Pluto!

[Jerry]

What you describe is in a broad sense true, and also why it is difficult for a planetary system to become stable. But when there are resonant orbits (1:2, 1:3...ratios) the minor perturbations of other planets are self correcting: if the smaller body gets 'ahead' on one orbit, it will be pulled back. If it gets behind, it will be pulled ahead on the next pass. The establishment of resonance has an overall stabilizing effect; and this is why the resonance between Saturn and Jupiter is so important.

[bknight]

If Jupiter reduces the perihelion of a smaller body,
that smaller body will still have an aphelion at or
beyond Jupiter's orbit. So unless the smaller body
has its orbit changed by hitting some other planet
or the Sun or by the galaxy's gravity gradient, it
will continue to interact with Jupiter and will either
hit Jupiter or be kicked out of the Solar system.

I interpret that to imply that Jupiter gets a net
push inward, with a larger mass of small bodies
being thrown out and never returning than being
thrown in and never returning.

-- Jeff, in Minneapolis

I was looking at ESA's web site and they had a diagram of Comet 67P. It occurred to me that since it intersects Jupiter's orbit twice there will be a good chance of either impact or ejection in the future. Has anyone done a calculation on an intercept?

[antoniseb]

I was looking at ESA's web site and they had a diagram of Comet 67P. ...

I'm being too lazy to try and figure out who took this thread on Pluto this far off topic, but please keep your posts here about Pluto.

[Jerry]

http://www.nasa.gov/image-feature/pl...m-new-horizons

Pluto’s surface geology alone – from the bladed terrain of Tartarus Dorsa to the mysterious dark mound of Morgoth Macula (just to mention a few informally named features with perplexing geologies) – continues to stump all of us on the New Horizons Geology and Geophysics Investigation (GGI) team...
...The dark materials are reminiscent of glacial moraines seen on Earth, but because this is Pluto, we have no idea what this dark material is, and whether or not the patterns we see are indeed moraines in the traditional terrestrial sense.

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."


Sherlock Holmes/Arthur Conan Doyle


Read more at http://www.brainyquote.com/quotes/au...oB8kRmjjPSv.99

[Jerry]

http://www.nasa.gov/image-feature/pl...-mons-in-color

This feature, known as Wright Mons, was informally named by the New Horizons team in honor of the Wright brothers. At about 90 miles (150 kilometers) across and 2.5 miles (4 kilometers) high, this feature is enormous. If it is in fact an ice volcano, as suspected, it would be the largest such feature discovered in the outer solar system...Mission scientists are intrigued by the sparse distribution of red material in the image and wonder why it is not more widespread.

(my bold)

If this were the Earth or Mars, the placement of the red material would not be an enigma at all; as it lies underneath the snow-covered peaks. On the earth, the snow is ice, on Mars it is mostly CO2 ice. On Pluto it could be water, ice, methanol or even methane (IR images should tell us which). But on Pluto, it is the underlying strata that is vexing mission planetary scientists: It should not be red because there is not sufficient mass budget in Pluto for the surface to be dominated by Earth or Mars-like regoth.

So what is the red stuff? Mission scientists are speculating that it is 'tholins' - thin layers of nitrated hydrocarbons synthesized in the thin atmosphere. These organics are red in appearence; but only if it is found in very thin layers. (The natural synthesis process of 'tholins' yields many hydrocarbons, and more than a thin layer of 'tholins' becomes predominately black).

Of course, much of the strata elsewhere on Pluto is red, and if the thin-layer hypothesis is correct; we should see patterns where the underlying strata appear white with a thin red vale. As more color and broad spectrum images are streamed down and analyzed, the picture could become more clear or more clouded.

My hand is betting entirely on more clouded; or to be more specific: Evidence that points to very thick layers of red materials with snowy caps; and likewise for Charon.

[eburacum45]

And the snail
http://www.chron.com/news/nation-wor...to-6753343.php

[Jerry]

And the snail
http://www.chron.com/news/nation-wor...to-6753343.php

The 'snail' is consistent in form with ejecta from a lava tube. Very strange.

[Jerry]

https://ac.arc.nasa.gov/p63rs4p8sf1/...&pbMode=normal

This is about a forty-five minute presentation; and I wish he would have had two to three times that.

Some high points: There is not water signature in the white 'Heart' region of Pluto, but there is water in the mountain and red areas.

The dark areas are very red.

The white colored strata in the north polar region, and on the mountain peaks, is spectrometrically determined to contain methane ice.

The white heart region is likely frozen nitrogen and has no signature of water-ice. There is evidence that it is geologically very young, and goes through a process of inversion; melting and rising from the bottom and refreezing. The Heart region is likely an impact basin that is not very deep.

There are nitrogen 'frozen lakes' within the mountains. Since water ice is lighter than most forms of nitrogen ice, it is thought that the mountains may be 'floating on nitrogen; (although this is somewhat at odds with the hypothesis that the heart is a shallow impact basin).

The atmosphere is perplexingly less extended than predicted by models. (This is also true of Titan.)

The red regions, in Stern's words, are "hypothesized to be tholins".

