A Bit More Detail

• Bad Astronomy's Phil Plait reports on the fragility of asteroid Ryugu.


• Centauri Dreams looks at the JUICE probe, planned to explore the three icy moons of Jupiter.


• John Quiggin at Crooked Timber reports on the fact that Jimmy Carter was warned in the 1970s about the possibility of global warming.


• D-Brief notes that the Earth might not be the best world for life, that watery worlds with dense atmospheres and long days might be better.


• Jessica Poling at the Everyday Sociology Blog writes about the construction of gender.


• Far Outliers looks at the Nigerian city of Agadez, at one point a sort of port city of the Sahel.


• Gizmodo asks a variety of experts their opinion on which species is likely to be next in developing our sort of intelligence. (Primates come up frequently, though I like the suggestion of bacterial colonies.)


• JSTOR Daily looks/a> at the genderless Quaker prophet Publick Universal Friend.


• Lawyers, Guns and Money comments on the interview of Amy Wax with The New Yorker.


• Marginal Revolution shares the enthusiasm of Tyler Cowen for Warsaw and Poland.


• Peter Pomerantsev writes at the NYR Daily about how the alt-right has taken to culture-jamming.


• Starts With A Bang's Ethan Siegel notes the exceptional power of cosmic rays.


• Window on Eurasia shares the lament of a Chuvash writer about the decline of her people's language.

• Centauri Dreams links to archival video painstakingly collected from the Voyager missions.


• Citizen Science Salon notes ways ordinary people can use satellite imagery for archaeological purposes.


• Good news: Asian carp can't find a fin-hold in Lake Michigan. Bad news: The lake is so food-deprived nothing lives there. The Crux reports.


• D-Brief notes that, once every second, a fast radio burst occurs somewhere in the universe.


• Dangerous Minds looks at the psychedelic retro-futurism of Swedish artist Kilian Eng.


• Dead Things notes the recovery of ancient human DNA from some African sites, and what this could mean for study.


• Cody Delistraty reconsiders the idea of the "coming of age" narrative. Does this make sense now that we have abandoned the idea of a unitary self?


• The Dragon's Gaze links to a paper examining the evolution of icy bodies around different post-main sequence stars.


• The Great Grey Bridge's Philip Turner notes anti-Putin dissident Alexei Navalny.


• Hornet Stories notes reports of anti-gay persecution in Azerbaijan.


• Language Log takes a look at the dialectal variations of southern Ohio.


• Lawyers, Guns and Money starts a discussion about what effective disaster relief for Puerto Rico would look like.


• The LRB Blog looks at the aftermath of the recent earthquake in Mexico, and the story of the buried girl who was not there.


• Marginal Revolution notes that Toronto real estate companies, in light of rent control, are switching rental units over to condos.


• Naked Anthropologist Laura Agustín takes a look at the origins and stories of migrant sex workers.


• The NYR Daily talks about the supposedly unthinkable idea of nuclear war in the age of Trump.


• Drew Rowsome gives a strongly positive--and deserved review to the Minmar Gaslight show The Seat Next to the King, a Fringe triumph now playing at the Theatre Centre.


• Starts With A Bang's Ethan Siegel explains how so many outer-system icy worlds have liquid water.


• Towleroad features Jim Parsons' exploration of how important is for him, as a gay man, to be married.


• Window on Eurasia suggests Russian language policy limiting minority languages in education could backfire, and wonders if Islamization one way people in an urbanizing North Caucasus are trying to remain connected to community.

• The Big Picture shares photos from the eruption of Mount Sinabung in Indonesia.


• The Broadside Blog's Caitlin Kelly writes about the importance of colleagues for solitary writers.


• D-Brief notes the rediscovery of the Blue-Eyed Ground Dove in Brazil, once believed extinct.


• The Dragon's Gaze notes reports of the discovery of massive planets via gaps in the protoplanetary disks of HL Tauri and HD 135344B.


• The Dragon's Tales notes a paper making specific projections about the shape of the Kuiper Belt if Planet Nine was around.


• A Fistful of Euros speculates as to the severity of the United Kingdom's post-Brexit recession.


• Language Log considers writing Shanghainese.


• The LRB Blog remembers Madeleine Lebeau, last survivor of the cast of Casablanca.


