We present the first set of trans-Neptunian objects (TNOs) observed on multiple nights in data taken from the DECam Ecliptic Exploration Project. Of these 110 TNOs, 105 do not coincide with previously known TNOs and appear to be new discoveries. Each individual detection for our objects resulted from a digital tracking search at TNO rates of motion, using two-to-four-hour exposure sets, and the detections were subsequently linked across multiple observing seasons. This procedure allows us to find objects with magnitudes m VR approximate to 26. The object discovery processing also included a comprehensive population of objects injected into the images, with a recovery and linking rate of at least 94%. The final orbits were obtained using a specialized orbit-fitting procedure that accounts for the positional errors derived from the digital tracking procedure. Our results include robust orbits and magnitudes for classical TNOs with absolute magnitudes H similar to 10, as well as a dynamically detached object found at 76 au (semimajor axis a approximate to 77 au). We find a disagreement between our population of classical TNOs and the CFEPS-L7 three-component model for the Kuiper Belt.

We present the methods and results from the discovery and photometric measurement of 26 bright VR > 24 trans-Neptunian objects (TNOs) during the first year (2019-20) of the DECam Ecliptic Exploration Project (DEEP). The DEEP survey is an observational TNO survey with wide sky coverage, high sensitivity, and a fast photometric cadence. We apply a computer vision technique known as a progressive probabilistic Hough transform to identify linearly moving transient sources within DEEP photometric catalogs. After subsequent visual vetting, we provide a photometric and astrometric catalog of our TNOs. By modeling the partial lightcurve amplitude distribution of the DEEP TNOs using Monte Carlo techniques, we find our data to be most consistent with an average TNO axis ratio b/a < 0.5, implying a population dominated by non-spherical objects. Based on ellipsoidal gravitational stability arguments, we find our data to be consistent with a TNO population containing a high fraction of contact binaries or other extremely non-spherical objects. We also discuss our data as evidence that the expected binarity fraction of TNOs may be size-dependent.

We present the DECam Ecliptic Exploration Project (DEEP) survey strategy, including observing cadence for orbit determination, exposure times, field pointings and filter choices. The overall goal of the survey is to discover and characterize the orbits of a few thousand Trans-Neptunian objects (TNOs) using the Dark Energy Camera (DECam) on the Cerro Tololo Inter-American Observatory Blanco 4 m telescope. The experiment is designed to collect a very deep series of exposures totaling a few hours on sky for each of several 2.7 square degree DECam fields-of-view to achieve approximate depths of magnitude 26.2 using a wide V R filter that encompasses both the V and R bandpasses. In the first year, several nights were combined to achieve a sky area of about 34 square degrees. In subsequent years, the fields have been re-visited to allow TNOs to be tracked for orbit determination. When complete, DEEP will be the largest survey of the outer solar system ever undertaken in terms of newly discovered object numbers, and the most prolific at producing multiyear orbital information for the population of minor planets beyond Neptune at 30 au.

We present here the DECam Ecliptic Exploration Project (DEEP), a 3 yr NOAO/NOIRLab Survey that was allocated 46.5 nights to discover and measure the properties of thousands of trans-Neptunian objects (TNOs) to magnitudes as faint as VR similar to 27 mag, corresponding to sizes as small as 20 km diameter. In this paper we present the science goals of this project, the experimental design of our survey, and a technical demonstration of our approach. The core of our project is "digital tracking," in which all collected images are combined at a range of motion vectors to detect unknown TNOs that are fainter than the single exposure depth of VR similar to 23 mag. Through this approach, we reach a depth that is approximately 2.5 mag fainter than the standard LSST "wide fast deep" nominal survey depth of 24.5 mag. DEEP will more than double the number of known TNOs with observational arcs of 24 hr or more, and increase by a factor of 10 or more the number of known small (<50 km) TNOs. We also describe our ancillary science goals, including measuring the mean shape distribution of very small main-belt asteroids, and briefly outline a set of forthcoming papers that present further aspects of and preliminary results from the DEEP program.

We present a detailed study of the observational biases of the DECam Ecliptic Exploration Project's B1 data release and survey simulation software that enables direct statistical comparisons between models and our data. We inject a synthetic population of objects into the images, and then subsequently recover them in the same processing as our real detections. This enables us to characterize the survey's completeness as a function of apparent magnitudes and on-sky rates of motion. We study the statistically optimal functional form for the magnitude, and develop a methodology that can estimate the magnitude and rate efficiencies for all survey's pointing groups simultaneously. We have determined that our peak completeness is on average 80% in each pointing group, and our magnitude drops to 25% of this value at m(25) = 26.22. We describe the freely available survey simulation software and its methodology. We conclude by using it to infer that our effective search area for objects at 40 au is 14.8 deg(2), and that our lack of dynamically cold distant objects means that there at most 8 x 10(3) objects with 60 < a < 80 au and absolute magnitudes H <= 8.

