planetary geology Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science discipline concerned with the geology of the celestial bodies such as the planets and their moons, asteroids, comets, and meteorites. Although the ge ...

, a corona (plural: coronae ) is an

oval An oval () is a closed curve in a plane which resembles the outline of an egg. The term is not very specific, but in some areas (projective geometry, technical drawing, etc.) it is given a more precise definition, which may include either one ...

-shaped feature. Coronae appear on both the planet

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...

and

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...

's moon Miranda and may be formed by upwellings of warm material below the surface.

Coronae on Venus

The geodynamic surface of Venus is dominated by patterns of basaltic volcanism, and by compressional and extensional tectonic deformation, such as the highly deformed

tesserae A tessera (plural: tesserae, diminutive ''tessella'') is an individual tile, usually formed in the shape of a square, used in creating a mosaic. It is also known as an abaciscus or abaculus. Historical tesserae The oldest known tessera ...

terrain and the concentrically-fractured coronae. On Venus, coronae are large (typically several hundred kilometres across), crown-like, volcanic features. Coronae were first identified in 1983, when the

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...

imaging equipment aboard the

Venera 15 Venera 15 (russian: Венера-15 meaning ''Venus 15'') was a spacecraft sent to Venus by the Soviet Union. This uncrewed orbiter was to map the surface of Venus using high resolution imaging systems. The spacecraft was identical to Venera 16 ...

and

Venera 16 Venera 16 (russian: Венера-16 meaning ''Venus 16'') was a spacecraft sent to Venus by the Soviet Union. This uncrewed orbiter was to map the surface of Venus using high resolution imaging systems. The spacecraft was identical to Venera 1 ...

spacecraft produced higher-resolution images of some features previously thought to be impact craters. It is believed that coronae are formed when plumes of rising hot material in the mantle push the crust upwards into a dome shape, which then collapses in the centre as the molten magma cools and leaks out at the sides, leaving a crown-like structure: the corona. The largest corona on

is the

Artemis Corona Artemis Corona is a corona found in the Aphrodite Terra continent, on the planet Venus, at . Named after Artemis In ancient Greek mythology and religion, Artemis (; grc-gre, Ἄρτεμις) is the goddess of the hunt, the wildernes ...

, which is 2100 km in diameter.

Coronae on Miranda

The small Uranian ovoid features coronae that are very large in relation to its size. They may be formed by

diapirs A diapir (; , ) is a type of igneous intrusion in which a more mobile and ductily deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh–T ...

: upwellings of warm ice.{{cite conference , first = Pappalardo , last = R. , author2=Greeley, R. , title = Structural evidence for reorientation of Miranda about a paleo-pole , book-title = In Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z , pages = 1111–1112 , year = 1993 , bibcode = 1993LPI....24.1111P

Notes

Surface features of bodies of the Solar System Planetary geology