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Cycles in space
\"As Earth moves around the sun, the seasons on Earth change. The movement of the moon affects the tides in Earth's oceans. What happens in space has an influence on our lives! In this book, readers explore the cycles in the space that most affect us and the space science taught in upper elementary science classes. Accessible language and simple explanations make this the perfect introduction to Earth's cycles for readers struggling with traditional textbooks. Diagrams of each cycle provide a great review of each cycle as well as another way to understand each concept.\"-- Provided by publisher.
Book
Making the Moon from a Fast-Spinning Earth: A Giant Impact Followed by Resonant Despinning
A common origin for the Moon and Earth is required by their identical isotopie composition. However, simulations of the current giant impact hypothesis for Moon formation find that most lunar material originated from the impactor, which should have had a different isotopie signature. Previous Moon-formation studies assumed that the angular momentum after the impact was similar to that of the present day; however, Earth-mass planets are expected to have higher spin rates at the end of accretion. Here, we show that typical last giant impacts onto a fast-spinning proto-Earth can produce a Moon-forming disk derived primarily from Earth's mantle. Furthermore, we find that a faster-spinning early Earth-Moon system can lose angular momentum and reach the present state through an orbital resonance between the Sun and Moon.
Journal Article
Earth Wind‐Driven Formation of Hematite on the Lunar Surface
The recent discovery of hematite (Fe2O3 ${\\text{Fe}}_{2}{\\mathrm{O}}_{3}$) in lunar high‐latitude regions challenges the notion that the Moon exists in a reduced state. However, the origin of hematite remains unclear. We conducted irradiation experiments using 10 keV O2+ ${\\mathrm{O}}_{2}^{+}$ and H2+ ${\\mathrm{H}}_{2}^{+}$ ions on Fe‐bearing minerals to simulate the exposure of lunar regolith to Earth wind, and 2 keV H2+ ${\\mathrm{H}}_{2}^{+}$ to represent solar wind irradiation. Our results demonstrate that Earth wind oxygen ions can anhydrously oxidize metallic Fe, iron sulfide, and ilmenite to hematite. High‐energy hydrogen ions can reduce hematite to metallic Fe, while low‐energy hydrogen ions are largely ineffective. Consequently, hematite retention depends on both the energy and the relative flux ratio of oxygen and hydrogen ions from Earth wind impacting the lunar surface. These findings provide new insights into the dynamic redox processes shaping the lunar surface as well as the effective mass transport within the Earth‐Moon system.
Journal Article
Dynamics around the Earth–Moon triangular points in the Hill restricted 4-body problem
This paper investigates the motion of a small particle moving near the triangular points of the Earth–Moon system. The dynamics are modeled in the Hill restricted 4-body problem (HR4BP), which includes the effect of the Earth and Moon as in the circular restricted 3-body problem (CR3BP), as well as the direct and indirect effect of the Sun as a periodic time-dependent perturbation of the CR3BP. Due to the periodic perturbation, the triangular points of the CR3BP are no longer equilibrium solutions; rather, the triangular points are replaced by periodic orbits with the same period as the perturbation. Additionally, there is a 2:1 resonant periodic orbit that persists from the CR3BP into the HR4BP. In this work, we investigate the dynamics around these invariant objects by performing a center manifold reduction and computing families of 2-dimensional invariant tori and their linear normal behavior. We identify bifurcations and relationships between families. Mechanisms for transport between the Earth, L4, and the Moon are discussed. Comparisons are made between the results presented here and in the bicircular problem (BCP).
Journal Article
NASE workshop: Eclipses with models and camera obscura
Ibn al-Haytham (known as Alhazen in occident), extensively studied the camera obscura phenomenon in the early 11th century. This instrument was used to obtain the projected image of a landscape on the screen and also was addopte by the scientists and famous painters along the centuries, to experiment with it until their final evolution as the modern photografic camera. The resource in the simple version of the “pinhole camera” can be used at the classroom to experience several phenomena, such us solar eclipses and Moon phases, and to each about optics and geometry. This contribution presents an application of this ingeniuos tool in the framework of solar eclipses, where the scale models are important to understand what really happens with the Sun-Earth-Moon system.
Journal Article
Forming a Moon with an Earth-like Composition via a Giant Impact
In the giant impact theory, the Moon formed from debris ejected into an Earth-orbiting disk by the collision of a large planet with the early Earth. Prior impact simulations predict that much of the disk material originates from the colliding planet. However, Earth and the Moon have essentially identical oxygen isotope compositions. This has been a challenge for the impact theory, because the impactor's composition would have likely differed from that of Earth. We simulated impacts involving larger impactors than previously considered. We show that these can produce a disk with the same composition as the planet's mantle, consistent with Earth-Moon compositional similarities. Such impacts require subsequent removal of angular momentum from the Earth-Moon system through a resonance with the Sun as recently proposed.
