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Since 2012, the Curiosity rover has been diligently studying rocky outcrops on Mars, looking for clues about past water, climate, and habitability. Grotzinger et al. describe the analysis of a huge section of sedimentary rocks near Gale crater, where Mount Sharp now stands (see the Perspective by Chan). The features within these sediments are reminiscent of delta, stream, and lake deposits on Earth. Although individual lakes were probably transient, it is likely that there was enough water to fill in low-lying depressions such as impact craters for up to 10,000 years. Wind-driven erosion removed many of these deposits, creating Mount Sharp. Science , this issue p. 10.1126/science.aac7575 , see also p. 167 Mount Sharp now stands where there was once a large intercrater lake system. [Also see Perspective by Chan ] The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp).

The distribution and origin of serpentine on Mars can provide insights into the planet's aqueous history, habitability, and past climate. In this study, we used dynamic aperture factor analysis/target transformation applied to 15,760 images from the Compact Reconnaissance Imaging Spectrometer for Mars, followed by validation with the radiance ratio method, to construct a map of Mg‐serpentine deposits on Mars. Although relatively rare, Mg‐serpentine was detected in diverse geomorphic settings across Noachian and Hesperian‐aged terrains in the southern highlands of Mars, implying that serpentinization was active on early Mars and that multiple formation mechanisms may be needed to explain its spatial distribution. We also calculated the amount of H2 produced during the formation of the observed deposits and conclude that serpentinization was likely more widespread on Mars than indicated by the observed distribution. Plain Language Summary Determining the location and origin of serpentine minerals on Mars can tell us about the past climate and history of water on Mars, as well as its potential to support ancient life. In this study, we used data mining methods to search for Mg‐rich serpentine in 15,760 images from the Compact Reconnaissance Imaging Spectrometer for Mars. Serpentine was detected in a variety of settings within the oldest Martian rocks, implying that serpentinization was active on early Mars. Although Mg‐rich serpentine appears rare on Mars, the formation of serpentine minerals was likely widespread. Key Points Mg‐rich serpentine was identified in 43 Compact Reconnaissance Imaging Spectrometer for Mars images, covering a surface area of ∼1.46 km2 on Mars Serpentine occurs in Noachian‐ and Hesperian‐aged terrains in a variety of geomorphic settings Despite the observed paucity of serpentine on Mars, H2 production rates indicate formation was likely widespread

We use the crystallinity of hydrated silica, represented by the 1.4 μm absorption position in orbiter spectroscopic data, as a proxy for the longevity of water–rock interaction in the Syrtis Major region. Geological maps and crater size–frequency distribution analyses are employed to contextualize mineral detections and estimate surface ages. Hydrated silica is detected within two distinct geological units: a younger “volcanic terrain” (vt) unit (∼2.4 Ga) and an older “highland terrain” (ht) unit (3.5–3.7 Ga). Hydrated silica in the vt unit typically has a band position <1.41 μm, consistent with amorphous opal‐A, suggesting these younger terrains have experienced limited interaction with water. In contrast, hydrated silica in the older highlands typically has a band position >1.41 μm, indicating opal‐CT, suggesting that these deposits have had more time to interact with water, while also producing accessory minerals such as kaolinite and Fe/Mg phyllosilicates. Plain Language Summary This study explores the interactions between water and rocks in a region on Mars known as Syrtis Major by investigating a mineral‐like substance called hydrated silica. The structure of hydrated silica helps us estimate the extent of water interaction and its effects on the rocks. We used satellite data to locate this mineral across Syrtis Major and infer its crystal structure. Furthermore, we developed detailed geological maps and estimated surface ages to understand the geological context. We found that hydrated silica is located in two different types of areas: (a) a younger volcanic region; and (b) an older highland region. In the younger volcanic areas, it appears that less crystalline hydrated silica formed by interaction with small amounts of water, possibly during later volcanic activity. In the older highlands, more crystalline hydrated silica likely interacted with water for a longer duration or in larger amounts. This information aligns with the idea that the older highlands experienced more extensive or long‐lasting interactions with water compared to the younger volcanic regions. It provides insights into different wet periods in Mars' past, aiding our understanding of the planet's geological history and the role water played in shaping its surface. Key Points We analyzed the crystallinity of hydrated silica in Syrtis Major to infer the extent and longevity of water–rock interaction Amorphous silica is found in young volcanic terrains within Nili and Meroe Paterae and more crystalline silica in the older highlands Older highland regions likely underwent a longer interaction with water compared to younger volcanic terrains

The NASA Perseverance rover discovered light-toned float rocks scattered across the surface of Jezero crater that are particularly rich in alumina ( ~ 35 wt% Al 2 O 3 ) and depleted in other major elements (except silica). These unique float rocks have heterogeneous mineralogy ranging from kaolinite/halloysite-bearing in hydrated samples, to spinel-bearing in dehydrated samples also containing a dehydrated Al-rich phase. Here we describe SuperCam and Mastcam-Z observations of the float rocks, including the first in situ identification of kaolinite or halloysite on another planet, and dehydrated phases including spinel and apparent partially dehydroxylated kaolinite. The presence of spinel in these samples is likely detrital in origin, surviving kaolinitization, pointing to an ultramafic origin. However, the association of low hydration with increased Al 2 O 3 abundances suggests heating-induced dehydration which could have occurred during the lithification or impact excavation of these rocks. Given the orbital context of kaolinite-bearing megabreccia in the Jezero crater rim, we propose an origin for these rocks involving intense aqueous alteration of the parent material, followed by dehydration/lithification potentially through impact processes, and dispersion into Jezero crater through flood or impact-related processes. Aqueous alteration followed by dehydration and dispersion into Jezero crater is indicated by the identification of kaolinite or halloysite, spinel and a dehydrated Al-rich phase in spectroscopic observations of light-toned float rocks by the Perseverance rover

