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Category Archives: Movies
Another movie: Ceci n'est pas un polar (#246)
April 19, 2015 9:47 am / Leave a comment
This post, like yesterday's post, also highlights a well-done recent Montréwood film. You may wish to check it out when it shows in your own part of Canada (Click here for you your local provincial Francophone association, which will be able to help you find showing dates and locations across Canada).
Ceci n'est pas un polar was showing in theatres yesterday. A Francophone buddy of mine drove into the city yesterday and we went to watch it together. I was not planning to watch a second movie, two days in a row — but the reviews were too good to turn this one down.
The word "polar" has two meanings in French. It means the North & South Poles, or other poles of attraction. But it also means a "criminal saga" (usually recounted in a book or a film). Thus the movie's title could mean "This is not a normal crime story".
The movie stars Roy Dupuis and Christine Beaulieu. Roy Dupuis is one of Montréwood's most famous actors. What most people do not realize is that Roy Dupuis is Franco-Ontario. He was born in Northern Ontario and lived in Ontario into his high-school years before his family moved to Québec.
Click below for the movie trailer
In the movie, a taxi driver falls in love with a customer, but finds himself captivated by too many strange aspects to her life which she does not want to explain to him. Out of love for her, he embarks on a journey as an amateur private detective to try to figure out why all the small things he is finding out about her are not making sense. The series of misplaced facts finally make sense at the end of the movie, but it was quite an adventure to get there.
Most Francophones in Québec and across Canada have watched Roy Depuis for more than two decades on television and in the movies. Even Anglophones across Canada may know him as the leading male role in the long-running television series Nakita.
But his role in this movie was probably one of his best ever (which is exactly what the critics have also been saying).
Check it out if you have the chance.
Below is a behind-the-scenes interview of the making of the movie:
Movie: Les Maîtres du suspense (#245)
I do not tend to watch a ton of movies (in English or in French). I suppose I'm like most people; I don't like to see obscure films which try to convey hidden messages of morals on life using metaphors and cinematic tools to invoke the suppressed character in me. Puke! Sorry, that's just not me.
Rather, like most people, I'm shallow, movies are expensive, and I want an instant fix from the movies I chose to see. I expect to be wowed, held in suspense (without having to expend too much brain power), or I expect to be keeling over with laughter. (By the way, if you're learning French, the informal word for "keeling over with laughter" is "cramper").
So in this sense, like the vast majority of people out there, I'm just plain picky and my choices are populist. I chose movies based on how the expensive effects look, or based on raving reviews.
Yet, yesterday I decided to see what was playing in French (with one of Canada's largest Francophone populations outside of Québec, Toronto is a great city for anything Francophone-related). A quick search revealed a few French-language movies playing at the cinema this weekend. Some were made in Québec and others in France.
I looked them up and Les Maîtres du suspense (one of our newest Québec films) was garnering some great reviews. So an hour later I was out the door, on the subway, and on my way downtown to check it out.
It was hilarious! I don't know how many times the entire theatre burst out laughing. But it also had a serious side to it — a very well made movie.
It was not released very long ago, so I'm quite curious what the box-office sales will be like over the next few weeks and months (in Canada, we count Canadian-made box-office sales in terms of months).
The movie was actually being shown in Toronto as part of a cross-Canada promotional tour. The film's writer, Stéphane Lapointe, surprisingly made an appearance on stage after the film's showing (I did not expect that at all) — to great applause might I add.
I would certainly recommend putting this movie on your list of must-sees. It can often be hit-and-miss with our Francophone (and Anglophone) films in Québec & Canada. But this one certainly was a hit.
In addition, it featured two very well-known household names as its main actors; Michel Côté and Antoine Bertrand (Michel Côté has been famous for two to three decades, and Antoine Bertrand is a young actor who has taken the film industry and comedy circuit by storm only over the last three years or so).
I'm not going to spoil the plot, but I will tell you that it was unlike any plot I have every seen before — very creative and captivating!!
See if you can check it out in your part of the country. If you're not sure where and when it will be showing in your city, give your local provincial Francophone association a call (click here for a list of contact info in all parts of Canada).
[As an aside, the theatre audience was very interesting. I expected it to be mostly Franco-Ontariens. Yet it was not. It was a packed house, perhaps half Anglophone / half Francophone. Toronto's Francophones are a very mixed bag, and it certainly showed last night. On one side of me were Francophones from Ontario, on the other side were people from Québec. Acadians and African Francophones were seated in front of me, and behind me were some Anglophones and Francophones from the Maghreb. And then there was that wacky "Alberta" guy sitting in my seat! 😉 On the 40 minute subway ride back home, the subway was full of the different French accents of those who went to see the movie. I really should try to make an extra effort to do more French activities in Toronto — it's such a fascinating mix of people here!]
Real-life documentary: Le Garage, "Bienvenue chez Normand" (#215)
March 21, 2015 8:28 am / Leave a comment
This documentary, "Le Garage", caught my eye the moment I first saw a short 20 second clip, and now I'm hooked!
I'll provide you with trailers, and an official link for online viewing a little further below.
This is one of the most "real" documentaries I think I have ever seen. I have never seen a documentary quite like this one before; one which has surprisingly left me with a feeling of having a strange bond with the people featured in it, despite never having met them.
At the very bottom, I'll provide you with links to official sites where you can watch the full hour-long documentary, officially approved for internet viewing.
The Trailer: Here's how the film maker, Michel Demers, describes his film (translation) : "It is along the banks of the North Coast where we find The Garage. Between forest and sea, adults, children, and grand-parents all gather in the garage to tell their stories and to gossip. In an atmosphere in which everyone has each other's back, you can sample the moose meat, trout, and mussels that everyone has pitched in to bring home together. Norman and his sons are mechanics, and are under the ever-so-watchful eyes of those who drop in and who watch from the side-lines".
C'est à Longue-Rive sur La Côte-Nord que nous retrouvons LE GARAGE. Entre mer et forêt, adultes, enfants et grands-parents s'y rencontrent pour raconter histoires et menteries. Dans une atmosphère de solidarité et d'entraide, on déguste orignal, truites et moules que l'on a capturé ensemble. Normand et ses fils y font de la mécanique sous les yeux des gens qui "veillent" dans le côté salon.
THE STORY LINE:
The film maker's brother, Norm, lives in a very small village, Longue-Rive, in the relatively remote region known as Québec's North Shore. Norm is a mechanic in the village, and works out of his garage set up on his property. In small towns and villages across Canada, particularly those which are quite remote, neighbours have grown up together and/or know each other very well. In such places, people often do not lock their doors at night, and villages take on a family atmosphere of sorts (you can walk into your neighbour's homes without knocking, everyone knows where everyone's chilren are at all times, and adults spend a lot of time with each other.
In Longue-Rive, there is no bar or cafe. But the blue-collar nature of the small town makes it so everyone has a garage where they work (either professionally or as a hobby), and everyday life revolves around the garage (much like everyday life may have revolved around kitchens 50, 70 or 100 years ago).