• Marginal Revolution engages with Peter Thiel's funding of Hulk Hogan's lawsuit against Gawker.


• The Planetary Society Blog notes sterling work reclaiming distorted images from the Voyager probes.


• pollotenchegg reports on the origins of migrants to Kyiv.


• The Power and the Money's Noel Maurer reports on Puerto Rico.


• Seriously Science notes that wild boar apparently wash their food before eating.


• Window on Eurasia looks at Putin's traditionalism, wonders if there might be a Russian Olympics boycott to spare the country the shame of being excluded, speculates about the North Caucasus' future within Russia, and reports Ukrainian worries of being isolated versus Russia.

In the "Grand Tack" (GT) scenario for the young solar system, Jupiter formed beyond 3.5 AU from the Sun and migrated as close as 1.5 AU until it encountered an orbital resonance with Saturn. Both planets then supposedly migrated outward for several 105 yr, with Jupiter ending up at ~5 AU. The initial conditions of the GT and the timing between Jupiter's migration and the formation of the Galilean satellites remain unexplored. We study the formation of Ganymede and Callisto, both of which consist of ~50% water and rock, respectively, in the GT scenario. We examine why they lack dense atmospheres, while Titan is surrounded by a thick nitrogen envelope. We model an axially symmetric circumplanetary disk (CPD) in hydrostatic equilibrium around Jupiter. The CPD is warmed by viscous heating, Jupiter's luminosity, accretional heating, and the Sun. The position of the water ice line in the CPD, which is crucial for the formation of massive moons, is computed at various solar distances. We assess the loss of Galilean atmospheres due to high-energy radiation from the young Sun. Ganymede and Callisto cannot have accreted their water during Jupiter's supposed GT, because its CPD (if still active) was too warm to host ices and much smaller than Ganymede's contemporary orbit. From a thermal perspective, the Galilean moons might have had significant atmospheres, but these would probably have been eroded during the GT in < 105 yr by solar XUV radiation. Jupiter and the Galilean moons formed beyond 4.5 (+/-0.5) AU and prior to the proposed GT. Thereafter, Jupiter's CPD would have been dry, and delayed accretion of planetesimals should have created water-rich Io and Europa. While Galilean atmospheres would have been lost during the GT, Titan would have formed after Saturn's own tack, because Saturn still accreted substantially for ~106 yr after its closest solar approach, ending up at about 7 AU.

There’s a big, weird bulge on Ganymede, the largest moon in the solar system. Protruding from a spot on the moon’s equator, the bulge is about 375 miles (600 kilometers) across, about the area of Ecuador, and two miles (three kilometers) tall, about half the height of Mount Kilimanjaro.

It’s not at all what scientists expected to find on this moon of Jupiter.

“I found it a bit by accident while I was looking to complete the global mapping of Ganymede,” says planetary scientist Paul Schenk of the Lunar and Planetary Institute, in Houston. He reported the weird feature on March 20 at the Lunar and Planetary Science Conference.

The size and location of Ganymede’s bulge, which appears to be made of thick ice, suggest that once upon a time, the moon’s icy shell rotated atop the rest of the moon, like an interplanetary Magic 8 Ball.

First, Schenk thinks, the bulge began growing at one of the poles. Then, once the bulge grew big enough, its mass began to drag the shell into a different position. The shell slid atop the ocean, while the moon’s interior stayed in the same orientation. Eventually, the part of the shell that once capped the poles ended up at the equator.

• blogTO shares photos of the destruction of the World's Biggest Bookstore.


• Centauri Dreams looks at a proposal for interstellar slingshots.


• The Dragon's Gaze links to a paper suggesting that tidally-locked Earth analogues will be habitable, avoiding scenarios where all their water is trapped on the nightside unless they have too little water.


• The Dragon's Tales notes a paper studying mechanisms for creating Ganymede's grooves.


• A Fistful of Euros' Alex Harrowell is skeptical of separatism in Catalonia, as in other relatively rich European regions, where it involves a desire to separate from poorer areas.


• Language Hat links to a paper suggesting that Taiwan is not the ultimate homeland of the Austronesian language family.


