geografia: Titan (moon)

Evidence: 100 • authority: 72

Titan is the largest moon of Saturn and the second largest in the Solar System. It is the only moon that is known to have a dense atmosphere (denser than that of Earth), and is the only known object in the Solar System besides Earth with clear evidence of stable bodies of surface liquid. Titan is one of seven gravitationally rounded moons of Saturn, and is the second-most distant among them. Frequently described as a planet-like moon, Titan is 48.16% larger in diameter than Earth's moon, and 80% more massive. It is the second-largest moon in the Solar System after Jupiter's Ganymede, and is larger than Mercury, and yet Titan is only 40% as massive as Mercury, because Mercury is mainly iron…

Evidence: 45 • authority: 72

Callisto ( kə-LIST-oh) is the second-largest moon of Jupiter, after Ganymede. It is also the third-largest moon in the Solar System, following Ganymede and Saturn's moon Titan, and nearly as large as the planet Mercury, but only about a third of that planet's mass. With a diameter of 4,821 km, Callisto is roughly a third larger than Earth's Moon and orbits Jupiter on average at a distance of 1.883 million km, which is about five times further out than the Moon orbiting Earth. It is the outermost of the four large Galilean moons of Jupiter, which were discovered in 1610 with one of the first telescopes, and is today visible from Earth with common binoculars. The surface of Callisto is the ol…

Evidence: 45 • authority: 72

Saturn has 293 moons with confirmed orbits as of June 2026, the most of any planet in the Solar System. Saturn's moons are diverse in size, ranging from tiny moonlets to Titan, which is larger than the planet Mercury and the second largest moon in the Solar System. Three of these moons possess particularly notable features: Titan has a nitrogen-rich atmosphere and a landscape featuring river networks and hydrocarbon lakes; Enceladus emits jets of ice from its south-polar region and is covered in a deep layer of snow; and Iapetus has contrasting black and white hemispheres as well as an extensive ridge of equatorial mountains which are among the tallest in the Solar System. Twenty-five of th…

Evidence: 45 • authority: 72

Ganymede is a natural satellite of Jupiter and is the largest and most massive moon in the Solar System. Like Saturn's largest moon, Titan, it is larger than the planet Mercury, but has somewhat less surface gravity than Mercury, Io, or Earth's Moon due to its lower density compared to the three. Ganymede orbits Jupiter in roughly seven days and is in a 1:2:4 orbital resonance with the moons Europa and Io, respectively. Ganymede is composed of silicate rock and water in approximately equal proportions. It is a fully differentiated body with an iron-rich, liquid metallic core, giving it the lowest moment of inertia factor of any solid body in the Solar System. Its internal ocean potentially…

Evidence: 42 • authority: 72

Iapetus () is the outermost of Saturn's large moons. With an estimated diameter of 1,469 km (913 mi), it is the third-largest moon of Saturn and the eleventh-largest in the Solar System. Named after the Titan Iapetus from Greek mythology, the moon was discovered in 1671 by Giovanni Domenico Cassini. A relatively low-density body composed mostly of ice, Iapetus is home to several distinctive and unusual features, such as a striking difference in coloration between its dark leading hemisphere and its bright trailing hemisphere, as well as a massive equatorial ridge that runs three-quarters of the way around the moon.

Evidence: 27 • authority: 92

The chemistry of habitable oceans in the Solar system.. Liquid water exists on the Earth and several other planetary bodies in our solar system. The chemical character of these aqueous reservoirs is central to evaluating their habitability. Here, we synthesize the chemical features of water reservoirs and their biological implications on the modern Earth. We then outline constraints on the evolutionary history of Earth's ocean chemistry and discuss its interplay with the biosphere. Furthermore, we examine the inferred chemical environments of water bodies on early Mars, dwarf planet Ceres, Jupiter's moon Europa and Saturn's moons Enceladus and Titan. We conclude by outlining priority questi…

Evidence: 21 • authority: 92

Origin and Evolution of the Galilean Satellites Within the Jovian System.. We review the key observations and theories relevant to the origin and evolution of the Galilean satellites. Key observations include: the potentially undifferentiated nature of Callisto; the increasing ice fraction with semi-major axis; the present-day existence of the Laplace resonance; the potential resurfacing of Ganymede mid-way through its evolution; and the metal-enriched nature of Jupiter's envelope. The most widely accepted theory for the formation of the satellites is the so-called "starved disk" model, although newer alternatives including decretion disks and pebble accretion have also been proposed. Model…

Evidence: 21 • authority: 92

Titan's strong tidal dissipation precludes a subsurface ocean.. The Cassini mission provided unprecedented insights into Saturn's largest moon, Titan, from its atmosphere to the deep interior 1 . The moon's large measured response to the tides exerted by Saturn was interpreted as evidence of the existence of a subsurface ocean 2,3 . This response, twice the value predicted in pre-Cassini studies, has escaped complete explanation. Here we show that the signature of tidal dissipation in Titan's gravity field is not consistent with the presence of an ocean. Our results arise from the detection of this signature through a reanalysis of the radiometric data acquired by Cassini with improved tech…

Evidence: 21 • authority: 92

Ammonia as a parameter shaping habitability on icy moons.. The search for life now extends beyond the traditional habitable zone to include the icy moons of Jupiter and Saturn. These moons feature ice-covered surfaces overlying substantial oceans formed primarily of liquid water and other potential constituents, such as ammonia. On Earth, ammonia supports biochemistry at low concentrations by providing nitrogen but becomes disruptive at higher concentrations. Ammonia could therefore influence the habitability of extraterrestrial oceans, yet this topic has received limited attention in the literature. This review synthesises current research on ammonia in Saturn's icy moons, Enceladus and Ti…