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Outer-space views go festive


False-color radar imagery shows the Ganges Delta in Bangladesh, as seen by the European Space Agency's Envisat satellite in 2009. Standard radar images do not detect color. In this case, readings from three different satellite passes were analyzed, and the different colors reflect the surface variations that occurred between those passes.

If you still have to send out your season's greetings, take your pick from a spectrum of holiday e-cards featuring spacey imagery from the European Space Agency.

The ESA selected pictures that have a festive look — such as this Envisat radar view of the world's largest delta, formed by the confluence of the Ganges, Brahmaputra and Meghna rivers in India and Bangladesh. This particular photo focuses on the Bangladeshi part of the delta.

Radar readings can show differences in surface height and reflectivity, but they can't show color directly. This picture combines radar data from three different satellite passes — on Jan. 20, Feb. 24 and March 31, 2009 — and uses the different colors of the rainbow to show the surface changes that occurred between passes. Envisat, the world's largest civilian Earth observation satellite, was launched in 2002 but went out of contact this year.

For a completely out-of-this-world radar view, check out the Cassini orbiter's picture of a hydrocarbon river delta on Titan, Saturn's largest moon.

Today's gander at the Ganges Delta is one of the last offerings from the Cosmic Log Space Advent Calendar, which has been serving up daily views of Earth from space this month. For more spacey goodies, follow the links below:

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other science and space news coverage, sign up for the Tech & Science newsletter, delivered via email. You can also check out "The Case for Pluto," my book about dwarf planets and the search for new worlds.