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Pluto's Expanding Atmosphere Confounds Researchers, Pluto Atomosphere
bagelverse
post Apr 19 2011, 08:26 PM
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Pluto's Expanding Atmosphere Confounds Researchers

http://news.sciencemag.org/sciencenow/2011...onf.html?ref=hp

Could these be evidence of geyers like on Triton?
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tasp
post Apr 19 2011, 11:53 PM
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Interesting.

A tenuous atmosphere extending almost 1/4 of the way to Charon. There won't be any rings, but as Pluto taketh away, so to it gives a bonus. We've seen discussed here earlier the effectiveness of an atmosphere like this for decel purposes for a lander/orbiter mission. (Most likely a very long time from now)

Nice that newly sensed characteristics of Pluto make it more interesting (good for stimulating mission concepts) and easier to maneuver a probe in it's environs.


Just doing a little math here, traversing 5000 kilometers of this 'atmosphere' at a start speed of 20 km/sec and slowing (uniformly, the math to do this right is beyond me) to near zero would occur in ~500 seconds. This does not seem unduly severe. (having a probe with an approach speed to Pluto of 20 km/sec seems kinda high though, but let's be generous) In actuality, peak decel would occur at closest approach to Pluto, and the decel rate would increase to that point and then taper off to zero as ones craft exited the other side. There would seem to be quite a variety of orbits available with this technique. (other than closely orbiting Pluto)


How big is the Plutonian Hill sphere?

As for geysers, sounds good. How does anyone feel about volcanoes?
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Paolo
post Apr 20 2011, 05:12 AM
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see also the paper Discovery of carbon monoxide in the upper atmosphere of Pluto on arXiv


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brellis
post Apr 20 2011, 10:41 AM
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This is fascinating stuff! The Pluto system is starting to get a much more detailed look from us earthlings.

I recall reading an article -- geez, ten years ago, or more -- about the change in Pluto's atmosphere as it got closer to the sun, and how time was of the essence to get New Horizons launched in time to get good readings before things froze back.

Thinking about the energy and investment it takes to get a large, robust spacecraft with complex instruments launched toward the outer planets:

What's the smallest craft that would be worth putting in orbit around or landing on a solar system object?

Can we get good science from something the size of a blackberry?

Have we learned enough from the Cassini/Huygens mission to apply that experience towards "even smaller, even better, even cheaper"?

Could a future Mother Ship the size of New Horizons carry several micro-orbiter/landers that get jettisoned behind it as it approaches each target? hehe, talk about a Goose laying golden eggs! smile.gif
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machi
post Apr 20 2011, 12:39 PM
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This idea is theoretically possible (you must "only" reduce masses in Ciolkovskyi equation, or use aerobraking), but now it's not feasible from technical point of view.


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Drkskywxlt
post Apr 20 2011, 01:32 PM
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Pluto's atmosphere is (almost certainly) hydrodynamically escaping. Basically, the solar wind blows the atmosphere off the planet. So, that leads to a very large height for the exobase of the atmosphere (several Pluto radii potentially). That coupled with the seasonal cycle when the atmosphere is thicker anyway, and you get a very extended, low density atmosphere.
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Floyd
post Apr 20 2011, 11:30 PM
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QUOTE (brellis @ Apr 20 2011, 05:41 AM) *
What's the smallest craft that would be worth putting in orbit around or landing on a solar system object?
Can we get good science from something the size of a blackberry?

My area is microbiology, but I will present my answer anyway. While the size of modern sensors can be very small, including cameras and scopes and maybe even thrusters & gyros for pointing, I see the major problem being energy for (and size of antenna) to communicate back to earth. Where does your iPad satellite get power--I'm not sure any blackberry has a battery that will sustain high data transmission rates for 10-20 years on a single charge. So, minimum size determined by power source (solar panels or nuclear/thermal) to power antenna/transmitter. If you had a big brother craft like Cassini nearby, then you could whisper your data to it rather than earth, but for your question, I think that would be cheating.