I've personally driven through Long-Rive a while back, as well as many other communities like it along the North Shore, and all across Canada. In villages like these, it tends to be more cultural the norm, rather than the exception, to see homes with detached garages, in which residents work or whittle away their time (even in my own family, we I have a number of relatives whose lives semi-revolve around their garage).
Culturally, it is very Canadian to see this phenomenon in remote, rural settings, in all provinces. It's something I have never really thought of before, but I think it's an aspect of our rural culture. It's a part of our culture which the film maker, Michel Demers, has captured beautifully.
In the absence of a bar or café in town, Norm's garage doubles as the local hang-out for family and friends. People drop by in their free time, pull up a chair (or a "living room recliner") and meet for a beer, to chat, to eat, organize group activities and just pass away the time. And it's not only the village men who have turned Norm's garage into their local "hang-out". Women and children also gather to gossip, joke, and play.
Because everyone shares the same lifestyle (a love of the outdoors, catching up on community news, bonding as a community, hunting, trapping, fishing, clam digging, ski-dooing, etc.), there are more than enough topics for everyone to talk and laugh about. There is rarely a dull moment. People bond, and the entire village becomes one big family.
WHAT I TOOK AWAY FROM WATCHING THIS DOCUMENTARY:
What I love about the film is its simple and genuine nature, its innocence, and how life is uncomplicated for those we see on the screen. If one member of the community falls on hard times, there will be a whole network of others around to help pick him/her up by their bootstraps and step in until that individual is back on their feet.
Although I now living in our largest city (with Toronto at the heart of the "Golden Horseshoe" which counts over 10 million people), and even though I have lived in a few cities overseas which have ranged from 8 million, to 17 million, to 25 million people people, a film like this still resonates so strongly with me because I see so many echoes of my own early childhood in it; be it clam-digging close to home with my family, ski-dooing with my dad and his buddies, spending time with my dad as he did odd things around his own garage, or simply growing up in a small, isolated community in which neighbours spent the bulk of their time together. I talked about many of these things in a couple of earlier posts:
Terrace et la côte nord de la Colombie-Britannique.
Végreville et les petites villes du Canada
It find it quite interesting that so many aspects of life on the North Coast of Québec (where the St. Lawrence meets the Atlantic) are almost identical to many aspects of life on the North Coast of British Columbia (where the Skeena meets the Pacific), and a good number of other places. Fascinating stuff!
INTERNATIONAL SCREENINGS:
Apart from the various Canadian cities in which this documentary has or will be screened (both inside and outside of Québec), it is also set to be screened or has been screened in cities as far away as Moscow, Marseilles, Brussels, Chicago and Mexico.
A NOTE ON THE STYLE OF FRENCH USED :
The French accents and expressions spoken are those commonly heard in Québec's North Coast region. This style of French has more in common with French spoken in Québec's Gaspé region, the Atlantic Province's Acadian regions, and the older generations of Prairie French speakers than it does Western Québec (which includes Montréal) or Ontario. (You can click the above links for more information on these various accent styles).
However, if your French is at an upper advanced level, and if you're used to hearing a couple of different Canadian French accents to a fluent level, you should not have much difficulty understanding what is being said. Just be aware that even if your French is perfectly fluent, or even if French is your first language (such as for those from Montréal or Québec City), but if you are not used to hearing a North Coast accent, the super-strong accents of a couple of Normand's buddies may throw you off here and there (there were a couple of times when I had to rewind to catch the words in a couple of different phrases).
SOME ADDITIONAL OUT-TAKES:
Here are some clips of people in the documentary talking about their lives and their"Garage" culture:
Here are some clips of reactions from local residents in Long-Rive when they first viewed a showing of "Bienvenue chez Normand".
The documentary's official website: http://www.micheldemers.com/?cat=67
HOW TO VIEW THE ENTIRE DOCUMENTARY ONLINE, FOR APPROVED VIEWING:
The documentary will be available on Radio-Canada's "Tou.tv" website for free viewing until approximately September 2015.
The direct link is as follows: http://ici.tou.tv/les-grands-reportages/S2015E189
Subtitles (in French) are available in the video if you need them (click the subtitle button at the the bottom of the screen).
Happy viewing !!
Patrick Huard (#212)
Two nights ago, Xavier Dolan's film Mommy cleaned house, yet again. This time it was an arm-full of trophes at Montréwood's Jutra awards.
The 2nd most important back-up actor in the film was Patrick Huard.
Regarding Montréwood cinéma, we often say if you want to know what film is worth watching (ie: what constitutes a "good" film), then follow the "director". Conversely, in Hollywood, more often than not it tends to be the reverse; people in Hollywood say you should follow the "actor" to find the "good" movies.
One major exception to the Québéc/Montréwood rule of following the "director" is in the case of the superstar actor, Patrick Huard. In Huard's case, if you follow the actor (just as you would in Hollywood), you are bound to find the best films.
With a few exceptions, if you look at the biggest of the big Montréwood films from the mid 1990s to present, Patrick Huard has held either a leading acting role, or a major back-up role.
I've never personally seen Huard walk down the streets in Québec, but I can only imagine he would be pounced upon from all directions by adoring fans looking for autographs.
Some of the more notable, very successful Montréwood films he has appeared in were:
Les Boys (1, 2 & 3) – all of which were among the highest grossing, and most viewed films in Canadian history
Bon Cop, Bad Cop – (Patrick Huard was the main actor)… the highest or second highest grossing film in Canadian history when it came out in 2006
The above films have gone down in the Montréwood, Québec and Canadian history books. I think it's fair to say that so has Patrick Huard.
If you want to hear a half-hour conversation between Patrick Huard and his co-star in Mommy, Anne Dorval, you can hear it on Radio-Canada's radio program, "L'autre jour à la table d'à côté" ("The Other Day at the Table Beside Us…"). Click HERE for the program on Radio-Canada's official website.
Check out some of his work… I think you'll be impressed.
Bon Cop, Bad Cop – ENGLISH TRAILER (the film was 50/50 French-English)
Starbuck – SUBTITLED English Trailer
Omertà – (Also starring Céline Dion's husband, René Angélil)
Mommy Trailer:
An embarrassing example of the "Two Solitudes" (#197)
March 3, 2015 5:59 pm / 3 Comments on An embarrassing example of the "Two Solitudes" (#197)
Yesterday I wrote this post in a different format. But after sleeping on it for a few hours, I realized the way I originally wrote it was not fair to Toronto, or its people as a whole. The comments the post received were in agreement with what I initially wrote, but that doesn't mean that how I wrote it was the right. If anything, the way I initially wrote the post shows how emotional an issue this subject can be (if I became emotional about it sitting here in Toronto, that can give you an idea of how it might be going over with many people in Québec).
I'm backtracking and I'm re-writing a good chunk of the post. Here is the re-written format…
This post is going touch upon a sensitive subject which occurs often enough… so I'm going to raise the issue again. It's something more people should be aware of (especially in media circles).
Yesterday were the Canadian Screen Awards organized by the Academy of Canadian Cinema & Television. (Website: http://www.academy.ca/About-the-Academy).
In a nutshell, these awards could be considered the Canadian equivalent of the U.S.A.'s Oscars.
