Like an ancient impact crater, the circular, raised rim around the supervolcano feature has been worn away, but although old Martian craters and Eden Patera might look similar on the outside, they are markedly different on the inside.
"If these things were impact craters, then they have experienced a lot of erosion," Michalski said. "That means they should be shallow … but these things are very deep, actually. They have a depth, which is something more like a pristine crater, but a pristine crater has all that stuff preserved. So, it doesn't make sense; it doesn't add up … They just don't look like impact craters."
Michalski and his team used data from instruments aboard the Mars Global Surveyor spacecraft (which stopped operations in 2006), the Mars Odyssey orbiter, the Mars Reconnaissance Orbiter and others. But two rovers on Mars also might help the scientists bolster their claims.
The volcanoes in the Arabia Terra region might be responsible for the powdery deposits NASA's Mars Curiosity rover and the agency's Opportunity rover found in the Gale Crater and Meridiani Planum landing sites, respectively.
"I agree with the authors that if such volcanoes have been widespread, disseminated and explosive, their findings are very important on the so-far-not-well-understood climate history and past habitability of Mars," Helmut Lammer, a senior scientist at the Space Research Institute at the Austrian Academy of Sciences who is not associated with the study, told SPACE.com in an email. "The importance in the study lies in the fact that our understanding on early Mars volcanism becomes better."
Although these results are exciting, Michalski hopes that other scientists will follow up on his work. "We suspect there very well may be more of them , but we just haven't been looking for them," Michalski said.
More from SPACE.com: