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Advanced spectroscopic sensors recently flown to the Moon have revealed unexpected discoveries about Earth’s nearest neighbor as well as provided detailed insights and constraints about how early crust evolves on an airless planetary body. Discussed here are (a) global assessment of the variety and distribution of major lunar mineral components and lithologies; (b) some of the remarkable new findings, such as the pervasive presence of OH across the surface and new rock types identified (Mg-spinel anorthosite) that are not identified in current lunar samples; and (c) expectations for the future as additional modern sensors provide a stronger foundation for remote compositional analysis of the Moon. Spectroscopic data continue to provide the cornerstone for identifying and understanding the regional and global character of lunar compositional variations and document key products and processes of crustal evolution.
Spectral modeling techniques have been developed for the analysis of planetary surfaces using large thermal infrared (TIR) spacecraft datasets. These techniques can be applied to three main spectral analysis problems: (1) correction for atmospheric effects for the recovery of surface emissivity; (2) isolation and separation of surface spectral endmembers for the characterization of surface mineralogy; and (3) determination of surface anisothermality for the retrieval of surface physical properties and correction for thermal emission in near-infrared spectral data. These modeling techniques have been extensively applied to martian and lunar spacecraft datasets, forming a basis for the retrieval of surface physical and compositional properties.
This chapter provides a brief review of missions using X-ray, gamma-ray, and neutron spectroscopy to determine the chemical composition of planetary surfaces. This chapter presents the history of planetary radiation measurements, including significant discoveries. Summary tables with links to the archived data provide a resource for readers interested in working in this field. Upcoming missions and possible future directions are described.
An ever-increasing number of laboratory facilities are enabling in situ spectral reflectance measurements of materials under conditions relevant to all the bodies in the Solar System, from Mercury to Pluto and beyond. Results derived from these facilities demonstrate that exposure of different materials to various planetary surface conditions can provide insights into the endogenic and exogenic processes that operate to modify their surface spectra, and their relative importance. Temperature, surface atmospheric pressure, atmospheric composition, radiation environment, and exposure to the space environment have all been shown to measurably affect reflectance and emittance spectra of a wide range of materials. Planetary surfaces are dynamic environments, and as our ability to reproduce a wider range of planetary surface conditions improves, so will our ability to better determine the surface composition of these bodies, and by extension, their geologic history.
Radar has proven to be a powerful tool in planetary exploration. Most of the major solid bodies of the Solar System have been observed with radar, either from Earth or from spacecraft. Planetary radar studies are reviewed in this chapter, with information on the various techniques of radar remote sensing provided along with key results. Recent radar results are emphasized. Concluding remarks are provided on future directions in planetary radar remote sensing.
This chapter first explores how early medieval writers, and especially Isidore and Bede, made fundamental contributions to a new understanding of the natural world and its workings. They both quarried classical works for factual information and empirical observations, and placed these within a Christian cosmological model. An outline is given of the monastic science of ‘computus’, which was fundamental for teaching on natural philosophy and for theories about the weather in particular. Summaries of introductory works by both Isidore and Bede demonstrate their respective meteorological models; Bede’s views on the powers of the planets are covered in detail. Special attention is given to Bede’s The Reckoning of Time and the complex information on astronomy and meteorology which it expounds. An important conclusion is that Bede produced an understanding of weather as the intelligible and predictable result of astronomical and climatic factors. Overall, the chapter argues that classically derived natural philosophy and Christian cosmology were successfully integrated, and that the two together provided the basis for a new approach to weather and its prediction.
