Inversion of the refractive phase delay from stellar occultations indicates a pressure of a few to perhaps 60 microbars, Nprev-- at most about 1% the Martian pressure.

Alan

If i recall, the Martian surface pressure is 0.7% of Earth's, so this would be 0.00007% of Earth's surface pressure. Don't forget the spacesuit!

Wow...that's just mind-blowingly thin, yet it's enough to foster frost formation! Thanks; that broadened my own horizons a bit with respect to what is possible.

If I did my units conversions right (table of pressure units), that works out to 46 microns of Hg.

Our current laboratory high vacuum line is pulling about 1400 microns of Hg. So Pluto has 30x LESS pressure than our laboratory vacuum line.

-Mike

And actually, the pressure (~10 microbars), temperature (~105K), and composition (N2-dominated) in Pluto's troposphere, are each very much like the same parameters in Earth's mesosphere, 80 km overhead, where noctilucent clouds form.

-Alan

The pressure estimated here was for Charon = .01% of Mars which equals 0.007% of Earth surface.

Pluto, by comparison, is an ocean of gaseous fluid.

I'm astonished, really 60 microbars ? It's 3-5 times more than pressure in Triton's atmosphere (12-20 microbars). Earlier results were much more conservative. Report from observations a multi-station stellar occultation by Charon (B. Sicardy, A. Bellucci, E. Gendron) give upper limits of 110 and 15 nanobar for an atmosphere around Charon, assuming respectively a pure nitrogen or pure methane atmosphere.
Charon's size and an upper limit on its atmosphere from a stellar occultation.

I am betting on 10 microbar class myself, it if doesn't collapse first, but since no one knows the depth below which the occultations have not probes, it is possible (originally John Stansberry's idea) that the prssre at the base could be many tens of microbars.

-Alan

NH went live on Facebook yesterday: http://www.facebook.com/profile.php?id=695...6532&ref=mf

A FB group page is also coming soon to a URL near you.

Summer hibernation ends next Tuesday, and within a week we'll have new C&DH software uploaded with new capabilities for the encounters.

Alan

Now that's what I call a superb "monthly" update!
Thanks Alan!

Would anybody have a detailed timeline of major events for the upcoming 3 months checkout & cruise science period? It would look good on my realtime simulation ...

I noticed from a recent Twitter entry that...

"During October in this annual checkout, New Horizons will use its LORRI imager observe Uranus, Neptune, and Pluto"

I am curious as to what resolution we will see? I recall that shortly after Jupiter LORRI observed Pluto as a lone pixel. While I'm sure October's observations will not resolve Pluto as a disc, is it expected that Uranus and/or Neptune will be?

Kelly

According to Emily, neither Uranus nor Neptune are expected to be resolved.


Paolo Amoroso

New Horizons is doing phase curves of Uranus, Neptune, Triton and Pluto (and later Charon) as we
cross the solar system and can look at these objects from illumination geometries only seen in the outer solar system. One does not need to resolve the objects to accomplish this unique science (which cannot be done from Earth or Earth orbit). That said, we *will* just marginally resolve Uranus, but no one should wet their pants, I am talking just over 1 LORRI resolution element (our highest resolution imager).

Alan

I guess Titania and Oberon aren't bright enough for phase curves? Or is it a viewing-angle issue?