Powerful volcanoes raise new questions about ancient Mars
Scientists believe Mars was more Earth-like in its early years

Ancient Mars was home to giant volcanoes capable of eruptions a thousand times more powerful than the one that shook Mount St. Helens in 1980, scientists said on Wednesday.
The finding raises fresh questions about conditions on Mars in its early years, a time when scientists believe the planet was much more Earth-like with a thick atmosphere, warmer temperatures and water on its surface.
Major volcanic eruptions likely would have triggered climate shifts that toggled Martian temperatures between cold spells when ash blocked sunlight and heat waves when greenhouse gases filled the skies, according to scientists.
Supervolcanoes may have made it more difficult for life to evolve on the planet’s surface, but underground steam vents and the release of water into the atmosphere also could have created niches for microbes to thrive, said geologist Joseph Michalski of the Planetary Science Institute in Tucson, Arizona.
The discovery of supervolcanoes on Mars comes from analysis of images from a quartet of Mars orbiters over the past 15 years.