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Highland paterae are broad, low-sloped volcanoes on Mars that have a large summit caldera and channeled flanks. Crater-modeled ages suggest they may represent some of the oldest central vent volcanoes on the planet. The presence of channeled flanks that surround a younger summit caldera with topographically smooth floor material has led to the interpretation that highland paterae record a transition from explosive volcanic eruptions to more effusive eruptive styles. In this chapter we describe the geology of seven highland paterae (Amphitrites Patera, Peneus Patera, Malea Patera, Pityusa Patera, Tyrrhena Patera, Hadriaca Patera, and Apollinaris Mons), discuss what that reveals about their history and origin, and then discuss possible avenues of future research on these intriguing Martian landforms.

Although we have seen that Mars has little (if not) water for a human colonization on a large scale, it still offers many opportunities for future explorations. These are related to the potential richness of its minerals, both on the surface and its subsurface, and a challenging environment where to test technological solutions for the exploitation of inhospitable worlds. We explore new methodologies for a drier extraction of minerals, with respect to current methods used in the mining industry on Earth, and existing concepts of human colony based on in-situ resource utilization (ISRU). 3D printing techniques will allow construction of buildings from the volcanic materials available on the surface of Mars.

Mars displays a variety of volcanic structures, thus giving us insight into the variety of volcanic eruption processes and lava flow morphologies. These eruption processes, from plumbing systems, supply rates, and magma mineralogy can all affect the eruption style. Understanding these different types of eruption styles represents a distinct geophysical process on Mars that in some cases resemble volcanic systems of Earth. The similarities are in the gas exsolution from magmas at shallow depth, but then depends on factors such as composition, volatile content, and temperature. The ascent of the magma can form dikes and sills, which may undergo chemical and physical evolution, which can then lead to a diversification of volcanic activity and lava flow viscosity. This chapter explores our current understanding of eruptive styles, magma reservoirs, and flow textures across Mars with a look at the thermodynamical perspectives of lava flow morphology.

Our knowledge of the formation and evolution of the Martian surface, and thus the fate of its volcanic regions, are revealed in the mineralogy of the crust (as observed by orbiters and landers) and the chemistry hidden within Martian meteorites. The composition of the Martian crust has been estimated from SNC (shergottite—nakhlite—chassignite) meteorites, which are chemically similar to terrestrial basalts. However, these meteorites reveal a complexity in other mineralogies, such as the silicic implications for volcanism across Mars. Although the exact locations of such SNCs are difficult to discern, the variety of geochemical data from these meteorites gives us a clue as to the mineralogical regions, and thus probable varieties of volcanism on Mars. In this chapter, we will explore the Martian meteorites and their clues to the Martian volcanic regions and crustal components of the North–South dichotomy.

We describe and interpret the geometry and surficial characteristics of an oblong 98 km depression named Hekla Cavus in the (informally named) Cthulhu Macula, Pluto. The feature is located near the equator west of Sputnik Planitia at the New Horizons Close Encounter Hemisphere. Images from the Long Range Reconnaissance Imager along with digital elevation maps reveal that the feature is located within a larger ridge-trough system, bounded by a raised rim with surficial fissures radiating from the rim. At the wall-floor contact, a mass wasting feature is also observed. The floor of the feature is asymmetric of near-elliptical shape with its long-axis oriented southwestward. This study also comparatively measures the dimensions of impact craters and sublimation pits of Pluto to define Hekla Cavus to be a rare feature. This feature is estimated to have a volume of 5617 km3 of removed ice with possible mechanisms of formation like that of a collapse from subsurface deflation, possibly from cryovolcanic processes. Plain language summary Hekla Cavus is a large, irregularly shaped depression that is part of a larger ridge-trough system through eastern Cthulhu Macula, Pluto. Recently acquired high-resolution images and topography derived from the New Horizons mission were used to describe the geometry and geologic setting of this possible subsurface collapse pit. Estimations of the removed ice volume at Hekla Cavus also provided insight to its possible collapse history. This study also comparatively measures the dimensions of impact craters and sublimation pits of Pluto to define Hekla Cavus to be a rare feature. Thus, the origins of Hekla Cavus may have been a subsurface cryovolcanic collapsing process.

The composition of two dune fields, Ogygis Undae and the NE–SW trending dune field in Gale crater (the “Bagnold Dune Field” and “Western Dune Field”), were analyzed using thermal emission spectra from the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) and the Mars Odyssey Thermal Emission Imaging System (THEMIS). The Gale crater dune field was used as a baseline as other orbital compositional analyses have been conducted, and in situ sampling results will soon be available. Results from unmixing thermal emission spectra showed a spatial variation between feldspar mineral abundances and pyroxene mineral abundances in Ogygis Undae. Other datasets, including nighttime thermal inertia values, also showed variation throughout the dune field. One explanation proposed for this variation is a bimodal distribution of two sand populations. This distribution is seen in some terrestrial dune fields. The two dune fields varied in both mineral types present and in uniformity of composition. These differences point to different source lithologies and different distances travelled from source material. Examining these differences further will allow for a greater understanding of aeolian processes on Mars.