It's a huge event. It is wider in scope than the Oscars/Academy awards because it grants awards to both Canada's movie and television industries in one fell swoop. It is not a Francophone award ceremony, nor is it an Anglophone award ceremony. The Canadian Screen Awards simply awards the best of the best in Canada, regardless of whether or not the recipients are Francophone or Anglophone.
The awards are held here in Toronto every year, and thus they are presented in English, in an English dominant environment (that of Toronto). They are supposed to be an all-inclusive ceremony.
But what happened yesterday really drives home the notion of the Two Solitudes. Frankly, it's embarrassing – and it has garnered a lot of attention today in Québec.
Here is what happened.
Mommy is one of the most successful Canadian movies of the past 20 years, and one of the most successful movies in Canadian history – full stop. After winning countless awards abroad over the past 10 months, Mommy finally had the opportunity yesterday to receive Canadian awards on home turf (apart from the Jutras which were held not long ago). In Québec, over the last several days, there was much excitement, suspense and publicity in the run-up to yesterday's awards in Toronto.
The movie, Mommy, is the creation of Xavier Dolan. It is considered a Québec film (abroad it is often held up as a Canadian film), it was created in French, and was released in May, 2014. Between May and now, Mommy basically won the prize for the "best film in the world" (for lack of a better term) at the Cannes Film Festival (the world's most prestigious and well-known international film festival). It also won many of the world's other most prestigious film awards.
But here's the crunch: Yesterday Xavier Dolan and the film's actors – who have been cheered and treated like super stars around the globe – showed up at the festival in Toronto, and guess what happened: Unless they were wearing name tags, many people at the event didn't know who they were, including those who were there to cover the event as media.
Because the event was broadcast live in Québec, the awkward treatment the film's creator and cast received at the gala did not go over very well with influential individuals in Québec or members of the public. A good number of people were hurt, angry, disappointed, and left confused.
Just to give you the context of how embarrassing this is, earlier this year, at the Cannes Festival (attended by all of Hollywood and the who's who of international film), Dolan and those who worked on Mommy were given an 8-minute standing ovation – yes… applause and cheers for a whole 8 minutes – by the biggest names in world of film. Even the elite of the American media industry attended, stood and applauded for 8 minutes straight (Oprah, Spielberg, Brad Pitt, you name it, the list goes on). This sort of accolade has never been given to a Canadian (or almost any other) film.
What happened last night when they won here in Toronto? Polite, timid (and awkward) applause from the seated audience who generally did not know who they were.
I'm dumbfounded.
I'm still trying to make sense of it all.
Last fall, I watched Mommy in the theatres here in Toronto, and it was packed (it was playing in regular theatres). Thus, what happened last night also took me off guard, as much as it did people in Québec.
I don't want to bash the gala event, and I don't want to bash Toronto either (after all, I love Toronto, its people, the vibe, its immigrants, immigrant communities and cosmopolitan nature. I love its freshness). But I am so embarrassed today by what happened at the awards ceremony.
I'm also quite embarrassed for the guests of the gala, because something like this could have been avoided. What happened yesterday occurred at one event (it was not a city-wide occurrence – and I'm not sure the expectation should have been that it was a city-wide event). Therefore, it could have been better contained with preventative management, and a bit of event-specific "education".
It's a sort of ignorance that is seen often enough at events like this, or though Toronto's "national" media when covering matters which cross the linguistic lines Yes, I see it in Toronto, but I have also seen it elsewhere in the country, AND I see also see it in reverse, in Francophone media, Francophone events and Francophone society. It's a two-way street.
However, the burden falls much heavier on Toronto's media shoulder, more so than any other media in the country – precisely because Toronto's media is Canada's national English-language media epicentre. That's a heavy burden for any city to have to carry. But because Toronto's media has this burden, they need to step up to the plate more so than elsewhere. That does not only pertain to presenters on the screen, but also to local behind-the-screen support staff such as camera operators, researchers, and those who decide what to cover and how to cover it. These people tend to be important in deciding who and what makes it on the screen, and how those subjects are portrayed to the public (ie: if a camera operator walks by the biggest star of an event because they don't know who that person is, then that simple action has huge implications, as we saw last night). It should be recognized that the support and technical staff are more apt to be hired from the general public in Toronto, and may not have had much interaction with Canada's Francophone culture (or other aspects of Canadian culture outside Toronto). Therefore there needs to be more education within those circles, or we'll see more things occur like what happened at the gala awards.
The implications of this type of ignorance can be significant when such ignorance is broadcast into people's homes, and when common people feel they have been slighted (the awards yesterday in Toronto were being followed live in Québec by a good deal of influential people – and thus the ignorance shown at the gala event spread like wildfire – the point that it made headline news in Québec).
I suppose it not only shows a that a much better effort could have been made on the part of the awards' organizers to ensure that the event's audience, staff and media were better informed regarding who was being invited (simple things like "promoting" the contents of the evening's program and nominees), but it also serves to highlight that segments of society (and hence the media) need to be better informed about culturally significant matters across our French/English linguistic lines.
But every cloud has its silver lining – and here is this story's silver lining: Canada's Anglophone media is very heavily concentrated in Toronto (that's why we often hear the expression "Toronto-centric media") Because there is a very wide range of people working in Toronto's media industry with very diverse personal backgrounds, it cannot be expected that everyone will be aware of culturally significant matters in Québec, matters across the linguistic divide, or elsewhere in Ontario or Canada (not everyone in Toronto's media industry speaks French, or went through immersion, or has travelled, or has lived in Canada long enough to understand all of Canada's cultural nuances – and that's ok and normal — because people are people). But this poses an amazing opportunity on a "national" level. Because Canada's "national" Anglophone media is so concentrated in one city – Toronto — it should not be very difficult to educate those who work in Canada's national media – at least much more efficiently and effectively, than say, if our "national" media were spread across several cities (like it is in the US, with NY being one hub, LA another, and Atlanta another with CNN).
Therefore, if by chance, there are people working in the media who are not sensitive to what is going on beyond a 100km radius (even within Ontario), it is a situation which can, in theory, be addressed and corrected.
Here are a few of the dangers if things do not change: (especially on the media front or regarding highly mediatized events): Anglophone Canada's media is watched and criticised in Québec (I would venture to say that Anglophone media is more visible in Québec than what Francophone's media is outside Québec). If the sort of ignorance we saw at the awards ceremony is not addressed, and that sort of ignorance is consistently conveyed by Anglophone Canada's media, then there is a risk that all of Anglophone Canada will be labelled as being just as ignorant — and that's precisely what happened yesterday evening at the awards ceremony, and it is continuing to play itself out today. There are political implications to it. People in the sovereignist camp in Québec has been tossing this one around like a hot-potato all day – they're really running to town with it — and it is in their interest to see that the issue remains front-and-centre. These types of things make an emotional impact, and emotions translate into how people vote. It's an issue.
This morning, the Radio-Canada (CBC French) headline in Québec was "Xavier Dolan feels the Two Solitudes at the Canadian Screen Awards". (The headlines should have been about the awards Mommy won at the gala).
