APOD: Galileo's Europa (2024 Mar 29)

[APOD Robot]

Galileo's Europa

Explanation: Looping through the Jovian system in the late 1990s, the Galileo spacecraft recorded stunning views of Europa and uncovered evidence that the moon's icy surface likely hides a deep, global ocean. Galileo's Europa image data has been remastered here, with improved calibrations to produce a color image approximating what the human eye might see. Europa's long curving fractures hint at the subsurface liquid water. The tidal flexing the large moon experiences in its elliptical orbit around Jupiter supplies the energy to keep the ocean liquid. But more tantalizing is the possibility that even in the absence of sunlight that process could also supply the energy to support life, making Europa one of the best places to look for life beyond Earth. The Juno spacecraft currently in Jovian orbit has also made repeated flybys of the water world, returning images along with data exploring Europa's habitability. This October will see the launch of the NASA's Europa Clipper on a voyage of exploration. The spacecraft will make nearly 50 flybys, approaching to within 25 kilometers of Europa's icy surface.

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[smitty]

Any educated speculation about the cause of the rusty coloration of the long, curving fractures?

[bystander]

Any educated speculation about the cause of the rusty coloration of the long, curving fractures?

...
Spectrographic evidence suggests that the darker, reddish streaks and features on Europa's surface may be rich in salts such as magnesium sulfate, deposited by evaporating water that emerged from within. Sulfuric acid hydrate is another possible explanation for the contaminant observed spectroscopically. In either case, because these materials are colorless or white when pure, some other material must also be present to account for the reddish color, and sulfur compounds are suspected.
...

[smitty]

Thank you, bystander!

[johnnydeep]

Any educated speculation about the cause of the rusty coloration of the long, curving fractures?

...
Spectrographic evidence suggests that the darker, reddish streaks and features on Europa's surface may be rich in salts such as magnesium sulfate, deposited by evaporating water that emerged from within. Sulfuric acid hydrate is another possible explanation for the contaminant observed spectroscopically. In either case, because these materials are colorless or white when pure, some other material must also be present to account for the reddish color, and sulfur compounds are suspected.
...

Alright, aren't "magnesium sulfate" and "sulfuric acid hydrate" themselves "sulfur compounds"? But that says both are colorless or white when pure, and then says that sulfur compounds" could explain the discoloration. So, what then - additional sulfur compounds?

[johnnydeep]

I can hardly wait the 6 more years for Europa Clipper to arrive at Jupiter! (Assuming it launches ok in October.)

[bystander]

...
Spectrographic evidence suggests that the darker, reddish streaks and features on Europa's surface may be rich in salts such as magnesium sulfate, deposited by evaporating water that emerged from within. Sulfuric acid hydrate is another possible explanation for the contaminant observed spectroscopically. In either case, because these materials are colorless or white when pure, some other material must also be present to account for the reddish color, and sulfur compounds are suspected.
...

Alright, aren't "magnesium sulfate" and "sulfuric acid hydrate" themselves "sulfur compounds"? But that says both are colorless or white when pure, and then says that sulfur compounds" could explain the discoloration. So, what then - additional sulfur compounds?

If some other material must also be present and sulfur is present, it seems reasonable to suspect sulfur compounds.

[johnnydeep]

...
Spectrographic evidence suggests that the darker, reddish streaks and features on Europa's surface may be rich in salts such as magnesium sulfate, deposited by evaporating water that emerged from within. Sulfuric acid hydrate is another possible explanation for the contaminant observed spectroscopically. In either case, because these materials are colorless or white when pure, some other material must also be present to account for the reddish color, and sulfur compounds are suspected.
...

Alright, aren't "magnesium sulfate" and "sulfuric acid hydrate" themselves "sulfur compounds"? But that says both are colorless or white when pure, and then says that sulfur compounds" could explain the discoloration. So, what then - additional sulfur compounds?

If some other material must also be present and sulfur is present, it seems reasonable to suspect sulfur compounds.

My point was that they've already identified two sulfur compounds that are white/clear, but seem to be implying there must be some other sulfur compound to explain the color seen!

[Roy]

On the left side of the picture there is a white fissure that tails off into brown. A fact mentioned on Wikipedia is that there is massive ionizing radiation on Europa, 540 REM per day, (100 REM is sufficient to kill a person) which could alter whatever is upwelling in the fissures.