Tag: Saturn

Crashing moonlets orbiting Saturn

1:32 pm

By comparing data from the Voyager fly-bys of Saturn in the 1980s with new data collected by Cassini in the past decade scientists think they can now explain the changes that have occurred in Saturn’s outer F ring.

“The F ring is a narrow, lumpy feature made entirely of water ice that lies just outside the broad, luminous rings A, B, and C,” notes French. “It has bright spots. But it has fundamentally changed its appearance since the time of Voyager. Today, there are fewer of the very bright lumps.” The bright spots come and go over the course of hours or days, a mystery that the two SETI Institute astronomers think they have solved.

“We believe the most luminous knots occur when tiny moons, no bigger than a large mountain, collide with the densest part of the ring,” says French. “These moons are small enough to coalesce and then break apart in short order.”

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The weather is finally changing on Titan

2:14 pm

New Cassini images of Titan have spotted the appearance of clouds above the planet’s northern seas, suggesting the overdue onset of the summer storms that climate models have predicted.

For several years after Cassini’s 2004 arrival in the Saturn system, scientists frequently observed cloud activity near Titan’s south pole, which was experiencing late summer at the time. Clouds continued to be observed as spring came to Titan’s northern hemisphere. But since a huge storm swept across the icy moon’s low latitudes in late 2010, only a few small clouds have been observed anywhere on the icy moon. The lack of cloud activity has surprised researchers, as computer simulations of Titan’s atmospheric circulation predicted that clouds would increase in the north as summer approached, bringing increasingly warm temperatures to the atmosphere there.

“We’re eager to find out if the clouds’ appearance signals the beginning of summer weather patterns, or if it is an isolated occurrence,” said Elizabeth Turtle, a Cassini imaging team associate at the Johns Hopkins University Applied Physics Lab in Laurel, Maryland. “Also, how are the clouds related to the seas? Did Cassini just happen catch them over the seas, or do they form there preferentially?”

Any conclusions drawn at this time about the seasonal weather patterns of Titan must be considered highly uncertain, since we only have been observing the planet for a period that only covers one very short portion of its very long 30 year-long year.

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Planet of geysers

2:54 pm

Using Cassini data assembled over the past seven years, scientists have now identified 101 distinct geysers erupting on the surface of the Saturn’s moon Enceladus.

Over a period of almost seven years, Cassini’s cameras surveyed the south polar terrain of the small moon, a unique geological basin renowned for its four prominent “tiger stripe” fractures and the geysers of tiny icy particles and water vapor first sighted there nearly 10 years ago. The result of the survey is a map of 101 geysers, each erupting from one of the tiger stripe fractures, and the discovery that individual geysers are coincident with small hot spots. These relationships pointed the way to the geysers’ origin.

The really important discovery here however is this:
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Radar images of Titan taken in 2013 by Cassini show a twelve-mile patch appear in one of the moon’s methane lakes, then disappear.

9:14 am

The mysteries of science: Radar images of Titan taken in 2013 by Cassini show a twelve-mile patch appear in one of the moon’s methane lakes, then disappear.

They really don’t know what this patch is.

Prior to the July 2013 observation, that region of Ligeia Mare had been completely devoid of features, including waves. Titan’s seasons change on a longer time scale than Earth’s. The moon’s northern hemisphere is transitioning from spring to summer. The astronomers think the strange feature may result from changing seasons.

In light of the changes, Hofgartner and the other authors speculate on four reasons for this phenomenon:

  • Northern hemisphere winds may be kicking up and forming waves on Ligeia Mare. The radar imaging system might see the waves as a kind of “ghost” island.
  • Gases may push out from the sea floor of Ligeia Mare, rising to the surface as bubbles.
  • Sunken solids formed by a wintry freeze could become buoyant with the onset of warmer temperatures during the late Titan spring.
  • Ligeia Mare has suspended solids, which are neither sunken nor floating, but act like silt in a terrestrial delta.

“Likely, several different processes – such as wind, rain and tides – might affect the methane and ethane lakes on Titan,” [says Hofgarnter]

It is very important to remember that Titan is a very alien planet to the Earth. While some features, its methane lakes, have a superficial resemblance to lakes on Earth, the materials and environment are completely different. For example, on Earth the only thing that generally floats on water is ice, so that when winter arrives the surface freezes while the water below remains liquid. On Titan, if the methane freezes the ice will sink.

