How was the Earth-Moon system formed? New insights from the geodynamo.

The most widely accepted scenario for the formation of the Earth-Moon system involves a dramatic impact between the proto-Earth and some other cosmic body. Many features of the present-day Earth-Moon system provide constraints on the nature of this impact. Any model of the history of the Earth must account for the physical, geochemical, petrological, and dynamical evidence. These constraints notwithstanding, there are several radically different impact models that could in principle account for all the evidence. Thus, in the absence of further constraints, we may never know for sure how the Earth-Moon system was formed. Here, we put forward the idea that additional constraints are indeed provided by the fact that the Earth is strongly magnetized. It is universally accepted that the Earth's magnetic field is maintained by a dynamo operating in the outer liquid core. However, because of the rapid rotation of the Earth, this dynamo has the peculiar property that it can maintain a strong field but cannot amplify a weak one. Therefore, the Earth must have been magnetized at a very early epoch, either preimpact or as a result of the impact itself. Either way, any realistic model of the formation of the Earth-Moon system must include magnetic field evolution. This requirement may ultimately constrain the models sufficiently to discriminate between the various candidates.

High abundance of solar wind-derived water in lunar soils from the middle latitude.

Remote sensing data revealed that the presence of water (OH/H2O) on the Moon is latitude-dependent and probably time-of-day variation, suggesting a solar wind (SW)-originated water with a high degassing loss rate on the lunar surface. However, it is unknown whether or not the SW-derived water in lunar soil grains can be preserved beneath the surface. We report ion microprobe analyses of hydrogen abundances, and deuterium/hydrogen ratios of the lunar soil grains returned by the Chang'e-5 mission from a higher latitude than previous missions. Most of the grain rims (topmost ~100 nm) show high abundances of hydrogen (1,116 to 2,516 ppm) with extremely low δD values (-908 to -992‰), implying nearly exclusively a SW origin. The hydrogen-content depth distribution in the grain rims is phase-dependent, either bell-shaped for glass or monotonic decrease for mineral grains. This reveals the dynamic equilibrium between implantation and outgassing of SW-hydrogen in soil grains on the lunar surface. Heating experiments on a subset of the grains further demonstrate that the SW-implanted hydrogen could be preserved after burial. By comparing with the Apollo data, both observations and simulations provide constraints on the governing role of temperature (latitude) on hydrogen implantation/migration in lunar soils. We predict an even higher abundance of hydrogen in the grain rims in the lunar polar regions (average ~9,500 ppm), which corresponds to an estimation of the bulk water content of ~560 ppm in the polar soils assuming the same grain size distribution as Apollo soils, consistent with the orbit remote sensing result.

Two light sensors decode moonlight versus sunlight to adjust a plastic circadian/circalunidian clock to moon phase.

Many species synchronize their physiology and behavior to specific hours. It is commonly assumed that sunlight acts as the main entrainment signal for ∼24-h clocks. However, the moon provides similarly regular time information. Consistently, a growing number of studies have reported correlations between diel behavior and lunidian cycles. Yet, mechanistic insight into the possible influences of the moon on ∼24-h timers remains scarce. We have explored the marine bristleworm Platynereis dumerilii to investigate the role of moonlight in the timing of daily behavior. We uncover that moonlight, besides its role in monthly timing, also schedules the exact hour of nocturnal swarming onset to the nights' darkest times. Our work reveals that extended moonlight impacts on a plastic clock that exhibits <24 h (moonlit) or >24 h (no moon) periodicity. Abundance, light sensitivity, and genetic requirement indicate that the Platynereis light receptor molecule r-Opsin1 serves as a receptor that senses moonrise, whereas the cryptochrome protein L-Cry is required to discriminate the proper valence of nocturnal light as either moonlight or sunlight. Comparative experiments in Drosophila suggest that cryptochrome's principle requirement for light valence interpretation is conserved. Its exact biochemical properties differ, however, between species with dissimilar timing ecology. Our work advances the molecular understanding of lunar impact on fundamental rhythmic processes, including those of marine mass spawners endangered by anthropogenic change.

