LA CANADA FLINTRIDGE – Small dark spots in photos of the icy surface of Mars’ south pole are likely geysers of sand and gas hundreds of feet tall, scientists said Wednesday.
“It’s sort of like Yellowstone in the middle of winter,” said geologist Phil Christensen of Arizona State University. “If I could have a national park on Mars, this is where I’d make it.”
For many years, planetary scientists believed the smears were places where the frozen carbon dioxide at the pole had melted, revealing the ground below.
More recent observations showed, however, that the spots were the same temperature as the ice. This suggested to scientists that dark Martian soil was being deposited on top of the ice, which “refrigerated” it, one researcher said.
Christensen and his colleagues used a camera on the orbiter Mars Odyssey to take daily pictures of this mysterious part of the south pole, known as the Cryptic region.
Their images showed that the spots appeared each Martian spring, when the sun first began to warm the ice.
“The sun can penetrate through this dry ice, and the ground can warm up,” Christensen said.
As the warm ground turns the bottom of the ice into gas, the new model suggests, “the whole ice slab actually starts to levitate a little bit until it cracks,” he said.
The gas then bursts out, shooting sand with it at more than 200 miles per hour.
“It’s one of the most active regions of the planet, and in particular – if this model is correct – it’s sort of violently active,” said Jeff Plaut, Odyssey’s project scientist at the Jet Propulsion Laboratory.
The explosive geysers also explain spider-like networks of channels visible in the soil once the ice cap melts each summer.
“The gas is rushing toward the vent from all directions,” Christensen said. “It’s eroding the ground and forming the spiders.”
Still unexplained, though, are why the geysers exist only in one-third of the planet’s south pole, and not at all in the north pole, Plaut said.
The absence of a dusty layer beneath the north pole’s carbon dioxide ice could be part of the explanation, he said, “but it’s not the whole story.”
Before those questions can be answered, though, the scientists hope to use Odyssey, Mars Global Surveyor, or the planet’s newest robotic arrival – the Mars Reconnaissance Orbiter – to capture proof of the geyser theory.
“We’ll try to actually image and catch one of these geysers when it’s erupting,” Christensen said. “That would be the final smoking gun.”
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