A Glimpse of Mars’ Ancient Volcano: Arsia Mons
A spacecraft’s-eye view over the landscapes of Mars has just given us a first-of-its-kind glimpse of the giant, ancient edifice known as Arsia Mons. The NASA satellite Odyssey captured the enormous equatorial volcano as its tip peeked above the morning clouds of water ice – a common feature at this time of the Martian year, when the red planet is at its furthest point from the Sun on its slightly elliptical orbit.
Arsia Mons belongs to a volcanic complex known as the Tharsis Montes; three shield volcanoes very close together in the Tharsis region of Mars. Arsia Mons is the tallest of the three, standing at a towering height of nearly 20 kilometers (12 miles).
That’s dramatically higher than any mountain on Earth, where the tallest peak above sea level (Mount Everest) stands 8.85 kilometers high and the tallest mountain, Mauna Kea, rises 9 kilometers above the sea floor. It also has around 30 times more volume than Earth’s largest volcano, Mauna Loa – and it’s not even the biggest volcano on Mars.
Its activity is thought to have lasted billions of years, peaking around 150 million years ago.
Odyssey usually has its cameras pointed down toward the surface of Mars. To obtain the new panorama, it had to rotate 90 degrees so that its camera pointed at the horizon. This angle is worth the effort: it allows scientists to make out layers and clouds in the thin Martian sky to better understand its atmospheric dynamics and processes.
Clouds form around Arsia Mons when expanding air rises up the slopes of the mountain, rapidly cooling, allowing ice crystals to form. At Mars’s current position in its journey around the Sun, a belt of clouds forms around the equator known as the aphelion cloud belt.
Curiosity captured this phenomenon from the surface several years ago; the new Odyssey panorama gives us a spectacular view from above.
“We picked Arsia Mons hoping we would see the summit poke above the early morning clouds,” says aerospace engineer Jonathon Hill of Arizona State University. “And it didn’t disappoint.”
