Starship Asterisk*

Roland wrote:
It is possible that the location of the volcanoes is caused by buster impacts.

a relatively thin crust would help account for the small number of more classical appearing impact craters.?!

http://en.wikipedia.org/wiki/Europa_%28moon%29 wrote:

[b][color=#0000FF]Europa's trailing hemisphere in approximate natural color. The prominent crater in the lower right is Pwyll and the darker regions are areas where Europa's primarily water ice surface has a higher mineral content. Imaged on 7 September 1996 by Galileo spacecraft.[/color][/b]

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<<Europa is one of the smoothest objects in the Solar System. The prominent markings crisscrossing the moon seem to be mainly albedo features, which emphasize low topography. There are few craters on Europa because its surface is tectonically active and young. Europa's icy crust gives it an albedo (light reflectivity) of 0.64, one of the highest of all moons. This would seem to indicate a young and active surface; based on estimates of the frequency of cometary bombardment that Europa probably endures, the surface is about 20 to 180 million years old. There is currently no full scientific consensus among the sometimes contradictory explanations for the surface features of Europa.

Slightly smaller than Earth's Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of water ice and is one of the smoothest in the Solar System. This surface is striated by cracks and streaks, while cratering is relatively infrequent. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, which could conceivably serve as an abode for extraterrestrial life. This hypothesis proposes that heat energy from tidal flexing causes the ocean to remain liquid and drives geological activity similar to plate tectonics. The radiation level at the surface of Europa is equivalent to a dose of about 5400mSv (540 rem) per day, an amount of radiation that would cause severe illness or death in human beings exposed for a single day.>>

BDanielMayfield wrote: Chlorophyll? (See my first post in this thread.)

Chris Peterson wrote: This is a false-color image. It consists of frames collected through infrared, green, and violet filters, which are then mapped in some unspecified way to red, green, and blue display channels. You'd need to go back to the original data to try and estimate the actual color of what is being displayed here as green, and probably use the multichannel data in a clever way to deduce the possible mineralogical possibilities for the regions displayed as green.

Chappy wrote:The green patches on Io are intriguing, any info on what chemical process creates such hues of green?

Wikipedia wrote:Io's volcanism is responsible for many of the satellite's unique features. Its volcanic plumes and lava flows produce large surface changes and paint the surface in various shades of yellow, red, white, black, and green, largely due to allotropes and compounds of sulfur.

Chappy wrote:The green patches on Io are intriguing, any info on what chemical process creates such hues of green?

Anthony Barreiro wrote:
I still hope that Juno will look at Io, if only for mythological reasons.

• Antony and Cleopatra (Folio) Act 3, Scene 10

Chris Peterson wrote:

Anthony Barreiro wrote:The first of these possibilities, that Io's rotation is faster than currently believed, should be fairly easy to test.

I think something got lost in translation in preparing the report you are referencing. The suggestion, as given, makes no sense. The rotational speed of Io is known with complete accuracy, because the moon is tidally locked to Jupiter. Its rotational period is exactly the same as its orbital period.

I don't know if they were referring to some sort of internal rotation of a fluid layer, or something to do with libration. But referring to the rotation of Io itself (as referenced to its surface) doesn't make sense.

Anthony Barreiro wrote:The first of these possibilities, that Io's rotation is faster than currently believed, should be fairly easy to test.

neufer wrote:

DavidGovett wrote:
Does anyone else see a semi-uniform distribution of volcanoes on Io?
The distribution does not seem random.

• Why would you expect the volcano distribution to be random

http://www.nasa.gov/topics/solarsystem/features/io-volcanoes-displaced.html wrote:
<<As Io gets closer to Jupiter, the giant planet's powerful gravity deforms the moon toward it and then, as Io moves farther away, the gravitational pull decreases and the moon relaxes. The flexing from gravity causes tidal heating -- in the same way that you can heat up a spot on a wire coat hanger by repeatedly bending it, the flexing creates friction in Io's interior, which generates the tremendous heat that powers the moon's extreme volcanism.

"Our analysis supports the prevailing view that most of the heat is generated in the asthenosphere, but we found that volcanic activity is located 30 to 60 degrees East from where we expect it to be," said Christopher Hamilton of the University of Maryland, College Park.

[...]

