First Pluto Papers Published
Planetary scientists have published their first official findings about the 9th planet (or dwarf planet), Pluto.
Since the first reconnaissance of the Pluto system by the New Horizons spacecraft in July 2015, news releases to the popular press have shown the latest brilliantly-detailed images and expressed the astonishment among scientists. We have relayed that information here. Now, Science Magazine devoted this week’s issue to Pluto, with nearly a dozen peer-reviewed scientific papers and a flurry of spectacular new images. Here are some highlights: first, from the popular press.
Pluto gives up its icy secrets as New Horizons data pours in (New Scientist). Scientists are struggling to come up with hypotheses for what they see, this article shows. “Pluto’s really tiny, so it doesn’t have the mass to hold on to an atmosphere over the age of the solar system – at least we wouldn’t have thought that.”
Pluto’s ‘Unprecedented’ Ice Provinces and Other Surprises from NASA’s New Horizons (Space.com). “Pluto, known for more than eight decades as just a faint, fuzzy and faraway point of light, is shaping up to be one of the most complex and diverse worlds in the solar system,” comparable to Earth and Mars, Mike Wall writes. His article includes several infographics of the mission. The scientists can’t invoke the usual heat sources they pretend to know from other bodies. “I think we have to rethink our whole understanding of geophysics — how you keep small planets active over time.”
Are Pluto’s Pebbled ‘Snakeskin’ Slopes Made of Ancient Stuff? (Space.com). In this companion article, Mike Wall wonders if the mountainous northern terrain predates Pluto’s existence. How could that be? “It’s unclear if pure methane ice is strong enough to maintain such steep slopes over long periods of time under Pluto conditions,” but maybe if methane clathrates were being formed before Pluto became a planet, they could outlast everything else.
Weird and wonderful Pluto spills its secrets (Nature). “The plains of Pluto’s Sputnik Planum look smooth and fresh after 4 billion years in the deep freeze of the outer Solar System,” Jeff Hecht writes. “Yet nearby highlands are saturated with impact craters. Welcome to weird and wonderful Pluto, as revealed by NASA’s New Horizons spacecraft.” This article discusses the bizarre variety of features, and Pluto’s “motley moons.”
Picture of Pluto further refined by months of New Horizons data (PhysOrg). This is a reprint of an article on The Conversation by Mike Summers, atmospheric scientist on the New Horizons team. Data analysis has revealed “surprises all over the place,” he says. He thinks some parts of Pluto are ancient, but then uses three exclamation marks:
Other areas, such as the informally named Sputnik Planum – the heart-shaped, Texas-sized nitrogen ice glacier – show no evidence of asteroid impacts at all, suggesting continual surface activity, such as convection of ices from underground. This surface can’t be more than 10 million years old – a blink of the eye on a geological time scale!
Pluto is geologically active! I doubt there’s a single person on Earth who would have expected to see that!
[Note: He really needs to get out more. We predicted it; see xx]
Science Papers Reveal New Aspects of Pluto and its Moons (Astrobiology Magazine). Quotable quote by Jeff Moore of the team: “Observing Pluto and Charon up close has caused us to completely reassess thinking on what sort of geological activity can be sustained on isolated planetary bodies in this distant region of the solar system, worlds that formerly had been thought to be relics little changed since the Kuiper Belt’s formation.”
How big is Pluto? (Space.com). Nola Taylor Redd provides facts about the Pluto system. New measurements show Pluto is larger than Eris, a Kuiper Belt object that was once thought to be larger.
Beautiful, Bewitching Pluto Poses in New Images from New Horizons Probe (Space.com). Calla Cofield’s article doesn’t disappoint, reproducing stunning new photos from the mission.
Here are highlights from the official team science papers that made the cover story of Science Magazine this week.
Gladstone et al., “The atmosphere of Pluto as observed by New Horizons” (Science). One surprise is that more methane is lost to space than nitrogen: as much as 28 meters over the age of the solar system. Nitrogen loss is 10,000 times less than predicted.
Bagenal et al., “Pluto’s interaction with its space environment: Solar wind, energetic particles, and dust” (Science). “Pluto continues to deliver surprises,” this paper begins. Atmospheric ccientists were particularly surprised by the high solar wind but relatively small loss of atmospheric gases.
Jeffrey Moore et al., “The geology of Pluto and Charon through the eyes of New Horizons” (Science). Fewer craters were found than expected from the Late Heavy Bombardment. Sputnik Planum and some other regions “are all very young,” the paper says. “No craters have been detected in SP [Sputnik Planum] down to 2-km diameter, which is a tighter size limit than reported previously and implies a model crater retention age of no greater than ∼10 million years, and possibly much less.” Note: 10 million years represents 1/450th the assumed age of the solar system. The scientists believe that Charon’s surface is 4 billion years old. “That Charon is so geologically complex, however, would seem to require a heat source for reshaping what would have otherwise been a heavily cratered surface,” they say. “If the ~4-Gy age of even the youngest of Charon’s surfaces is correct, then this activity dates back to an early warmer epoch.” The last two paragraphs give a good flavor of the confusion these two bodies present:
Pluto and Charon are strikingly different in surface appearance, despite their similar densities and presumed bulk compositions. With the possible exception of MM [Mordor Macula, a dark red area on Charon’s north pole], the dynamic remolding of landscapes by volatile transport seen on Pluto is not evident on Charon, whose surface is instead dominated spectrally by the signature of water ice. Whether this is because Charon’s near-surface volatile ices have sublimated and have been totally lost to space owing to that body’s lower gravity, or whether something more fundamental related to the origin of the binary and subsequent internal evolution is responsible, remains to be determined.
