Aurion Mission: Mysteries of Io's volcanic plumes etc...

Friday, July 15, 2011

Mysteries of Io's volcanic plumes etc...


Moons - Jupiter

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Electric Io Revisited
Electric Jets on Io
Europa and Mars
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Io and the "Greatest Surprise"
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Io's "Volcano" Prometheus
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Predicting the Electrical Etching of Io
Retrospective on Io
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Tvashtar in Motion
This five-frame sequence of New Horizons images captures the giant plume from Io's Tvashtar volcano. Snapped by the probe’s Long Range Reconnaissance Imager (LORRI) as the spacecraft flew past Jupiter earlier this year, this first-ever “movie” of an Io plume clearly shows motion in the cloud of volcanic debris, which extends 330 kilometers (200 miles) above the moon’s surface. Only the upper part of the plume is visible from this vantage point – the plume’s source is 130 kilometers (80 miles) below the edge of Io's disk, on the far side of the moon.
The appearance and motion of the plume is remarkably similar to an ornamental fountain on Earth, replicated on a gigantic scale. The knots and filaments that allow us to track the plume’s motion are still mysterious, but this movie is likely to help scientists understand their origin, as well as provide unique information on the plume dynamics.
Io's hyperactive nature is emphasized by the fact that two other volcanic plumes are also visible off the edge of Io's disk: Masubi at the 7 o'clock position, and a very faint plume, possibly from the volcano Zal, at the 10 o'clock position. Jupiter illuminates the night side of Io, and the most prominent feature visible on the disk is the dark horseshoe shape of the volcano Loki, likely an enormous lava lake. Boosaule Mons, which at 18 kilometers (11 miles) is the highest mountain on Io and one of the highest mountains in the solar system, pokes above the edge of the disk on the right side.
The five images were obtained over an 8-minute span, with two minutes between frames, from 23:50 to 23:58 Universal Time on March 1, 2007. Io was 3.8 million kilometers (2.4 million miles) from New Horizons; the image is centered at Io coordinates 0 degrees north, 342 degrees west.
The pictures were part of a sequence designed to look at Jupiter's rings, but planners included Io in the sequence because the moon was passing behind Jupiter's rings at the time.
Release date: May 14, 2007
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Science Photos

Tvashtar Movie


Detecting Extraterrestrial Volcanism

A recent study by members of the Harvard-Smithsonian Center for Astrophysics has been getting a lot of attention - one where it was suggested that we are very close to the ability to detect volcanic eruptions on extrasolar (not in our solar system) planets with 30 light years. This comes from our increasing ability to detect chemical compounds and elements in atmospheres of distant worlds, so theoretically if we detect large amounts of sulfur dioxide that might come and go in atmosphere of these planets, it could be from a volcanic eruption.
Now, before you get ready to add a bunch of new volcanoes to the directory, Dr. Lisa Kaltenegger, one of the lead scientists on the research, says that "using the James Webb Space Telescope, we could spot an eruption 10 to 100 times the size of Pinatubo for the closest stars." Remember, Pinatubo was a VEI 6 eruption that released upwards of 17 million tonnes of sulfur dioxide. So, Kaltenegger is saying that we may be able to currently detect eruptions on Earth-like bodies in other solar systems that are at smallest a VEI 7-8 and releasing hundreds of millions tonnes of sulfur dioxide - akin to the 1815 Tambora eruption! Interesting, yes, but if extrasolar Earth-like planets are similar to Earth in terms of volcanic activity, it could be few and far between. However, that is a big "if" - we really have a limited data set about volcanic activity on other planets. The only planets or moons in our solar system that we have observed active volcanism* is Earth and Io, although there is a lot of evidence that Venus and Mars may have geologically-recent eruptions as well.
We have observed volcanism on Io from afar - that is how we discovered that the inner Jovian moon is so volcanically active. However, it appears that a lot of the volcanic activity on Io is mafic to ultramafic magmatism**. The plumes of some of the Ioan eruptions can reach >300 km - thanks to the lower gravity of the moon - and vast fissure eruptions were captured by the Galileo orbiter during its tenure around Jupiter.
* This isn't counting the cryovolcanism of moons like Enceladus or Triton.
** UPDATEEruptions reader Elli reminded me that the idea that magmatism on Io isn't likely to be sulfur-based. Here is the rationale (from How Volcanoes Work):
Data from Galileo's NIMS instrument indicates that the average temperature of active lavas on Io is about 1600 degrees Centigrade. There has been some speculation that some of the lavas may be composed of liquid sulfur. Sulfur, however, boils vigorously on Io's surface at at about 500 degrees Centigrade. Therefore, the lavas on Io are certainly of a silicate composition. High-temperature lavas on earth have a mafic composition (rich in magnesium and relatively depleted in silica). The extraordinarily high temperatures of the lavas on Io suggest that they are of an ultramafic composition.
Thanks for correcting me, Elli (and to everyone, always feel free to point out errors or misconceptions on my part!)
Top left: Sulfur-silicate volcanism at Pillan Patera on Io.
Gallery: Science Photos

