How Explosive Was Ancient Mars?


Abstract

  • Mars displays ancient and vast deposits of volcanic materials including lava flows and ash. Furthermore, models to explain atmospheric and surface chemistry usually evoke degassing from ancient volcanoes. However, very few ancient volcanic centers have been identified on Mars. To explain this conundrum it is suggested that ancient martian volcanoes might have been eroded away or buried by younger deposits. However, a third possibility is that we have not yet recognized what ancient volcanoes on Mars look like. A general trend is suggested that recent martian volcanic activity was dominated by effusive (non-explosive) eruptions, whereas the oldest recognized volcanoes display evidence for explosive eruptions. Is it possible that ancient martian volcanoes are not easily recognized because they were highly explosive and distributed material regionally, if not globally, in such a manner that they did not form large mountainous volcanic constructs? This type of eruption is equivalent to the most explosive eruptions known to have occurred on Earth, and are known in a non-technical way as supervolcanoes. Supervolcanoes are identified on Earth as large volcanic depressions, or caldera, often lacking pronounced flanks. This presentation explores large depressions in Arabia Terra, Mars, that might be the equivalent of supervolcanoes on Mars.