Journal Article
The seismicity of Mars
The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed in Elysium Planitia on Mars on 26 November 2018 and fully deployed its seismometer by the end of February 2019. The mission aims to detect, characterize and locate seismic activity on Mars, and to further constrain the internal structure, composition and dynamics of the planet. Here, we present seismometer data recorded until 30 September 2019, which reveal that Mars is seismically active. We identify 174 marsquakes, comprising two distinct populations: 150 small-magnitude, high-frequency events with waves propagating at crustal depths and 24 low-frequency, subcrustal events of magnitude Mw 3–4 with waves propagating at various depths in the mantle. These marsquakes have spectral characteristics similar to the seismicity observed on the Earth and Moon. We determine that two of the largest detected marsquakes were located near the Cerberus Fossae fracture system. From the recorded seismicity, we constrain attenuation in the crust and mantle, and find indications of a potential low-S-wave-velocity layer in the upper mantle.Mars is seismically active: 24 subcrustal magnitude 3–4 marsquakes and 150 smaller events have been identified up to 30 September 2019, by an analysis of seismometer data from the InSight lander.
Journal Article
Earth and Moon impact flux increased at the end of the Paleozoic
The terrestrial impact crater record is commonly assumed to be biased, with erosion thought to eliminate older craters, even on stable terrains. Given that the same projectile population strikes Earth and the Moon, terrestrial selection effects can be quantified by using a method to date lunar craters with diameters greater than 10 kilometers and younger than 1 billion years. We found that the impact rate increased by a factor of 2.6 about 290 million years ago. The terrestrial crater record shows similar results, suggesting that the deficit of large terrestrial craters between 300 million and 650 million years ago relative to more recent times stems from a lower impact flux, not preservation bias. The almost complete absence of terrestrial craters older than 650 million years may indicate a massive global-scale erosion event near that time.
Journal Article
Ancient eclipses and long-term drifts in the Earth–Moon system
We study anomalies in the Earth–Moon system using ancient eclipse data. We identify nine groups of anomalous eclipses between AD 400 and 1800 recorded in parts of India that should have completely missed the subcontinent according to NASA simulations (Espenak, F. and Meeus, J., NASA/TP 2006–214141, 2011). We show that the typical correction in lunar location required to reconcile the anomalous eclipses is relatively small and consistent with the fluctuations in the length of day that are observed in recent periods. We then study how the change in the moment of inertia of the Earth due to differential acceleration of land and water can account for this discrepancy. We show that 80% of these discrepancies occur when the Moon is at a declination greater than 10° and closer to its major standstill of 28° while it spends 46% of the time in this region. We simulate the differential interaction of the Moon's gravity with land mass and water using finite element method to account for land mass and watermass. We show that the results of eclipse error are consistent with the estimate of a small differential acceleration when the Moon is over land at high latitudes. However, we encounter some examples where the results from simulation studies cannot explain the phenomenon. Hence we propose that the ΔT corrections have to be coupled with some other mechanism, possibly a small vertical oscillation in the Moon's rotational plane with period of the order of a few hundred years to achieve the required adjustment in eclipse maps.
Journal Article
Dynamics of tethered satellites in the vicinity of the Lagrangian point L2 of the Earth–Moon system
This paper analyzes the dynamical evolution of satellites formed by two masses connected by a cable—
tethered satellites
. We derive the Lagrangian equations of motion in the neighborhood of the collinear equilibrium points, especially for the
L
2
, of the restricted problem of three bodies. The rigid body configuration is expanded in Legendre polynomials up to fourth degree. We present some numerical simulations of the influence of the parameters such as cable length, mass ratio and initial conditions in the behavior of the tethered satellites. The equation for the collinear equilibrium point is derived and numerically solved. The evolution of the equilibria with the variation of the cable length as a parameter is studied. We also present a discussion of the linear stability around these equilibria. Based on this analysis calculate some unstable Lyapunov orbits associated to these equilibrium points. We found periodic orbits in which the tether travels parallel to itself without involving the angular motion. The numerical applications are focused on the Earth–Moon system. However, the general character of the equations allows applications to the
L
1
equilibrium and obviously to systems other than the Earth–Moon.
Journal Article