On spring days on Mars, powerful geysers sometimes spew carbon dioxide “steam” and dust to great heights, a phenomenon unlike anything ever seen on Earth, scientists said on Tuesday.
These eruptions can be so strong that the falling dirt creates fan-shaped patterns extending hundreds of yards meters. “Here’s a place that looks wildly different than anything on Earth,” NASA scientist Candice Hansen said at a meeting of the American Geophysical Union. Mars and Earth are similar in that both are small, rocky planets with seasons caused by tilts in their axes, although the Martian year is twice as long as ours is. Nevertheless, the seasonal geysers illustrate one result of their vast differences in climate. In winter, the southern pole of Mars is – 129 °C, so cold that carbon dioxide in the atmosphere freezes to form a layer of dry ice about 20 inches thick. On spring days, dry ice warmed by sunlight begins to turn into gas, some of which is trapped between the planet’s surface and the remaining ice. When the pressure grows strong enough, the gas erupts through cracks like a steamy jet, Hansen said.
As the planet’s surface warms, the eruptions become larger. By midday, the gas also carries dust, which by evening has fallen on the surface in long fan-shaped patterns. In the spring, sunlight warms the ground, vaporizing carbon dioxide at the base of the ice layer. The gas flows uphill, carving channels in the underlying soil.
At weak points in the ice, the gas erupts in small geysers. The release of pressure causes the carbon dioxide gas to freeze solid and fall as white snow — the white parts of the fan-like patterns. Dust blown out with the carbon dioxide falls on the ground to form the dark parts of the fans. Indiatimes.
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