Photo Credit: Image Credit: NASA/JPL/Space Science Institute

What is this blue arc? Is it the shimmering tail of one of those bizarre fluorescent deep sea creatures? Or a new kind of steel being forged? Maybe it’s an artist’s picture of the event horizon of a black hole.

Don’t peek at the answer until you’ve given this a good try! Then, scroll down a bit and the truth will be revealed to you.

This is an image of a geyser erupting from the surface of Enceladus, one of Saturn’s moons. On March 12, 2008, the spacecraft Cassini flew through a geyser just like this one, and grabbed a sample of the water vapor, ice pellets, and organic compounds that make up the jets. Surprise! The inside of Saturn’s moon resembles the chemistry of a comet. Why is that a big deal? “Comets have tails and orbit the sun, Enceladus’ activity is powered by internal heat while comet activity is powered by sunlight. Enceladus’ brew is like carbonated water with an essence of natural gas,” said Hunter Waite, of the Southwest Research Institute in San Antonio.

Another surprise is the high temperatures of the giant fissures, nicknamed “tiger stripes,” that produce the geysers. Maybe negative 135 degrees Fahrenheit seems chilly to you, but it’s 207 degrees warmer than other areas of the moon. “Enceladus has got warmth, water and organic chemicals, some of the essential building blocks needed for life,” said Dennis Matson, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

The spacecraft Cassini snapped a bunch of pictures of these intriguing plumes on November 27, 2005. This one is a composite of three taken at nearly the same time, and colored blue for dramatic effect. Scientists use images like this one to identify source locations for individual jets.