NH Arrokoth (formerly Ultima Thule) Encounter Observations & Results, post-flyby discussion as the data arrives |
NH Arrokoth (formerly Ultima Thule) Encounter Observations & Results, post-flyby discussion as the data arrives |
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#1
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![]() Merciless Robot ![]() ![]() ![]() ![]() Group: Admin Posts: 8784 Joined: 8-December 05 From: Los Angeles Member No.: 602 ![]() |
This will be where we talk about the data as it arrives over the next 20 months or so.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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#2
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 ![]() |
re: resurfacing, we're certainly looking at a world where geology doesn't apply in the usual sense, but there are still mechanisms at this scale that can blank the surface:
• The shaking that occurs with a straight-on impact could cause material to flow down slopes. • An impact could shower the surface with material causing a new surface to overlie the old one. • Porous portions of the body could collapse inward to a new configuration at higher density. • Electrostatic accumulation of fine-grained material burying the old surface. More? |
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#3
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![]() Member ![]() ![]() ![]() Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 ![]() |
re: resurfacing, we're certainly looking at a world where geology doesn't apply in the usual sense, but there are still mechanisms at this scale that can blank the surface: • The shaking that occurs with a straight-on impact could cause material to flow down slopes. • An impact could shower the surface with material causing a new surface to overlie the old one. • Porous portions of the body could collapse inward to a new configuration at higher density. • Electrostatic accumulation of fine-grained material burying the old surface. More? Cohesion • Tholin ("Sagan's star tar") surface weathering cementing sun-facing surfaces into a crust WITH sun-facing surface darkening over a wide spectral range. ReDistribution • YORP (natural photon drive) effects spinning the lobes up/down over time, depending on their current orientation and frost coverage/albedo patterns. •sYORP (natural photon+cryovolatile gas drive) effects spinning the lobes up/down depending on their current orientation and frost coverge/albedo patterns. Observation- The patterns on the surface of Ultima Thule resembles the heat/flow patterns you get on a breakfast pancake- a thin surface layer breaking and creeping as the interior slumps and spreads out. Let's assume UT consists of unconsolidated material high in volatiles. Apply heat (sunlight/hot pan) to form a crust/tholins, and you find that the bulk material spreads out (YORP, sYORP, heat driven sublimation to the limb) into a thin disk. Hypothesis- Tholin formation causes "browning" which forms a skin,then -A YORP/sYORP spin or -B ammonia/volatile sublimation push material towards the edge/shadowed limb of the dark side. This mass transfer to the edges results in a "pancake" shape where a tough tholin skin develops on two sides and sublimating material "squishes" out along the perimeter. |
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#4
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 ![]() |
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#5
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![]() Member ![]() ![]() ![]() Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 ![]() |
MU69 is far from the Sun and large(ish). wouldn't YORP be negligible on such a body? Normally yes. But, like raindrops wearing down a mountain range seems negligible, over geologic or astronomical timeframes it should add up. A recent paper mentions ammonia sublimation and deposition as a resurfacing possibility, Ultima Thule (486958; 2014 MU69): Necklace, Composition, Rotation, Formation https://arxiv.org/abs/1902.00997 so if there is enough heat from photos to drive sublimation, there should be enough photons for YORP or sYORP. And a hamburger shaped dark-red body is a pretty good candidate for YORP/sYORP effects, especially if there is a white frosty coating on one side. So, it seems like we are looking at a pair of spheroids, resembling a "bag of oranges" or "bag of grapes". ![]() Wait, I finally read the extended caption, -the blue dotted lines are the range of uncertainty!?! ![]() "The dashed blue lines span the uncertainty in that hemisphere, which shows that Ultima Thule could be either flatter than, or not as flat as, depicted in this figure. " So, these could be incredibly flattened! |
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