The uncertain origin of the Ismenia Patera crater on Mars

Ismenia Patera (Image ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO)
Ismenia Patera (Image ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO)

ESA has published new images of a crater called Ismenia Patera on the planet Mars captured by the Mars Express space probe. The red planet is full of craters but this is unique because generally those formations are the result of a meteorite impact while Ismenia Patera could be what remains of a supervolcano that was active when Mars was very young. A very violent volcanic activity may have caused the destruction of other traces of a supervolcano at the same time creating the strange, somewhat irregular formation we see today.

Ismenia Patera is part of the region of Mars called Arabia Terra, is about 75 kilometers across and has a central area surrounded by a number of small hills and rocky lumps that may derive from materials ejected into the crater by nearby impacts. Those materials also created small dips and depressions that can be seen inside the crater.

Gullies and channels run from the edge of the crater to its bottom, covered with ice deposits that show signs of flows and movements. They’re probably similar to rocky and ice-rich glaciers where they accumulated over time thanks to the cold and arid climate. The recent images captured by the Mars Express space probe show details that could be very useful in determining the origins of Ismenia Patera, still unclear.

According to the impact theory, a meteorite generated the original crater which was later filled with ice. Subsequently, the crater collapsed and erosive phenomena started generating the irregular formations that exist today. According to the supervulcano theory, an ancient eruption threw huge amounts of magma in the surroundings causing at the same time its own collapse.

It’s not certain that supervolcanoes existed on the planet Mars in the first place. Scientists are reconstructing the red planet’s geological history and when it was young certainly volcanic activity was also remarkable but not enough to establish that there were also supervulcanoes, capable of ejecting amounts of materials in a single eruption much greater than normal volcanoes.

Arabia Terra hosts a system of ancient rivers’ beds but was also the scene of volcanic activity and therefore one of the possible candidates for the presence of a supervolcano. In particular, another crater of that region called Siloe Patera, with a diameter of about 39 kilometers, could have that origin.

The doubts about those craters’ origin are due, among other things, to some features of Arabia Terra. The shapes irregularity and the lack of traces of ejected materials around the crater are among those that suggest a volcanic origin. The problem is that they don’t indicate it with certainty because they could be the result of interactions with the surrounding environment that occurred after a meteorite impact.

The history of Arabia Terra and therefore also of Ismenia Patera is complex so its reconstruction will require further study. It’s an area of ​​transition between Mars’ northern and southern regions with remarkable topographic differences. Understanding what happened will also help to reconstruct the climate collapse that transformed a planet that in some ways was similar to the Earth into today’s desert.

Perspective view of Ismenia Patera (Image ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO)
Perspective view of Ismenia Patera (Image ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO)

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