File:Enceladus moon atmosphere PIA03552.jpg

Summary[edit]

• Original caption : On July 11, 2005, the Cassini ultraviolet imaging spectrograph observed the star Bellatrix as it passed behind Enceladus, as seen from the spacecraft. The starlight was observed to dim when it got close to Enceladus, indicating the presence of an atmosphere, as illustrated in figure A. The ultraviolet imaging spectrograph team was able to identify water vapor as the composition of the atmosphere from absorption features in the spectrum of the star. From the depth of the absorption features, it was also possible to estimate the quantity of water vapor the starlight passed through. The colors show the undimmed star signal (blue) versus the dimmed star signal (pinkish).

Enceladus' atmosphere is localized, not global in extent. As Bellatrix re-emerged from behind Enceladus, there was no dimming of the starlight observed. An occultation of the star Lambda Scorpius in February also showed no sign of an atmosphere, as illustrated in figure B. In figure A and B, the arrow marks the path of the star as it was blocked from view by Enceladus. In figure A, the dimming of the starlight shows as a gradual decrease in brightness, while in figure B the starlight drops abruptly just at the point in time that the star goes behind Enceladus.

• image source: http://photojournal.jpl.nasa.gov/catalog/PIA03552

Licensing[edit]

	This file is in the public domain in the United States because it was solely created by NASA. NASA copyright policy states that "NASA material is not protected by copyright unless noted". (See Template:PD-USGov, NASA copyright policy page or JPL Image Use Policy.)
	Warnings: Use of NASA logos, insignia and emblems is restricted per U.S. law 14 CFR 1221. The NASA website hosts a large number of images from the Soviet/Russian space agency, and other non-American space agencies. These are not necessarily in the public domain. Materials based on Hubble Space Telescope data may be copyrighted if they are not explicitly produced by the STScI.[1] See also {{PD-Hubble}} and {{Cc-Hubble}}. The SOHO (ESA & NASA) joint project implies that all materials created by its probe are copyrighted and require permission for commercial non-educational use. [2] Images featured on the Astronomy Picture of the Day (APOD) web site may be copyrighted. [3] The National Space Science Data Center (NSSDC) site has been known to host copyrighted content. Its photo gallery FAQ states that all of the images in the photo gallery are in the public domain "Unless otherwise noted."