New Pluto Images Even More Perplexing
Pluto has terrain like no other world, leaving scientists perplexed; Enceladus’ activity is also inexplicable for “geologic time”.
More images of Pluto just came down from New Horizons on the 24th. Audible gasps come from the scientists, and from anyone seeing them for the first time. Most eye-catching of all is this “snakeskin” image of Pluto looking toward the terminator:
The image below — showing an area near the line that separates day from night — captures a vast rippling landscape of strange, aligned linear ridges that has astonished New Horizons team members.
“It’s a unique and perplexing landscape stretching over hundreds of miles,” said William McKinnon, New Horizons Geology, Geophysics and Imaging (GGI) team deputy lead from Washington University in St. Louis. “It looks more like tree bark or dragon scales than geology. This’ll really take time to figure out; maybe it’s some combination of internal tectonic forces and ice sublimation driven by Pluto’s faint sunlight.”
Other high-resolution images show apparent mountain tops protruding through vast, featureless plains of Sputnik Planum—yet the plains show corrugations suggestive of sublimation or wind erosion. At a larger scale, segments of the plains have polygonal edges suggestive of either convection or rotation of blocks then re-freezing. The highest-resolution image yet reveals “features that resemble dunes, the older shoreline of a shrinking glacial ice lake, and fractured, angular water ice mountains with sheer cliffs.”
The ridges in the “snakeskin” are tens of kilometers long, “giant features,” Nature says, running in parallel and covered with rust-colored material. Could wind have formed such features?
So far, Pluto has turned out to be strikingly active for an icy world 5 billion kilometres from the Sun. Nitrogen glaciers swirl around the base of towering mountains that are held up by the sheer rigidity of ice at about −235 °C, 38 degrees above absolute zero.
A new methane map has created a chicken-and-egg problem, NASA says; some places, like Sputnik Planum, have abundant methane, but the mountains and other areas have none.
The distribution of methane across the surface is anything but simple, with higher concentrations on bright plains and crater rims, but usually none in the centers of craters or darker regions. Outside of Sputnik Planum, methane ice appears to favor brighter areas, but scientists aren’t sure if that’s because methane is more likely to condense there or that its condensation brightens those regions.
The poor scientists were already reeling from September 10th’s photos and data (Space.com). There’s a bit of a good-news, bad-news story in another Space.com article. The good news is that scientists have explained Charon’s red north pole: it’s material escaping from Pluto’s atmosphere. The bad news is that Pluto’s atmosphere is finite and can’t keep painting Charon for billions of years.
The rapid escape of nitrogen (500 tons per hour*) has them grasping for options for how Pluto can resupply it (see Science Daily, Astrobiology Magazine and Nature). “More nitrogen has to come from somewhere to resupply both the nitrogen ice that is moving around Pluto’s surface in seasonal cycles and the nitrogen that is escaping off the top of the atmosphere as the result of heating by ultraviolet light from the sun,” one scientist from Southwest Research Institute (SWRI) says in Live Science‘s article. A resupply is needed, they assume, because these processes must have been going on for 4.5 billion years. The only plausible source to last for eons would be from the interior, but it has to get out somehow—requiring heat from a body that should be the coldest in the solar system.
Additionally, more mountains were identified (Space.com), photos suggest that nitrogen flows in glaciers (PhysOrg), and the team is wondering if Pluto has a liquid ocean under its surface (PhysOrg). New Horizons had “already exceeded expectations” (PhysOrg) before the snakeskin photo showed up today. Speaking of the icy mountains with flowing nitrogen glaciers, a planetary scientist from MIT shared his astonishment:
Until now, scientists have only seen surfaces like this on active worlds such as Earth and Saturn’s moon Enceladus. “No one dared imagine such a thick and localized buildup of geologically young ices, that even at 40 kelvins [-388 degrees Fahrenheit], have enough viscosity to create local landforms,” he said.
Asked what was the most surprising thing New Horizons has found, Geraint Lewis from the University of Sydney answered that it’s all the evidence of geological activity on a world thought to be dead.
