New images of Saturn's moons Enceladus, Janus and Dione were captured this week by NASA's Cassini spacecraft.
Jets of water ice and vapor can be seen bursting out of Enceladus's south polar region in the main image above.
After imaging Enceladus's stunning geysers, Cassini flew to within 74 kilometres (46 miles) of the surface in order to 'taste' the geysers so that scientists can learn more about their composition.
"More than 90 jets of all sizes near Enceladus's south pole are spraying water vapor, icy particles, and organic compounds all over the place. Cassini has flown several times now through this spray and has tasted it. And we have found that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth's oceans," said Carolyn Porco, leader of the Imaging Science team for Cassini.
Porco believes Enceladus is the most promising place in the solar system for a "flagship-scale" astrobiology mission to search for microbial life. In an interview with NASA Science she reasoned:
"The kind of ecologies Enceladus might harbor could be like those deep within our own planet. Abundant heat and liquid water are found in Earth's subterranean volcanic rocks. Organisms in those rocks thrive on hydrogen (produced by reactions between liquid water and hot rocks) and available carbon dioxide and make methane, which gets recycled back into hydrogen. And it's all done entirely in the absence of sunlight or anything produced by sunlight."
A flyby planned for October 2015 will bring Cassini even closer to the south pole region, to a distance of about 25 kilometres (16 miles).
Enceladus has a diameter of 504 kilometres (313 miles) and its icy surface is highly reflective of sunlight. The icy jets burst out of the southern region where the moon is scarred by its "tiger stripes" - four parallel claw marks scratched into the smooth icy surface. The tiger stripes are about 120 kilometres in length.
The ice and dust that form's Saturn's E ring have been found to originate from Enceladus itself so that the moon forges the ring in which it sits.
After its study of Enceladus, Cassini flew by the small moon of Janus (pronounced 'jay-nuss'). Janus, discovered in 1966, has a diameter of just 179 kilometres. Cassini flew by at a distance of 44,000 kilometres (27,000 miles).
Janus, from Cassini flyby March 27, 2012. Credit: NASA/JPL/Space Science Institute
On March 28, Cassini captured some more images of Dione from a similar distance to its flyby of Janus, approximately 44,000 kilometres (27,000 miles).
Dione is an icy moon and is phase locked with Saturn so that the same side of the moon always faces its parent (also the same as Earth's Moon). Among other observations, Cassini collected a nine-frame mosaic depicting the side of the moon that faces away from Saturn in its orbit.
Dione, discovered by Giovanni Cassini in 1684, is one of Saturn's larger moons with a diameter of 1,123 km (698 miles).
It takes Dione just 2.7 (Earth) days to orbit Saturn at a distance of 377,400 km (234,000 miles), a very similar orbital distance to our Moon, which orbits Earth at an average of 238,000 miles.
Dione imaged by Cassini on March 28, 2012. Credit: NASA/JPL/Space Science Institute
Saturn has over 60 moons, a vast range of different worlds.
Cassini was launched in 1997 and entered Saturn's orbit in 2004. Cassini continues to provide much information and stunning images of Saturn, its rings and its moons.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.
The Cassini imaging operations center (CICLOPS) and team leader (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.
NASA's Jet Propulsion Laboratory, Pasadena, California, a division of the California Institute of Technology, manages the overall mission for NASA.
The Cassini orbiter was designed, developed and assembled at JPL. The Cassini plasma spectrometer team and the ion and neutral mass spectrometer team are based at Southwest Research Institute, San Antonio.