Daily Archives: November 10, 2010

Saturn Emits Energy Unevenly


click image to make it gigantic

This false-color composite image, constructed from data obtained by NASA’s Cassini spacecraft, shows Saturn’s rings and southern hemisphere. The composite image was made from 65 individual observations by Cassini’s visual and infrared mapping spectrometer in the near-infrared portion of the light spectrum on Nov. 1, 2008. The observations were each six minutes long.

In this image constructed from data collected in the near-infrared wavelengths of light, scientists designated blue to indicate sunlight reflected at a wavelength of 2 microns, green to indicate sunlight reflected at 3 microns and red to indicate thermal emission at 5 microns. Saturn’s rings reflect sunlight at 2 microns, but not at 3 and 5 microns, so they appear deep blue. Saturn’s high altitude haze reflects sunlight at both 2 and 3 microns, but not at 5 microns, and so it appears green to blue-green. The heat emission from the interior of Saturn is only seen at 5 microns wavelength in the spectrometer data, and thus appears red. The dark spots and banded features in the image are clouds and small storms that outline the deeper weather systems and circulation patterns of the planet. They are illuminated from underneath by Saturn’s thermal emission, and thus appear in silhouette.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.

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WISE eyes its first cool brown dwarf

“The brown dwarfs jump out at you like big, fat, green emeralds,” said Amy Mainzer, the deputy project scientist of WISE at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Mainzer, who makes jewelry in her spare time, explained that the brown dwarfs appear like green gems in WISE images because the methane in their atmospheres absorbs the infrared light that has been coded blue, and because they are too faint to give off the infrared light that is color-coded red. The only color left is green.

Like Jupiter, brown dwarfs are made up of gas — a lot of it in the form of methane, hydrogen sulfide, and ammonia. These gases would be deadly to humans at the concentrations found around brown dwarfs. And they wouldn’t exactly smell pretty.

“If you could bottle up a gallon of this object’s atmosphere and bring it back to Earth, smelling it wouldn’t kill you, but it would stink pretty badly — like rotten eggs with a hint of ammonia,” said Mainzer.


That green dot in the middle of this image might look like an emerald amidst glittering diamonds, but it is actually a dim star belonging to a class called brown dwarfs. This particular object is the first ultra-cool brown dwarf discovered by WISE. Image credit: NASA/JPL-Caltech/UCLA

The melting of the Arctic ice cap is a complex process

You’ve heard that the Arctic ice cap has shrunk, and that there are sea lanes open in the northern summer that had not been open previously, and on and so forth.

Since the start of the satellite record in 1979, scientists have observed the continued disappearance of older “multiyear” sea ice that survives more than one summer melt season. Some scientists suspected that this loss was due entirely to wind pushing the ice out of the Arctic Basin — a process that scientists refer to as “export.” In this study, Ron Kwok and Glenn Cunningham at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., used a suite of satellite data to clarify the relative role of export versus melt within the Arctic Ocean.*


A mosaic of satellite images shows the movement of fragmented ice away from ice edges, which scientists use to track the loss of multiyear ice due to melt. Image credit: NASA Earth Observatory. Click to hugify.

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An ironic death

Two weeks ago Julia and I took the road from the cabin to Longville and back and noticed that they had put up a new sign at each end of the curvy, hilly treacherous part, where you drive dangerously high above bogs and wooded kettles with no guard rail and there is one blind curve after another. Of treacherous roads I’ve been on, I’d say this bit of rural highway ranks about … 10 thousandth, but I’ve driven thousands of kilometers in the Congo, so the comparison is not really fair. Anyway, the signs are large like the kind that might announce the entrance to a national forest or the boundary of a state … bigger than the signs at county or town boundaries and smaller than the sign for Yellowstone Park … and they read “Winding road ahead.”
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That rocket was probably a contrail of a regular air plane

The evidence is starting to add up. First, we have the absence of evidence, which is always tricky but sometimes relevant: Nobody picked up a rocket on radar, aircraft pilots did not see a vertical high speed accelerating object, etc. etc. Then we have the alternative explanations, including the shape and nature of the contrail, curves in the contrail unlikely from a ballistic missile, and so on.

I’m betting on routine aircraft contrail. This will be an interesting one to pick apart later when all the conjectures are in.