And this is truly astounding. Remember, distant Pluto is smaller than our cold, dead moon, but the many surface features revealed by New Horizons are signs of a geologically young Pluto, a Pluto which is constantly changing, driven by processes underway in its core. Why isn’t Pluto as dead as the moon, with a similarly ancient surface? What is driving the internal processes, churning over the surface? And how does Pluto’s surface change over its almost 250 Earth-year long year, during which it dives even more deeply into the outer reaches of the Solar System?
Speaking of Enceladus, a new paper in Icarus theorizes that the geysering moon of Saturn (also surprisingly active for a small body) has a global subsurface ocean. That’s the only way Cassini scientists were able to explain patterns of wobbling, called librations, that stem from its small orbital eccentricity and slightly elongated shape. Another Icarus paper tries to explain the “bookshelf faulting” and tectonic history of the south polar terrain (where the geysers are) in terms of gravity and shear forces. The first paper also notes that other portions of the little moon seem to have terrains that resemble the currently-active south pole, indicating a sustained history of activity that has wandered around over time. The geysers are not a new phenomenon, in other words: Enceladus has probably always been active.
The global-ocean hypothesis was rapidly picked up as gospel truth by the usual uncritical suspects at Science Daily, the BBC News, and Live Science as a “discovery” of the scientists, even though they admitted that it is “not directly observable.” No matter; National Geographic was all ready with its hydrobioscopic boilerplate to tantalize the world about life in the Enceladus ocean: “Such alien oceans are prime candidates in the search for life beyond Earth,” Nadia Drake writes. NASA is not about to quench their enthusiasm, because it needs public support for a proposed “life-hunting mission” to Enceladus that would bring back samples from the geyser spray, Space.com reports.
What the reporters are not saying is more scientifically pressing: how can this little moon, only the diameter of Arizona, support an ocean for 4.5 billion years, the assumed age of the solar system? (A.S.S.) The authors in the Icarus “ocean” paper admit that it’s a serious problem. There’s not enough tidal energy, and radiogenic heat would be long gone before now. “The maintenance of a global ocean within Enceladus is problematic according to many thermal models and so may constrain satellite properties or require a surprisingly dissipative Saturn.” Yes, it would be surprising for Saturn to tidally squeeze Enceladus that hard, generating enough gravitational heat to exceed the power output of Yellowstone, and leave its similar-size neighbor Mimas (closer to Saturn) unaffected. Science Magazine came in to help with more ad-hoc theory rescue devices, suggesting Enceladus might have a fluffy core with a lot of antifreeze. Any such hypotheses are going to have to explain why they apply to Enceladus and not the other moons of Saturn—indeed to similar-sized bodies all over the solar system.
Oh, by the way: Jupiter’s aggressively volcanic moon Io is still erupting like gangbusters. Scientists are refining their maps of the hotspots (Icarus), and taking every opportunity to speak the L-word life (Astrobiology Magazine), but are strangely silent about how all that energy can be sustained for billions of years. At least Astrobiology’s article includes some nice photos of the eruptions taken by New Horizons in 2007 as it swung by on the way to Pluto.
*Correction from “tons per minute” to “tons per hour” made 10/11/15– Ed.
Why must Io be old? Why must Enceladus be old? Why must Pluto be old? Youth is staring these scientists in the face, and they not only refuse to consider it; that option is completely absent from their mental categories.
It’s too early to offer theories about Pluto’s snakeskin, smooth plains, glaciers and mountains; right now, we’re in the thrill-of-discovery mode. The engineers who made this craft and flew it are heroes. The images are breathtaking. The expressions on scientists’ faces are priceless. Sure, they will come up with moyboy hypotheses as time goes on, but their initial exclamations of astonishment must be documented for the history books. They didn’t expect any of this. Their predictions were falsified—but ours were confirmed. Untethered from the A.S.S., we predicted—before the encounter—an active surface, a rapid escape rate of the atmosphere, and evidence the moons were not formed by a collision (7/09/15).
So for relief of shortness of breath caused by gasping at these evidences of recent activity, might we suggest to NASA scientists that they negotiate with us a little? We won’t haggle over thousands of years if they would be willing to come down a few orders of magnitude from billions. Maybe a million years here, a few tens of millions there, down to the 108 or 107 range, let’s say; how about that? Whaddya say? No? Why not?
O, we see. The priests of the Bearded Buddha are glaring at you from the biology department. Pay them no mind. You are a scientist, remember? You follow the evidence where it leads.