Much of what we see on Pluto can be attributed to surface-atmosphere interactions and the mobilization of volatile ices by insolation. Other geological activity requires or required internal heating. The convection and advection of volatile ices in SP can be powered by present-day radiogenic heat loss (supplementary materials). However, the prominent mountains at the western margin of SP, and the strange, multikilometer-high mound features to the south are both young geologically and presumably composed of relatively strong, water-ice–based geological materials. Their origin, and what drove their formation so late in solar system history, remain uncertain. What is more certain is that all three major Kuiper belt bodies (past or present) visited by spacecraft so far—Pluto, Charon, and Triton—are more different than similar and bear witness to the potential diversity awaiting the future exploration of their realm.
Grundy et al., “Surface compositions across Pluto and Charon” (Science). If at any time in Pluto’s history its atmosphere froze and collapsed to the surface, “in the absence of an atmosphere, coloration could arise as quickly as a few years, even on unilluminated surface regions, much faster than the ~40,000-year time scale for tholin haze deposition from Pluto’s atmosphere.” Pluto swings much farther out from the sun than it was at encounter time. Is this not a possibility? With its orbital period of 248 years, Pluto would have reached aphelion over 18 million times by now if it is 4.5 billion years old. In addition, Charon’s ammonia ice deposits would have been destroyed by solar radiolysis in ten million years, “implying that these deposits are relatively recent.” Another statement about this: “The latitudinal distribution of Charon’s polar reddening suggests a thermally controlled production process, and the existence of highly localized patches rich in NH3 ice on its surface implies relatively recent emplacement.” A “thermally controlled” production process implies that the reddened molecules “hop” to cold traps after they are produced by solar radiation and warmed by the sun, much like the dark material on Iapetus becomes thermally segregated over time (12/14/09).
Weaver et al., “The small satellites of Pluto as observed by New Horizons” (Science). “The Pluto system is surprisingly complex, comprising six objects that orbit their common center of mass in approximately a single plane and in nearly circular orbits.” The chance of getting circular orbits out of a collision, the conventional scenario, is very low. The polar inclinations vary, and the small moons have retrograde rotations; “This collection of inclinations is inconsistent with an isotropic distribution” and only has a 1% probability of being a uniform distribution. “These results on the rotational properties have not been seen in other regular satellite systems in the solar system.” Nix and Hydra, seen more clearly than the other small moons, appear to have a regolith, which means the others probably do, too, but not by “regolith sharing” with Charon. Surface colors are not uniform; Hydra, for instance, is bluer than Nix. All have high albedos; why no darkening or “space weathering” in billions of years? Furthermore, the crater ages of the small moons appears to conflict with their orbital evolution. “Rapid rotations and large obliquities imply that tidal despinning has not played a major role in the moons’ rotational histories,” they note. “The moons have probably never reached the state of near synchronicity where chaotic perturbations by Charon have been predicted to dominate; determining whether chaos plays a role in the moons’ current rotational dynamics is deferred to a future study.”
It’s exciting to see new things from a mission of discovery from a far location. This is a once in a lifetime adventure. More data will keep coming down till late summer, but what has been discovered so far is amazing. The Pluto system is “yold” (see Darwin Dictionary), but there are reasons to favor the young side. The scientists like to say, based on crater counts, that some portions of Pluto, Charon and the other moons are billions of years old. But we have reported many times that crater count dating is unreliable (e.g., 5/22/12).
It’s much easier to fix upper limits than lower limits, because scientists can measure the rates of some processes, like atmospheric escape or space weathering. When they calculate that a surface like Sputnik Planum cannot be “more than” 10 million years (and possibly much younger), big doubts should arise about the assumed dates of the older features. Why? Because, now, the scientists have to figure out a scenario for what happened recently. Four billion years, the age of the solar system (A.S.S.), is a long time! Why would anything change in the last 1/450th of that timeline?
Secular planetary scientists have a worldview bias against any phenomenon that would suggest humans are lucky to be observing something that happened recently. Anything that could have happened should have happened in Pluto’s 18+ million orbits since it formed (in the secular timeline). Nothing should be left to happen recently. This is why, scientifically speaking, believing Pluto is young is more plausible than believing it is old. Complaining that old King Charlie needs the time is not a good excuse for explaining away observable, empirical evidence.