Project description:The Moon has a magmatic and thermal history that is distinct from that of the terrestrial planets1. Radioisotope dating of lunar samples suggests that most lunar basaltic magmatism ceased by around 2.9-2.8 billion years ago (Ga)2,3, although younger basalts between 3 Ga and 1 Ga have been suggested by crater-counting chronology, which has large uncertainties owing to the lack of returned samples for calibration4,5. Here we report a precise lead-lead age of 2,030 ± 4 million years ago for basalt clasts returned by the Chang'e-5 mission, and a 238U/204Pb ratio (µ value)6 of about 680 for a source that evolved through two stages of differentiation. This is the youngest crystallization age reported so far for lunar basalts by radiometric dating, extending the duration of lunar volcanism by approximately 800-900 million years. The µ value of the Chang'e-5 basalt mantle source is within the range of low-titanium and high-titanium basalts from Apollo sites (µ value of about 300-1,000), but notably lower than those of potassium, rare-earth elements and phosphorus (KREEP) and high-aluminium basalts7 (µ value of about 2,600-3,700), indicating that the Chang'e-5 basalts were produced by melting of a KREEP-poor source. This age provides a pivotal calibration point for crater-counting chronology in the inner Solar System and provides insight on the volcanic and thermal history of the Moon.
Project description:The distribution range, time-varying characteristics, and sources of lunar water are still controversial. Here we show the Chang'E-5 in-situ spectral observations of lunar water under Earth's magnetosphere shielding and relatively high temperatures. Our results show the hydroxyl contents of lunar soils in Chang'E-5 landing site are with a mean value of 28.5 ppm, which is on the weak end of lunar hydration features. This is consistent with the predictions from remote sensing and ground-based telescopic data. Laboratory analysis of the Chang'E-5 returned samples also provide critical clues to the possible sources of these hydroxyl contents. Much less agglutinate glass contents suggest a weak contribution of solar wind implantation. Besides, the apatite present in the samples can provide hydroxyl contents in the range of 0 to 179 ± 13 ppm, which shows compelling evidence that, the hydroxyl-containing apatite may be an important source for the excess hydroxyl observed at this young mare region.
Project description:KREEP materials were thought to be last crystallized at the lunar crust and mantle boundary. Impact cratering and volcanism are mainly responsible for their distributions on the lunar surface. Therefore, observation of global KREEP materials and investigation of distributions in the areas of large basins are of critical importance to understand the geologic history of the Moon. Here we report the new global potassium distribution on the Moon detected by Chang'E-2 Gamma-ray Spectrometer. We found that our new measurements are in general agreement with previous observation. A new finding and an important difference is that relatively higher K abundances in the Mare Crisium and Mare Orientale than their surrounding rims were detected for the first time. In light of our observations in these two areas, we propose that Crisium and Orientale basin-forming impact events may have penetrated to the lower crust and excavate the deeper materials to the lunar surface.
Project description:The Apollo-derived tenet of an anhydrous Moon has been contested following measurement of water in several lunar samples that require water to be present in the lunar interior. However, significant uncertainties exist regarding the flux, sources and timing of water delivery to the Moon. Here we address those fundamental issues by constraining the mass of water accreted to the Moon and modelling the relative proportions of asteroidal and cometary sources for water that are consistent with measured isotopic compositions of lunar samples. We determine that a combination of carbonaceous chondrite-type materials were responsible for the majority of water (and nitrogen) delivered to the Earth-Moon system. Crucially, we conclude that comets containing water enriched in deuterium contributed significantly <20% of the water in the Moon. Therefore, our work places important constraints on the types of objects impacting the Moon ∼4.5-4.3 billion years ago and on the origin of water in the inner Solar System.
Project description:Water and/or hydroxyl detected remotely on the lunar surface originates from several sources: (i) comets and other exogenous debris; (ii) solar-wind implantation; (iii) the lunar interior. While each of these sources is interesting in its own right, distinguishing among them is critical for testing hypotheses for the origin and evolution of the Moon and our Solar System. Existing spacecraft observations are not of high enough spectral resolution to uniquely characterize the bonding energies of the hydroxyl molecules that have been detected. Nevertheless, the spatial distribution and associations of H, OH- or H2O with specific lunar lithologies provide some insight into the origin of lunar hydrous materials. The global distribution of OH-/H2O as detected using infrared spectroscopic measurements from orbit is here examined, with particular focus on regional geological features that exhibit OH-/H2O absorption band strengths that differ from their immediate surroundings.This article is part of the themed issue 'The origin, history and role of water in the evolution of the inner Solar System'.
