Saturn’s moon Enceladus has a huge ocean of liquid water, scientists confirm

[Reefa]

Just a few years ago, scientists discovered that one of Saturn’s moons was violently spewing something far, far into space. That’s a pretty odd discovery on its own, but even stranger were the readings given off by the resulting plume of material: rather than being made of super-heated rock or steam, it was made almost entirely of frozen material. Enceladus, Saturn’s sixth-largest moon, is sending out a 500-kilometre jet of solid granular hydrocarbons and, more importantly, crystals of water ice. The engine behind this massive ejection is thought to be gravitational force exerted by Saturn itself, but that hypothesis relies on the assumption that Enceladus is hiding enormous reserves of liquid water just beneath its frozen surface. (See a larger version of the image above.)

This week, scientists from NASA confirmed that assumption, presenting evidence that Enceladus has a huge reservoir of liquid water beneath many kilometres of ice. The moon is actually quite small, just a few hundred kilometres across, so the surface area of the main ocean seems to be about that of Lake Superior. It is also up to 50 times as deep, however, making this alien ocean vast indeed. The blue “tiger stripes,” as they are known, are fractures in the moon’s surface through which this water and ice can escape. The exact points of eruption are known as “cryovolcanoes.” [Research paper: DOI: 10.1126/science.1250551 - "The Gravity Field and Interior Structure of Enceladus]

A Cassini image of Enceladus, showing the plumes thrown into space by cryovolcanoes

To confirm the existence of liquid water, this NASA team make extremely fine measurements of the moon’s gravitational field, looking for evidence of its density distribution. When water becomes solid (freezes), the polar atoms come to rest in a conformation that minimizes the overall chemical repulsion between molecules — this results in each molecule of H2O holding its neighbors at arm’s length, which in turn leads water to slightly expand when it freezes. This is why closed bottles sometimes break or explode when frozen, and why the oceans don’t freeze solid each winter; since it is less dense than liquid water, ice floats and forms and insulating shell that protects lower depths from freezing.

This density change in frozen water can affect the shape of the moon’s gravity well, and this study used a fascinating technique to measure it. Rather than using direct gravity-measuring devices, measurements were collected from the microwave carrier signal of the Cassini satellite, which has orbited Saturn since 2004. Though this is not an analytical signal at its heart, NASA use its worldwide Deep Space Network of radio telescopes to measure minute changes in the probe’s orbit. These changes, if measured accurately enough, can show the distribution of mass within Enceladus.

An artist’s rendering of the great cryovolcanoes of Enceladus.

The readings show that Enceladus has an enormous body of liquid water directly below its south pole, indicated by a so-called “negative mass anomaly” in that region. The readings even show that the ocean likely stretches below all of the visible tiger stripes.

The presence of liquid water is assumed to be one of the most vital factors in allowing the formation of life. Many have referred to Enceladus (along with Jupiter’s moon Europa) as the most likely place to find life in our solar system, though that idea was based on the assumption that liquid water lurked below the surface. Now, that assumption is supported by direct physical evidence. Additionally, Enceladus has been shown to have large amounts of organic compounds that could be the products of life — though they could easily be the product of some nonliving planetary process as well.

Getting to this ocean for study will be quite a challenge, however. The great ice-drilling project at Lake Vostok in Antarctica, the longest in history, only managed to bore down to a depth of four kilometers (2.5 miles), while the water on Enceladus could be as deep as 50 kilometers (31 miles). Still, Lake Vostok was found to house an enormous array of life despite having been sealed off for hundreds of thousands of years. Expect to hear proposals for a mission to Enceladus, and expect to hear them soon. Who knows, maybe the US government will force NASA to fly to Enceladus, just like it’s forcing a mission to Jupiter’s moon Europa.

Source

[shorty6100]

Great idea. Pour billions of dollars into this as opposed to, say, education.