The heat extracted from the core by the overlying mantle across the core-mantle boundary controls the thermal evolution of the core. This in turn leads to the solidification of the inner core in association with the exsolution of light alloying elements into the liquid outer core. Although the temperature (T) at the inner core boundary (ICB) would be adjusted to account for the effects of the light elements, the melting T of Fe places an upper bound at the ICB and it is a vital point in the thermal profile of the core. Here, we determine the melting T of Fe in the multi-anvil press by characterizing the interface of Fe-W interaction. Our data place a tighter constraint on the melting curve of Fe between 8 and 21 GPa, that is directly applicable to small planetary bodies and serves as an anchor for melting curve of Fe at higher pressure.

We have studied cubanite, CuFe2S3 (orthorhombic, space group Pcmn, a = 6.46, b = 11.10, c = 6.22 angstrom), using single-crystal X-ray diffraction in a diamond-anvil cell at room temperature from 0 to 3.68 GPa. Refinements were performed at 0, 1.76, and 3.59 GPa, and cell parameters were measured at 20 pressures up to 3.68 GPa. The linear compressibilities of the a, b, and c crystal axes are 0.00513(5), 0.00479(5), and 0.00575(4) GPa-1, respectively. Compressibility data were fitted to a Birch-Murnaghan equation of state with parameters K0 = 55.3 +/- 1.7 GPa with K0' constrained to be 4. High-pressure refinement data indicate that the principal response of the crystal structure to compression is a reduction in Cu-S bond lengths, whereas Fe-S bond lengths remain essentially unchanged. Results are compared to bulk moduli and polyhedral bulk moduli of other sulfides.

Collocated crystal sizes and mineral identities are critical for interpreting textural relationships in rocks and testing geological hypotheses, but it has been previously impossible to unambiguously constrain these properties using in situ instruments on Mars rovers. Here, we demonstrate that diffracted and fluoresced x-rays detected by the PIXL instrument (an x-ray fluorescence microscope on the Perseverance rover) provide information about the presence or absence of coherent crystalline domains in various minerals. X-ray analysis and multispectral imaging of rocks from the Seitah formation on the floor of Jezero crater shows that they were emplaced as coarsely crystalline igneous phases. Olivine grains were then partially dissolved and filled by finely crystalline or amorphous secondary silicate, carbonate, sulfate, and chloride/oxychlorine minerals. These results support the hypothesis that Seitah formation rocks represent olivine cumulates altered by fluids far from chemical equilibrium at low water-rock ratios.

Rain-fed agricultural systems, which solely depend on green water (i.e. soil moisture from rainfall), sustain 60% of global food production and are particularly vulnerable to vagaries in temperature and precipitation patterns, which are intensifying due to climate change. Here, using projections of crop water demand and green water availability under warming scenarios, we assess global agricultural green water scarcity-defined when the rainfall regime is unable to meet crop water requirements. With present-day climate conditions, food production for 890 million people is lost because of green water scarcity. Under 1.5°C and 3°C warming-the global warming projected from the current climate targets and business as usual policies-green water scarcity will affect global crop production for 1.23 and 1.45 billion people, respectively. If adaptation strategies were to be adopted to retain more green water in the soil and reduce evaporation, we find that food production loss from green water scarcity would decrease to 780 million people. Our results show that appropriate green water management strategies have the potential to adapt agriculture to green water scarcity and promote global food security.

Encryption makes information available only to those with the decoding key. We propose that microbes, living in a chemical environment, encrypt nutrients, thereby making them available only to those with the decoding enzymes, such as their kin. Examples of encrypted nutrients include cobamides, which are expensive to make and valuable for microbial fitness. Furthermore, we propose that hosts encrypt nutrients to encourage desirable colonizers. For instance, plant root exudates and breast milk oligo-saccharides encourage beneficial microbes.