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Rob Pinnegar
post Apr 21 2011, 12:39 AM
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QUOTE (Drkskywxlt @ Apr 20 2011, 06:32 AM) *
Pluto's atmosphere is (almost certainly) hydrodynamically escaping.


If gas escape is occurring, would the region of greatest gas escape tend to concentrate around the anti-Charon point?

With such a huge scale height to the atmosphere, centripetal acceleration (due to Pluto's motion around the system's barycentre) might be just enough to give gas molecules the heave-ho on the anti-Charon side.
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nprev
post Apr 21 2011, 12:45 AM
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That sort of begs the question of whether Pluto had a much more extensive atmosphere in the past, unless the formation of Charon (and presumably Nix & Hydra) were relatively recent events in geological terms. Also makes me wonder what a reasonable rate of Plutonian outgassing over time might be.


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Greg Hullender
post Apr 21 2011, 04:40 AM
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QUOTE (tasp @ Apr 19 2011, 04:53 PM) *
Just doing a little math here, . . .In actuality, peak decel would occur at closest approach to Pluto

That's not what I get. The way I figure it, peak deceleration can easily come earlier than closest approach. It's an interesting differential equatation, but it depends a lot on data about the actual composition of the plutonian atmosphere.

I do hope that NH is passing far enough from the atmosphere not to have to worry about it.

--Greg
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AndyG
post Apr 21 2011, 10:03 AM
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QUOTE (Drkskywxlt @ Apr 20 2011, 02:32 PM) *
Pluto's atmosphere is (almost certainly) hydrodynamically escaping.

And therefore Charon, almost certainly, will have a ex-Plutonian transient atmosphere.

Fascinating!

This solar system just gets better and better. smile.gif

Andy
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Den
post Apr 21 2011, 10:08 AM
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QUOTE (tasp @ Apr 20 2011, 12:53 AM) *
A tenuous atmosphere extending almost 1/4 of the way to Charon. There won't be any rings, but as Pluto taketh away, so to it gives a bonus. We've seen discussed here earlier the effectiveness of an atmosphere like this for decel purposes for a lander/orbiter mission. (Most likely a very long time from now)

Nice that newly sensed characteristics of Pluto make it more interesting (good for stimulating mission concepts) and easier to maneuver a probe in it's environs.

Just doing a little math here, traversing 5000 kilometers of this 'atmosphere' at a start speed of 20 km/sec and slowing (uniformly, the math to do this right is beyond me) to near zero would occur in ~500 seconds. This does not seem unduly severe.


Decelerating from 20 km/s to 0 in 500 seconds requires 4g deceleration. Pluto atmosphere can't do anything like that, it's too rarefied.
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Paolo
post Apr 21 2011, 10:18 AM
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may someone with some time to spare and Pluto and Charon masses and distance at hand compute where the L1 lagrangian point would lie?
I was thinking: how much would the atmosphere of Pluto need to inflate before mass transfer to Charon begins? this is what happens on some classes of double stars including some kinds of supernovae


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James Van Allen
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AndyG
post Apr 21 2011, 11:30 AM
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I get L1 for Pluto lying around 5050km from the centre of Charon, 14520km from the centre of Pluto. About 4/5ths of the way from Pluto to Charon.

Andy
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Drkskywxlt
post Apr 21 2011, 12:35 PM
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QUOTE (AndyG @ Apr 21 2011, 06:03 AM) *
And therefore Charon, almost certainly, will have a ex-Plutonian transient atmosphere.


Perhaps. There's been at least one stellar occultation that allowed Bruno Sicardy and his team to place an upper limit on the atmosphere of either 110 or 15 nbar (depending on assumptions). http://www.nature.com/nature/journal/v439/...ature04351.html

We'll probably have to wait for New Horizons since stellar occultations of Charon are so rare.
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