<p>Quoting from Nat.Geo. article (which has that same UV image), </p>

<blockquote>
  <p>Then, in 2010 and 2011, Hubble took a close look at the moon. More
  specifically, it looked at the auroral bands ringing Ganymede’s poles.
  Hubble studied the auroras in the ultraviolet, but Saur said the
  shimmering lights would be visible to human eyes.</p>
  
  <p>“If somebody could be standing on Ganymede looking up into the night
  sky, it would appear as red aurora, to you,” he described.</p>
</blockquote>

CC BY-SA 4.0
2020-01-15T05:28:47.827Z
Yes. Keep in mind that while Ganymede's atmosphere is very thin, Earth's aurorae are also generated in an extremely thin part of its atmosphere (the thermosphere), and are of course entirely visible. It's just that in the case of Ganymede, the "suitably thin" layer starts much closer to, if not at, the surface.
The_Sympathizer
CC BY-SA 4.0
2020-01-14T19:14:27.703Z
2020-01-14T19:14:27.703Z
Carl Witthoft
<p><a href="https://hubblesite.org/contents/media/images/2015/09/3505-Image.html" rel="noreferrer">GANYMEDE AURORAE</a></p>

<p>NASA's Hubble Space Telescope observed a pair of auroral belts encircling the Jovian moon Ganymede. The belts were observed in ultraviolet light by the Space Telescope Imaging Spectrograph and are colored blue in this illustration.<a href="https://i.sstatic.net/Pw1wR.png" rel="noreferrer"><img src="https://i.sstatic.net/Pw1wR.png" alt="enter image description here"></a></p>

<p>Why is Ganymede's aurora only visible in ultraviolet while Earth's is in the visible part of the spectrum?</p>

CC BY-SA 4.0
2020-01-14T18:16:21.600Z
Did you do any prior research on what the composition of the UV-emitting particles is?
AtmosphericPrisonEscape
CC BY-SA 4.0
2020-01-15T03:08:41.260Z
@AtmosphericPrisonEscape This is what I came across during my research, "Follow-up observations will be difficult because the auroras were only visible in ultraviolet light," https://www.astrobio.net/history/ganymedes-auroras-point-to-ocean-below-its-icy-surface-2/
Bob516
CC BY-SA 4.0
2020-01-15T08:14:06.480Z
I suppose in visible light it's much harder to see Ganimede's aurora in telescope, because it's swamped in reflected light from the surface.
Heopps
CC BY-SA 4.0
2020-01-15T12:36:30.213Z
@JanDoggen. As cited in my comment to AtmosphericPrisonEscape I had reason to believe the Ganymede aurora could not be detected in visible light. Also, I did not say Earth's aurora did not emit in the UV part of the spectrum, I only pointed out that it emits in the visible part of the spectrum, though I may have worded it imperfectly.
Bob516
<hubble-telescope><aurora><electromagnetic-spectrum>
Why is Ganymede's aurora only visible in ultraviolet while Earth's is bright green and red?
Bob516
# Why is Ganymede's aurora only visible in ultraviolet while Earth's is bright green and red?

(Asked by: username_0 on 2020-01-14)

[GANYMEDE AURORAE](https://hubblesite.org/contents/media/images/2015/09/3505-Image.html)

NASA's Hubble Space Telescope observed a pair of auroral belts encircling the Jovian moon Ganymede. The belts were observed in ultraviolet light by the Space Telescope Imaging Spectrograph and are colored blue in this illustration.[![enter image description here](https://i.sstatic.net/Pw1wR.png)](https://i.sstatic.net/Pw1wR.png)

Why is Ganymede's aurora only visible in ultraviolet while Earth's is in the visible part of the spectrum?

**Tags:** hubble-telescope, aurora, electromagnetic-spectrum
> **Comments:**
> **username_1**: Did you do any prior research on what the composition of the UV-emitting particles is?  
> **username_0**: @AtmosphericPrisonEscape This is what I came across during my research, "Follow-up observations will be difficult because the auroras were only visible in ultraviolet light," https://www.astrobio.net/history/ganymedes-auroras-point-to-ocean-below-its-icy-surface-2/  
> **username_2**: I suppose in visible light it's much harder to see Ganimede's aurora in telescope, because it's swamped in reflected light from the surface.  
> **username_0**: @JanDoggen. As cited in my comment to AtmosphericPrisonEscape I had reason to believe the Ganymede aurora could not be detected in visible light. Also, I did not say Earth's aurora did not emit in the UV part of the spectrum, I only pointed out that it emits in the visible part of the spectrum, though I may have worded it imperfectly.  

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## 1 answers

### Answer by username_3 on 2020-01-14. Score: 14

Quoting from Nat.Geo. article (which has that same UV image),

> Then, in 2010 and 2011, Hubble took a close look at the moon. More
> specifically, it looked at the auroral bands ringing Ganymede’s poles.
> Hubble studied the auroras in the ultraviolet, but Saur said the
> shimmering lights would be visible to human eyes.
>
> “If somebody could be standing on Ganymede looking up into the night
> sky, it would appear as red aurora, to you,” he described.

> **Comments:**
> **username_4**: Yes. Keep in mind that while Ganymede's atmosphere is very thin, Earth's aurorae are also generated in an extremely thin part of its atmosphere (the thermosphere), and are of course entirely visible. It's just that in the case of Ganymede, the "suitably thin" layer starts much closer to, if not at, the surface.  

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