plume – Behind The Black – Robert Zimmerman

The mystery of Martian plumes

February 16, 2015 9:27 am Robert Zimmerman

The uncertainty of science: Scientists struggle to explain the discovery by amateurs of Martian atmospheric plumes 125 to 150 miles high.

Amateur astronomers spotted the bizarre feature rising off the edge of the red planet in March and April of 2012. It looked like a puff of dust coming off the surface, but it measured some [125 to 155] kilometres high. That is much higher than would be expected from the lower-altitude dust storms that rage across the planet. Now a team of astronomers proposes that the plume was either a cloud of ice particles or a Martian aurora. But neither possibility fully explains the plume — raising new questions about the state of the Martian atmosphere.

Read it all. No explanation really works to explain the plume’s height.

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Cassini directly samples the plumes from Enceladus and finds an ocean-like Spray

June 22, 2011 5:57 pm Robert Zimmerman

Cassini has directly sampled the plumes from Enceladus and discovered a salty ocean-like spray.

The new paper analyzes three Enceladus flybys in 2008 and 2009 with the same instrument, focusing on the composition of freshly ejected plume grains. The icy particles hit the detector target at speeds between 15,000 and 39,000 mph (23,000 and 63,000 kilometers per hour), vaporizing instantly. Electrical fields inside the cosmic dust analyzer separated the various constituents of the impact cloud.

The data suggest a layer of water between the moon’s rocky core and its icy mantle, possibly as deep as about 50 miles (80 kilometers) beneath the surface. As this water washes against the rocks, it dissolves salt compounds and rises through fractures in the overlying ice to form reserves nearer the surface. If the outermost layer cracks open, the decrease in pressure from these reserves to space causes a plume to shoot out. Roughly 400 pounds (200 kilograms) of water vapor is lost every second in the plumes, with smaller amounts being lost as ice grains. The team calculates the water reserves must have large evaporating surfaces, or they would freeze easily and stop the plumes.