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Scientists have found that Saturn’s hexagon-shaped jet stream is deeply rooted and that its rotation might be revealing the planet’s rotation as well.

11:57 am

Scientists have found that Saturn’s hexagon-shaped jet stream is deeply rooted and that its rotation might be revealing the planet’s rotation as well.

Due to the tilt of approximately 27º of the planet Saturn, its polar atmosphere undergoes intense seasonable variations with long polar nights lasting over seven years, followed by a long period of 23 years of variable illumination. However, the seasonal variations do not affect the hexagon and its jet stream at all, so both are part of an extensive wave, deeply rooted in Saturn’s atmosphere. The UPV/EHU researchers suggest that the hexagon and its stream are the manifestation of a “Rossby wave” similar to those that form in the mid-latitudes of the earth. On our planet the jet stream meanders from west to east and brings, associated with it, the system of areas of low pressure and anticyclones which we have been seeing regularly on weather maps.

On Saturn, a hydrogen gas planet, ten times the size of the Earth, cold in its upper clouds, without a solid surface, and with an atmosphere as deep as that of an ocean, “the hexagonal wavy motion of the jet stream is expected to be propagated vertically and reveal to us aspects of the planet’s hidden atmosphere,” pointed out Agustín Sánchez-Lavega, Head of the Planetary Sciences research group. “The movement of the hexagon could therefore be linked to the depths of Saturn, and the rotation period of this structure, which, as we have been able to ascertain, is 10 hours, 39 minutes and 23 seconds, could be that of the planet itself,” he added. Saturn is the only planet in the Solar System whose rotation period is not yet known.

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Is a natural rain of diamonds occurring on Jupiter and Saturn? Two scientists say yes!

5:07 am

Is a natural rain of diamonds occurring on Jupiter and Saturn? Two scientists say yes!

In their scenario, lightning zaps molecules of methane in the upper atmospheres of Saturn and Jupiter, liberating carbon atoms. These atoms then stick onto each other, forming larger particles of carbon soot, which the Cassini spacecraft may have spotted in dark storm clouds on Saturn3. As the soot particles slowly float down through ever-denser layers of gaseous and liquid hydrogen towards the planets’ rocky cores, they experience ever greater pressures and temperatures. The soot is compressed into graphite, and then into solid diamonds before reaching a temperature of about 8,000 °C, when the diamond melts, forming liquid diamond raindrops, they say. Inside Saturn, the conditions are right for diamond ‘hail’ to form, beginning at a depth of about 6,000 kilometres into the atmosphere and extending for another 30,000 km below that, says Baines. He estimates that Saturn may harbour about 10 million tonnes of diamond produced this way, with most of it made up of rocks no bigger than a millimetre and perhaps some chunks spanning 10 centimeters.

But don’t invest your money yet in a diamond gathering expedition. This is only a theory, which many scientists dispute.

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Cassini has found hints of activity coming from the Saturn moon Dione.

4:26 pm

Cassini has found hints of activity coming from the Saturn moon Dione.

The spacecraft’s magnetometer has detected a faint particle stream coming from the moon, and images showed evidence for a possible liquid or slushy layer under its rock-hard ice crust. Other Cassini images have also revealed ancient, inactive fractures at Dione similar to those seen at Enceladus that currently spray water ice and organic particles.

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Scientists have released the first topo map of Titan.

4:40 pm

Scientists have released the first topo map of Titan.

Whereas Earth’s tallest mountain towers nearly 9 kilometers above sea level, Titan’s topographic variations are mild: Its highest point is just half a kilometer above the mean and its lowest just 1.7 kilometers below.

Overall the detail here is not very great. None of the instruments on Cassini can see anything smaller than a half kilometer, about 1,500 feet, so the data doesn’t really show us the rough details. Moreover, the best data is spotty, as it has been accumulated by about a hundred Cassini fly-bys, rather than systematically by an orbiting spacecraft.

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

7:01 pm

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.

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