Tvashtar Montage
Click on image to enlarge.
Tvashtar Montage
Release Date: Oct 9, 2007
Keywords: gas, Hubble, Io, Jupiter, LORRI, plume(s), sulfur, Tvashtar, volcano
The Tvashtar plume on Io, seen by the Hubble Space Telescope (HST) and by New Horizons.

(A): The image in which the plume was discovered, taken by HST in ultraviolet light on Feb. 14, 2007, at a wavelength of 260 nm. The red diamond indicates location of the Tvashtar hot spot seen later by New Horizons. (B): An HST image of Io and the Tvashtar plume seen against Jupiter; sulfur gas in the plume absorbs ultraviolet light, making the plume look reddish in this color composite. The composite is composed of images taken at 260 nm (blue), 330 nm (green), and 410 nm (red). Other images in this montage are in visible light from the Long-Range Reconnaissance Imager (LORRI). The scale bar is 200 kilometers long and the yellow star indicates the projected location of the hot spot at the Tvashtar plume source. The dashed line is the terminator, the line dividing day from night on Io. (C): The highest-resolution view of the full plume, at a resolution of 12.4 kilometers (7.7 miles) per pixel and a solar phase angle of 102 degrees, showing the complex filamentary structure of the plume. The images are sharpened by un-sharp masking; the dark line at the edge of the disk is an artifact of this sharpening. (D): An image at 145-degree phase angle at 22.4 kilometers (13.8 miles) per pixel, showing the time variability of the details of the plume structure and its persistent bright top. (F-J): Sequence of frames at 2-minute intervals showing dynamics in the upper part of the plume (the source is on the far side of Io). Colored diamonds track individual features whose speeds, projected on the plane of the sky, are shown in (E).

This image appears in the Oct. 12, 2007, issue of Science magazine, in a paper by John Spencer, et al.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Gallery: Science Photos

Io Eclipse Montage
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Io Eclipse Montage
Release Date: Oct 9, 2007
Keywords: atmosphere, auroral, gas, Io, Jupiter, lava, LEISA, LORRI, moon(s), plume(s), Ralph, shadow, volcano
New Horizons took this montage of images of Jupiter’s volcanic moon Io, glowing in the dark of Jupiter’s shadow, as the Pluto-bound spacecraft sped through the Jupiter system on Feb. 27, 2007.

(A): In this picture from the Long-Range Reconnaissance Imager (LORRI), dark blotches and straight lines are artifacts. The brightest spots (including the volcanoes Pele [P] and East Girru [EG]) are incandescent lava from active volcanoes. The more diffuse glows, and the many faint spots, are from gas in the plumes and atmosphere, glowing due to bombardment by plasma in Jupiter’s magnetosphere, in a display similar to the Earth’s aurorae. (B): The same image with a latitude/longitude grid, showing that the cluster of faint spots is centered near longitude 0 degrees, the point on Io that faces Jupiter. The image also shows the locations of the plumes seen in sunlit images (indicated by red diamonds), which glow with auroral emission in eclipse. (C): Simulated sunlit view of Io with the same geometry, based on sunlit LORRI images. (D): A combination of the sunlit image (in cyan) and the eclipse image (in red), showing that all point-like glows in the eclipse image arise from dark volcanoes in the eclipse image. (E): This infrared image, at a wavelength of 2.3 microns, obtained by New Horizons Linear Etalon Spectral Imaging Array (LEISA) an hour after the LORRI image, showing thermal emission from active volcanoes. Elongation of the hot spots is an artifact. (F): Combined visible albedo (cyan) and LEISA thermal emission (red) image, showing the sources of the volcanic emission. That most of the faint point-like glows near longitude zero, seen in visible light in images A, B, and D, do not appear in the infrared view of volcanic heat radiation, is one reason scientists believe that these glows are due to auroral emission, not heat radiation.

