April 13 (UPI) -- ESA's Mars Express has photographed a unique and mysterious geologic structure on the Martian surface.
Astronomers aren't sure of the crater's origins. The crater, dubbed Ismenia Patera, may have been created by a meteorite impact. It's also possible the imprint was left behind by an ancient supervolcano.
The layout and structural patterns seen in and around Ismenia Patera are different and more complex than the typical impact crater. Uneven lumps of rock are found scattered around the outer edge of the crater.
Scientists believe the rocky deposits are debris ejected by neighboring impacts. These miniature impacts have created their own system of gullies inside Ismenia Patera.
The crater's floor is dynamic, too, showing signs of movement. The floor is likely composed of a rocky, ice-rich glacier, with layers of ice built up over time.
The European Space Agency's Mars Express probe has been circling the Red Planet since 2003, providing high-resolution imagery of the planet's surface. The probe's images can help astronomers analyze unusual formations like Ismenia Patera.
For planetary scientists, the hardest -- and perhaps the most important -- part of interpreting geologic features is creating a timeline, a succession of events. Researchers want to determine what created the larger, overall structure, and then figure out what kinds of processes and subsequent events altered its appearance.
Ismenia Patera is a perfect example of the kind of dynamic features that challenge scientists. The crater was created by an origin event of sorts. But over time, it became altered, or textured, by separated events.
Even the simplest geologic features evolve, or change, after their formation.
So what created Ismenia Patera to begin with? Scientists only have theories.
One possibility is that a meteor left an imprint that was then filled in by flowing deposits of ice and rock. The deposits weigh down the crater floor, causing it to crack, yielding the uneven landscape still observable today.
The second possibility is that Ismenia Patera was a supervolcano that exploded violently and then collapsed.
Planetary scientists aren't certain whether Mars hosted supervolcanos, volcanoes that produce massive, violent eruptions, but the Red Planet does feature large volcanic structures. Mars' Olympus Mons is the largest volcanic structure in the solar system.
To determine Ismenia Patera's origin story with certainty, researchers need more evidence than what ESA's Mars Express can provide, which is why both ESA and NASA are planning missions to Mars to study Mars' interior and subsurface.