Last night in Montréal, Xavier Dolan was interviewed on television on 24/60 byAnne-Marie Dussealt. The interview devoted a significant segment to his reaction of what just happened in Toronto. Dussealt is the Québec equivalent of Larry King (and 24/60 would be the equivalent of Larry King Live). However, she's probably a bit more like Piers Morgan because her own social & political views come across much more than what Larry King's did.
She asked him what it was like to receive an award in Toronto. Click HERE for the link to Radio-Canada's article and the interview video on their official website.
Below, at the end of this post, I'm providing you with a translation of Dolan's response to Dussault's questions (it begins at 2:40 minutes, and ends at 7:50 minutes).
I have to admit, when Radio-Canada first published the article, they did not post the video, and they only quoted sound-bites. The initial article was less-than-flattering (it left far too much to innuendo – and it went viral). Comments flooded in over the course of the day, and now people are talking about this on the streets in Québec. It's not good.
Fortunately, Radio-Canada posted the video clip later in the day, and what Dolan actually said was much more nuanced than what the article first lead people to believe. But unfortunately, damage has been done, and we're now all painted as being completely ignorant in English Canada, and out of touch with reality or anything in Québec for that matter.
Likewise, I'm not sure that many people in Québec have the nuanced context to be able to distinguish sectors of Toronto's media industry from the rest of ordinary people in English Canada (Toronto's media industry is far too often is held up as being "representative" of Canada).
In this case, I truly believe it boils down to a question of Two Solitudes between "Québec & Toronto's media industry" rather than "Québec and English Canada".
Big sigh – truly. Hopefully our mayor (of Toronto), John Tory, will jump in to say that what happened last night is not representative of most people in our city or of our country. At least I hope he will.
TRANSLATION OF RELEVANT QUOTES FROM THE 24/60 INTERVIEW.
Question — Anne-Marie Dusseault: What does it represent to you for your film to have had this sort of presence in Toronto? What does this sort of recognition represent? The Jutra awards are around the corner, I'm not sure if there is a hierarchy it. There were the Caesars. But what does your presence in Toronto represent? Especially since I would say that it's in a very particular universe for you.
Answer — Dolan: It's a universe which is quite specific. It's one of English Canadian stardom. Thus it has more to do with stars from English Canadian television. I would venture to say that it's owing more to this than the Gala groups together for both television and movies.
It's rather strange because we arrived there on the red carpet. And we were standing there on the red carpet. And you know, despite all the euphoria going on around us – after all it was a ceremony like any other and we were happy that our work was noticed, appreciated by peers, highlighted… even if we didn't win and were just nominated, regardless if it's here, in France, or elsewhere… the effect is the same – we are always honoured that our work is recognized.
But in Toronto, we arrived on the red carpet, and without our name tags, the cards which actually had our names and who we were… the photographers were completely… you know…
Dusseault: …lost !
Dolan: … completely lost. They had absolutely no idea who we were – which, without being pretentious, is rather peculiar. You know, if you think about it, the film garnered a fair amount of good international success. And… you know, one would like to think that Mommy is considered part of the… … I consider that Mommy is part of Canadian films, as much as it Québécois. In that sense, it represented Québec and Canada in all those foreign festivals, ceremonies, gala award events where it was nominated – that sort of thing.
But it's still rather particular that we were presenting it in a universe where all the stars of English Canadian television …
Dusseault: … don't know who you are. You're a complete unknown to them.
Dolan: It's to say that the industry… those in the artistic community who sawMommy, they came up to us and they were proud of Mommy. But apart from that, we could see we were in a world surrounded by a very specific English Canadian journalistic and photography corps which is… well, it's now a cliché to say it, but it's still an expression which aptly describes the situation – theTWO SOLITUDES.
I find it rather baffling and curious. If you think about it, it's really quite strange, because the gala started with a sort of "ode" to Canadian cinematography, in all its splendour and richness. But we felt the estrangement… well, no, not estrangement, but rather… hmmm… perhaps "ignorance" towards Québec cinema in the overall picture of things.
Question — Dusseault: I was kind of wondering this. Right up to the last minute, we were not sure if you were going to be in Toronto, if you had the time to get there. Did this make you ask yourself "What am I even doing here? What's the point of being here?"… Right?
Answer — Dolan: No, I didn't ask myself "What am I doing here?" becauseMommy was a film financed by Telefilm Canada. Factually speaking, let's be honest; it's a film which was made in Canada and it's a Canadian film. Let's not deviate from that, regardless of people's political allegiances. It was made within a certain artistic context – political also. And I'm happy that theCanadian Industry Awards have recognized our work. After all, it's our peers who vote for who wins. So in that sense, I don't ask myself what's the point of being there. I'm happy we were there. I'm of course happy that Anne was there, and that all the actors were there.
But the atmosphere, all-in-all, reveals… I have to say, a gulf between the two cultures, which would otherwise stand to gain if they were to learn from each other.
You know, I read the newspapers this morning. English Canadian journalists, who were covering the ceremonies, made the point of saying that each year it is the same thing for them – that there will always be "one" Québécois film, without ever knowing what it will be, which will always triumph above the rest. Then it will simply sweep all the prizes, and it will always irritate them. But they still acknowledge it, and they write it.
So in that sense, the whole thing is just so interesting to watch itself play out, and to see the journalists talk about this.
Dusseault: It is rather interesting to watch itself play out. Yesterday I was following it on Twitter, and then I'd switch back-and-forth to CBC, and the awards were always making way for "English Canadian Television".
Dolan: In that sense, I'm not going to criticize them, because I understand their logic. I get the impression that if they group together movies and television, it's because in English Canada, what English Canadians know better than anything else in their own world are the stars of their television – those on CBC, CTV, on their national TV shows. In a sense, it's by formatting it this way that the gala event would make English Canadians want to tune in to it. If they were to only celebrate English Canadian cinema (versus television), I'm not sure the gala event would attract many viewers. Movies and television were separated in the past, and from what I understand, it didn't work very well in that format.


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Bundesstraße – strada federale in Austria
Bundesstraße – strada federale in Germania

redpajama_set_name: RedPajamaWikipedia


1Department of Applied Geology, Curtin University of Technology, G.P.O. Box U1987, Perth, Western Australia 6845, Australia.
2Planetary Science Institute, 1700 East Fort Lowell Road, Suite 106, Tucson, AZ 85719, USA.
Department of Applied Geology, Curtin University of Technology, G.P.O. Box U1987, Perth, Western Australia 6845, Australia.
Planetary Science Institute, 1700 East Fort Lowell Road, Suite 106, Tucson, AZ 85719, USA.