This image appears in the Oct. 12, 2007, issue of Science magazine, in a paper by John Spencer, et al.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Gallery: Science Photos

Changes on Io
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Changes on Io
Release Date: Oct 9, 2007
Keywords: Io, Jupiter, lava, LORRI, moon(s), plume(s), volcano
A: A global map of Jupiter’s moon Io derived from eight images taken by the Long Range Reconnaissance Imager (LORRI) on the New Horizons spacecraft, as it passed Jupiter on its way to Pluto in late February 2007. Details as small as 12 kilometers (7 miles) are visible. The map shows the comprehensive picture of Io’s volcanism obtained by New Horizons. Yellow ovals denote areas with new, faded or shifted plume deposits since the last images taken by the Galileo spacecraft in 2001. Green circles denote areas where probable new lava flows have occurred. Cyan diamonds indicate locations of active volcanic plumes, and orange hexagons are volcanic hot spots detected by the Linear Etalon Imaging Spectral Array (LEISA) instrument. For plumes and hot spots, symbol size indicates the approximate relative size and brightness of the features.

B-F: Comparison of New Horizons (NH) and earlier images of major surface changes discovered by New Horizons at Io’s volcanoes Masubi (45 degrees S, 57 degrees West) and North Lerna (55 degrees S, 290 degrees W). The scale bars are 200 kilometers long, and a is the solar phase angle. At Masubi, old lava flows seen by Voyager and Galileo (B) have been obscured at low phase angles (C) by deposits from two active plumes associated with a new 240-kilometer (150-mile) long dark lava flow, which is the longest lava flow known to have been erupted in the solar system since the discovery of Io volcanism in 1979. At North Lerna, a recent eruption has generated a 130-km long lava flow (F), as well as an active plume that has produced a concentric pattern of deposits.

This image appears in the Oct. 12, 2007, issue of Science magazine, in a paper by John Spencer, et al.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Gallery: Science Photos

A 'Plumefall' on Io
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A 'Plumefall' on Io
Release Date: May 1, 2007
Keywords: Io, Jupiter, LORRI, moon(s), plume(s), Tvashtar, volcano
New Horizons took this image of Jupiter's volcanic moon Io with its Long Range Reconnaissance Imager (LORRI) at 15:15 Universal Time on February 28, 2007, nearly 10 hours after the spacecraft’s closest approach to Jupiter. The image is centered at Io coordinates 5 degrees south, 92 degrees west, and the spacecraft was 2.4 million kilometers (1.5 million miles) from Io. Io's diameter is 3,640 kilometers (2,262 miles).

Io’s dayside was deliberately overexposed in this image to bring out details on the nightside and in any volcanic plumes that might be present. Io cooperated by producing an enormous plume, 330 kilometers (200 miles) high, from the volcano Tvashtar. Near Io's north pole, Tvashtar was active throughout New Horizons’ Jupiter encounter.

In this image, volcanic debris from the plume, illuminated by the setting sun, rains down onto Io's nightside. Hot, glowing lava at the source of the plume is the bright point of light on the sunlit side of the terminator (the line separating day and night). Elsewhere along the terminator, mountains catch the setting sun. The nightside of Io is lit up by light reflected from Jupiter.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Gallery: Science Photos

Tvashtar in Motion
Click on image to enlarge.
Tvashtar in Motion
Release Date: May 14, 2007
Keywords: animation/video, Io, LORRI, moon(s), plume(s), Tvashtar, volcano

Click here to view this animation.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute


