Mars is pockmarked with indents and holes due to its complex geological history. But one particular crater has been confusing the scientists studying the Red Planet’s surface because, to put it simply, they have no idea how it got there.
Known as Ismenia Patera, from the Latin for “flat bowl”, the 75-kilometers-wide (46 miles) hole in a particularly level region of Mars is a pretty notable feature. To get a better understanding of how it formed, researchers over at the European Space Agency (ESA) have been taking some pretty impressive snaps of the crater. And well, they’re still not certain.
Those studying the surface features and geography of Mars currently have two theories as to how Ismenia Patera came into being. The first suggests that an asteroid smacked into the surface, spraying the surrounding plane with debris, while the second no less dramatic explanation involves a supervolcano catastrophically erupting so much magma that the volcano collapsed in on itself.
Just like Earth – and every planet in our Solar System – it is not unusual for Mars to be bombarded with rocks as they hurtle about space. In fact, some think that both of Mars’ moons were likely formed by asteroid impacts so great that bits of the planet were ejected into orbit, before coalescing into Phobos and Deimos.
So it would seem that a meteor strike would be the likely cause of Ismenia Patera. As a chunk of rock smacked into the northern lowlands, it would have caused the deep impact crater we currently see. Over a period of a few million years, sedimentary deposits and ice may have flowed down into the crater, weakening it until it collapsed and formed the uneven, cracked surface today.
But this theory has its problems, namely that there is little evidence for any surrounding debris that would have been kicked up after such a large impact. This has led some researchers to suggest an alternate cause behind Ismenia Patera, in the form of a massive volcano.
They argue that there may have once been a volcano so big – again not unusual considering Mars is home to the tallest volcano in the Solar System in the form of Olympus Mons – that when it erupted and spewed all of its molten rock skyward it simply collapsed in on itself as a result.
The Arabia Terra region does show signs of once being an active volcanic region, so this would fit. Yet the problem here is that a volcano of this size, with such a large volume of magma held within, would be classed as a supervolcano, but we didn’t think that Mars had any (despite its clearly massive size, Olympus Mons is not technically a supervolcano).
Here's hoping that more data on the surface and interior of Mars might one day solve this mystery.