Primordial asteroids accreted as a mixture of nebular fines, ice, and coarse spherules (chondrules). Carbonaceous chondrite meteorites sample these asteroids. A subset of these meteorites shows evidence of significant hydrothermal alteration, apparently occurring within their asteroid parent bodies [for example, see the study of Brearley (1)]. Counterintuitively, the most chemically pristine meteorites (CI and CM chondrites) have experienced the most pervasive aqueous alteration. CI and CM meteorites contain abundant water and organics and have chemical compositions that are a close match to the solar photosphere—in the case of CI chondrites, at least 40 elements within 10% of the photosphere value (2, 3). The solar/meteoritic ratio is independent of volatility or geochemical affinity. When considering the hydrothermal history of a geological body, it is also independent of solubility. Highly soluble elements, such as Na, K, and F, are also within 10% of solar (2, 3). The unusual chemistry of CI and CM chondrites, abundant water, and mix of complex organics have led many to identify these meteorites as plausible terrestrial planet precursors or candidates for delivery of terrestrial volatiles. A desire to understand their geological history, and the early evolution of water and organics in the solar system, has been a driver for numerous asteroid-scale numerical modeling studies (4–10).
Hydrothermal alteration transformed the mineralogy of these rocks—CI chondrites are composed of >95% secondary phases, with only a trace of their original anhydrous mineralogy remaining (11)—without changing their chemistry. This "isochemical" alteration may result from negligible fluid flow—a closed system at scales larger than 1 mm. However, earlier numerical studies have consistently predicted large-scale (tens of kilometers) water transport in model asteroids (4–10). This type of convective heat transfer is an effective way of moderating temperatures within an asteroid parent body [for example, see the study of Travis and Schubert (8)], something that is particularly important in the case of CI and CM chondrites, because almost all of these rocks appear to have experienced alteration over a narrow temperature range and at relatively low temperatures (<150°C). However, in addition to asteroid-scale convection, which might fractionate aqueous species, a problem with numerical studies is that they often produce only narrow bands within model asteroids that match CM chondrite conditions (4–6, 8, 10). A consideration of the material properties of chondrite precursors (note, not extant meteorites, because hydrothermal alteration and impact processing have—in almost all cases—profoundly changed their material properties) suggests very low permeability (12): Earlier geophysical models may have used permeability estimates around six orders of magnitude higher (12). As a result, liquid water flow would be reduced to millimeter-scale distances at most, even in a high-porosity, water-saturated asteroid. Low permeability provides a mechanism for isochemical alteration, but in the absence of convective motion of water (a "closed-system" scenario), we are required to posit small (less than tens of kilometers in diameter) primordial parent bodies to moderate temperatures during alteration (12). In addition, carbonate grains in some CMs exhibit a large range in δ18O [for example, see the study of Jenniskens et al. (13)], requiring varying temperatures and water/rock (WR) ratio over short length scales—difficult to achieve in a low-permeability, closed-system environment. This is interpreted by some as suggesting open-system WR interaction and an asteroid that is zoned with respect to O-isotope composition (5). Achieving this O-isotope heterogeneity at the thin section scale would require a dense network of channels [an additional benefit would be that fractures and channels would increase permeability and permit efficient heat transfer (14)]. However, this type of fracture/channel network feature has not been observed in any chondrite, on any scale). Reaction modeling (15) predicts abundant CH4(g) and H2(g) as a consequence of asteroidal aqueous processing, requiring an open system at least with respect to gaseous species. Finally, young CM chondrite dolomite ages [3.4 to 4.5 My (million years) (16) after calcium- and aluminum-rich inclusion (CAI) (17)] raise questions as to whether a late-accreting body, containing substantial water ice, could even melt and achieve temperatures consistent with dolomite formation (defining Tpeak for most CMs at ~150°C).
It is apparent that a variety of well-supported model constraints, data and observations, and existing numerical approaches are not converging on a holistic scenario for the hydrothermal evolution of primitive, water-rich (CM and CI chondrite) asteroids. This is unfortunate, because a well-founded geophysical model for the aqueous and thermal alteration that occurred in these objects would give us a framework for understanding the evolution of water and organics in the early solar system and the geological history of objects that may have been the precursors to the terrestrial planets. Here, we propose an alternative that reconciles these competing lines of evidence. All previous studies of water/rock interaction in asteroids have assumed that the object is lithified: An anhydrous coherent rock reacts with water. However, there is no a priori reason why this should be the case. On accretion, nebular fines, ice, and chondrules would not be lithified. On melting, chondrules might become a suspended load in a viscous mud. Water and solids would move together. The notion of open or closed system would no longer apply.
Here, we explore this concept with the MAGHNUM numerical simulator, previously used to model thermal evolution of consolidated carbonaceous chondrite parent bodies (8, 18). New features include particle transport using Stokes-Rubey settling (19, 20), minimum porosity from packing models, mud viscosity, serpentinization, and dehydration. The code tracks chondrules. Dimensionless tracer particles scattered throughout the mud allow us to track movement, temperature, and WR ratio path of dimensionless mud "grains" (which might translate to individual phyllosilicate or carbonate grains in CM chondrite matrix), as they evolve within the body over time. Another novel code feature concerns porosity and permeability. In an unconsolidated particulate bed, especially at low G, these parameters are dynamic. Nonuniform flow can generate feedbacks, increasing (or decreasing) porosity and permeability through particulate movement, which in turn can increase (or decrease) flow, eventually creating structure in initially uniform media. The code handles this nonlinear dynamic interplay of porosity and permeability and flow in an unconsolidated bed, at each time step at each node. Model asteroids are unconsolidated mixtures of coarse particles (chondrules) and mud (initially a uniform mix of fines and ice), with starting compositions chosen to provide a comparison to CM chondrite parent bodies at plausible accretion times. We vary mud/chondrule ratio and mud viscosity. Chondrule packing density is the mud-filled porosity between clasts. We typically use a packing density value of 50% (that is, 50% chondrules, with interstices having a volume of 50%, filled by mud), which approximates a terrestrial sand, although we do vary this in some simulations. The viscosity of the mud in our model follows a power law (21). Shoji and Kurita (22) used an almost identical relationship. Mud volcano viscosities (23) lie in the same range, and data from the geologic literature (24, 25) bracket the other (21, 22) curves. The viscosity of mud shows considerable dependence on particle type and fines content/load fraction [for example, see the studies of Zoporowski and Miller (23) (and references therein), Fritz and Moore (24), and Grim (25)]. To illustrate the impact of a higher mud viscosity, we ran cases with a 10-fold increase in viscosity. We still see convective motion, reduced somewhat in strength but qualitatively the same. We also vary WR ratio [a bulk initial WR of 0.6 and 1.0, bracketing estimates for CM chondrites (26)]. WR varies over time and affects mud viscosity, as water is consumed in alteration reactions. At 60:40 matrix/chondrule mix, a bulk initial WR of 0.6 and 1.0 translates to an initial matrix WR of 1 and 1.67. Simulations span asteroid radii from 50 to 500 km. Although the canonical view is that chondrite parent bodies accreted a population of chondrules that had already been sorted in the disk (and sorted chondrule populations in chondrite groups that have low matrix abundance testify that this occurred), to explore whether mud convection is also capable of segregating chondrules based on size, we begin with an unsorted population made up of 1-mm, 0.5-mm, 0.1-mm, 50-μm, and 10-μm particles in a 10:20:30:30:10 ratio. Simulations beginning with a sorted chondrule population produce qualitatively similar results (in terms of Tpeak and thermal structure within the body).
