New data suggests that the icy crust of Titan is twice as thick as previously estimated.

New data suggests that the icy crust of Titan is twice as thick as previously estimated.

“The picture of Titan that we get has an icy, rocky core with a radius of a little over 2,000 kilometers, an ocean somewhere in the range of 225 to 300 kilometers thick and an ice layer that is 200 kilometers thick,” [said Howard Zebker of Stanford University]. Previous models of Titan’s structure estimated the icy crust to be approximately 100 kilometers thick.

This means that the methane lakes and rivers of Titan are flowing across a bedrock of ice, which at the cold temperatures there would be as solid as rock is here on Earth.

Data of the tidal fluxes on Titan by the Cassini spacecraft now suggest that there is a liquid ocean below Titan’s icy crust.

Data of the tidal fluxes on Titan by the Cassini spacecraft now suggest that there is a liquid ocean below Titan’s icy crust.

The team’s analyses suggest that the surface of the moon can rise and fall by up to 10 metres during each orbit, says Iess. That degree of warpage suggests that Titan’s interior is relatively deformable, the team reports today in Science1. Several models of the moon’s internal structure suggest such flexibility — including a model in which the moon is solid but soft and squishy throughout. But the researchers contend that the most likely model of Titan is one in which an icy shell dozens of kilometres thick floats atop a global ocean. The team’s findings, together with the results of previous studies, hint that Titan’s ocean may lie no more than 100 km below the moon’s surface.

Is it snowing microbes on Enceladus?

Is it snowing microbes on Enceladus?

“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,” says Carolyn Porco, an award-winning planetary scientist and leader of the Imaging Science team for NASA’s Cassini spacecraft. “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.”

Engineers have gone to a back up radio system on Cassini after a primary unit did not respond as expected in late December.

Engineers have gone to a back up radio system on Cassini after a primary unit did not respond as expected in late December.

The cause is still under investigation, but age may be a factor. The spacecraft launched in 1997 and has orbited Saturn since 2004. Cassini completed its prime mission in 2008 and has had two additional mission extensions. This is the first time its ultra-stable oscillator has had an issue.

Sponge in space

Hyperion

On August 25 Cassini did a close fly-by of the small Saturn moon Hyperion, getting as close as 15,500 miles. The mission has just released images from that fly-by.

Looks like a sponge, doesn’t it? This moon is small, only 168 miles across, which makes it about half the size of the asteroid Vesta that Dawn is presently orbiting. Why it is so peppered with craters is of course the big science question. I would guess this has something to do with the environment around Saturn, with its rings and the innumerable particles that come from it. Yet, other moons of Saturn are not as crater-filled, so there is obviously more to this than meets the eye.

This fly-by was the second closest of Hyperion that Cassini has done, the first passing over the the moon’s surface by only 310 miles. Because the irregularly-shaped moon’s rotation is more like a chaotic tumble, scientists could not predict what part of the surface they would see. To their luck the new images captured new territory.

Another fly-by is scheduled in only three weeks, on September 16, 2011. This time, however, the spacecraft won’t get as close, passing at a distance of about 36,000 miles.

Space Boat: A Nautical Mission to an Alien Sea

The Titan Mare Explorer: A nautical mission to an alien sea.

If [NASA] green-lights the mission, the capsule will lift off in 2016. By 2023, TiME will be about 800 million miles away in Titan’s north-polar region, home to its biggest lakes and seas. The capsule will take photographs, collect meteorological data, measure depth, and analyze samples. TiME will have no means of propulsion once it is on Titan, so it will float, carried by breezes across the sea’s surface. Then, by the mid-2020s, it will enter a decade-long winter of darkness as the moon’s orbit takes it to the dark side of Saturn, away from the sun and communication. It won’t have a line of sight to Earth to beam back more data until 2035.

Enceladus rains water onto Saturn

The Herschel space telescope has discovered that the water expelled from the tiger stripes on Enceladus eventually rains down on Saturn.

Enceladus expels around 250 kg of water vapour every second, through a collection of jets from the south polar region known as the Tiger Stripes because of their distinctive surface markings. These crucial observations reveal that the water creates a doughnut-shaped torus of vapour surrounding the ringed planet. The total width of the torus is more than 10 times the radius of Saturn, yet it is only about one Saturn radius thick. Enceladus orbits the planet at a distance of about four Saturn radii, replenishing the torus with its jets of water.

Ethane lakes in a red haze: Titan’s uncanny moonscape

Titan’s ethane lakes in a red haze.

So far, there are no recognisable signs of organic life. That’s not surprising: by terrestrial standards, Titan is a deep freeze with surface temperatures at a chilly -180°C. Yet Titan is very much alive in the sense that its atmosphere and surface are changing before our eyes. Clouds drift through the haze and rain falls from them to erode stream-like channels draining into shallow lakes. Vast dune fields that look as if they were lifted from the Sahara sprawl along Titan’s equator, yet the dark grains resemble ground asphalt rather than sand. It is a bizarrely different world that looks eerily like home. Or as planetary scientist Ralph Lorenz puts it: “our prototype weird-world exoplanet”.

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