Mars has been extensively photographed by cameras and compositionally detected by spectrometers onboard orbiters on a global scale, and explored in-situ by landers and rovers at both local and outcrop scales in different locations. The results have proved that the Martian surface is rich in Earth-like geomorphologies, and the study of terrestrial analogs to Mars has been listed as one of the highest priorities of Martian science. With increasing new discoveries by in-situ explorations, Mars exploration has begun to enter the era of focusing on detailed analyses at regional to outcrop levels, rather than global mapping. Analog studies are playing a crucial role in this transition, making this book, which introduces the methodology and provides cases for readers, essentially important.Dozens of sites on Earth have been listed as analog targets for comparative study with the geomorphology, geology, geochemistry, environment and habitability of Mars. However, due to the diversity of landforms and forming mechanisms, and the long history of Mars, no single analog site on Earth can be fully compared to Mars. Nonetheless, the Qaidam Basin has been listed as an unique Mars analog site for studying the red planet's geomorphology, geology, and environmental changes, particularly regarding the evolution of paleolakes on Mars. This kind of setting has always been listed as a top priority for the search of life on Mars.This book contains first-hand information and on-site images obtained by the work's contributing authors, and is an essential read for anyone interested in Martian geomorphology and its evolution processes and history.

Many facets of studies in planetary science are dependent on analyzing large volumes of in-situ and spacecraft data. Our understanding of the lunar evolution and its connection to deeper interior layers has been dramatically improved by the so-called deep space exploration missions, including NASA’s lunar reconnaissance orbiter narrow-angle camera, China’s Moon and Mar exploration program, and Chang’e series lunar relay satellite program, in coordination with Earth-based supporting observations. From Apollo 17 lunar surface operations (1972), there are many related operations including China’s lunar and deep space exploration (Chang’e-1 2007; Chang’e-2 2010; Chang’e-3 2013; Chang’e-4 2018; Chang’e-5 2020). On the 50th anniversary of the final Apollo mission to the Moon, this topic will bring together theory, numerical models, and observations capable of advancing our understanding of lunar evolution.

Thanks to NASA's Dawn mission, the last half-decade has witnessed a significant advance in our understanding of Ceres. The largest object between the orbits of Mars and Jupiter, Ceres is the most water-rich body in the inner solar system after Earth which shows evidence of brine-driven activity in its recent history, and even possibly at the present. The potential existence of a subsurface ocean or regional seas in Ceres and its salt- and organic-rich composition underscore its astro-biological significance. After signaling the discovery of the asteroid belt more than two centuries ago, Ceres once again reveals new insights for us to understand the formation, evolution, and habitability of this large icy body in our solar system.This book reviews the current state of knowledge about Ceres after the extensive scientific exploration by the Dawn mission. Starting from the introduction of the discovery of Ceres and what we know about this enigmatic world before Dawn's arrival, each chapter focuses on one aspect of Ceres, including its surface composition, its geology, the role of water ice in shaping Ceres's surface, its interior structure, and expressions of cryovolcanic or brine activity at the surface. Following this framework, the book addresses the astro-biological significance of Ceres. The last chapter summarizes the new questions opened by the Dawn mission and the next step to exploring the dwarf planet closest to Earth.Related Link(s)

Astronomy has been associated with the detection of electromagnetic waves or photons from within and beyond the solar system, ranging from Radio to Gamma-ray Astronomy. Particle Astrophysics, including Neutrino and Dark-Matter Astrophysics today, started with the discovery of cosmic rays in 1911. The Space Age expanded particle observations to in-situ studies of lower energy electrons and ions with a variety of charge states in space plasmas traversed by spacecraft. Remote observation of space plasmas became possible only after the discovery of energetic neutral atoms (ENAs) in space in 1950.This book is a primer for those who wish to learn more about the origins of ENAs, related detection techniques, and how ENA images and spectra can be used to study space plasmas beyond the reach of spacecraft. It tells a comprehensive story from the first encounters with ENAs in the Earth's magnetosphere to Neutral-Atom Astronomy of the edge of the heliosphere and the interstellar medium. This story includes how ion mass spectrographs evolved into ENA imagers, overcoming the technical challenges, how to extract information from ENA data, and a variety of diagnostic applications on the magnetosphere, interplanetary space, other solar-system objects, the heliospheric boundary, the local interstellar medium, and a glimpse into the future of Neutral-Atom Astronomy.The authors hope to inform and inspire readers to further enrich this field of study.

Gullies on Mars resemble terrestrial gullies involved in the transport of abundant material down steep slopes by liquid water. However, liquid water should not be stable at the Martian surface. The articles in this volume present the two main opposing theories for Martian gully formation: climate-driven melting of surficial water-ice deposits and seasonal dry-ice sublimation. The evidence presented ranges from remote-sensing observations, to experimental simulations, to comparison with Earth analogues. The opposing hypotheses imply either that Mars has been unusually wet in the last few million years or that it has remained a cold dry desert – both with profound implications for understanding the water budget of Mars and its habitability. The debate questions the limits of remote-sensing data and how we interpret active processes on extra-terrestrial planetary surfaces, even beyond those on Mars, as summarized by the review paper at the beginning of the book.

Martian surface contains diverse lithologies (from sedimentary rocks to mafic-ultramafic igneous rocks) and ground patterns. These rocks record the late-stage evolution on the Martian surface from a temperate environment with bodies of liquid water to the current cold and hyper-arid environment. The constraints on the key parameters and processes for water-rock interaction, sedimentation of materials, and geomorphological development can provide important insights into the environmental change and habitability on the Martian surface. However, due to the difficulty in accessing Martian samples and limited remote-sensing data available from the Martian surface, most of the mysteries on Mars remain unraveled. In this proposed research topic we will focus on geological settings on Earth that are similar to the conditions on Mars. These Mars analogs are employed to infer possible processes on Mars and their impact on habitability and the search for life. The Mars analogs on Earth span a variety of environments, such as the super-arid sedimentary plains (e.g., the Qaidam Basin in the north of the Tibetan Plateau, the Mojave Basin in the USA, and the Atacama Desert in South America), the subsurface fracture waters in Precambrian cratons (e.g., the Canadian Shield, the Fennoscandian Shield, and the Kaapvaal Craton), high salinity localities (e.g. Laguna de Tírez, salt mines, and deep-sea brines) as well as extremely cold and highly radiative environments (e.g., polar regions, thin atmosphere). These settings on Earth are more accessible for collecting high-quality mineralogical, geochemical, geochronological, and microbiological data by the state-of-the-art facilities. These data can provide a solid cornerstone for us to understand the cycles of water and other life-essential elements, and their impact on habitability and biodiversity in extreme environments on Earth as well as the limits of life and the detection of biosignatures. Such research can also provide vital insights on the search for life on other planets and moons.

This Research Topic is the second volume of the 'Community series-Extremophiles: Microbial Genomics and Taxogenomics'. Please see the first volume here. Extreme habitats exist across the globe and span over three quarters of our planet. They can be widely different from a physical-chemical perspective as they include diverse types of extreme, such as temperature, pH, salinity, radiation, pressure, low water activity, low nutrient availability, etc. Organisms capable of adjusting, surviving, or thriving in those habitats, which are so hostile that they were previously thought to be adverse or lethal for life, are called “extremophiles”.