Possibilities to explain the offset include a faster than expected rotation for Io, an interior structure that permits magma to travel significant distances from where the most heating occurs to the points where it is able erupt on the surface, or a missing component in existing tidal heating models, like fluid tides from an underground magma ocean, according to the team.>>

DavidGovett wrote:
Does anyone else see a semi-uniform distribution of volcanoes on Io?
The distribution does not seem random.

• Why would you expect the volcano distribution to be random

http://www.nasa.gov/topics/solarsystem/features/io-volcanoes-displaced.html wrote:

[b][color=#0000FF]Convection cells on the Sun, with North America superimposed[/color][/b]

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<<As Io gets closer to Jupiter, the giant planet's powerful gravity deforms the moon toward it and then, as Io moves farther away, the gravitational pull decreases and the moon relaxes. The flexing from gravity causes tidal heating -- in the same way that you can heat up a spot on a wire coat hanger by repeatedly bending it, the flexing creates friction in Io's interior, which generates the tremendous heat that powers the moon's extreme volcanism.

"Our analysis supports the prevailing view that most of the heat is generated in the asthenosphere, but we found that volcanic activity is located 30 to 60 degrees East from where we expect it to be," said Christopher Hamilton of the University of Maryland, College Park.

Hamilton and his team performed the spatial analysis using the a new, global geologic map of Io, produced by David Williams of Arizona State University, Tempe, Ariz., and his colleagues using data from NASA spacecraft. The map provides the most comprehensive inventory of Io's volcanoes to date, thereby enabling patterns of volcanism to be explored in unprecedented detail.

Assuming that the volcanoes are located above where the most internal heating occurs, the team tested a range of interior models by comparing observed locations of volcanic activity to predicted tidal heating patterns.

"We performed the first rigorous statistical analysis of the distribution of volcanoes in the new global geologic map of Io," says Hamilton. "We found a systematic eastward offset between observed and predicted volcano locations that can't be reconciled with any existing solid body tidal heating models."

Possibilities to explain the offset include a faster than expected rotation for Io, an interior structure that permits magma to travel significant distances from where the most heating occurs to the points where it is able erupt on the surface, or a missing component in existing tidal heating models, like fluid tides from an underground magma ocean, according to the team.>>

DavidGovett wrote:Does anyone else see a semi-uniform distribution of volcanoes on Io?
The distribution does not seem random.

MichelleEH wrote:I am surprised that the photo seems to have been scrubbed of its coronal atmosphere. The photo shows numerous plumes of volcanic smoke but no ring around the moon to show the atmosphere that has to be there. We all know of the photographic evidence of plumes that seem to eject miles above the surface but are drawn back by Io's gravity.

Any thoughts?

garyj wrote:
I've read that scientists have been able to ascribe only about 10% of Io's heating (which causes volcanism and infrared surface radiation) to tidal effects. They are still looking for the source of the other 90%.

https://en.wikipedia.org/wiki/Io_%28moon%29#Tidal_heating wrote:
<<Unlike the Earth and the Moon, Io's main source of internal heat comes from tidal dissipation rather than radioactive isotope decay, the result of Io's orbital resonance with Europa and Ganymede. Such heating is dependent on Io's distance from Jupiter (= 421,700 km vs. 384,399 km for our Moon), its orbital eccentricity (= 0.004 v. 0.055 for our Moon), [its orbital period (= 1.77 d vs. 27.32 for our Moon)] the composition of its interior, and its physical state. Its Laplace resonance with Europa and Ganymede maintains Io's eccentricity and prevents tidal dissipation within Io from circularizing its orbit. The resonant orbit also helps to maintain Io's distance from Jupiter; otherwise tides raised on Jupiter would cause Io to slowly spiral outward from its parent planet. The vertical differences in Io's tidal bulge, between the times Io is at periapsis and apoapsis in its orbit, could be as much as 100 m. The friction or tidal dissipation produced in Io's interior due to this varying tidal pull, which, without the resonant orbit, would have gone into circularizing Io's orbit instead, creates significant tidal heating within Io's interior, melting a significant amount of the moon's mantle and core. The amount of energy produced is up to 200 times greater than that produced solely from radioactive decay. This heat is released in the form of volcanic activity, generating its observed high heat flow (global total: 0.6 to 1.6×10¹⁴ W). Models of its orbit suggest that the amount of tidal heating within Io changes with time, however the current amount of tidal dissipation is consistent with the observed heat flow. Models of tidal heating and convection have not found consistent planetary viscosity profiles which simultaneously match tidal energy dissipation and mantle convection of heat to the surface.>>