Space missions have shown that most terrestrial bodies have an internally generated magnetic field in their metallic core and/or a crustal field due to remanent magnetism. The latter indicates the presence of an old dynamo at the time of crust formation. Information on the two together helps to uncover the body’s magnetic field history, and it is generally accepted that convection flows driven by thermal or compositional buoyancy in the cores are the most likely source for maintaining global planetary magnetic fields. The convection flow in the core, in turn, is closely related to the interior dynamics of the mantles above and the thermal evolution of the body. This chapter describes the mechanisms for dynamo generation either by thermal or compositional convection in the core. It discusses the magnetic field evolution of Mercury, Moon, Mars, Ganymede, and planetesimals and will also address the possibility of dynamo generation in rocky exoplanets
Negative interactions between people and large carnivores are common and will probably increase as the human population and livestock production continue to expand. Livestock predation by wild carnivores can significantly affect the livelihoods of farmers, resulting in retaliatory killings and subsequent conflicts between local communities and conservationists. A better understanding of livestock predation patterns could help guide measures to improve both human relationships and coexistence with carnivores. Environmental variables can influence the intensity of livestock predation, are relatively easy to monitor, and could potentially provide a useful predictive framework for targeting mitigation. We chose lion predation of livestock as a model to test whether variations in environmental conditions trigger changes in predation. Analysing 6 years of incident reports for Pandamatenga village in Botswana, an area of high human–lion conflict, we used generalized linear models to show that significantly more attacks coincided with lower moonlight levels and temperatures, and attack severity increased significantly with extreme minimum temperatures. Furthermore, we found a delayed effect of rainfall: lower rainfall was followed by a significantly increased severity of attacks in the following month. Our results suggest that preventative measures, such as introducing deterrents or changing livestock management, could be implemented adaptively based on environmental conditions. This could be a starting point for investigating similar effects in other large carnivores, to reduce livestock attacks and work towards wider human–wildlife coexistence.
Like the Sun, the Moon moves eastward relative to the stars but at a faster rate, completing its motion in one month. The apparent motion of the Moon relative to the Sun produces the cycle of lunar phases as well as both lunar and solar eclipses. Ancient Greek mathematicians devised ways of estimating the distances and sizes of the Sun and Moon from observational data, including the phenomenon of parallax. The planets, too, appear to move relative to the stars. They generally move eastward relative to the stars but occasionally they halt their eastward motion and move westward (in retrograde motion) before resuming their normal eastward trek. The planets can be classified into two groups, inferior and superior, each of which displays certain characteristics of motion.
This appendix provides mathematical details to supplement the ideas presented in the main text. Topic covered include: angular measurement, apparent diameter, trigonometry, finding the Sun’s altitude from the length of a shadow, determining the relative distances of the Sun and Moon, and finding the distance to an astronomical object using parallax measurements. In addition, this appendix shows how to calculate the sizes of epicycles in the Ptolemaic theory and the periods and sizes of planetary orbits in the Copernican theory. Mathematical details are also provided for Kepler’s Laws of Planetary Motion, Galileo’s measurement of mountains on the Moon, Galileo’s studies of falling bodies and projectiles, Newton’s universal gravitational force, and Bradley’s theory of the aberration of starlight.
In 1671 Robert Hooke thought he had detected an annual parallax for the star Gamma Draconis, thus proving that the Earth orbits the Sun. Setting aside the uncertainty of Hooke’s meagre measurements, there remained the problem of how the Earth could orbit the Sun. Hooke thought he knew: the planets orbited the Sun because of a combination of straight line inertial motion and an attraction toward the Sun. But it was left to Hooke’s rival, Isaac Newton, to work out the mathematical details. While working out these details Newton established an entirely new physics based on three fundamental laws of motion and a universal gravitational attraction between all massive objects. Newton’s physics explained not only the orbits of planets, but also the motion of projectiles, the orbits of the Moon and comets, the precession of the equinoxes, and the tides. Newton’s physics was hailed in England but many European natural philosophers initially dismissed universal gravitational attraction as an “occult quality.”
This paper presents my own recollections of the difficult relations that existed between the IAU and a fraction of the public, especially in the USA, following the IAU decision to reclassify Pluto as a dwarf planet at the 2006 General Assembly in Prague, and which ultimately led the IAU to organize the NameExoWorlds international contest to give public names to selected exoplanets and their host stars. In spite of the success of the International Year of Astronomy in 2009, the Pluto controversy continued, and its consequences climaxed during my term (2012-2015), as NASA’s New Horizons probe approached Pluto for a flyby just before the 2015 General Assembly in Honolulu. It was during this period that the IAU launched the NameExoWorlds contest, which also came to a conclusion in Honolulu after over half a million votes were cast from all over the world. While the inside story of how the contest was organized has appeared elsewhere, here I focus on the historical and sociological context that made Pluto such a sensitive issue, especially in the USA, explaining why this contest generated another controversy between the IAU and the New Horizons team. However, after the world-wide success of NameExoWorlds, the IAU and the New Horizons team eventually reached an agreement on finalizing the characterization and names of a number of newly discovered Pluto and Charon surface features (an on-going process), while a new edition of NameExoWorlds is in preparation for the IAU centennial in 2019.
