The Big Island of Hawai‘i presents ample opportunities for young planetary volcanologists to gain firsthand field experience in the analysis of analogs to landforms seen on Mercury, Venus, the Moon, Mars, and Io. In this contribution, we focus on a subset of the specific features that are included in the planetary volcanology field workshops described in the previous chapter in this volume. In particular, we discuss how remote-sensing data and field localities in Hawai‘i can help a planetary geologist to gain expertise in the analysis of lava flows and lava flow fields, to understand the best sensor for a specific application, to recognize the ways in which different data sets can be used synergistically for remote interpretations of lava flows, and to gain a deeper appreciation for the spatial scale of features that might be imaged in the planetary context.

Central pit craters are common on ice-rich bodies, such as Mars, Ganymede, and Callisto. Mars and Ganymede represent the two end members regarding target characteristics (mixed ice and soil for Mars vs. almost pure ice for Ganymede). Comparisons of central pit craters on these two bodies can provide insights into the environmental conditions under which these craters form and provide constraints on the proposed formation models. This analysis includes 1604 central pit craters on Mars and 471 central pit craters on Ganymede. Martian central pit craters are divided into floor pits and summit pits, whereas all central pit craters on Ganymede are floor pits. Central pit craters form in similar-diameter ranges on both Mars and Ganymede when gravity differences are considered, and both bodies show no regional variations in pit crater distribution within the ±60° latitude zone. Martian floor pits are larger relative to their parent crater than summit pits, but the Ganymede pit/crater diameter ratio is larger than for either central pit type on Mars. Central pits have formed over the entire history of both bodies, and there is no indication that excavation depths have varied over time. Lack of crater floor updoming in Martian floor pit craters indicates that low concentrations of ice (estimated at ~20%) still allow production of central pits. The results of this study argue against central peak collapse as the formation mechanism for central pit craters. Excavation into a subsurface liquid layer cannot be ruled out but is difficult to support based on the distributions and consistencies in excavation depth on both bodies. These results support the model of vaporization and gas escape for central pit formation on both Mars and Ganymede.

The discovery of numerous extra-terrestrial volcanoes, including active ones, has stretched our traditional definition of what a volcano is. We now know that the nature of volcanism is highly variable over the solar system, and the traditional definition of a volcano as defined for Earth needs to be modified and expanded to include processes such as cryovolcanism, in which aqueous mixtures are erupted from the interior to the surface. In this chapter, we review past volcanism on the Moon, Mercury, and Mars, active volcanism on Io, and cryovolcanism in the moons of the outer solar system. We suggest the following definition that encompasses the different forms of volcanic activity seen in other worlds: A volcano is an opening on a planet or moon's surface from which magma, as defined for that planetary body, and/or magmatic gas is erupted .