NASA’s Mars Curiosity rover has made plenty of amazing discoveries in the years it has sepnt roaming the Red Planet, but its latest discovery may prove to be one of its most interesting.

Scientists had long thought of Mars as a stable planet as it has no tectonic plates, but a new study suggests that violent volcanoes once tore apart its surface in the distant past.

Scientists examined data from the rover and found evidence of epxlosive volcanoes. They found high concentrations of the mineral tridymite at the Gale crater, a mineral commonly found in volcanoes on Earth. Researchers think this mineral may have been carried to various places on the surface of Mars by ancient water streams.

More research will be necessary to confirm that the tridymite didn’t come from some other method, but it’s pretty strong circumstantial evidence of volcanoes.

The finding raises some interesting questions, including whether or not Mars once had tectonic plates, and if not how volcanoes developed.

“Tridymite, a SiO2 mineral that crystallizes at low pressures and high temperatures (>870 °C) from high-SiO2 materials, was detected at high concentrations in a sedimentary mudstone in Gale crater, Mars,” the abstract of the paper states. “Mineralogy and abundance were determined by X-ray diffraction using the Chemistry and Mineralogy instrument on the Mars Science Laboratory rover Curiosity. Terrestrial tridymite is commonly associated with silicic volcanism where high temperatures and high-silica magmas prevail, so this occurrence is the first in situ mineralogical evidence for martian silicic volcanism. Multistep processes, including high-temperature alteration of silica-rich residues of acid sulfate leaching, are alternate formation pathways for martian tridymite but are less likely. The unexpected discovery of tridymite is further evidence of the complexity of igneous petrogenesis on Mars, with igneous evolution to high-SiO2 compositions.”