The Perseverance rover landed in Jezero crater on Mars, which once contained a lake of liquid water. We report the rock properties encountered by Perseverance during a 10-kilometer traverse extending over 400 meters in elevation, from beneath Jezero's western sedimentary fan to the upper crater rim. These rocks consist of coarse-grained olivine, magnesium and iron carbonates, silica, and phyllosilicates, including some of the oldest materials exposed within Jezero. We infer that these rocks formed by olivine accumulation in an igneous system of layered intrusions, followed by exposure to water and carbon dioxide, which caused extensive carbonation of the silicate minerals. Aqueous alteration was more pronounced at lower elevations. Higher-elevation exposures on the crater rim appear similar to olivine-rich rocks distributed over the wider Nili Fossae region.
Producing stable 58Ni in Type Ia supernovae (SNe Ia) requires sufficiently high-density conditions that are not predicted for all origin scenarios, so examining the distribution of 58Ni using the near-infrared (NIR) [Ni II] 1.939 mu m line may observationally distinguish between possible progenitors and explosion mechanisms. We present 79 telluric-corrected NIR spectra of 22 low-redshift SNe Ia from the Carnegie Supernova Project-II, ranging from +50 to +505 days, including 31 previously unpublished spectra. We introduce the Gaussian Peak Ratio, a detection parameter that confirms the presence of the NIR [Ni II] 1.939 mu m line in eight SNe in our sample. Nondetections occur at earlier phases (<=+100 days) when the NIR Ni line has not emerged yet or in low signal-to-noise spectra, yielding inconclusive results. Subluminous 86G-like SNe Ia show the earliest NIR Ni features around similar to+50 days, whereas normal-bright SNe Ia do not exhibit NIR Ni until similar to+150 days. NIR Ni features detected in our sample have low peak velocities (v similar to 1200 km s-1) and narrow line widths (<= 3500 km s-1), indicating stable 58Ni is centrally located. This implies high-density burning conditions in the innermost regions of SNe Ia and could be due to higher mass progenitors (i.e., near-Mch). NIR spectra of the nearly two dozen SNe Ia in our sample are compared to various model predictions and paired with early-time properties to identify ideal observation windows for future SNe Ia discovered by upcoming surveys with Rubin-LSST or the Roman Space Telescope.
In Earth’s deepest mantle (D″), shear wave speeds can vary with propagation and vibration direction of the wave because of convection-driven mantle deformation, a phenomenon known as seismic anisotropy. Although D″ anisotropy has been mapped globally at long wavelengths (>4000 km laterally) in tomographic inversions, models exhibit disagreements at smaller scales (100s to 1000s of kilometers). Here, we present 70,000 differential splitting SKS-SKKS and PKS–SKKS measurements from a global seismic dataset that samples nearly 75% of Earth’s D″ layer, predominantly in the highest seismic wave speed regions. Anisotropy is found in about two-thirds of our sampled area, almost tripling the area where seismic anisotropy has been investigated at short wavelengths. Although the overall distribution is complex, lowermost mantle deformation is frequently detected in locations associated with putative deeply subducted slabs, thereby linking D″ deformation processes to the subduction of tectonic plates. In these colder, slab-dominated regions, the observed pervasive seismic anisotropy is consistent with the crystallographic preferred orientation of postperovskite as a significant contributor.
Martian fluvial valleys provide evidence for the surface flow of liquid water, making them a key target for rover-based investigations of ancient habitability. The Mars 2020 Perseverance rover spent similar to 85 sols exploring the Bright Angel formation, exposed across the floor of Neretva Vallis: the western inlet channel of Jezero crater. This study documents the sedimentology and stratigraphy of the Bright Angel formation to reconstruct its depositional setting. The unit preserves a concave-up bedding structure consistent with a young channel-fill deposit, rather than an older unit exposed by incision of Neretva Vallis. The lower stratigraphy displays a fining-up sequence from coarse-grained sediments up to pebble-conglomerates (the Tuff Cliff member) into a >= 10-m-thick succession of laminated mudstone (the Walhalla Glades member), interpreted as a transgressive sequence recording the onset of lacustrine conditions in Neretva Vallis. Lenses of matrix-supported granule-conglomerate adjacent to the valley wall (the Fern Glen Rapids member) may preserve locally derived debris flows entering the lake. These are overlain by a polymict, matrix-supported, boulder-conglomerate (the Mount Spoonhead member), interpreted as a high-energy debrite derived from the watershed. The sequence is capped by cross-stratified sediments (the Serpentine Rapids member), preserving lake margin deposits. The Bright Angel lacustrine sequence occurs similar to 10-50 m higher in elevation than the lake level anticipated for the Jezero western delta, requiring an additional period of lacustrine activity. The structure and spatial distribution of the unit leads us to propose that a late-stage blockage of Neretva Vallis may have facilitated the formation of a perched, valley-confined lake upstream.
Reliable knowledge of the crustal properties beneath the North Anatolian fault (NAF), seismically silent for more than 250 years beneath the Marmara Sea (MS), is crucial for understanding seismic hazard and mitigating the potential for disaster on an enormous scale. In the present work, the first three-dimensional inverse modeling performed on a magnetotelluric dataset of the MS has unveiled localized weak and locked fault segments along this shear deformation zone. Low-resistivity regions along the northern branch of the NAF beneath the Central and Çınarcık-Imralı basins are likely attributed to the presence of fluids, which may represent a fault zone conductor in a fractured zone and can explain the densely populated microseismicity. These low-resistivity anomalies surrounded by higher resistivity structures imply that the segmented, multi-branched NAF system extends beneath the MS, following the Intra-Pontide suture zone. The resistive anomalies, between the Central and Çınarcık basins, along with those at the western and eastern extremities of the MS, presumably signify regions of stress accumulation, shedding light on the ongoing processes of fault mechanics at play in this critical region.