In simulations of unconsolidated asteroids that have a high mud/chondrule ratio, chondrules settle rapidly to form an unconsolidated chondrule + mud "core" and mud ocean (85 to 98% mud) mantle capped with an undifferentiated frozen crust (see the Supplementary Materials regarding the stability of the crust). Because there are no empirical constraints on the initial, bulk, accreted ratio of chondrules to matrix in primordial asteroids (the tacit assumption is that the object was lithified: the observed ratio in the meteorite is taken to be representative of the ratio in the parent body), this is a free parameter. In most simulations presented here, we chose a ratio that allows us to visualize and explore an outcome that is unique to the mud model: differentiation between a core that is richer in chondrules and a mud mantle. However, note that this is not predictive of CM parent body structure. Different choices for initial chondrule fraction and packing density translate to differences in core/mantle volume and core chondrule/matrix ratio. A larger accreted chondrule fraction, lower packing density, and less compaction with depth lead to a reduced—or nonexistent—mud mantle, as illustrated in Fig. 1 in the high viscosity example.
Fig. 1 Particle size distribution in sample model asteroids that accrete a range of chondrule sizes, showing the variety of chondrule sorting [note: if the object accretes a sorted population (the current canonical view), then no additional sorting will occur].
It is apparent that asteroid radius (lower-gravity objects show less efficient sorting), mud viscosity, and WR ratio (which also influences viscosity) affect sorting. Other factors include chondrule packing density and accretion time (objects that accrete earlier show stronger convection and more efficient sorting). In scenarios where sorting occurs, we typically see an inner core region dominated by 1- and 0.5-mm chondrules, surrounded by 0.1-mm particles, with 50-μm particles concentrated at the edge of the core and 10-μm particles distributed evenly either throughout the object or at the core-mantle boundary. Mud convection complicates this picture, with particles depleted in upwelling regions and concentrated relative to the average in downwelling regions. Particle oscillations reflect a feedback between fluid flow and particle transport. Objects with ×10 higher viscosity show no sorting (although convection still occurs).
Mud convection can provide an efficient chondrule sorting mechanism (Fig. 1), although, once again, if the object accretes a sorted population via some aerodynamic mechanism [for example, turbulent concentration in the disk (27)]—the canonical view—then additional sorting in the parent body cannot occur. There are a number of model inputs that affect the degree of sorting: asteroid radius (smaller objects, with lower gravity, show less efficient sorting), initial viscosity (higher viscosity reduces or removes sorting), WR ratio (lower WR ratio translates to higher viscosity, and because WR evolves over time, so does viscosity), packing density (lower packing density reduces sorting), and accretion time (objects that accrete earlier show stronger convection and more efficient sorting). If sorting occurs (in high-viscosity scenarios, it is absent), then we typically see an inner core region dominated by 1- and 0.5-mm chondrules, surrounded by 0.1-mm particles, with 50 μm concentrated at the edge of the core. Particles (10 μm) are distributed evenly either throughout the object or at the core mantle boundary (Fig. 1). In a number of scenarios, we see particle oscillations, which reflect a feedback between fluid flow and particle transport. Sufficiently strong convective plumes loft coarse particles, which spread out in space (in a manner similar to a chromatograph) because of their size (Stokes-like flow, which depends on particle size). The smaller particles are more susceptible to lofting. Upwelling convective flowing mud lofts particles upward and sideways, with convergence in downwellings. This motion tends to cause particles to be depleted in upwelling regions and concentrated relative to the average in downwelling regions. This type of clustering occurs primarily while particles are falling from the melt front rather than after core formation. It is at this point in the hydrothermal evolution of the parent body when convection is most intense, driven by serpentinization's exothermic reaction and decay of short-lived radionuclides. Core formation is not instantaneous, taking from 25,000 to >100,000 years, depending on the fine/coarse (f/c) ratio, object size, and WR value. Once coarse particles reach the maximum packing density in any core bed node, the bed becomes immobile (but is not consolidated) at that location.
Convection is not restricted to the mud mantle but extends into the core, where convection consists of mud moving through the porous bed formed by coarse particles. If the accreted f/c ratio (and packing density) allows for differentiation, then we may see plumes in the mud ocean driven partly by plumes in the core that exit to the ocean bottom, as well as cold downwellings dropping off the frozen crust. We can visualize convection by tracking the history of individual dimensionless tracer particles scattered throughout the mud. Considering a scenario that has a 100-km-radius object accreting at 3 My after CAI with a bulk WR of 1.0, Fig. 2 shows individual trajectories for tracer particles that begin at a level of 20 km (Fig. 2A), 50 km (Fig. 2B), and 80 km (Fig. 2C) in this object. Ice melting and serpentinization begin at around 0.9 My after accretion. The figure shows how convection strengthens over time. By 2 My, discrete trajectories for particles that started at all three levels span the entire object—from the core up to the base of the ice lid. Objects accreting after 4 My do not melt. Asteroids accreting at 3 and 3.5 My after CAI take 0.3 to 0.6 My to warm to 0°C from decay of short-lived radioisotopes, where temperature buffers at 0°C for 0.5 to 2 My, whereafter internal heating overcomes the latent heat of ice melting (higher WR and later accretion delay melting). Temperature then increases rapidly, driven by serpentinization. The Ttime trajectory varies depending on the size of the object, but interior to the ice shell, the thermal stratigraphy—the Tavg profile, where temperature is averaged across all longitudinal coordinates at the same level in the object—is essentially the same, despite the fact that the model asteroids span a ×1000 range in mass (Fig. 3). At Tpeak, a Ceres-class object with WR = 1.0 accreting at CAI + 3 My, a 100-km object with WR = 0.6 accreting at CAI + 3.5 My, and a 100-km object with WR = 1.0 all have an approximately flat Tavg profile from the interior to the ice shell and similar temperatures of Tavg = 125 ± 20°C throughout the bulk of the object. Mud convection moderates temperature and minimizes any internal thermal gradient across all model asteroid sizes. Cooling rate is a significant variable with respect to object size: 150 My to reach 50°C in a Ceres-class object (mud convection is still occurring at this time) versus 5 to 10 My in smaller objects. Scenarios with lower f/c ratio, lower packing density, and higher viscosity (Fig. 3E) show somewhat lower temperatures. Mud convection still occurs in these cases, and the Tavg profile is still flat, but chondrules are not sorted (Fig. 1) and no clear core forms. Peak temperature is cooler than when a core forms, because heat generation is roughly homogeneous throughout the body: Approximately half of the heat generation is in the outer 20% radially; being closer to the surface, the object cools faster.
Fig. 2 Visualizing individual particle trajectories (dimensionless tracer particles scattered throughout the mud) in a 100-km-radius object accreting at CAI + 3 My with WR = 1.0.
The figure shows the range of tracer particle histories for all latitudinal coordinates at a given level in the model asteroid, for particles beginning at a level of 20 km (A), 50 km (B), and 80 km (C). We see the effect of convection strengthening over time; until by 2 My, mud convection is transporting tracer particles that started at all three levels through the entire object—from the core up to the base of the ice lid.
