Want the ultimate in powder snow? Ski Enceladus, a little moon of Saturn. The snow is deep and vast. Drawbacks: except for occasional craters and steep canyons, the land is flat; there are no ski lifts; there is no air; you would weigh one or two pounds, and transportation will cost you billions of dollars. Other than that, science news outlets are advertising it as a great place for snow lovers!
“Enceladus weather: Snow flurries and perfect powder for skiing.” That’s PhysOrg’s travel ad (a.k.a. science report) earlier this month. Cassini took two close passes by Enceladus this month, #14 on October 1 at 99 km, and #15 on October 19 at 765 miles. In the second, the spacecraft was able to watch the light of two stars flicker on and off through the plumes. The Cassini Imaging Team site Ciclops.org posted a preview of raw images from the latest flyby. Another one, #16, comes up on November 6 at 496 km. After a pause, there will be more close passes in March, April and May.
That this little moon should have powder snow is astonishing. The fine talcum-powder-size ice settles down by gravitational attraction from the particles spewing out of the moon’s south pole geysers. PhysOrg said the snow is not composed of snowflakes like we have on Earth, which require an atmosphere. Instead, tiny ice particles fall on ballistic paths from the ejection sites (long, deep canyons called “tiger stripes” at the south pole). Although it’s impossible to know the texture and depth of the deposits directly, scientists can infer the particle composition by comparing visible, ultraviolet and near-infrared measurements of the same regions. According to Dr. Paul Schenk of the Lunar and Planetary Institute in Houston, the accumulated particles would be ideal for skiing.
How long has this been going on? The PhysOrg article stated, “Mapping of these deposits indicate that the plumes and their heat source are relatively long-lived features lasting millennia and probably tens of million years or more, and have blanketed areas of the surface in a thick layer of tiny ice particles.” The error bars on that statement extend four orders of magnitude. The problem with the higher figure (tens of millions of years) is keeping that amount of power going on this little moon for so long. In fact, to believe that this moon is the assumed age of Saturn, little Enceladus would be coating itself with powder snow for 4.5 billion years. Is there that much source water available? If the geysering started more recently, what turned it on?….
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