Lunar rhythms and their carry-over effects may shape environmental sex determination in a coral reef fish.

Lunar rhythms shape spawning phenology and subsequent risks and rewards for early life-history stages in the sea. Here, we consider a perplexing spawning phenology of the sixbar wrasse (Thalassoma hardwicke), in which parents spawn disproportionately around the new moon, despite the low survival of these larvae. Because primary sex determination in this system is highly plastic and sensitive to social environments experienced early in development, we ask whether this puzzling pattern of spawning is explained by fitness trade-offs associated with primary sexual maturation. We used otoliths from 871 fish to explore how spawning on different phases of the moon shapes the environments and phenotypes of settling larvae. Offspring that were born at the new moon were more likely to settle (i) before other larvae, (ii) at a larger body size, (iii) at an older age, (iv) to the best quality sites, and (v) as part of a social group-all increasing the likelihood of primary maturation to male. Selection of birthdates across life stage transitions suggests that the perplexing spawning phenology of adults may reflect an evolutionarily stable strategy that includes new moon spawning for compensatory benefits later in life, including preferential production of primary males at certain times.

Increased suicide risk among younger women in winter during full moon in northern Europe. An artifact or a novel finding?

Available evidence suggests that there is no effect of moon phases on suicidal behavior. However, a Finnish study recently reported elevated suicide rates during full-moon, but only among premenopausal women and only in winter. This could not be replicated in an Austrian study and stirred a discussion about whether the Finnish finding was false-positive or if there are unaccounted moderator variables differing between Finland and Austria. The goal of the present study was to provide another replication with data from Sweden, which is geographically more comparable to Finland than Austria. We also investigated the discussed moderator variables latitude and nightly artificial brightness. There were 48,537 suicides available for analysis. The fraction of suicides during the full-moon quarter in winter did not differ significantly from the expected 25% among premenopausal women (23.3%) and in the full sample (24.7%). The incidence risk ratios for full moon quarter in Poisson regression models were 0.96 (95% CI: 0.90-1.02) for premenopausal women and 1.01 (95% CI: 0.99-1.04) for the full sample. According to Bayes-factor analysis, the evidence supports the null-hypothesis (no association) over the alternative hypothesis (some association). We found similar results when we split the data by latitude and artificial nightly brightness, respectively. In line with the Austrian study, there was no increase of suicides in Sweden among premenopausal women in winter during full-moon. The results from the Finnish study are likely false positive, perhaps resulting from problematic but common research and publication practices, which we discuss.

Lunar Age-Dependent Oscillations in Expression of the Genes for Kisspeptin, GnIH, and Their Receptors in the Grass Puffer during the Spawning Season.

Grass puffer is a semilunar-synchronized spawner: spawning occurs on beaches only for several days of spring tide around new moon (lunar age 0) and full moon (lunar age 15) every 2 weeks from spring to early summer. To investigate the role of kisspeptin and gonadotropin-inhibitory hormone (GnIH) in the semilunar-synchronized spawning, lunar age-dependent expression of the genes encoding kisspeptin (kiss2), kisspeptin receptor (kissr2), GnIH (gnih), GnIH receptor (gnihr), gonadotropin-releasing hormone 1 (GnRH1) (gnrh1), and three gonadotropin (GTH) subunits (gpa, fshb, lhb) was examined in the male grass puffer, which was kept in an aquarium under natural light condition in a lunar month during the spawning period. In the brain, both kiss2 and kissr2 showed lunar variations with a peak at lunar age 10, while both gnih and gnihr showed semilunar variations with two peaks at lunar age 0 and 20. On the other hand, gnrh1 showed semilunar variation with two peaks at lunar age 0 and 15. In the pituitary, kiss2, kissr2, gnih, and gnihr showed similar variations to those shown in the brain. The fshb and lhb mRNA levels showed semilunar variations with two peaks at lunar age 0 and 15. The present study shows lunar and semilunar oscillations of kiss2/kissr2 and gnih/gnihr expressions, respectively, with their peaks around spring tide in the brain and pituitary along with the semilunar expressions of gnrh1 and the pituitary GTH subunit genes. These results suggest that the lunar age-dependent expressions of the kisspeptin, GnIH, and their receptor genes may be primarily important in the control of the precisely timed semilunar spawning of the grass puffer.

