The solar photosphere is depleted in refractory elements compared to most solar twins, with the degree of depletion increasing with an element's condensation temperature. Here, I show that adding 4 Earth masses of Earth-like and carbonaceous-chondrite-like material to the solar convection zone brings the Sun's composition into line with the mean value for the solar twins. The observed solar composition could have arisen if the Sun's convection zone accreted material from the solar nebula that was depleted in refractory elements due to the formation of the terrestrial planets and ejection of rocky protoplanets from the asteroid belt. Most solar analogs are missing 0-10 Earth masses of rocky material compared to the most refractory-rich stars, providing an upper limit to the mass of rocky terrestrial planets that they possess. The missing mass is correlated with stellar metallicity. This suggests that the efficiency of planetesimal formation increases with stellar metallicity. Stars with and without known giant planets show a similar distribution of abundance trends. If refractory depletion is a signature of the presence of terrestrial planets, this suggests that there is not a strong correlation between the presence of terrestrial and giant planets in the same system.

We report five new transit epochs of the extrasolar planet OGLE-TR-111b, observed in the v-HIGH and Bessell I bands with the FORS1 and FORS2 at the ESO Very Large Telescope between 2008 April and May. The new transits have been combined with all previously published transit data for this planet to provide a new transit timing variations (TTVs) analysis of its orbit. We find no TTVs with amplitudes larger than 1.5 minutes over a four-year observation time baseline, in agreement with the recent result by Adams et al. Dynamical simulations fully exclude the presence of additional planets in the system with masses greater than 1.3, 0.4, and 0.5 M-circle plus at the 3: 2, 1: 2, and 2:1 resonances, respectively. We also place an upper limit of about 30 M-circle plus on the mass of potential second planets in the region between the 3:2 and 1:2 mean-motion resonances.

We numerically explore the obliquity (axial tilt) variations of a hypothetical moonless Earth. Previous work has shown that the Earth's Moon stabilizes Earth's obliquity such that it remains within a narrow range, between 22.1 degrees and 24.5 degrees. Without lunar influence, a frequency map analysis by Laskar et al. (Laskar, J., Joutel, F., Robutel, P. [1993]. Nature 361, 615-617) showed that the obliquity could vary between 0 degrees and 85 degrees. This has left an impression in the astrobiology community that a big moon is necessary to maintain a habitable climate on an Earth-like planet. Using a modified version of the orbital integrator mercury, we calculate the obliquity evolution for moonless Earths with various initial conditions for up to 4 Gyr. We find that while obliquity varies significantly more than that of the actual Earth over 100,000 year timescales, the obliquity remains within a constrained range, typically 20-25 degrees in extent, for timescales of hundreds of millions of years. None of our Solar System integrations in which planetary orbits behave in a typical manner show obliquity accessing more than 65% of the full range allowed by frequency-map analysis. The obliquities of moonless Earths that rotate in the retrograde direction are more stable than those of prograde rotators. The total obliquity range explored for moonless Earths with rotation periods less than 12 h is much less than that for slower-rotating moonless Earths. A large moon thus does not seem to be needed to stabilize the obliquity of an Earth-like planet on timescales relevant to the development of advanced life. (C) 2011 Elsevier Inc. All rights reserved.

We analyze new/archival VLT/NaCo and Gemini/NICI high-contrast imaging of the young, self-luminous planet beta Pictoris b in seven near-to-mid IR photometric filters, using advanced image processing methods to achieve high signal-to-noise, high precision measurements. While beta Pic b's near-IR colors mimic those of a standard, cloudy early-to-mid L dwarf, it is overluminous in the mid-infrared compared to the field L/T dwarf sequence. Few substellar/planet-mass objects-i.e., kappa And b and 1RXJ 1609B-match beta Pic b's JHK(s)L' photometry and its 3.1 mu m and 5 mu m photometry are particularly difficult to reproduce. Atmosphere models adopting cloud prescriptions and large (similar to 60 mu m) dust grains fail to reproduce the beta Pic b spectrum. However, models incorporating thick clouds similar to those found for HR 8799 bcde, but also with small (a few microns) modal particle sizes, yield fits consistent with the data within the uncertainties. Assuming solar abundance models, thick clouds, and small dust particles (< a > = 4 mu m), we derive atmosphere parameters of log(g) = 3.8 +/- 0.2 and T-eff = 1575-1650 K, an inferred mass of 7(-3)(+4) M-J, and a luminosity of log(L/L-circle dot) similar to -3.80 +/- 0.02. The best-estimated planet radius, approximate to 1.65 +/- 0.06 R-J, is near the upper end of allowable planet radii for hot-start models given the host star's age and likely reflects challenges constructing accurate atmospheric models. Alternatively, these radii are comfortably consistent with hot-start model predictions if beta Pic b is younger than approximate to 7 Myr, consistent with a late formation well after its host star's birth similar to 12(-4)(+8) Myr ago.

