Artemis Corona

Artemis Corona is a corona found in the Aphrodite Terra continent, on the planet Venus, at 35°S 135°E.

Named after Artemis, the virgin goddess of hunting, it is the largest corona on Venus, with a diameter of 2,600 kilometers. It is largely enclosed by the near circular Artemis Chasma - a circular belt of arc-shaped features believed to be largely of compressional origin.

Artemis is an unusual feature on Venus as it has been interpreted to be the site of plate tectonics operating on a regional scale. There are grabens and compressional arcs which rise above the surrounding plains. As a whole, Artemis is not elevated like other coronae. Regions within Artemis are in fact some 4 km below the surrounding plains. The differences between the highest and the lowest point within Artemis are in the order of 7.5 km.

The central rift region of Artemis has been interpreted as a spreading zone (Britomartis Chasma) which has been offset - with clear signs of strike-slip faulting offsetting the central rift zone. Retrograde subduction is interpreted to occur at the circular arc belts of Artemis Chasmata.

Debate during the past decade has resulted in the proposal of at least four hypotheses for Artemis’ formation.

The first (herein referred to as H1) is that Artemis Chasma represents a zone of northwest-directed convergence and subduction.

The second hypothesis (herein referred to as H2) is that Artemis consists of a composite structure with a part of its interior region marking the exposure of deformed ductile deep-crustal rocks analogous to a terrestrial metamorphic core complex.

The third (herein referred to as H3) is that Artemis reflects the surface expression of an ancient (>3.5 Ga) huge bolide impact event on cold strong lithosphere.

The fourth hypothesis (herein referred to as H4) is that Artemis marks the surface expression of a deep mantle plume.

Each of these hypotheses holds different implications for Venus geodynamics and evolution processes, and for terrestrial planet processes in general.

Viability of H1 would provide support that terrestrial-like plate-tectonic processes once occurred on Earth’s sister planet.

The feasibility of H2 would require high values of crustal extension and therefore imply that significant horizontal displacements occurred on Venus—displacement that may or may not be related to terrestrial-like plate-tectonic processes.

The possibility of H3 would suggest that Venus’ surface is extremely old, and that Venus has experienced very little dynamic activity for the last 3.5 billion years or more; this would further imply that Venus is essentially tectonically dead, and has been for most of its history. This view contrasts strongly with studies that highlight a rich history of Venus including activity at least as young as 750 million years ago, and quite likely up to the present.

If H4 has credibility, then Artemis could provide clues to cooling mechanisms of Earth’s sister planet. Each of these hypotheses might be tested through geologic mapping aimed at unraveling the geologic history of Artemis and its surroundings.

Artemis lies almost completely within the bounds of the Artemis Chasma quadrangle, V–48, which encompasses more than seven million square kilometers of Venus’ southern hemisphere, extending from 25° to 50° S. and 120° to 150° E. Thus, construction of a 1:5 million-scale geologic map of Artemis Chasma quadrangle allows for unraveling the geologic history of Artemis to test various hypotheses of Artemis’ evolution.

As a result of geological mapping, Roger A. Bannister and Vicki L. Hansen (Sept 2010) propose a hybrid hypothesis for Artemis’ formation.

The hybrid hypothesis, which represents a modification to the plume hypothesis, involves the formation of an interior spreading center and newly formed crust, similar to that formed at a terrestrial divergent planet-boundary, as a result of a mantle plume; shortening of this crust within the chasma, which moves outward with continued formation of interior crust, might represent a failed Venusian attempt at subduction; the surface crust did not recycle to the mantle. Interior tectonomagmatic centers form broadly synchronously with interior crust formation. It is unclear when Artemis formed within Venus’ evolution, although we postulate that it formed on thin lithosphere. Through this hybrid hypothesis we postulate that Artemis may record Venus’ failed attempt at terrestrial plate-tectonic-like processes.

External links

• A picture of Artemis Corona and its Chasma from NASA
• A 3-dimensional profile of Artemis region See: http://www.windows.ucar.edu/tour/link=/venus/interior/V_coronae.html&fr=t