Saturn

Origin of Enceladus’ 101 Geysers Revealed

Jets of liquid water can be seen shooting out of Enceladus' icy surface. They are seen "spewing 200kg of water vapour and ice particles into space each second – enough to fill an Olympic swimming pool every few hours" (Cosmos) Credit: NASA/JPL

Jets of liquid water can be seen “spewing 200kg of water vapour and ice particles into space each second – enough to fill an Olympic swimming pool every few hours” (Cosmos). Image Credit: NASA/JPL

Using data provided by the Cassini-Huygens spacecraft scientists have pinpointed 101 geysers on Enceladus, one of Saturn’s icy moons. Issued in a press release by NASA, July 28th, 2014, the findings are helping scientists understand the geological processes that may allow for liquid water to exist on the moon’s surface.

The first geysers were spotted nearly ten years ago on the moon. Since then scientists have been able to resolve not only where they were being formed, but also how. Early hypothesis’ suggested that pressure built up by the flexing of the small moon’s surface was heating ice into vapor; once an enough tidal friction melted an opening on the surface, a geyser would erupt allowing the pressure to be released.

Using Cassini scientists were able to triangulate the locations of 101 fountains and have found the south pole of the moon to be a breeding ground for the geysers. Tiger stripe fractures run across the terrain of Enceladus in this area. Measurements taken over the last seven years have indicated that the geysers are erupting from hot spots along these striped fractures. This is a great clue for the scientists because it offers a possible origin for the water that spews from these vents.

Scientists have been able to correlate the intensity of the jets to thermal radiation as well as tidal stressors. It was apparent that higher temperatures were associated with the vents, however, it was unknown if increased temperatures were causing the geysers or vice versa. By analyzing high-resolution data gathered by Cassini’s heat-sensing technology in 2010 and 2012, the scientists could say definitively which came first, the chicken or the egg. In this case, it is the geysers that are causing the increased temperatures on the surface of Enceladus. Carolyn Porco, leader of the Cassini image team said in a report published in the Astronomical Journal, “[The results] told us the geysers are not a near-surface phenomenon, but have much deeper roots.”

Image Credit: NASA/JPL-Caltech/Space Science Institute

Image Credit: NASA/JPL-Caltech/Space Science Institute

Scientists now believe that the underground sea that resides on the moon is the most plausible source of these watery fountains. “They also found that narrow pathways through the ice shell can remain open from the sea all the way to the surface, if filled with liquid water.” Enceladus’ sea is believed to be nearly 10 kilometers deep, covered by 30-40 kilometers of ice near its south pole. It is still unclear why much of the moon’s water appears to be concentrated in this region. Porco had long suspected that Enceladus was releasing heat from within. Small silica particles have been spotted in the plumes, this combined with the newest evidence of deep channels connecting the moon’s surface with its underground sea gives scientists more hope of possibly finding life here.

In an article published in the journal Nature, in April, 2014, it states, “At the bottom of the Enceladus ocean, the water presumably comes in contact with the moon’s rocky core. “What matters about the new result is they say they have evidence for the ocean contacting rock,” says Christopher McKay, an astrobiologist at NASA’s Ames Research Center in Moffett Field, California. “That’s very important because pure water is not interesting biologically — the water needs to interact with rock in order to put in the stuff that’s useful for life.”

Hydrothermal vents on Earth act as transmitters of heat and chemicals from within the planet’s interior and they have been found to harbor the most extreme forms of life. Only further research will tell if similar underwater outlets are heating Enceladus, and whether or not biological life may be hiding there.

Verifying the Expected: Saturn’s Dancing Aurorae

A view of Saturn's aurora (Credit: NASA/JPL/University of Arizona/University of Leicester)

A view of Saturn’s aurora (Credit: NASA/JPL/University of Arizona/University of Leicester)

Just as anticipated, scientists have confirmed that Saturn’s elaborate aurora displays are caused by the fluctuations of its magnetosphere. The findings are not necessarily surprising; in fact, they reiterate what was already expected to be the case. Nonetheless, a recent collaboration between the Hubble Telescope and the Cassini–Huygens spacecraft has increased our knowledge of planetary light shows.

 

PROTECTIVE SHIELDS

Saturn’s core produces a magnetosphere that helps protect it from the Sun’s assailing high-energy particles. Fortunately, this field stops its atmosphere from being blown away by solar winds; perhaps even more fortunate for us, it also allows for the spectacular sight of aurorae!

A labeled diagram of a magnetosphere (Credit: ESA)

A labeled diagram of a magnetosphere (Credit: ESA)

The Earth and Saturn are both planets that produce magnetic field lines; collectively, these lines are called a magnetosphere. Think of it as a bubble surrounding the planet; though instead of it being spherical, the bubble is compressed on the side closest to the sun and an elongated tail is produced at the opposite end, this is called the magnetotail. The Sun’s wind is comprised of plasma- ionized particles that are affected by magnetism. Large amounts of solar energy cause the field lines to stretch and twist; like pulling on one end of a rubber band, eventually the magnetotail becomes so extended that it must snap back and reconnect to the planet. This causes the solar energy trapped within the field lines to discharge into the atmosphere at the poles. On Earth, we see the majority of aurorae as green, but this doesn’t mean that solar energy itself is green in any way. In fact, what it means is that energized particles (electrons and protons) are colliding with gases in the atmosphere and this interaction produces the release of light. It is the atmospheric gases involved that determine which colors are visible; we mostly see green aurorae on Earth because oxygen atoms are being excited.

 

SATURN’S LIGHT SHOWS

But what about Saturn? What colors are produced by its aurorae? By examining the planet in April and May of 2013, scientists were able to capture the twirling images of the light from all angles of the planet, and indeed, they were impressive! Saturn’s intense winds helped amplify the effect; clocking in at an impressive 1,120 mph. Some would even travel three times faster than the rotation of planet.

Several images of an aurora on Saturn’s north pole taken in April and May 2013 by the Hubble Space Telescope. Credit: NASA/ESA, Acknowledgement: J. Nichols (University of Leicester)

Several new images of an aurora brewing on Saturn’s north pole (these were taken by Hubblein April and May 2013) (Credit: NASA/ESA, Acknowledgement: J. Nichols (University of Leicester)

Cassini, which has been orbiting Saturn since 2004, took photographs of the aurorae, but because the atmosphere is primarily made of hydrogen and helium, the light emitted is bluish-red and violet. Perhaps most alluring are the images taken by Hubble using its “Advanced Camera for Surveys.” This instrument allow us to see what is normally not visible to the human eye, a majestic display of ultraviolet light. These findings have recently been accepted for publication in the Geophysical Research Letters.

 

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This article was written by me, Cassidi Schambre and originally published by From Quarks To Quasars
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