Indigenous crops, commonly known as orphan, forgotten, or neglected crops, are understudied, but have important roles in the diet and economy of the communities that cultivate them. Here, we review po-tential benefits of Indigenous crop research and highlight the impor-tance of an anticolonial framework to prevent exploitation of these unique resources.

Microbes are found in nearly every habitat and organism on the planet, where they are critical to host health, fitness, and metabolism. In most organisms, few microbes are inherited at birth; instead, acquiring microbiomes generally involves complicated interactions between the environment, hosts, and symbionts. Despite the criticality of microbiome acquisition, we know little about where hosts' microbes reside when not in or on hosts of interest. Because microbes span a continuum ranging from generalists associating with multiple hosts and habitats to specialists with narrower host ranges, identifying potential sources of microbial diversity that can contribute to the microbiomes of unrelated hosts is a gap in our understanding of microbiome assembly. Microbial dispersal attenuates with distance, so identifying sources and sinks requires data from microbiomes that are contemporary and near enough for potential microbial transmission. Here, we characterize microbiomes across adjacent terrestrial and aquatic hosts and habitats throughout an entire watershed, showing that the most species-poor microbiomes are partial subsets of the most species-rich and that microbiomes of plants and animals are nested within those of their environments. Furthermore, we show that the host and habitat range of a microbe within a single ecosystem predicts its global distribution, a relationship with implications for global microbial assembly processes. Thus, the tendency for microbes to occupy multiple habitats and unrelated hosts enables persistent microbiomes, even when host populations are disjunct. Our whole-watershed census demonstrates how a nested distribution of microbes, following the trophic hierarchies of hosts, can shape microbial acquisition.

The Sample Analysis at Mars (SAM) suite instrument on board NASA's Curiosity rover has characterized the inorganic and organic chemical composition of seven samples from the Glen Torridon (GT) clay-bearing unit. A variety of organic molecules were detected with SAM using pyrolysis (up to similar to 850 degrees C) and wet chemistry experiments coupled with evolved gas analysis (EGA) and gas chromatography-mass spectrometry. SAM EGA and GCMS analyses revealed a greater diversity and abundance of sulfur-bearing aliphatic and aromatic organic compounds in the sediments of this Gale crater unit than earlier in the mission. We also report the detection of nitrogen-containing, oxygen-containing, and chlorine-containing molecules, as well as polycyclic aromatic hydrocarbons found in GT, although the sources of some of these organics may be related to the presence of chemical reagents in the SAM instrument background. However, sulfur-bearing organics released at high temperature (>= 600 degrees C) are likely derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources and consistent with the presence of recalcitrant organic materials in the sample. The SAM measurements of the GT clay-bearing unit expand the inventory of organic matter present in Gale crater and is also consistent with the hypothesis that clay minerals played an important role in the preservation of ancient refractory organic matter on Mars. These findings deepen our understanding of the past habitability and biological potential of Gale crater.

The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater's sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Seitah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide-rich water under water-poor conditions. Overlying Seitah is a unit informally named Maaz, which we interpret as lava flows or the chemical complement to Seitah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks have been stored aboard Perseverance for potential return to Earth.

The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigated the petrology of olivine and carbonate-bearing rocks of the Seitah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the Perseverance rover, we performed a petrographic analysis of the Bastide and Brac outcrops within this unit. We found that these outcrops are composed of igneous rock, moderately altered by aqueous fluid. The igneous rocks are mainly made of coarse-grained olivine, similar to some martian meteorites. We interpret them as an olivine cumulate, formed by settling and enrichment of olivine through multistage cooling of a thick magma body.