Project description:A new thermal correction model and experimentally validated relationships between absorption strength and water content have been used to construct the first global quantitative maps of lunar surface water derived from the Moon Mineralogy Mapper near-infrared reflectance data. We find that OH abundance increases as a function of latitude, approaching values of ~500 to 750 parts per million (ppm). Water content also increases with the degree of space weathering, consistent with the preferential retention of water originating from solar wind implantation during agglutinate formation. Anomalously high water contents indicative of interior magmatic sources are observed in several locations, but there is no global correlation between surface composition and water content. Surface water abundance can vary by ~200 ppm over a lunar day, and the upper meter of regolith may contain a total of ~1.2 × 1014 g of water averaged over the globe. Formation and migration of water toward cold traps may thus be a continuous process on the Moon and other airless bodies.
Project description:Lander-Waterman's coverage bound establishes the total number of reads required to cover the whole genome of size G bases. In fact, their bound is a direct consequence of the well-known solution to the coupon collector's problem which proves that for such genome, the total number of bases to be sequenced should be O(G ln G). Although the result leads to a tight bound, it is based on a tacit assumption that the set of reads are first collected through a sequencing process and then are processed through a computation process, i.e., there are two different machines: one for sequencing and one for processing. In this paper, we present a significant improvement compared to Lander-Waterman's result and prove that by combining the sequencing and computing processes, one can re-sequence the whole genome with as low as O(G) sequenced bases in total. Our approach also dramatically reduces the required computational power for the combined process. Simulation results are performed on real genomes with different sequencing error rates. The results support our theory predicting the log G improvement on coverage bound and corresponding reduction in the total number of bases required to be sequenced.
Project description:Our Moon periodically moves through the magnetic tail of the Earth that contains terrestrial ions of hydrogen and oxygen. A possible density contrast might have been discovered that could be consistent with the presence of water phase of potential terrestrial origin. Using novel gravity aspects (descriptors) derived from harmonic potential coefficients of gravity field of the Moon, we discovered gravity strike angle anomalies that point to water phase locations in the polar regions of the Moon. Our analysis suggests that impact cratering processes were responsible for specific pore space network that were subsequently filled with the water phase filling volumes of permafrost in the lunar subsurface. In this work, we suggest the accumulation of up to ~ 3000 km3 of terrestrial water phase (Earth's atmospheric escape) now filling the pore spaced regolith, portion of which is distributed along impact zones of the polar regions of the Moon. These unique locations serve as potential resource utilization sites for future landing exploration and habitats (e.g., NASA Artemis Plan objectives).
Project description:Pathogen detection tools with high reliability are needed for various applications, including food and water safety and clinical diagnostics. In this study, we designed and validated an in situ-synthesized biochip for detection of 12 microbial pathogens, including a suite of pathogens relevant to water safety. To enhance the reliability of presence/absence calls, probes were designed for multiple virulence and marker genes (VMGs) of each pathogen, and each VMG was targeted by an average of 17 probes. Hybridization of the biochip with amplicon mixtures demonstrated that 95% of the initially designed probes behaved as predicted in terms of positive/negative signals. The probes were further validated using DNA obtained from three different types of water samples and spiked with pathogen genomic DNA at decreasing relative abundance. Excellent specificity for making presence/absence calls was observed by using a cutoff of 0.5 for the positive fraction (i.e., the fraction of probes yielding a positive signal for a given VMG). A split multiplex PCR design for simultaneous amplification of the VMGs resulted in a detection limit of between 0.1 and 0.01% relative abundance, depending on the type of pathogen and the VMG. Thermodynamic analysis of the hybridization patterns obtained with DNA from the different water samples demonstrated that probes with a hybridization Gibbs free energy of approximately -19.3 kcal/mol provided the best trade-off between sensitivity and specificity. The developed biochip may be used to detect the described bacterial pathogens in water samples when parallel and specific detection is required.
Project description:The 2003 Beagle 2 Mars lander has been identified in Isidis Planitia at 90.43° E, 11.53° N, close to the predicted target of 90.50° E, 11.53° N. Beagle 2 was an exobiology lander designed to look for isotopic and compositional signs of life on Mars, as part of the European Space Agency Mars Express (MEX) mission. The 2004 recalculation of the original landing ellipse from a 3-sigma major axis from 174 km to 57 km, and the acquisition of Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE) imagery at 30 cm per pixel across the target region, led to the initial identification of the lander in 2014. Following this, more HiRISE images, giving a total of 15, including red and blue-green colours, were obtained over the area of interest and searched, which allowed sub-pixel imaging using super high-resolution techniques. The size (approx. 1.5 m), distinctive multilobed shape, high reflectivity relative to the local terrain, specular reflections, and location close to the centre of the planned landing ellipse led to the identification of the Beagle 2 lander. The shape of the imaged lander, although to some extent masked by the specular reflections in the various images, is consistent with deployment of the lander lid and then some or all solar panels. Failure to fully deploy the panels-which may have been caused by damage during landing-would have prohibited communication between the lander and MEX and commencement of science operations. This implies that the main part of the entry, descent and landing sequence, the ejection from MEX, atmospheric entry and parachute deployment, and landing worked as planned with perhaps only the final full panel deployment failing.