Near the middle of this photo from the High Resolution Stereo Camera on the European Space Agency’s Mars Express is the Siloe Patera. Siloe Patera lies in the Arabia Terra region of Mars, and measures 20 km by 40 km. Recent research suggests it could be the remains of a supervolcano.
Image credit: ESA/DLR/FU Berlin/CC BY-SA 3.0 IGO
Comparing the features of a number of these depressions on Mars to impact craters and caldera (a collapse of land following a volcanic eruption), some scientists have come to the conclusion that Arabia Terra is home to Yellowstone-like supervolcanoes. Explains the European Space Agency:
[Siloe Patera] is characterised by two depressions with steep-sided walls, collapse features and low topographic relief. The two depressions could even represent two different eruptive episodes due to collapse as the underlying magma pressure was released, or as the magma chamber migrated below the surface.
By comparison, impact craters include features such as a central peak, uplifted crater rims and ejecta blankets surrounding them. Indeed, impact craters are widespread in this scene: textbook examples can be found in the two side-by-side craters just above Siloe Patera, and in the large crater at the far right of the scene. These craters each exhibit a central peak, terraced crater walls and a surrounding ejecta blanket.
An impact crater with depth to diameter ratio comparable to Siloe Patera would be expected to show these features – unless perhaps the crater had undergone extensive erosion or modification – but it does not.
In order to be sure whether Siloe Patera and its siblings are craters or the remains of supervolcanic eruptions, there needs to be — as always — more data.
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