• Robert Farley of Lawyers, Guns and Money links to an article of his commenting on what China learned from the Gulf War of 1991.


• Marginal Revolution notes that Brazil once enjoyed roaring economic growth until the 1980s. Is this China's future?


• Personal Reflections' Jim Belshaw has a forum post seeking to explore stereotypes of Australia, as a country as a whole and as component regions.


• The Russian Demographics Blog links to an article suggesting that the shrinkage of Russia's working-age population may lead to a decline of the oil industry, if it lacks sufficient workers.


• Torontoist looks at the new TTC Pioneer Village station being worked on.


• Towleroad notes furor creating by the decision of a transgender woman to bury her as a man.


• Towleroad looks at problems with PReP.


• Window on Eurasia notes non-recognition of Crimean annexation and suggests that Russian minorities outside Russia are now in a weaker position because of Russian irredentism.

"Ganymede's ocean might be organized like a Dagwood sandwich," said Steve Vance of NASA's Jet Propulsion Laboratory in Pasadena, Calif., explaining the moon's resemblance to the "Blondie" cartoon character's multi-tiered sandwiches. The study, led by Vance, provides new theoretical evidence for the team's "club sandwich" model, first proposed last year. The research appears in the journal Planetary and Space Science.

The results support the idea that primitive life might have possibly arisen on the icy moon. Scientists say that places where water and rock interact are important for the development of life; for example, it's possible life began on Earth in bubbling vents on our sea floor. Prior to the new study, Ganymede's rocky sea bottom was thought to be coated with ice, not liquid -- a problem for the emergence of life. The "club sandwich" findings suggest otherwise: the first layer on top of the rocky core might be salty water.

"This is good news for Ganymede," said Vance. "Its ocean is huge, with enormous pressures, so it was thought that dense ice had to form at the bottom of the ocean. When we added salts to our models, we came up with liquids dense enough to sink to the sea floor."

NASA scientists first suspected an ocean in Ganymede in the 1970s, based on models of the large moon, which is bigger than Mercury. In the 1990s, NASA's Galileo mission flew by Ganymede, confirming the moon's ocean, and showing it extends to depths of hundreds of miles. The spacecraft also found evidence for salty seas, likely containing the salt magnesium sulfate.

Previous models of Ganymede's oceans assumed that salt didn't change the properties of liquid very much with pressure. Vance and his team showed, through laboratory experiments, how much salt really increases the density of liquids under the extreme conditions inside Ganymede and similar moons. It may seem strange that salt can make the ocean denser, but you can see for yourself how this works by adding plain old table salt to a glass of water. Rather than increasing in volume, the liquid shrinks and becomes denser. This is because the salt ions attract water molecules.

The models get more complicated when the different forms of ice are taken into account. The ice that floats in your drinks is called "Ice I." It's the least dense form of ice and lighter than water. But at high pressures, like those in crushingly deep oceans like Ganymede's, the ice crystal structures become more compact. "It's like finding a better arrangement of shoes in your luggage -- the ice molecules become packed together more tightly," said Vance. The ice can become so dense that it is heavier than water and falls to the bottom of the sea. The densest and heaviest ice thought to persist in Ganymede is called "Ice VI."

By modeling these processes using computers, the team came up with an ocean sandwiched between up to three ice layers, in addition to the rocky seafloor. The lightest ice is on top, and the saltiest liquid is heavy enough to sink to the bottom. What's more, the results demonstrate a possible bizarre phenomenon that causes the oceans to "snow upwards." As the oceans churn and cold plumes snake around, ice in the uppermost ocean layer, called "Ice III," could form in the seawater. When ice forms, salts precipitate out. The heavier salts would thus fall downward, and the lighter ice, or "snow," would float upward. This "snow" melts again before reaching the top of the ocean, possibly leaving slush in the middle of the moon sandwich.

• City of Brass' Aziz Poonawalla takes issue with Muslims who have issues with Valentine's Day. What's wrong with celebrating love?


• Discover's D-Brief notes the new official survey of Jupiter's largest moon, Ganymede.


• The Dragon's Tales notes a study from China suggesting that while reforested areas are cooler in daytime, they are also warmer at night.


• Eastern Approaches notes that coalition politics in the Czech Republic mean that country's post-Communist lustration laws won't be revised.


