<p>In Wikipedia they write that Eris has an atmosphere when around perihelion (close to the Sun) which collapses when Eris moves away from the Sun. So it behaves similar to a comet's tail. However, they thought the same of Pluto's atmosphere, and the information on Wikipedia is from prior to the New Horizons Pluto flyby which proved that Pluto has a permanent atmosphere.</p>

<p>Could they be wrong on Eris too or does Eris <em>really</em> go far enough from the Sun so that its atmosphere collapses? It is possible that they are right with Eris for its aphelion is about twice as far as Pluto's, but are we sure about its atmosphere?</p>

CC BY-SA 4.0
2020-02-11T19:08:26.040Z
You have to be careful with how you interpret 'collapse'. In nature not all collapse or evacuation processes are 'total' in any sense of the word. Plutos atmosphere expanded for example between 1988 and 2012 from 6 to 18 nbar. So maybe you would think that 6 nbar in 1988 is a collapsed atmosphere, somebody else might not. However Eris' distance to the sun varies by a factor 3, so it is hard to imagine the same ratios of min/max pressures apply.
AtmosphericPrisonEscape
CC BY-SA 4.0
2020-02-11T19:11:21.703Z
@AtmosphericPrisonEscape The 6 nbar you're referring to: do you mean on Pluto or on Eris?
user30007
CC BY-SA 4.0
2020-02-11T19:30:42.920Z
Pluto. Have you read the paragraph about pressure in the article about Plutos atmosphere?
AtmosphericPrisonEscape
CC BY-SA 4.0
2020-02-11T19:45:00.240Z
@AtmosphericPrisonEscape It writes that Pluto's air pressure was 0.4 pa (4000 nbar) in 1988.  That is a thousand times higher than the maximum value on Io's surface, so it is far from a "collapsed" atmosphere. Is your value for Eris?
user30007
CC BY-SA 4.0
2020-02-11T19:54:30.907Z
I might have misrembered the units, but that's the data for Pluto. You should define what you mean with collapsed then. You seem to be aware of Io's collapsing atmosphere, so I am not sure what you're asking.
AtmosphericPrisonEscape
CC BY-SA 4.0
2020-02-12T06:17:08.573Z
@AtmosphericPrisonEscape I'm asking whether Eris has an atmosphere throughout its entire year that is more than just an exosphere.
user30007
<planetary-atmosphere><eccentric-orbit><trans-neptunian-object>
Could Eris have a permanent atmosphere?
user30007
# Could Eris have a permanent atmosphere?

(Asked by: username_0 on 2020-02-11)

In Wikipedia they write that Eris has an atmosphere when around perihelion (close to the Sun) which collapses when Eris moves away from the Sun. So it behaves similar to a comet's tail. However, they thought the same of Pluto's atmosphere, and the information on Wikipedia is from prior to the New Horizons Pluto flyby which proved that Pluto has a permanent atmosphere.

Could they be wrong on Eris too or does Eris *really* go far enough from the Sun so that its atmosphere collapses? It is possible that they are right with Eris for its aphelion is about twice as far as Pluto's, but are we sure about its atmosphere?

**Tags:** planetary-atmosphere, eccentric-orbit, trans-neptunian-object
> **Comments:**
> **username_1**: You have to be careful with how you interpret 'collapse'. In nature not all collapse or evacuation processes are 'total' in any sense of the word. Plutos atmosphere expanded for example between 1988 and 2012 from 6 to 18 nbar. So maybe you would think that 6 nbar in 1988 is a collapsed atmosphere, somebody else might not. However Eris' distance to the sun varies by a factor 3, so it is hard to imagine the same ratios of min/max pressures apply.  
> **username_0**: @AtmosphericPrisonEscape The 6 nbar you're referring to: do you mean on Pluto or on Eris?  
> **username_1**: Pluto. Have you read the paragraph about pressure in the article about Plutos atmosphere?  
> **username_0**: @AtmosphericPrisonEscape It writes that Pluto's air pressure was 0.4 pa (4000 nbar) in 1988.  That is a thousand times higher than the maximum value on Io's surface, so it is far from a "collapsed" atmosphere. Is your value for Eris?  
> **username_1**: I might have misrembered the units, but that's the data for Pluto. You should define what you mean with collapsed then. You seem to be aware of Io's collapsing atmosphere, so I am not sure what you're asking.  
> **username_0**: @AtmosphericPrisonEscape I'm asking whether Eris has an atmosphere throughout its entire year that is more than just an exosphere.  

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