We present a novel technique for mapping single-phase observations of Cepheids in any given band into their time-averaged values, using strong priors on the known interrelations of the multiwavelength widths of Cepheid period-luminosity (PL) relations, combined with the physical ordering of individual Cepheids within and across the instability strip, as a function of temperature (or radius). The method is empirically calibrated and tested using high-precision published multiwavelength observations of Cepheids in the LMC. The example, given herein, takes a single-epoch B-band PL relation and transforms those random-phase observations to within +/- 0.05-0.06 mag of their time-averaged values. For high-precision single-phase data points, this method can transform single-phase magnitudes into mean magnitudes (without additional observations), bringing the statistical error budget for the PL relation at that wavelength down to the systematic floor. This technique is of particular importance for use with space-based facilities (e.g., Hubble Space Telescope or JWST) where limits on the availability of telescope time preclude dense phase coverage, often resulting in only single-epoch observations being available.

We use SEDz*-a code designed to chart the star formation histories (SFHs) of 6 < z < 12 galaxies-to analyze the spectral energy distributions (SEDs) of 894 galaxies with deep JWST/NIRCam imaging by JADES in the GOODS-S field. We show how SEDz* matches observed SEDs using stellar-population templates, graphing the contribution of each epoch by epoch to confirm the robustness of the technique. Very good SED fits for most SFHs demonstrate the compatibility of the templates with stars in the first galaxies-as expected, because their light is primarily from main-sequence A stars, free of post-main-sequence complexity, and insensitive to heavy-element compositions. We confirm earlier results from Dressler et al. (1) There are four types of SFHs: SFH1, burst; SFH2, stochastic; SFH3, "contiguous" (three epochs), and SFH4, "continuous" (four to six epochs). (2) Starbursts-both single and multiple-are predominant (similar to 70%) in this critical period of cosmic history, although longer SFHs (0.5-1.0 Gyr) contribute one-third of the accumulated stellar mass. These 894 SFHs contribute 10(11.14), 10(11.09), 10(11.00), and 10(10.60)M(circle dot) for SFH1-4, respectively, adding up to similar to 4 x 10(11)M(circle dot) by z = 6 for this field. We suggest that the absence of rising SFHs could be explained as an intense dust-enshrouded phase of star formation lasting tens of Myr that preceded each of the SFHs we measure. We find no strong dependencies of SFH type with the large-scale environment; however, the discovery of a compact group of 30 galaxies, 11 of which had first star formation at z = 11-12, suggests that long SFHs could dominate in rare, dense environments.

The abundance of H in planetary building blocks is of fundamental importance for constraining the evolution of the terrestrial planets. It is commonly assumed that chondrites are the principal sources of Earth's H; however, recent studies have suggested that primitive achondrites and achondrites may retain a small complement of H. There are few constraints on the H budgets of primitive achondrites, which represent the transition from unmelted to melted planetesimals, but prior work suggests that bulk parent body H contents are several orders of magnitude lower than typical chondritic values. Therefore, to provide further constraints on H retention during the transition from unmelted to melted planetesimals, we have measured the H contents of olivine, orthopyroxene, clinopyroxene, and plagioclase from a suite of acapulcoite-lodranite clan meteorites. Acapulcoitelodranite clan meteorites represent the "prototypical" primitive achondrite parent body and have bulk major element compositions more akin to the Earth than previously studied primitive achondrites (e.g., the ureilites). We find that the H2O contents of olivine (-5-12 mu g/g H2O), orthopyroxene (-3-10 mu g/g H2O), and clinopyroxene (-5-8 mu g/g H2O) are broadly similar, while plagioclase (-2.5-5 mu g/g H2O) tends to be offset to lower values. Using a simple, single -stage batch -melting model, we calculate a preferred maximum acapulcoitelodranite parent body H2O content of 38 mu g/g, which is similar to other estimates for primitive achondritic and achondritic parent bodies. Furthermore, assuming chondrite-like precursor materials, our data are consistent with efficient loss of H prior to or during the onset of melting of early -formed planetesimals. This requires that Earth's H -budget was dominated by building blocks that underwent minimal thermal processing.