Fig. 3 Temperatures in various model asteroids at a similar stage in their evolution following the onset of convection.
(A) A 50-km-radius object accreting 3 My after CAI with WR = 0.6 and an f/c ratio of 60:40, 0.9 My after melting. (B) A 100-km-radius object accreting at CAI + 3.5 My with WR = 0.6 and an f/c ratio of 60:40, 2.4 My after melting. (C) A 100-km-radius object accreting at CAI + 3 My with WR = 0.6 and an f/c ratio of 60:40, 1 My after melting. (D) A 100-km-radius object accreting at CAI + 3 My with WR = 1.0 and an f/c ratio of 60:40, 1.3 My after melting. (E) A 100-km-radius object accreting at CAI + 3 My with WR = 0.8, an f/c ratio of 28:72, and ×10 higher viscosity, 2.0 My after melting. (F) A Ceres-class object accreting at CAI + 3 My with WR = 0.6 and an f/c ratio of 60:40, 1.6 My after melting. (G) A Ceres-class object accreting at CAI + 3 My with WR = 1.0 and an f/c ratio of 60:40, 2 My after melting. It is noteworthy that although the model asteroids span a ×1000 range in mass and a large range in viscosity, WR ratio, and f/c ratio, they show a very similar temperature profile: Tpeak < 170°C observed in all the objects, with mud convection minimizing any internal thermal gradient.
Our simulations are not intended to be predictive of CM parent body structure (varying f/c ratio, packing density, viscosity, degree of sorting in the accreted chondrule population, or having a sorted chondrule population gives rise to a range of parent body stratigraphies). Some of these variables (for example, accreted f/c ratio) cannot be constrained. However, a robust result is that over a wide range of input parameters, mud convection occurs, generating simulations that are a close match to the conditions for CM chondrite alteration and chronology, from petrographic and isotopic studies. Young CM carbonate ages [formation at ~4 My after CAI (16, 28)] are expected. A planetesimal can accrete earlier, incorporating sufficient short-lived radionuclides to melt, but it will experience an ~1- to 2.4-My delay between accretion and Tmax. Compared to other chondrite groups, CM chondrites record hydrothermal alteration over a relatively narrow (and low) temperature range (29). Inferred alteration temperatures from isotopic analyses of CM carbonates are 20° to 71°C (30) and 0° to 130°C (31). The presence of dolomite indicates a (relatively) high initial parent body temperature, in excess of 120°C (32). Reaction modeling of phyllosilicate formation (15, 33) predicts temperatures at the lower end of this range. These observations suggest a CM parent body where internal temperature was moderated and that did not have a steep thermal gradient (not an onion shell). This thermal structure is observed in all of our simulations, and the fact that we see similar Tavg temperature profiles (and parent body histories) across all simulations suggests that the mudball scenario offers a general model for CM chondrite alteration. CM-like rocks can be extracted from asteroids of a range of sizes that accrete at varying times, with varying WR ratios and viscosities, and from a range of depths within the parent body. This prediction of asteroid-scale homogeneity is consistent with recent observations of CM-like main belt (Ch/Cgh spectral type) asteroids (34) and contrasts with highly stratified model objects from previous work (4–6, 8, 10).
Possible asteroid-scale homogeneity gives way to fine-scale chemical and isotopic heterogeneity in CM and CI chondrites. The mudball model provides an explanation for this. Heterogeneity in carbonate oxygen requires formation at varying temperatures and WR ratios, previously interpreted as consistent with large-scale open-system circulation of fluids through the body (5). Carbonate heterogeneity is not limited to O-isotopes. "Clumped" isotope and C-isotope data (30, 31, 35), and chemical data (35), also indicate formation over a range of temperatures [even in the same meteorite (30)] and in different alteration environments under different physicochemical conditions (for example, redox states)—this heterogeneity is observed at fine scales [hundreds of micrometers (35)]. This is surprising if we assume a lithified rock, where neighboring components could be expected to witness similar conditions. However, it is a necessary outcome of a model where grains forming in a range of environments, over extended time scales, are mixed via mud convection. In the mud model grains forming at different times, temperatures and WR ratios will be brought together in their final configuration only at the end of convection. To constrain the degree of heterogeneity, we track the variety of dimensionless tracer particle histories for temperature and WR trajectories for fines, for particles that begin at the same level in an asteroid (Fig. 4). Carbonate formation appears to have been relatively inefficient in CM parent bodies (31), occurring throughout the active phase of aqueous alteration. Although this process (continual secondary mineral formation and partial back-reaction) is not explicitly modeled in our simulations, we can visualize its effect using the tracer particle tracking approach (again, we take the example of a 100-km-radius object accreting at CAI + 3 My with bulk WR = 1.0). Average temperatures throughout the object are moderated by convection (Fig. 3). This is observed on a particle basis as well (Fig. 4). By tracking individual tracer particles starting at 60 km (Fig. 4A), we see that in the first 0.5 My after melting, most experience T-t trajectories in the 120 ± 20°C range. However, a significant minority experience T-t paths far outside this range—excursions up to 200°C, and 0°C for material eroded from the ice lid. In addition, temperature variability is much greater for particles that begin at higher levels in the object (Fig. 4B, 90 km). By 2 My, this variability has reduced—no particles have trajectories outside ~130 ± 30°C. Serpentinization occurs rapidly (<1000 years), and with it the main modification in WR (Fig. 4, C and D). However, as mud convection strengthens, strong upwelling occasionally degrades portions of the ice lid, leading to transient spikes in WR at high levels in the model asteroid [Fig. 4, C (70 km) and D (90 km)]. In our 100-km-radius example, this period lasts from around 1 to 1.3 My after accretion. It is apparent that there is a significant range in possible T-t and WR-t paths. In addition, continual secondary mineral formation will record changing conditions as the body cools. Compositional and isotopic heterogeneity over short length scales at the end of convection is expected.
Fig. 4 Visualizing individual tracer particle histories in a 100-km-radius object accreting at CAI + 3 My with WR = 1.0.
The figure shows particle histories for all latitudinal coordinates at a given level in the model asteroid over time. There is significant range in particle T-t and WR-t trajectories: Compositional and isotopic heterogeneity over short length scales at the end of convection is expected. (A and B) Range of T-t histories for particles starting at 60 and 90 km (respectively) in our model asteroid. Although mud convection moderates temperature, there are significant excursions, particularly at early times. (C and D) Range of WR histories for particles starting at 70 and 90 km (respectively). The main modification in WR is global serpentinization at 0.9 My. However, as mud convection strengthens, strong upwelling degrades portions of the ice lid, leading to transient spikes in WR at these levels in the model asteroid. The result when convection ceases, and the arrangement of grains is locked in (perhaps approximating what we see in the meteorite), will be a material with significant grain-grain variability over short (100 μm) length scales in grain T-t and WR-t histories. This variability will be increased if secondary mineral growth occurs continually during alteration, while the whole body cools (not accounted for in our model).
