarimetry in the classification of aerosols and the associated role they play in the atmospheric energy budget that directly ties them to the chemistry and circulation structure of the atmosphere.
Hannah R. Wakeford, Laura C. Mayorga, Joanna K. Barstow, Natasha E. Batalha, Ludmila Carone, Sarah L. Casewell, Theodora Karalidi, Tiffany Kataria, Erin M. May, Michiel Min
Comments: Towards the Habitable Worlds Observatory: Visionary Science and Transformational Technology SCDD, to be presented at HWO2025 and submitted to Astronomical Society of the Pacific following community comments. Feedback welcomed Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM) Cite as: arXiv:2506.22839 [astro-ph.EP] (or arXiv:2506.22839v1 [astro-ph.EP] for this version) https://doi.org/10.48550/arXiv.2506.22839 Focus to learn more Submission history From: Hannah R Wakeford [v1] Sat, 28 Jun 2025 10:40:20 UTC (1,037 KB) https://arxiv.org/abs/2506.22839 Astrobiology,
CDC On April 1, CDC confirmed one human HPAI A(H5N1) infection in a person with exposure to dairy cows in Texas that were presumed to be infected with the virus. This is thought to be the first instance of likely mammal to human spread of HPAI A(H5N1) virus. In May 2024, CDC began reporting additional, sporadic human cases in people who had exposure to infected dairy cows. That latest human case counts are available at H5N1 Bird Flu: Current Situation Summary.