Exploring the mystical relationship between the Moon, Sun, and birth rate.

OBJECTIVE: The Moon has a noticeable influence on the Earth due to its gravity, the most visible manifestation of which are tides. We aimed to see if the Moon's daily cycle, like the Sun's, affects the prevalence and incidence of childbirth. METHODS: In this retrospective cohort study, we examined all deliveries at the Academic Hospital of Udine between 2001 and 2019. All consecutive singleton pregnancies with spontaneous labor and vaginal delivery were included. RESULTS: During the period, 13,349 singleton pregnancies with spontaneous labor and vaginal delivery were delivered in 6939 days. A significantly higher prevalence of deliveries was found with the Moon above the horizon (50.63% vs. 49.37%, p < 0.05). Moreover, during the day, there was a significantly higher prevalence of deliveries than during nighttime (53.74% vs. 45.79%, p < 0.05). Combining the Moon and Sun altitude, the majority of deliveries were registered when both were above the horizon (27.39% vs. 26.13%, 23.25%, or 23.24%, p < 0.05). These findings were confirmed in multivariate analysis after adjusting for parity, gestational age, or season. We found no correlation between birth and the Moon phase. CONCLUSIONS: Our data support the interaction of the Moon and the Sun in determining the time of birth. More research is needed to understand these phenomena and improve our understanding of labor initiation mechanisms.

Moonrise timing is key for synchronized spawning in coral Dipsastraea speciosa.

Synchronized mass coral spawning typically occurs several days after a full moon once a year. It is expected that spawning day is determined by corals sensing environmental change regulated by the lunar cycle (i.e., tide or moonlight); however, the exact regulatory mechanism remains unknown. Here, we demonstrate how moonlight influences the spawning process of coral, Dipsastraea speciosa When corals in the field were shaded 1 and 3 d before the full moon or 1 d after the full moon, spawning always occurred 5 d after shading commenced. These results suggest moonlight suppresses spawning: a hypothesis supported by laboratory experiments in which we monitored the effects of experimental moonlight (night-light) on spawning day. Different night-light treatments in the laboratory showed that the presence of a dark period between day-light and night-light conditions eliminates the suppressive effect of night-light on spawning. In nature, moonrise gets progressively later during the course of the lunar cycle, shifting to after sunset following the day of the full moon. Our results indicate that this period of darkness between sunset and moonrise triggers synchronized mass spawning of D. speciosa in nature.

Quantitative evaluation of the feasibility of sampling the ice plumes at Enceladus for biomarkers of extraterrestrial life.

Enceladus, an icy moon of Saturn, is a compelling destination for a probe seeking biosignatures of extraterrestrial life because its subsurface ocean exhibits significant organic chemistry that is directly accessible by sampling cryovolcanic plumes. State-of-the-art organic chemical analysis instruments can perform valuable science measurements at Enceladus provided they receive sufficient plume material in a fly-by or orbiter plume transit. To explore the feasibility of plume sampling, we performed light gas gun experiments impacting micrometer-sized ice particles containing a fluorescent dye biosignature simulant into a variety of soft metal capture surfaces at velocities from 800 m ⋅ s-1 up to 3 km ⋅ s-1 Quantitative fluorescence microscopy of the capture surfaces demonstrates organic capture efficiencies of up to 80 to 90% for isolated impact craters and of at least 17% on average on indium and aluminum capture surfaces at velocities up to 2.2 km ⋅ s-1 Our results reveal the relationships between impact velocity, particle size, capture surface, and capture efficiency for a variety of possible plume transit scenarios. Combined with sensitive microfluidic chemical analysis instruments, we predict that our capture system can be used to detect organic molecules in Enceladus plume ice at the 1 nM level-a sensitivity thought to be meaningful and informative for probing habitability and biosignatures.