APOD: Io in True Color (2022 Dec 11)

[APOD Robot]

Io in True Color

Explanation: The strangest moon in the Solar System is bright yellow. The featured picture, an attempt to show how Io would appear in the "true colors" perceptible to the average human eye, was taken in 1999 July by the Galileo spacecraft that orbited Jupiter from 1995 to 2003. Io's colors derive from sulfur and molten silicate rock. The unusual surface of Io is kept very young by its system of active volcanoes. The intense tidal gravity of Jupiter stretches Io and damps wobbles caused by Jupiter's other Galilean moons. The resulting friction greatly heats Io's interior, causing molten rock to explode through the surface. Io's volcanoes are so active that they are effectively turning the whole moon inside out. Some of Io's volcanic lava is so hot it glows in the dark.

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[Ann]

Io in True Color Image Credit: NASA, JPL, Galileo Project

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Io may not be quite as yellow as it looks in the APOD. Check out this graph:

Image: NASA / JPL / UA / Jason Perry

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The graph shows the seven filters used by Galileo when it took the picture of Io. Galileo was equipped with one violet filter, one green filter and one red filter, as well as four filters sensitive to infrared light.

As you can see, there is a big gap between the filter range of the violet filter and the green filter, or to put it differently: Galileo was unable to detect blue light with wavelengths between 450 and 500 nm from Io. But as you can see from the sloping black line, which represents the albedo (the reflectivity) of Io at different wavelengths, Io reflects more blue than violet light.

In short: Io reflects more blue light than the Galileo image suggests, and therefore is not as brightly yellow as Galileo made me look.

A RECONSTRUCTION OF IO'S TRUE COLOR The left image is a straight red-green-violet color combination from Galileo. The right image has a blue channel synthesized from violet and green filter images (blue = 0.55*green + 0.45*violet) and may be a closer representation of the color that Io would appear to the human observer.Image: NASA / JPL / UA / color composite by Jason Perry

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Read more about Jason Perry's attempts to reconstruct Io's true color here.


We may also note that Io has volcanic eruptions with blue (or violet?) plumes.

Io, with two plumes erupting from its surface. One plume is seen at Io's limb, and it is 140 kilometers (86 miles) high. The second plume is located close to the equator near the terminator, the boundary between day and night. The vent of that eruption is near the center of the bright and dark rings. We don't see the blue plume from this angle, but the plume casts a red shadow on the ground. Image: NASA's Galileo spacecraft

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Io is the most volcanically active body in the Solar system.

Ann

[JohnD]

Luke Jerram is an English installation artist - his works have included the Museum of the Moon:

And Gaia,

Both have been seen around the world, including at the Lancaster Priory. Huis latest work, Mars, is on tour.

What a good subject would Io be for his work!

John

[Chris Peterson]

Io may not be quite as yellow as it looks in the APOD. Check out this graph:

It's hugely challenging to figure out what something would look like to our eyes from any image data source. The number of variables is staggering. We have the nature of the object, which may have a combination of continuum reflection (the color of which also depends on the nature of the illumination) along with some narrow band reflection (or in some cases emission). We have the complex passbands of the filters that are used. This goes through some kind of processing and gets mapped to three channels, which go to our display devices, which have their own complex emission bands for each of those channels. And most people don't have calibrated displays, so there's a lot of variation there. The brightness of our displays and of the environment we view them in also changes our color perception. And all of this is putting light into our eyes, which have no receptors for red, green, or blue at all! So yet another mapping as our two yellow and one violet sensors respond.

Oh my!

[orin stepanek]

Back a few years ago; when I first saw Galileo's photos of Io; I was
amazed at how much it looked like a pizza! It still does!
Beautiful view; I like it!

[Chris Peterson]

ioprometheus_galileo.jpg
Back a few years ago; when I first saw Galileo's photos of Io; I was
amazed at how much it looked like a pizza! :mrgreen: It still does! :lol2:
Beautiful view; I like it!

Not like any pizza I want to eat! Maybe a pizza that's been sitting in a dumpster for a week.

[orin stepanek]

ioprometheus_galileo.jpg
Back a few years ago; when I first saw Galileo's photos of Io; I was
amazed at how much it looked like a pizza! It still does!
Beautiful view; I like it!

Not like any pizza I want to eat! Maybe a pizza that's been sitting in a dumpster for a week.

I don't eat pizza any more; but it resembles a cheese pizza without any sauce!

[johnnydeep]

Io in True Color

Explanation: The strangest moon in the Solar System is bright yellow. The featured picture, an attempt to show how Io would appear in the "true colors" perceptible to the average human eye, was taken in 1999 July by the Galileo spacecraft that orbited Jupiter from 1995 to 2003. Io's colors derive from sulfur and molten silicate rock. The unusual surface of Io is kept very young by its system of active volcanoes. The intense tidal gravity of Jupiter stretches Io and damps wobbles caused by Jupiter's other Galilean moons. The resulting friction greatly heats Io's interior, causing molten rock to explode through the surface. Io's volcanoes are so active that they are effectively turning the whole moon inside out. Some of Io's volcanic lava is so hot it glows in the dark.

What's the significance of this statement, if any, to the tidal friction - "damps wobbles caused by Jupiter's other Galilean moons"? I would think any "wobble" would only contribute to increasing the effect of tidal friction!

I do read at Wikipedia the following:

Unlike 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.[48] Such heating is dependent on Io's distance from Jupiter, its orbital eccentricity, the composition of its interior, and its physical state.[85] 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.[89] The tidal forces experienced by Io are about 20,000 times stronger than the tidal forces Earth experiences due to the Moon, and the vertical differences in its tidal bulge, between the times Io is at periapsis and apoapsis in its orbit, could be as much as 100 m (330 ft).[90] 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 Io's mantle and core.

Does the mentioned "wobble dampening" refer to any of that, or something else?

[Tekija]

Io may not be quite as yellow as it looks in the APOD. Check out this graph:

It's hugely challenging to figure out what something would look like to our eyes from any image data source. The number of variables is staggering. We have the nature of the object, which may have a combination of continuum reflection (the color of which also depends on the nature of the illumination) along with some narrow band reflection (or in some cases emission). We have the complex passbands of the filters that are used. This goes through some kind of processing and gets mapped to three channels, which go to our display devices, which have their own complex emission bands for each of those channels. And most people don't have calibrated displays, so there's a lot of variation there. The brightness of our displays and of the environment we view them in also changes our color perception. And all of this is putting light into our eyes, which have no receptors for red, green, or blue at all! So yet another mapping as our two yellow and one violet sensors respond.

Oh my!

https://midimagic.sgc-hosting.com/huvision.htm

[heehaw]

...that's Amore!

[hypatia]

ioprometheus_galileo.jpg
Back a few years ago; when I first saw Galileo's photos of Io; I was
amazed at how much it looked like a pizza! It still does!
Beautiful view; I like it!

My first thought was moldy cheese.

[orin stepanek]

ioprometheus_galileo.jpg
Back a few years ago; when I first saw Galileo's photos of Io; I was
amazed at how much it looked like a pizza! It still does!
Beautiful view; I like it!

My first thought was moldy cheese.

Blue cheese?

[hypatia]

ioprometheus_galileo.jpg
Back a few years ago; when I first saw Galileo's photos of Io; I was
amazed at how much it looked like a pizza! It still does!
Beautiful view; I like it!

My first thought was moldy cheese.

Blue cheese?

Nope, a truly bad, moldy cheese.