Gale crater on Mars was once a lake fed by rivers and groundwater. Hurowitz et al . analyzed 3.5 years of data from the Curiosity rover’s exploration of Gale crater to determine the chemical conditions in the ancient lake. Close to the surface, there were plenty of oxidizing agents and rocks formed from large, dense grains, whereas the deeper layers had more reducing agents and were formed from finer material. This redox stratification led to very different environments in different layers, which provides evidence for Martian climate change. The results will aid our understanding of where and when Mars was once habitable. Science , this issue p. eaah6849 Gale crater on Mars was once a lake that separated into layers with differing chemical conditions. In 2012, NASA’s Curiosity rover landed on Mars to assess its potential as a habitat for past life and investigate the paleoclimate record preserved by sedimentary rocks inside the ~150-kilometer-diameter Gale impact crater. Geological reconstructions from Curiosity rover data have revealed an ancient, habitable lake environment fed by rivers draining into the crater. We synthesize geochemical and mineralogical data from lake-bed mudstones collected during the first 1300 martian solar days of rover operations in Gale. We present evidence for lake redox stratification, established by depth-dependent variations in atmospheric oxidant and dissolved-solute concentrations. Paleoclimate proxy data indicate that a transition from colder to warmer climate conditions is preserved in the stratigraphy. Finally, a late phase of geochemical modification by saline fluids is recognized.

Before the Perseverance rover landing, the acoustic environment of Mars was unknown. Models predicted that: (1) atmospheric turbulence changes at centimetre scales or smaller at the point where molecular viscosity converts kinetic energy into heat1, (2) the speed of sound varies at the surface with frequency2,3 and (3) high-frequency waves are strongly attenuated with distance in CO2 (refs. 2,3,4). However, theoretical models were uncertain because of a lack of experimental data at low pressure and the difficulty to characterize turbulence or attenuation in a closed environment. Here, using Perseverance microphone recordings, we present the first characterization of the acoustic environment on Mars and pressure fluctuations in the audible range and beyond, from 20 Hz to 50 kHz. We find that atmospheric sounds extend measurements of pressure variations down to 1,000 times smaller scales than ever observed before, showing a dissipative regime extending over five orders of magnitude in energy. Using point sources of sound (Ingenuity rotorcraft, laser-induced sparks), we highlight two distinct values for the speed of sound that are about 10 m s−1 apart below and above 240 Hz, a unique characteristic of low-pressure CO2-dominated atmosphere. We also provide the acoustic attenuation with distance above 2 kHz, allowing us to explain the large contribution of the CO2 vibrational relaxation in the audible range. These results establish a ground truth for the modelling of acoustic processes, which is critical for studies in atmospheres such as those of Mars and Venus.

Purpose of review Anxiety is a prevalent mental health condition which manifests as a disproportionate response of fear to a perceived threat. Different types of anxiety disorders vary in their pathophysiology, symptoms and treatments. The causes of anxiety disorders are complex and largely unknown; however, it has been suggested that a number of brain mechanisms and neurotransmitters are involved in the development of these conditions. While there are non-pharmacological treatments for anxiety, many patients are prescribed medications such as selective serotonin reuptake inhibitors, serotonin and noradrenaline reuptake inhibitors and/or benzodiazepines. Unfortunately, these medications have issues with efficacy and safety, and therefore, there is a continuing need for newer medicines. The cannabis constituents of tetrahydrocannabinol (THC), cannabidiol (CBD) and terpenes have been proposed as a potential treatment for anxiety conditions. Recent findings Medicinal cannabis constituents act on the endocannabinoid system (ECS) and other targets. The ECS affects several physiological functions through modulation of the central nervous system and inflammatory pathways. In particular, CBD has been suggested to exhibit anxiolytic properties, whereas THC can either have an anxiogenic or anxiolytic effect, depending on the dose, route of administration and individual genetic and environmental factors. There is also evidence that terpenes could be effective in anxiety management. Summary Currently, there is a gap in the literature as to whether standardised CBD and/or THC preparations can be used for anxiety disorders. Further information is required to know the precise doses and CBD-THC ratios from human clinical trials and real-world patient use.

This review article considers the role of fatty acids and the mutual association of their long-chain (e.g. C18) alkyl and alkenyl groups in some important aspects of papermaking. In particular, published findings suggest that interactions involving fatty acids present as condensed monolayer films can play a controlling role in pitch deposition problems. Self-association among the tails of fatty acids and their soaps also helps to explain some puzzling aspects of hydrophobic sizing of paper. When fatty acids and their soaps are present as monolayers in papermaking systems, the pH values associated with their dissociation, i.e. their pKa values, tend to be strongly shifted. Mutual association also appears to favor non-equilibrium multilayer structures that are tacky and insoluble, possibly serving as a nucleus for deposition of wood extractives, such, as resins and triglyceride fats, in pulp and paper systems.