In planetary geology

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...

, a corona (plural: coronae) is an oval

Oval

An oval is any curve resembling an egg or an ellipse, such as a Cassini oval. The term does not have a precise mathematical definition except in one area oval , but it may also refer to:* A sporting arena of oval shape** a cricket field...

-shaped feature. Coronae appear on both the planet Venus

Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

 and Uranus

Uranus

Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

's moon Miranda

Miranda (moon)

-External links:* at * at The Nine8 Planets* at Views of the Solar System* * from the...

 and may be formed by upwellings of warm material below the surface.

Coronae on Venus

On Venus, coronae are large (typically several hundred kilometres across), crown-like, volcanic features.

Coronae were first identified in 1983, when the radar

Radar

Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

 imaging equipment aboard the Venera 15

Venera 15

Venera 15 was a spacecraft sent to Venus by the Soviet Union. This unmanned orbiter was to map the surface of Venus using high resolution imaging systems...

 and Venera 16

Venera 16

Venera 16 was a spacecraft sent to Venus by the Soviet Union. This unmanned orbiter was to map the surface of Venus using high resolution imaging systems...

 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 Venus

Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

 is the Artemis Corona

Artemis Corona

Artemis Corona is a corona found in the Aphrodite Terra continent, on the planet Venus, at .Named after Artemis, the virgin goddess of hunting, it is the largest corona on Venus, with a diameter of 2,600 kilometers...

, which is 2100 km in diameter.

Coronae on Miranda

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

Diapir

A diapir is a type of 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-Taylor instability-type structures in regions with low tectonic stress...

s: upwellings of warm ice.