kosmos: Comparative planetary science

Evidence: 100 • authority: 72

Comparative planetary science or comparative planetology is a branch of space science and planetary science in which different natural processes and systems are studied by their effects and phenomena on and between multiple bodies. The planetary processes in question include geology, hydrology, atmospheric physics, and interactions such as impact cratering, space weathering, and magnetospheric physics in the solar wind, and possibly biology, via astrobiology. Comparison of multiple bodies assists the researcher, if for no other reason than the Earth is far more accessible than any other body. Those distant bodies may then be evaluated in the context of processes already characterized on Ear…

Evidence: 46 • authority: 92

What the Solar System Can Teach Us About Rocky Exoplanets.. The number of rocky extrasolar planets being discovered continues to increase, but so too does the apparent diversity of such worlds. As we work to understand the likely bulk properties and thermal, geological, and climatological attributes we might expect of rocky exoplanets, we can look to the Solar System for guidance. Here, we review the interior, surface, and atmospheric characteristics of modern Earth, and discuss how our homeworld has changed through Solar System history. We then visit in turn Venus, Mars, Mercury and Earth's Moon, and Io, noting how these terrestrial planets are alike, how they are different, and how they h…

Evidence: 46 • authority: 72

Planetary science (or more rarely, planetology) is the scientific study of celestial bodies (such as planets (including Earth), moons, asteroids, comets) and planetary systems (in particular those of the Solar System) and the processes of their formation. It studies objects ranging in sizes from micrometeoroids to huge gas giants, with the aim of determining their composition, dynamics, formation, interrelations and history. It is a strongly interdisciplinary field, which originally grew from astronomy and Earth science, and now incorporates many disciplines, including planetary geology, cosmochemistry, atmospheric science, physics, oceanography, hydrology, theoretical planetary science, gl…

Evidence: 41 • authority: 92

Exo-Geoscience Perspectives Beyond Habitability.. This article reviews the emerging field of exo-geoscience, focusing on the geological and geophysical processes thought to influence the evolution and (eu)habitability of rocky exoplanets. We examine the possible roles of planetary interiors, tectonic regimes, continental coverage, volatile cycling, magnetic fields, and atmospheric composition and evolution in shaping long-term climate stability and biospheric potential. Comparisons with Earth and other planets in the Solar System highlight the diversity of planetary conditions and the rarity of conditions relevant to life. We also discuss contingency and convergence in planetary and biologi…

Evidence: 36 • authority: 72

This article includes a list of the most massive known objects of the Solar System and partial lists of smaller objects by observed mean radius. These lists can be sorted according to an object's radius and mass and, for the most massive objects, volume, density, and surface gravity, if these values are available. These lists contain the Sun, the planets, dwarf planets, many of the larger small Solar System bodies (which includes the asteroids), all named natural satellites, and a number of smaller objects of historical or scientific interest, such as comets and near-Earth objects. Many trans-Neptunian objects (TNOs) have been discovered; in many cases their positions in this list are appro…

Evidence: 36 • authority: 72

A planet is a large, rounded astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets by the most restrictive definition of the term: the terrestrial planets Mercury, Venus, Earth, and Mars, and the giant planets Jupiter, Saturn, Uranus, and Neptune. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young protostar orbited by a protoplanetary disk. Planets grow in this disk by the gradual accumulation of material driven by gravity, a process called accretion. The word planet comes fro…

Evidence: 32 • authority: 92

On the coincidence between the close passage of HD7977 and the Pliocene-Pleistocene transition.. The Oort Cloud's dynamical evolution is significantly influenced by both the galactic tide and stellar flybys. This study investigates the particular case of HD7977's close encounter 2.47 Myr ago, which likely repopulated the Inner Oort Cloud and potentially triggered a significant comet shower on Earth. Our results demonstrate that the shower's intensity strongly depends on HD7977's impact parameter (b), with possible flyby distances ranging from 2,300 AU to ∼ 13,000 AU. For the closest approach ([Formula: see text] AU), the terrestrial impact probability of 1 km comets increases by an order of…

Evidence: 32 • authority: 72

Science fiction (often shortened to sci-fi or abbreviated SF) is the genre of speculative fiction that imagines advanced and futuristic changes in technology, scientific knowledge, or biological systems. The elements common to science fiction have increased over time: from space exploration, extraterrestrial life, time travel, and robotics; to parallel universes, dystopian societies, and biological manipulations; and, most recently, to information technology, transhumanism, posthumanism, and environmental challenges. Science fiction often explores human responses to the consequences of these types of projected or imagined scientific advances. The precise definition of science fiction has lo…

Evidence: 32 • authority: 72

The Solar System is the gravitationally bound system of the Sun and the masses that orbit it, most prominently its eight planets, of which Earth is one. The Solar System is an isolated single-star planetary system (not part of a larger star system) within the Milky Way Galaxy. The system formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, creating the Sun and a protoplanetary disc from which the orbiting bodies assembled. The Sun accounts for 99.86% of the Solar System's total mass. Inside the Sun's core, hydrogen is fused into helium, releasing energy that is emitted through the Sun's photosphere. This creates the heliosphere and a decreasing temperature…