• Language Log notes the utter failure of an app supposed to make its users write like Hemingway (it doesn't like Hemingway's writing) and observes just how recently passed comedian Sid Caesar was able to learn his famed double-talk.


• The Power and the Money's Noel Maurer observes turbulence in Argentina's oil sector.


• Supernova Condensate commemorates the Valentine's Day gamma-ray burst of 1990.


• Torontoist notes another Rob Ford conflict of interest, this time involving fundraising in 2011.


• Towleroad traces the background behind Nigeria's anti-gay law.


• The Volokh Conspiracy maps the liberalization of gun laws across the United States.


• Window on Eurasia notes that, of the three traditionally Buddhist minorities of Russia, the Buryats have gone furthest towards a revival--the more shamanistic Tuvans and the Stalin-deported Kalmyks have further to go.

The Twitterverse is buzzing this morning with news that the Science Programme Committee of the European Space Agency has recommended that the next large European mission be JUICE, a mission to explore the three icy Galilean satellites and eventually to orbit Ganymede. The recommendation is not binding; it must be voted upon (a simple majority vote, according to BBC News), at a meeting of the Science Programme Committee, consisting of representatives of all 19 ESA member states, on May 2. The committee is likely to green-light this recommendation, but it shouldn't be taken as a certain decision just yet.

JUICE is being recommended over ATHENA (an x-ray observatory) and NGO (a gravitational wave observatory). It would launch in June 2022, enter Jupiter orbit in January 2030, and end in Ganymede orbit in June 2033. It is a concept that has been modified from JGO, the Jupiter Ganymede Orbiter, originally conceived as Europe's half of a US-Europe two-spacecraft mission to Jupiter, where NASA had originally proposed to provide a Jupiter Europa Orbiter. NASA canceled its plans to participate in that mission just as it canceled its participation in ExoMars more recently, and as with ExoMars, ESA appears ready to go forward without the USA. In fact, ESA has modified the originally proposed JGO mission to incorporate some of the science goals that would have been accomplished by NASA's Europa mission.

Here's the mission description and profile from the ESA document:

Science goals

The JUICE mission will visit the Jupiter system concentrating on the characterization of Ganymede, Europa and Callisto as planetary objects and potential habitats and on the exploration of the Jupiter system considered as an archetype for gas giants in the solar system and elsewhere. The focus of JUICE is to characterize the conditions that may have led to the emergence of habitable environments among the Jovian icy satellites, with special emphasis on the three ocean-bearing worlds, Ganymede, Europa, and Callisto. The mission will also focus on characterizing the diversity of processes in the Jupiter system which may be required in order to provide a stable environment at Ganymede, Europa and Callisto on geologic time scales, including gravitational coupling between the Galilean satellites and their long term tidal influence on the system as a whole.

Mission profile

The mission will be launched in June 2022 by an Ariane 5 ECA and will perform a 7.5 yr cruise toward Jupiter based on an Earth-Venus-Earth-Earth gravitational assist. The Jupiter orbit insertion will be performed in January 2030, and will be followed by a tour of the Jupiter system, comprising a transfer to Callisto (11 months), a phase studying Europa (with 2 flybys) and Callisto (with 3 flybys) lasting one month, a "Jupiter high-latitude phase" that includes 9 Callisto flybys (lasting 9 months) and the transfer to Ganymede (lasting 11 months). In September 2032 the spacecraft is inserted into orbit around Ganymede, starting with elliptical and high altitude circular orbits (for 5 months) followed by a phase in a medium altitude (500 km) circular orbit (3 months) and by a final phase in low altitude (200 km) circular orbit (1 month). The end of the nominal mission is foreseen in June 2033.

[. . .]

This selection -- if it is accepted -- represents a big win for planetary science and a big loss for space-based astrophysics in Europe. Which is, one can't help but notice, opposite to what the currently-proposed NASA budget represents.

