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NH Arrokoth (formerly Ultima Thule) Encounter Observations & Results, post-flyby discussion as the data arrives
Gladstoner
post Jan 24 2019, 10:36 PM
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This faint white ring is... interesting:

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So far, it doesn't seem to be associated with topographical features.

I wonder if some Kuiper belt objects will display relic binary-contact collars, i.e. talus rings left over after the binary components separated by some process (impacts, gravitational interactions). I suppose they could be thought of as 'kiss marks'.

Since this ring is near the rotational pole, and rather thin, it probably isn't an example.
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Explorer1
post Jan 24 2019, 10:51 PM
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Amazing new image! It really does look more like the smaller lobe has massive impact on it (like Phobos' Stickney crater) or Damodar on Mathilde.....
This confirms the closest approach images were captured successfully? Big sigh of relief!

Any idea where exactly the rotation pole is? I'm assuming near the centre of mass, on the right side of the circle Gladstoner added.
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abalone
post Jan 24 2019, 11:04 PM
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I get the impression that its possibly evidence of been put together like a hailstone accretion and the lines and lumpy appearance might be an artifact of that. https://upload.wikimedia.org/wikipedia/comm.../94/Granizo.jpg Could also be the reason for the 'hamburger' shape if the individual lobe were slowly rotating during the accretion process before coming together.
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hendric
post Jan 24 2019, 11:15 PM
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Yeah that's my thought too, kinda like a kid with a snowball that keeps packing more snowballs onto it. Maybe the Thule lobe is just large enough to hold itself together, while the smaller objects just slumped.


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Ian R
post Jan 24 2019, 11:32 PM
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It's a jaw-dropping image: congratulations to the NH science team. blink.gif

Here's a colorized version, purely for aesthetic purposes:


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Marcin600
post Jan 24 2019, 11:38 PM
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QUOTE (hendric @ Jan 25 2019, 12:15 AM) *
Yeah that's my thought too, kinda like a kid with a snowball that keeps packing more snowballs onto it. Maybe the Thule lobe is just large enough to hold itself together, while the smaller objects just slumped.


a bit like a flattened hail https://ljkrakauer.com/LJK/00s/weirdhail.htm


covered with a tholin shell
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dudley
post Jan 25 2019, 12:20 AM
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One side of that dim ring on Ultima appears to be made up of two slightly separated arcs, on the side nearest Thule. The ring looks lopsided at first glance, but appears to have bilateral symmetry, on either side of a line running across it diagonally toward the dark cleft on one side of the 'neck' region.
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HSchirmer
post Jan 25 2019, 05:48 AM
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QUOTE (Ian R @ Jan 25 2019, 12:32 AM) *
It's a jaw-dropping image: congratulations to the NH science team. blink.gif

Here's a colorized version, purely for aesthetic purposes:


Attached Image


Very interesting how there's a scarp where the surface crust appears to end at the lower right,
and the highly defined craters are only on the area where there is no scarp.

There was a paper that calculated that the grooves on the Martian moon Phobos could be caused by low velocity impact with boulders that rolled along the surface.

Sorta looks like Thule and Ultima made contact around 5 o'clock, and rolled along ripping up the crust until it settled at 1 o'clock.


Soo, basically, it looks like a Bert the Turtle from 1950s civil defense films.
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serpens
post Jan 25 2019, 07:01 AM
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The news article comments on differences in the geologic character of the two lobes of Ultima Thule. Whether the suspected difference is compositional or textural this could imply the lobes developed separately. If so then when Ultima and Thule came together there would potentially have been a few scrapes, bounces and heat as linear and angular momentum was sorted out. In this respect the light ring Gladstoner refers to seems to fit the crater in the smaller lobe. Bit of a stretch but not beyond the bounds of possibility.
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Ian R
post Jan 25 2019, 11:23 AM
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The two best views of UT thus far (courtesy of LORRI and MVIC):


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Steve5304
post Jan 25 2019, 01:08 PM
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QUOTE (Ian R @ Jan 25 2019, 11:23 AM) *
The two best views of UT thus far (courtesy of LORRI and MVIC):


Attached Image



Man...that ring...what the blink.gif

The further out we get the stranger things are. It looks like a sad snowman! The media will jump all over this laugh.gif
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stevesliva
post Jan 25 2019, 02:26 PM
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If we think back to the fact that they're more hamburgers than spheres that ring might be circumpolar (well, the pre-merger rotational pole) and Ultima might've looked like Saturn's moon Atlas or Pan before getting a remora.
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Gladstoner
post Jan 25 2019, 03:53 PM
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The sparse cratering is intriguing. So far, the bodies don’t seem to be crater-saturated as one would expect for small, primitive bodies. Either they were resurfaced, or we are seeing a barely altered primordial surface. I don’t know of any other body in the solar system where this is close to being the case. Of course, forthcoming images will provide more details.

Plus, the crater size distribution seems to be one large depression on Thule and a few pits near the limit of resolution. So far, there appears to be a dearth of intermediate sizes. It’ll be interesting to find out what this says — if anything— about object distribution in this part of the solar system, assuming these are impact craters.

Also, there seem to be a number of concave scarps that are outward facing. Could these be slumping that occurred on an earlier, rapidly-rotating Ultima?
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Webscientist
post Jan 25 2019, 04:38 PM
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Very nice work!
Some "scientific artists" of the past had anticipated the shape of that new type of solar system object. Really remarkable! blink.gif

At first sight, I would bet that the density of Thule is higher than the density of the external blanket of Ultima since Ultima seems to have been more distorted by the relatively soft impact wheras Thule seems more uniform (or less distorted).

Can the gravitational interactions between the two parts in the rotation process engender landslides or resurfacing events erasing some craters?


QUOTE (Ian R @ Jan 25 2019, 12:32 AM) *
It's a jaw-dropping image: congratulations to the NH science team. blink.gif

Here's a colorized version, purely for aesthetic purposes:


Attached Image

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Steve5304
post Jan 25 2019, 05:59 PM
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I would think that you just don't have that much out that far...it unlikely to be any sort of resurfacing...how would that even happen that far out on a dead object like this?? Accretion over millions of years??

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