New Horizons Pluto System Final Approach, 28 Jun-13 Jul 15 Options

[fredk]

A lot of people are treating the tidal forces are point sources - Pluto is a point and Charon is a point. But, in reality, relative to the distance of Pluto from Charon, there are different gravitational forces over a wider area on each body.

There are no tidal forces at all for two point masses. For Pluto and Charon, there are definitely tidal forces. But unless they are changing (which, as you say, would have to be over extremely long time scales) it doesn't matter. The surfaces of the bodies will just settle to some ellipsoidal-ish shape (along constant potential surfaces) instead of spherical and stay there. After equilibrium is reached, constant tidal forces can't pull bits of ground apart or squish out fluids or anything.

[peter59]

Perhaps it is just an illusion, but I am convinced that in the region of the head of a whale, we'll see an image very similar to the surface of Triton.

[alan]

A video made simulating Voyager's approach to Triton which may be useful in guessing when various features are distinguishable from artifacts.

https://www.nasa.gov/jpl/voyager/triton-20140821

[MahFL]

A video made simulating Voyager's approach to Triton which may be useful in guessing when various features are distinguishable from artifacts.

https://www.nasa.gov/jpl/voyager/triton-20140821

That's a pretty cool movie. When I watch those kinds of movies I always think the spacecraft is going to actually hit the object it's approaching.

[Ian R]

Made by UMSF's very own Dr. Paul Schenk!

[Mongo]

Noted at NASASpaceFlight.com from Twitter:

Gladstone: "There's hints of frost transport all over the place" in images coming down now. #PlutoFlyby

[Sherbert]

I would be interested to know from the Charonlight images if a matching band appears on the southern flanks of the equatorial mountain bands. It would then be analogous to the Tropic of Cancer and Capricorn. A demarcation of seasonal effects, in this case the transport of material across the surface by volatiles sublimating from the surface. There is an ice line in the solar system, these I suspect mark the northern and southern extent of sublimated gases moving towards the colder opposite hemisphere, at and beyond which they condense as frost, taking the very lightest interplanetary dust and organics to the surface with it to create this lighter grey band. There were strong hints in ZVD experimental images that there is a demarcation in height at this boundary too, of several hundred metres.

Others speculated about the evolution of Charon's orbit, are there visible signs of past orientations. I believe the heart shape bright plateau is clear evidence of two different orbital orientations of Charon. This face is opposite the barycentre of the system so the maximum gravity on Pluto's surface will be acting here. Less sublimating gas escapes the atmosphere, condensing frost is squashed flatter and heavier dust/organics can not be transported up onto the plateau by the available vapour pressure. I would expect to see cantaloupe terrain in the temperate latitude basins and on the heart plateau.

As for craters. I think many of the impact craters on Pluto are obscured under millions of years of frost layers, the rims and central mountains still outlined by more subtle elevation changes and dust deposition in sheltered or shadowed spots. This gives the mottled appearance so evident in the July 11th image. The seasons on Pluto are very long, imagine everyday, all day, for 50 years a thin layer of Hoare frost settled outside your house and never melted, drifts, ridges, hills and mountains can be built that way in Pluto's small gravity. It would seem the balance between energy from the Sun, Pluto's gravity field and the compositional nature of the icy surface, results in a very tenuous, but fluid atmosphere at times during Pluto's seasons. Like others, I think, liquids on the surface, seems highly improbable, subsurface just possibly.

Charon however with a more refractory and dense Water ice based surface that can exert a greater internal pressure on sublimating gases, subsurface liquid Nitrogen or Neon may be trapped below. The lack of colour from Thollins on Charon suggests most of the Nitrogen and Ammonia are trapped within and below the surface. I suspect Charon has a nano atmosphere of Carbon Monoxide with traces of Neon and Nitrogen resulting in similar, but at a much smaller scale, results as Pluto. On Charon the evidence of impacts is less hidden and it looks like there have been a couple of very large impacts spreading ejecta over significant portions of the face currently visible.

[Superstring]

Here's my attempt to bring out color from yesterday's image. I started with Phil's b&w version and tried to match the previous color releases as much as possible.

[neo56]

My take on LORRI pictures of 11 July colorized with MVIC pictures:

[machi]

Table with the planned Ralph observations.
Table with the planned LORRI observations.

[pioneer]

Does anyone know approximately how much data will be returned in terms of mega or gigabytes? I know the 2 solid state recorders on board have a capacity of 8 gigabytes each according to the John Hopkins site, but will all of that be used for scientific data? How will this compare with the amount of data from Voyager 2's encounter with Neptune in 1989?

[Bjorn Jonsson]

Here is an updated flyby movie showing which areas on Pluto are visible to New Horizons around closest approach. The movie covers the period from 09:36 to 13:36 on July 14 (closest approach is at 11:49:57). It includes the solar occultation shortly after closest approach.

The difference from the previous movie I posted on July 6 is that now I have an up to date and accurate trajectory for New Horizons and I'm using the most recent version of my map of Pluto. Charon is not included in the animation.

 pluto_nh_flyby_0935_1335.avi ( 889.1K ) Number of downloads: 3533

[FOV]

That is a fantastic preview of closest approach Bjorn. NH getting close to the "heart".

[nprev]

FORUM NOTE: Due to the large size of this topic (17 pages), another thread will become active NLT 13 Jul/1400 GMT for coverage & commentary during the near encounter phase. A link will be posted. NASA TV coverage will begin with the flyby pre-briefing on 13 Jul/1430 GMT (note that this has been advanced by 30 min.)

This new thread will remain open until the final data download of this period on or about 20 Jul, after which we'll return here.

Rationale here is to somewhat organize the discussion for future reference and archival purposes. Also, as those of you who have experienced major events on UMSF before know, these are hectic, fun times here so it's been our custom to run reserved threads for such occurrences.

Thanks!

[John Broughton]

There are no tidal forces at all for two point masses. For Pluto and Charon, there are definitely tidal forces. But unless they are changing (which, as you say, would have to be over extremely long time scales) it doesn't matter. The surfaces of the bodies will just settle to some ellipsoidal-ish shape (along constant potential surfaces) instead of spherical and stay there. After equilibrium is reached, constant tidal forces can't pull bits of ground apart or squish out fluids or anything.

Correct me if I'm wrong but shouldn't the position of the barycentre relative to Pluto be constantly changing, given this is a sextuple-body system. Wouldn't that be responsible for generating tidal forces in the equatorial zone?