Scientists have long predicted that Mars had significant volcanic activity in the first billion years of its history, but images of the planet's surface haven't delivered as much evidence of volcanoes as they expected.
New research suggests, however, that scientists may have been looking for the wrong kind of volcanoes.
A new study in the journal Nature argues that a handful of geological formations on Mars that were thought of as impact craters were once, instead, supervolcanoes. They never looked like mountains; rather, they formed when the ground collapsed on itself in violent explosions.
"This is a totally new kind of process that we hadn't thought about for Mars, and it changes the way we view the evolution of the planet," said lead study author Joseph Michalski of the Planetary Science Institute in Tucson, Arizona, and the National History Museum in London.
The volcanic eruptions likely represented the biggest explosions in the history of Mars, Michalski said. These explosions would have occurred more than 3.5 billion years ago.
He and NASA colleague Jacob Bleacher focused on a region on Mars called Arabia Terra, which is speckled with craters. Bleacher could not discuss the study Wednesday, Michalski said, because of the United States government shutdown that furloughed most of NASA's employees. (But Mars rover operations, including driving and using scientific instruments, are continuing this week, a NASA spokesman said).
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