I'm pretty ignorant of the internal and external politics involved in these decisions, and also of the relative merits of JUICE, ATHENA, and NGO, so while I admit I'm happy the planetary mission got selected, I don't feel qualified to comment on whether it should have or shouldn't have been the one that ESA picked. But, as a member of the American public, I can't help but see this decision as Europe stepping in to the sucking vacuum left by NASA in the exploration of the outer planets. NASA's inability to follow up on decades of spectacular successes in outer solar system exploration with any mission beyond Cassini's end in 2017 leaves an opportunity for Europe to take over the leadership of Earth's exploration of the solar system beyond the asteroid belt. It remains a challenge that Europe doesn't currently have the capability to produce radioisotope power sources for spacecraft; limited to solar power at present, that means Europe can't get beyond Jupiter. But Jupiter is far enough, for now.

The outer planets science community is a small and international one, so for sure there will be American participation in the science team, and probably also in the payload; the ESA document says specifically that "NASA has expressed an interest in contributing to the payload." Science instruments on ESA missions work differently from NASA. They aren't paid for by ESA; ESA builds and pays for the spacecraft, but different member states propose, build, and operate the science instruments using their own funds. ESA estimates that the spacecraft will cost €830 million and that ESA member states will spend an estimated €241 million to build instruments. NASA may contribute up to €68 million toward the payload. I hope it contributes the full amount; it'd be hard to imagine a way to get more bang for one's bucks than to pay for a couple of instruments and 10 or 20 scientists to work on a mission being built, developed, launched, and operated by someone else.

First, let's get the painfully obvious stuff out of the way: yes, Callisto is a bit on the bland side. It doesn't have an atmosphere, like Titan. It doesn' have volcanoes, like Io, or geysers, like Enceladus. It probably doesn't have a huge internal ocean of water like Europa. It's not part of a "double planet" like Charon. It doesn't have a magnetic field, like Ganymede. It's just a large, icy moon with a heavily cratered surface. So, yes, you could say that Callisto is less interesting than some other places.
Except that you'd be stupid to say that, because Callisto is actually pretty damn interesting.

Let's start with the most common misconception, which is that Callisto is "geologically dead". We're told that its surface is "saturated" with craters, so that any new crater would obliterate one or more old ones. Craters, nothing but craters. Right?

Wrong. Much of Callisto's surface is -- wait for it -- eroded. Yes, it's full of craters, but there are vast regions where the craters have been degraded to the point where you can hardly recognize them. All that's left are smooth, undulating basins with lumps or spires in the middle.

What's causing the erosion? Well, take a moment to consider how odd Callisto actually is. It's a large icy world that's relatively warm -- daytime surface temperatures get up to around 160 Kelvin, or about -170 Fahrenheit, and can peak at another 10 K higher than that at noon on the equator. That's actually pretty toasty for an ice moon. The other moons of Jupiter are all 30 or 40 degrees cooler than that. Callisto is warmer because it's dark -- it has a really low albedo. (Why? We're not sure. One guess is that radiolysis has broken down organic compounds, leaving a sooty residue.) Whatever the reason, Callisto is the warmest large icy body in the Solar System.

So Callisto gets warm enough that water ice can sublime. That's very different from, say, someplace like Titan. At Titan's 95 K, water ice is completely inert, dead as granite. But at 160 K? Water can actually have a vapor pressure. A very tiny vapor pressure, to be sure. But over geological time, many millions of years, water ice will slowly sublime away into the vacuum. The sharp edges of craters will gradually blur and then slump. Much of the vapor is lost to space, but some condenses as bright, reflective frost. That's what we're seeing when we look at Callisto... mostly dark stuff, but with gleaming shiny bright bits. So if you could walk around the surface of Callisto, it wouldn't look much like Earth's Moon, all gravel and sharp edges. Instead, most features would be rounded and soft-edged.

[. . .]

You'll still see a lot of people saying that Callisto's surface is "old", "ancient", or even "pristine". No. Even at the macro level, all those big craters have been softened by erosion, and the composition of the surface has been dramatically changed by radiolysis and the movement of volatiles. It's like the difference between a bright new shiny penny, and one that's old, worn down, and tarnished. And at the micro level, the scale of a human walking around, Callisto's surface has been completely transformed. It's not old at all.

And it's probably still evolving. Callisto's surface is being shaped by subtle, slow processes -- sublimation, condensation, radiolysis -- working over geologic time. These things aren't flashy. But they get results, and they're just as interesting as the faster and more blatant processes taking place on Io or Titan.