[Jerry]

http://www.nasa.gov/image-feature/pl...read-water-ice

[Roger E. Moore]

If Pluto has a subsurface ocean, it's a big one. (Cool photos.)

https://www.sciencenews.org/article/...a-new-horizons

https://www.hou.usra.edu/meetings/lpsc2020/pdf/1497.pdf (2 pages)

[Swift]

A nice video on the latest Pluto findings from analysis of New Horizons data.
LINK

[geonuc]

A nice video on the latest Pluto findings from analysis of New Horizons data.
LINK

I like that last bit about the view of the Alpha Centauri system from New Horizon's perspective. Before watching the video, I'd have guessed the change in view would be very slight. Not so.

[Trebuchet]

Going to watch that a little later. Meanwhile, I think (corrections welcome) that Alpha Centauri is near enough for paralax to be noted even from earth locations six months apart.

[geonuc]

Going to watch that a little later. Meanwhile, I think (corrections welcome) that Alpha Centauri is near enough for paralax to be noted even from earth locations six months apart.

Yes, but I thought it was a very slight change and expected NH's view to be not much more than that. In fact, the difference in parallax is quite a lot. Just goes to show how far out the spacecraft is.

[Roger E. Moore]

Making the most of a stellar occultation, with tiny Pluto in fact.

https://arxiv.org/abs/2011.04737

Study of Pluto's Atmosphere Based on 2020 Stellar Occultation Light Curve Results

Farzaneh Ahangarani Farahani, Atila Poro, Maryam Rezaee, Maryam Hadizadeh, Fatemeh Najafi kodini, Mahsa Seifi gargari, Fereshteh Mosavat

On 6 Jun 2020 a stellar occultation by Pluto was successfully observed at a ground-based observatory and detected in order to derive the height of Pluto's atmosphere and investigate its atmospheric parameters. A height of 1411+-2 km for Pluto's atmosphere was obtained [from Pluto's center, radius 1188.3 km] from fitting transit timings according to the Pluto radius derived from the New Horizons space mission. The constructed light curve was satisfactorily fitted with an atmospheric model by assuming a clear and pure N2 atmosphere. For the upper atmosphere we find that Pluto's atmospheric pressure remains at 4.86 {\mu}bar at the derived half-light level of 1217 km. According to our results the N2 condensation processes in the Sputnik Planitia glacier are still continuing which is consistent with the previous occultation study of Pluto. Therefore, our estimated pressure shows a decrease.

[ngc3314]

Yes, but I thought it was a very slight change and expected NH's view to be not much more than that. In fact, the difference in parallax is quite a lot. Just goes to show how far out the spacecraft is.

It is impressive, especially for Proxima Centauri. From talking with a team member before this was finalized, the targets had to be in a well-visible part the sky (Wolf 359 gets a surprisingly amount of scattered sunlight as it is), and as nearly as possible perpendicular to the baseline form Earth to NH. Also, faint stars are better because the dynamic range makes it really hard to get the background stars at the same time as, say, the Alpha Centauri binary itself. I'll toss in my version of the Proxima Centauri blink comparison, using data from Chile a few weeks earlier before the pandemic shutdown took out our remote telescope due to lack of engineering support.

We may see these image pairs in the equivalent of textbooks for decades, because these are the first sets of parallax images that really look like the diagrams - unmistakable image shifts from one end of the baseline to the other and plenty of background stars. Finally parallax in images shows as more than a subtle effect.

[Roger E. Moore]

Outstanding images!

[Trebuchet]

Going to watch that a little later.

Watched. There's just something really annoying to me about the narration. It sounds almost, but not quite, entirely unlike a human voice.

[Roger E. Moore]

Thanks to New Horizons, a new view of the long history and current state of the Pluto-Charon system.

https://arxiv.org/abs/2011.14030

Formation, Composition, and History of the Pluto System: A Post-New-Horizons Synthesis

William B. McKinnon, Christopher R. Glein, Tanguy Bertrand, Alyssa R. Rhoden

The Pluto-Charon system provides a broad variety of constraints on planetary formation, composition, chemistry, and evolution. Pluto was the first body to be discovered in what is now known as the Kuiper belt, its orbit ultimately becoming a major clue that the giant planets underwent substantial orbital migration early in Solar System history. This migration has been linked to an early instability in the orbits of the giant planets and the formation of the Kuiper belt itself, from an ancestral trans-Neptunian planetesimal disk that included Pluto. Pluto-Charon is emblematic of what are now recognized as small or dwarf planets. Far from being a cold, dead, battered icy relic, Pluto displays evidence of a complex geological history, with ongoing processes including tectonism, cryovolcanism, solid-state convection, glacial flow, atmospheric circulation, surface-atmosphere volatile exchange, aeolian processes, and atmospheric photochemistry, microphysics, and haze formation. Despite Pluto's relatively modest scale, the combination of original accretional heat, long-term internal radiogenic heat release, and external solar forcing, when combined with sufficiently volatile (and thus mobile) materials, yields an active world. Pluto may have inherited a large organic mass fraction during accretion, which may responsible, in part, for its surface and atmospheric volatiles. Charon, Pluto's major moon, displays evidence of extensive early tectonism and cryovolcanism. Dwarf planets are thus truly planetary in terms of satellite systems and geological and atmospheric complexity (if not ongoing activity). What they may lack in mass is made up in number, and the majority of the Solar System's dwarf planets remain undiscovered.

[Roger E. Moore]

Spectacular Snowcapped Mountains Discovered on Pluto Are Very Different to Those on Earth.

https://scitechdaily.com/spectacular...hose-on-earth/