Beware: Io Dust

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Beware: Io Dust
Jupiter's moon Io is shooting tiny volcanic bullets at passing spacecraft.
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September 14, 2004: Jupiter's moon Io is peppered with volcanoes, the hottest, most active volcanoes in our solar system. Sizzling vents spew plumes of gas and dust as much as 400 km high. They surge, spit, subside and surge again, non-stop.
see captionThe towering plumes, outlined by graceful arcs of rising and falling ash, are eerily beautiful. Their tops jut into space, freezing. Beneath them, scientists believe, it snows. Sulfurous flakes crystallize in the plume-tops and drift gently down to coat Io's colorful terrain.
Right: A volcanic plume on Io, photographed by NASA's Galileo spacecraft. [More]
High above the falling snow something unexpected happens: At the apex of the plumes, some of the ash and dust that ought to turn around and fall ... doesn't. Defying gravity, it keeps going up, not slowing but accelerating, 2 times, 10 times, hundreds of times faster than a speeding bullet, away from Io and into deep space.
Passing spacecraft beware: Io is shooting at you.
The Ulysses spacecraft, a joint mission of NASA and the European Space Agency, made the discovery in 1992 when, approaching Jupiter, it was hit by a breakneck stream of volcano dust.
"What a surprise," recalls Harold Krueger of the Max Planck Institute in Heidelberg, the principle investigator for Ulysses' dust detector. "We expected to encounter dust," he says. The solar system is littered with flakes from comets and asteroids. "But nothing like this."

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The dust came in a tight stream, like water from a garden hose, and it was moving extraordinarily fast, about 300 km/s (670,000 mph). "This makes it some of the fastest-moving material in the solar system," says Krueger, "second only to the solar wind." Fortunately the dust-bits were small, similar in size to particles in cigarette smoke, so they didn't penetrate the ship's hull in spite of their extreme velocity. At first, no one suspected Io. Ulysses was 100 million kilometers from Io when the stream blew by, supposedly beyond the reach of volcanic plumes. Plus, the speed of the dust didn't make sense. Particles emerge from Io's vents traveling 1 or 2 km/s, not 300 km/s.
Baffled, researchers considered several possibilities: Could Jupiter's dark rings be responsible? There's plenty of dust there, but how could rings manufacture fast-moving jets? Comet Shoemaker-Levy 9 was another suspect. The comet flew so close to Jupiter in 1992 that it was torn apart. Comets are known to produce streams of dust, but not so fast as the stream that hit Ulysses.
see captionRight: Ulysses visits Jupiter: an artist's concept. [More]
NASA's Galileo spacecraft eventually solved the puzzle. Like Ulysses, Galileo was pelted by dust when it approached Jupiter in 1995. Unlike Ulysses, which merely flew past the giant planet, Galileo settled into orbit. As data accumulated over a period of years, scientists were able to correlate volcanic activity with dust events, and they showed, furthermore, that dust streams were modulated by Io's orbital motion.
The source was definitely Io.
Regarding the extreme velocity of the dust: "Jupiter is responsible for that," explains Krueger.
Jupiter is not only a giant planet, but also a giant magnet, which spins once every 9 hours and 55 minutes. Spinning magnetic fields produce electric fields, and the electric fields around Jupiter are intense. Io-dust, like dust on your computer monitor, is electrically charged, so Jupiter's electric forces naturally accelerate the grains. 300 km/s is no problem.
In 2000 when the Cassini spacecraft sailed past Jupiter en route to Saturn, it too was hit. Cassini's dust detector is more capable than Ulysses'. In addition to mass, speed, charge and trajectory, it can also measure elemental composition. Cassini found hints of sulfur, silicon, sodium and potassium--all signs of volcanic origin.
"This raises an interesting possibility," says Krueger. "We can analyze the hot interior of Io from a great distance." There's no need to get too close to the sizzling vents when you can catch the ash millions of miles away.
see captionIo dust can even reach Earth, says Krueger, but don't expect a meteor shower. Bright meteors such as Perseids and Leonids are caused by sand-sized comet dust. Io dust is much smaller. A typical grain is only 10 billionths of a meter wide. If a bit of it disintegrated in Earth's atmosphere, you probably wouldn't notice.
Left: Impact rates of Io dust streams measured by Ulysses. [More]
End of story? Not quite.
Ulysses visited Jupiter again in early 2004 and once again the craft was pelted. Io's volcanoes were still at work. But something was wrong: The dust was shooting in the wrong direction.
"Io dust is supposed fly out of Jupiter's equatorial plane," says Krueger, "because that's the way the accelerating electric fields point." This time Ulysses approached Jupiter's north pole (75 degrees north latitude to be exact) where no dust should go. Yet the spacecraft was pelted anyway.
Jupiter, it seems, flings Io-dust in every direction, which is hard to understand, says Krueger. Future missions to the giant planet might unravel the mystery. Every blast of dust will remind: we've still got a lot to learn.