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The space probe Cassini, our emissary to Saturn and its fascinating satellites, has made several new discoveries that lend further credence to the idea that microbial life could evolve on the icy moon Enceladus or the moon Titan, with its lakes of methane. During a flyby of Enceladus Cassini snapped pictures of the moon’s surface and the cracks in its icy crust from which jets of water vapor routinely burst upward. The new pictures suggest that the cracks form when the crust splits and spreads apart in a way that is similar to the mid-ocean ridges central to the tectonic system on our own planet. On Earth the spreading of the sea floor is driven by molten rock; Nasa scientists speculate that the liquid beneath the south pole of Enceladus may be water. “Bit by bit, we’re accumulating the evidence that there is liquid water on Enceladus” [Telegraph], said Cassini scientist Carolyn Porco.

Enceladus is already known to have some of the fundamental chemistry required to make and sustain life. Liquid water currently is the major missing ingredient. Dr Porco commented: “We first discovered this region in early 2005 and now it’s nearly four years later, so it’s still kind of brand new; but already there are some of us who really want to go back with a spacecraft that focuses on the south pole of Enceladus and investigates whether or not it is a site of either pre-biotic or biotic processes” [BBC News].

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When NASA’s Cassini spacecraft swooped past Saturn’s moon Enceladus last year, it got a close-up view of the water vapor and ice plumes that stream away from the small moon. After analyzing the data, researchers say the evidence suggests that the material in the plumes originates as liquid water trapped beneath the moon’s icy surface, which increases the possibility that microbial, extraterrestrial life could exist in the lakes. “We think liquid water is necessary for life and there is more evidence that there is liquid water there,” said lead researcher Candice Hansen…. Scientists are aware of only three places where liquid water exists near the surface of a planet or other body - Earth, Jupiter’s moon Europa and now Enceladus [Telegraph].

Researchers identified four distinct jets within the plume where the water vapor appears to be traveling faster than 1,300 miles per hour. Such high speeds imply that the jets are fed by pressurised water vapour that shoots through narrow openings - which act like rocket nozzles - in the moon’s icy surface. The simplest way to generate such pressures is by evaporating a reservoir of liquid water that lies close to the moon’s surface [New Scientist], researchers say.

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Researchers have unveiled the clearest images yet of the massive cyclone that revolves over Saturn’s south pole, and revealed that the southern storm is matched by an equally powerful cyclone at the planet’s north pole. Time-lapse images, taken by the Cassini spacecraft, show that the northern cyclone has wind speeds of 325 miles per hour, more than twice as fast as Earth’s strongest hurricanes. Says Cassini scientist Kevin Baines: “In a lot of ways, these are the most powerful cyclones ever seen…. They would expand over the whole planet if it was the Earth” [Discovery News].

The source of heat that powers these massive storms is not yet clear; Earth’s cyclones draw heat from the oceans that they drift across, but Saturn’s fixed cyclones have no bodies of water at their bases. They may be driven by Saturn’s internal heat, which can create giant weather patterns by causing massive parcels of atmospheric gases, most likely ammonium hydrosulfide, to rise and fall. It’s also possible that sunlight trapped in the planet’s atmosphere could drive the motions [Science News].

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The Cassini spacecraft that has been busily exploring Saturn and its moons swooped to within 30 miles of the tiny moon Enceladus yesterday, and has already begun sending back images of the fissures near the moon’s south pole. The icy moon, which is about 310 miles wide, has tantalized scientists with geyser-like eruptions of icy water vapor that were first spotted in 2005…. The eruptions produce a halo of frozen water vapor and gas that replenishes Saturn’s E-ring as Enceladus circles the planet [SPACE.com].

The Cassini took images of the fissures, which scientists call the moon’s “tiger stripes,” in the infrared spectrum as well, to gain further information about the temperatures in the vents; previous studies had shown temperatures there can reach a relatively balmy -135 degrees Fahrenheit, which is 200 degrees Fahrenheit warmer than the rest of the moon. While the material sprayed out of the fissures consists of frozen water vapor, scientists disagree on whether an internal ocean of [liquid] water, life’s crucial ingredient, hides within the tiny moon [USA Today].

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NASA’s Cassini spacecraft has discovered a liquid lake the size of Earth’s Lake Ontario on the south pole of Titan, Saturn’s largest moon. Researchers say that Cassini’s instruments reveal that the chilly reservoir … Titan, is composed of a key component of crude oil — liquid ethane [Science News].

The new find supports the common belief that Titan is a promising place to look for extraterrestrial life. Some astrobiologists have speculated that life could develop in the moon’s hydrocarbon lakes, although it would have to be substantially different from known life on Earth, which requires liquid water [Wired News].

The Cassini orbiter has racked up a number of accomplishments since it began investigating Saturn and its moons in 2004, but its most exciting missions have focused on Titan, where the thick nitrogen and methane atmosphere resembles the atmosphere that existed on primordial Earth.

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