The top image shows a relatively cloud-free air, while the bottom captures widespread cloud cover.
(NASA/JPL-Caltech/SSI/Univ. Arizona/Univ. Idaho)
Mysterious, thin, wispy clouds hide under the hazy upper atmosphere of Saturn’s largest moon, Titan.
NASA’s Cassini spacecraft flew over Titan on 7 June and 25 July, and captured strikingly different pictures of the moon’s high northern latitude using the probe Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (vim’s). Only the vim’s (the bottom edge in the color image) was able to by means of peer the moon’s hazy atmosphere to capture an infrared image of the elusive clouds. The vim’s image shows widespread cloud cover, both during the vicinity.
The different views captured by Cassini’s two onboard cameras raise the question of why the clouds would be visible in some images but not others, according to a NASA description of the image. This is particularly strange because the two photos were taken fairly close together in time. [Giant Ice Cloud Spotted on Saturn Moon Titan (Photos)]
ISS consists of a wide-angle and narrow-angle digital camera, which are sensitive to visible light with a wavelength of light and some infrared and ultraviolet wavelengths. The monochrome image on the top was captured by the ISS at a distance of about 398,000 km and is almost cloud-free. However, the bottom picture is made of over 28,000 km by the vim’s on the longer, infrared wavelength, and the light clouds are visible in Titan’s northern sky .
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“Although these views were taken at different wavelengths, researchers would expect at least a hint of the clouds in the top image,” NASA officials said in a statement. “So, they have tried to understand what is behind the difference.”
On the basis of atmospheric models, scientists have predicted that the clouds are increasingly at high northern latitudes in the summer on Titan. Since 2004, Cassini has documented changes in weather patterns as the seasons change on Titan. Images collected by Cassini will help in the beginning of the clouds in the north, where the Titan’s lakes and seas, NASA officials said.
“The answer to what can be caused by the difference [between the ISS and the vim’s images] seems to lie with the Titan’s hazy atmosphere, that is much easier to see through in the longer infrared wavelengths that vim’s is sensitive to (up to 5 microns), than the shorter, near-infrared wavelength used by ISS to image Titan’s surface and lower atmosphere (0.94 microns),” NASA officials said in the statement .
Differences in the illumination of the geometry or changes in the clouds themselves were excluded, since the photos taken by ISS and CIMS are made over the same 24-hour period.
“High, thin cirrus clouds that are optically thicker than the atmospheric haze at longer wavelengths, but optically thinner than the haze of the short wavelength of the ISS observations, can be detected by vim’s, and at the same time lost in the mist of the ISS — similar to trying to be a thin cloud layer on a cloudy day on Earth,” NASA officials said. “This phenomenon is not seen since July of 2016, but Cassini has several more opportunities to observe Titan during the last months of the mission in 2017 , and the scientists will be watching to see if and how the weather changes.”
Original article on Space.com.