Newly released analysis from the Mars Reconnaissance Orbiter shows that the Arabia Terra region on Mars experienced powerful volcanic eruptions.
by Jeffrey L. Hunt
The earliest close-up photos of Mars captured by NASA’s robot spacecraft revealed a tortured, cratered surface, possible river beds, volcanoes, and a continent-long canyon. In 1971, Mariner 9, the first spacecraft to go into orbit around Mars, extensively photographed Olympus Mons, a large shield volcano, resembling the Hawaiian volcanoes, but taller and wide enough to cover the entire island chain. Three other volcanoes are nearby.
In this image, the large volcano Olympus Mons and the three Tharsis Ridge volcanoes are shield volcanoes (NASA)
NASA’s Mars Reconnaissance Orbiter has been studying the planet from orbit since 2005. Its cameras captured detailed images for a heavily cratered region known as Arabia Terra that is nearly on the opposite side of the planet from the large volcanoes.
In a paper, by a team led by NASA’s Patrick Whelley, the cameras revealed that the Arabia Terra regions experienced thousands of “super eruptions,” the biggest volcanic eruptions known, over a 500-million-year period.
Unlike the shield volcanoes where rivers of lava run down the sides of the volcanoes, the Arabia Terra events were explosive, ejecting water vapor, carbon dioxide, and sulfur dioxide into the sky.
“Each one of these eruptions would have had a significant climate impact – maybe the released gas made the atmosphere thicker or blocked the Sun and made the atmosphere colder,” said Whelley.
The year 1816 on Earth is sometimes called “the year without summer,” after the eruption of Mt. Tambora, although this eruption was considerably smaller than Mars’ explosive volcanoes. The summer was hazy and it had little sunlight. Crops failed across North America and Europe.
The Martian eruptions may have blasted the equivalent of 400 million Olympic-size swimming pools of molten rock and gas through the surface, spreading a thick blanket of ash up to thousands of miles from the eruption site.
A giant hole, known as a caldera, remains after these eruptions. Seven calderas in the Aria Terra region were the first indicators that eruptions may have occurred. Initially, the holes were thought to be craters, but careful study suggested they were not from impacting bodies.
Mars may not be the only place with explosive volcanoes. They might be on Jupiter’s moon Io or Venus.
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