We explain nucleosynthesis in evolving stars and use this foundation to understand the chemical composition of our own star and of the Solar System. Element abundances are determined from the Sun’s spectrum, and from laboratory measurements of the solar wind and chondritic meteorites. The metal-rich Solar System composition reflects the recycling of elements formed in earlier generations of stars. Condensation models of a cooling nebular gas having this composition produced the minerals found in refractory inclusions in chondrites. The deuterium enrichment in organic matter in chondrites suggests that hydrocarbons formed at low temperatures in molecular clouds and were subsequently processed into complex molecules in the solar nebula and in parent bodies. Ices condensed far from the Sun and were incorporated into the giant planets and comets. Element fractionations in the nebula were largely controlled by element volatility or by the physical sorting of solid grains. Separation of isotopes by mass was common in the nebula, although oxygen shows mass-independent fractionation.

Planetary volatiles occur in gas, liquid, and solid forms. In this chapter, we will see that the terrestrial planets have secondary atmospheres formed by outgassing of their interiors. The chemical compositions of the atmospheres of Venus and Mars are dominated by CO2, but the Earth’s atmosphere is distinct because CO2 is sequestered in the lithosphere and life has added O2 to the mix. Giant planet atmospheres are mostly hydrogen with some helium. Titan has an atmosphere of N2 and reducing gases, along with seas of hydrocarbons. Mars has briny groundwater and had lakes and possibly oceans in the distant past. Some moons of the giant planets have subsurface oceans. Noble gases and stable isotopes hold keys to the origin and evolution of volatiles. Differences in temperature and pressure cause atmospheric circulation, controlled by planetary rotation and energy transport. Frozen volatiles are common as polar deposits and sometimes permafrost, but they are especially abundant in the outer Solar System, where they may comprise the crusts of giant planet satellites. Volatile behaviors can be described in terms of geochemical cycles. Greenhouse warming has important implications for planetary climates.

Planetary exploration typically advances in step with technology. Improvements in spatial and spectral resolution yield discoveries that progress from global to regional scales, and exploration on a planet’s surface provides ground truth for remote sensing data and a level of observation and measurement that geologists crave. Samples that can be analyzed in the laboratory provide geochemical and geochronologic information that complements spacecraft data and enhances its interpretation. We illustrate how data at all these scales have been integrated to characterize the complex geology of Mars and to constrain its geologic history.

In this chapter, an overview is provided of the types of fibre and matrix in common use and of how they are assembled into composites. Many types of reinforcement, mostly fibres, are available commercially. Their properties are related to atomic structure and the presence of defects, which must be controlled during manufacture. Matrices may be based on polymers, metals or ceramics. Choice of matrix is usually related to required properties, component geometry and method of manufacture. Certain composite properties may be sensitive to the nature of the reinforcement/matrix interface; this topic is covered in Chapter 7. Properties are also dependent on the arrangement and distribution of fibres, i.e. the fibre architecture, an expression that encompasses intrinsic features of the fibres, such as their diameter and length, as well as their volume fraction, alignment and spatial distribution. Fibre arrangements include laminae (sheets containing aligned long fibres) and laminates that are built up from these. Other continuous fibre systems, such as woven configurations, are also covered. Short fibre systems can be more complex and methods of characterising them are also briefly described.

Only a quarter of a century ago, the only planets known to exist were those orbiting our Sun. Now we know that other stars host extrasolar planets, or “exoplanets.” The earliest discoveries were made using Earth-based telescopes that detected stellar wobbles caused by nearby orbiting planets. To be detectable, these exoplanets must be large and orbit very close to their stars. Using a different method, NASA’s Kepler orbiting space telescope (2009–2013) observed partial eclipses as planets transited in front of stars (Batalha, 2014). Kepler’s high-precision measurements – only possible in space where stars don’t twinkle – have enabled the discovery of ~4000 candidate planets; of these candidates, perhaps 90 percent are thought to be real planets (Lissauer et al., 2014). The list includes nearly 700 multiple planet systems (Figure E.1), and the large numbers imply that these must be very common. Planetary orbits in multi-planet systems are usually coplanar, consistent with their formation within accretion disks (like our own Solar System’s ecliptic plane).

In addition to spectroscopy, planetary geoscience uses some other tools familiar to most geologists, and some tools that are either unique or involve new twists in how they are employed. We explain how stratigraphic principles are adapted for planets (using strata produced by impacts), how the density of craters can be quantified to derive relative ages of geologic units, and how radioisotope measurements on samples, where available, give absolute ages. We explain how images from orbiting and landed spacecraft are used, along with chronologic and remote-sensing data, to make planetary geologic maps at different scales. We consider various geophysical techniques that are used on spacecraft to obtain information about planetary potential fields, interior structure, and surface topography. We summarize the kinds of extraterrestrial materials that are available for laboratory investigations, and briefly describe the analytical techniques used to characterize their mineralogy, petrology, and geochemistry. We also examine some techniques that are adapted as remote sensing tools for analyses of rocks and soils on planetary surfaces.