The search for habitable environments and biomarkers in exoplanetary atmospheres is the holy grail of exoplanet science. The detection of atmospheric signatures of habitable Earth-like exoplanets is challenging owing to their small planet-star size contrast and thin atmospheres with high mean molecular weight. Recently, a new class of habitable exoplanets, called Hycean worlds, has been proposed, defined as temperate ocean-covered worlds with H2-rich atmospheres. Their large sizes and extended atmospheres, compared to rocky planets of the same mass, make Hycean worlds significantly more accessible to atmospheric spectroscopy with JWST. Here we report a transmission spectrum of the candidate Hycean world K2-18 b, observed with the JWST NIRISS and NIRSpec instruments in the 0.9-5.2 mu m range. The spectrum reveals strong detections of methane (CH4) and carbon dioxide (CO2) at 5 sigma and 3 sigma confidence, respectively, with high volume mixing ratios of similar to 1% each in a H2-rich atmosphere. The abundant CH4 and CO2, along with the nondetection of ammonia (NH3), are consistent with chemical predictions for an ocean under a temperate H2-rich atmosphere on K2-18 b. The spectrum also suggests potential signs of dimethyl sulfide (DMS), which has been predicted to be an observable biomarker in Hycean worlds, motivating considerations of possible biological activity on the planet. The detection of CH4 resolves the long-standing missing methane problem for temperate exoplanets and the degeneracy in the atmospheric composition of K2-18 b from previous observations. We discuss possible implications of the findings, open questions, and future observations to explore this new regime in the search for life elsewhere.

As basaltic rocks formed at the base of the oceanic floor are transported back to the Earth's mantle along sub-duction zones, they undergo transitions and introduce compositional and thermal heterogeneities in the deeper parts of the mantle. Studying the melting phase relations of basaltic lithologies at elevated pressures and tem-peratures provides insights into what potentially happens at different depths in the lower mantle now and throughout the past billion years of active plate tectonics. Using laser heated - diamond anvil cell experiments combined with in situ X-Ray Diffraction measurements at synchrotron sources, we revisit the crystallization and melting properties of natural basaltic samples at 60-100 GPa and up to 4000 K. Diffraction patterns highlight the major phases: bridgmanite and Ca-perovskite, followed by crystallization of Si-rich phases (mainly stishovite) and Calcium Ferrite (CF-type) Na and Al-rich phase. Recovered samples were prepared using focused ion beam techniques for detailed chemical analyses of the extracted thin sections by electron microscopies in order to resolve sub-micron features and understand the chemical partitioning of elements induced by melting at high pressure and temperature conditions. We confirm that the liquidus phase is Ca-perovskite, which segregates during melting and is recovered as rings that encapsulate a melt pool throughout the studied pressure range. The melt pocket shows a concentric structure consisting of an alumino-silicate envelope surrounding an Fe-rich silicate part. At the center of samples, an Fe-O-S metal pond is often observed. We associate the observation of segregation of liquid phases to capillary forces. The differentiation of melt pockets into three melts is tenta-tively attributed to Marangoni effects, i.e. temperature-induced surface tension gradients in the samples. Central metal ponds are indirectly best interpreted as related to the disproportionation reaction of Fe2+ into Fe3+ and Fe(0) in bridgmanite whereas the two silicate-melt pools could be associated to the formation of two immiscible liquids upon melting of basalts. On the basis of these observations, we propose that melting of basaltic lithologies at lower mantle pressures could lead to important chemical differentiation mostly characterized by Fe enrich-ment at increasing depth.

In this study, we investigated phase transformations of CaTiO3 perovskite using x-ray diffraction at high pressure and high temperature up to 170 GPa and 4500 K in a laser-heated diamond-anvil cell. We report a high-pressure dissociation of CaTiO3 into CaO-B2 and CaTi2O5 with a monoclinic P2/m structure, instead of the expected transformation of the orthorhombic distorted perovskite structure into a post-perovskite phase. We propose that this transition may be favored by the B1 to B2 phase change of CaO at around 60 GPa. In order to provide additional information on the high pressure properties of CaTiO3 perovskite, we measured its melting temper-ature using CO2 laser heated diamond anvil cell up to 55 GPa yielding a fit of the melting curve to a Kraut-Kennedy empirical law according to: Tm (K) = 2188 * [1 + 4.23 * (Delta V/V0)]. To provide some further insight into the thermodynamic properties of CaTiO3, we determined the P-V-T equation of state of the orthorhombic mineral perovskite, fitted by using a third order Birch-Murnaghan equation of state and a Berman thermal expansion model. The fit of the data yields to K0 = 180.6(4) GPa, K ' 0 = 4 (fixed), partial differential K/ partial differential T =-0.022(1) GPa K-1, alpha 1 = 3.25(5) x 10-5 K-1, alpha 2 = 1.3(1) x 10-8 K-2