We compared the number of lunar craters with diameters greater than 15 km with age less than 1.1 Gyr in the region of the Oceanus Procellarum with the estimates of the number of craters made based on the number of near-Earth objects and on the characteristic times elapsed before collisions of near-Earth objects with the Moon. Our estimates allow the increase of the number of near-Earth objects after a recent catastrophic disruption of a large main-belt asteroid. However, destruction of some old craters and variations in orbital distribution of near-Earth objects with time could allow that the mean number of near-Earth objects during the last billion years could be close to the present value.
Computer simulations of migration of planetesimals from beyond the Jupiter’s orbit to the terrestrial planets have been made. Based on obtained arrays of orbital elements of planetesimals and planets during the dynamical lifetimes of planetesimals, we calculated the probabilities of collisions of planetesimals with planets, the Moon, and their embryos. The results of calculations showed that for the total mass of planetesimals of about 200 Earth masses, the mass of water delivered to the Earth from beyond the orbit of Jupiter could be about the mass of the terrestrial oceans. For the growth of the mass of the Earth embryo up to a half of the present mass of the Earth, the mass of water delivered to the embryo could be up to 30% of all water delivered to the Earth from the zone of Jupiter and Saturn. The water of the terrestrial oceans and its D/H ratio could be the result of mixing of water from several exogenic and endogenic sources with large and low D/H ratios. The ratio of the mass of water delivered from beyond the orbit of Jupiter to a planet to the mass of the planet for Venus, Mars, and Mercury was not smaller than that for the Earth. The mass of water in planetesimals that collided the Moon and migrated from beyond the Jupiter’s orbit could be not more than 20 times smaller than that for the Earth.
Trans-Neptunian satellite systems and embryos of the Earth-Moon system could be formed as a result of contraction of rarefied condensations. The angular momenta of rarefied condensations needed for such formation could be acquired at collisions of condensations. The angular momentum of the present Earth-Moon system could be acquired at a collision of two rarefied condensations with a total mass not smaller than 0.1ME, where ME is the mass of the Earth. The mass of the condensation that was a parent for the embryos of the Earth and the Moon could be about 0.01ME, if we take into account the growth of the angular momentum of the embryos with growth of their masses. The Moon embryo could get by an order of magnitude more material ejected from the Earth embryo than that fell directly onto the Moon embryo.
Heading angle is a vital parameter in maintaining a vessel's track along a planned course and should be guaranteed in a stable and reliable way. An innovative method of heading determination based on a fisheye camera, which is almost totally unaffected by electromagnetism and geomagnetism, is proposed in this paper. In addition, unlike traditional astronomical methods, it also has a certain degree of adaptability to cloudy weather. Utilising the super wide Field Of View (FOV) of the camera, it is able to simultaneously image the Moon and the horizon. The Moon is treated as the observed celestial body and the horizon works as the horizontal datum. Two experiments were conducted at sea, successfully proving the feasibility of this method. The proposed heading determination system has the merits of automation, resistance to interference and could be miniaturised, making application viable.
Speculation on near-term scientific reasons for the exploration of lunar pits is offered alongside comments on possible longer-term human exploitation. It is proposed that in order to determine whether or not one or more of the pits offer access the large subsurface voids e.g. a non-collapsed lava tube, a preliminary reconnaissance mission solely focused on obtaining lateral images (and/or LiDAR maps) is needed. Possible concept options for such a preliminary reconnaissance mission are discussed. It is suggested that one of the best possible strategies is to employ a micro-sized probe (~0.3 m) that would hop from a nearby main landing spacecraft to the selected pit. After the surface position of the main lander is determined accurately, the probe would perform a ballistic hop, or hover-traverse, a distance of ~3 km over the lunar surface using existing propulsive and guidance technology capability. Once hovering above the pit, the probe or a separate tethered imaging unit would then be lowered into the pit to acquire the necessary subsurface void topology data. This data would then be transmitted back to Earth, directly, via the lander, or via a store-and-forward orbiting relay. Preliminary estimates indicate that a probe of ~14 kg (dry mass) is viable using a conventional hydrazine monopropellant system with a propellant mass fraction of less than ~0.2 (20%) including margins, suggesting a piggyback architecture would be feasible.