There is petrographic evidence in favor of the mudball model. The edges of carbonate grains are abraded in CM chondrites, suggested to be a consequence of fluidization of the matrix (28). Chondrule abrasion and layers of different particle sizes and/or particle types have also been described (36). Textures interpreted as arising from compaction following impact (37) are entirely consistent with mud flow, and a ubiquitous feature of CMs is also explained by it. Rims of fine-grained matrix material surround chondrules in CMs (and other carbonaceous chondrites). Often referred to as "accretionary rims," they may have acted to cushion impacts, enabling the aggregation of the first solids (38). Evidence in favor of a nebula accretionary origin is the relationship between the radius of the clast and the thickness of the fine-grained rim (39). The mud model may offer an alternative. CM chondrules will be continually moving through mud during settling or while lofted by strong plumes. Mud convection extends into the chondrule-rich core—mud will be flowing through the porous chondrule-rich bed until convection ceases. In this environment, rim textures may be a meteoritic equivalent of pisoliths in terrestrial sedimentary settings. Chondrule rims in CMs would still be accretionary, but they would have accreted in the parent body rather than the nebula. In addition to explaining this feature of CM petrography, it would have the effect of increasing the matrix/chondrule ratio from the base level, defined by our choice of matrix/chondrule packing density (50%). Whether or not it is a complete rim, any accretion of matrix material onto chondrules will have this effect. It is noteworthy that CM2 chondrites have highly variable matrix abundances, from 58% (Murray) to 85% (Nogoya).
Finally, the mudball model circumvents the isochemical alteration paradox, where the most chemically pristine meteorites are the most aqueously altered. Solubility-related chemical fractionation is only an issue where water is moving through a lithified rock matrix. In a viscous mud, fines and water move together. In all scenarios, convection of mud—whether in a mud mantle or through a porous bed formed by coarse particles—is occurring throughout the entire object up to the ice lid. The system is thoroughly mixed, so alteration will necessarily be isochemical: Local solubility-related fractionation will be reduced or removed by mud flow.
The computational model MAGHNUM combines modeling features described in previous work (8, 10, 18, 40), with additional features for particulates flowing in mud and forming an unconsolidated porous, permeable bed. It solves equations for mass conservation, momentum conservation, energy conservation, and solute conservation, with equation of state and constitutive relations, as summarized below. In addition, several issues of interest are discussed.
(1)where sice is the fraction of H2O that is ice (sm + sice = 1) and Xwm is the fraction of water in mud.
(2)where um is the mud velocity and k is the permeability.
Permeability. As coarse particles fall from the melting front and settle toward the center, they form the core bed. Until the packing of coarse particles reaches a maximum at a computational mesh grid node, coarse particles may be lofted by upwelling mud convective currents. Once maximum packing is reached at a grid point, we assume that the coarse particles become immobile and form part of the core bed. The remaining mud, consisting of water plus fines, can flow through the core bed. The permeability of each grid cell in the porous, permeable core bed depends on porosity and the size distribution of particles in each grid cell. The effective permeability keff = Π kiυi, where ki is the permeability of a layer having just the particle size i and υi, is the volume fraction of coarse particles occupied by particle size i, and the product is taken over the particle sizes present in each grid cell of the core. There are a number of relationships between porosity and particle size and permeability; here, permeability ki is taken from the data of Berg (41). Different soil types—sandy, silty, and clayey—are reflected in the particle size distributions for each type. The distribution of this study is a combination of sandy and silty types for coarse particles and silty-clayey for the fines.
Velocity components are computed from Eq. 4. For these simulations, the terms on the left side of Eq. 4 are very small and are dropped.
(6)where Rx is the fraction of olivine remaining, that is, the fraction of olivine (and pyroxene) that has not yet converted to serpentine.
Thermal conductivity and specific heat of rock are assumed to be constant. Thermodynamic properties of water (density, internal energy, enthalpy, viscosity, and specific heat) are functions of temperature and pressure and are interpolated from tables generated by the SUPCRT92 model (44).
(12)In the mantle and ice shell layers, Dc is enhanced by the same Ra number factor for the thermal diffusivity to reflect turbulent sub-gridscale mixing. A similar transport is applied for Xwm and Rx.
Boundary conditions. At the surface, P = C = 0, Tsrf = Tpolar + ΔT cos(θ); θ = 0 at equator. At the surface, P = 0, T = surface temperature, ∂C/∂r = 0, and ūm = 0 are required. At the mantle-core and mantle-crust interfaces, continuity of P, T, C, and ūm is required. At the center, ūm = 0, ∂P/∂r = 0, ∂T/∂r = 0, and ∂C/∂r = 0 are required.
Numerical algorithm. The numerical procedure consists, at each time step, of solving for pressure using an implicit numerical discretization; determining velocities, followed by updating mass, energy, and solute transport; and then using the equation of state to reconcile ice and salt (if any) and temperature variables. Time step size is computed after each time step and is controlled by the Courant restriction.
Particle transport. A new feature is the transport of particles. A distribution of coarse particle sizes having different settling velocities can be tracked [although the model allows us to track a range of chondrule/particle sizes, as noted above, if the body accretes a sorted population (the canonical assumption), Tpeak and Tavg are qualitatively similar, but no further sorting occurs]. For the unsorted simulations, particles are divided into coarse (five sizes from 1 mm down to 10 μm) and fine (<1 μm) classes. The Stokes settling velocity for each particle size is added to the fluid velocity to determine each particle's total velocity. Fine particles are assumed to remain suspended indefinitely; this assumption is justified for a duration of a few million years of the simulations analyzed. Water plus fines constitutes a mud.
(16)where Vs is the settling velocity (cm/s), d is the particle diameter (mm), ρp is the particle density, and ρf is the fluid density.
In our model, particle velocity Vp = Vs + um, where um is the mud velocity. At larger sizes (>0.25 mm), particle settling velocity deviates from the Stokes settling relationship. Rubey's curve provides accuracy in those cases (19, 20).
Settling rates of the sand-sized particles (1 mm down to 50 μm) range from about 2 km/year to about 25 m/year, respectively, in the smallest body considered, which are much faster than the rate at which the thaw front moves outward (~1 m/year). The settling rate for the silty-clayey component (10 μm and smaller) is in the range of 1 to 0.001 m/year, which is on the order of, or less than, the mud convective flow rates, certainly during the most intense phase of convection. The smallest particles can remain suspended for a very long time, especially if flow is occurring. Mud rapidly evolves into a mixture containing mostly the smaller particles.
(17)where ε0 and pscl are user-supplied. This relation roughly approximates data on changes in porosity seen in sandstones (45).
(18)where μw is the water viscosity (a function of temperature), c is the volume fraction of particles, and c.lim is the concentration at which the mixture locks up (c.lim = 0.75), following Roscoe (21). Shoji and Kurita (22) used an almost identical relationship. Zoporowski and Miller's (23) viscosities used for mud volcano flows lie in the range of what our model used. Data from the oil and gas exploration literature bracket Roscoe's curve (21). Fritz and Moore (24) and Grim (25) presented data on sand and clayey particle types. They found roughly one to two orders of magnitude difference between curves for the same concentration. The Roscoe curve (21), based on glass spheres, lies roughly midway between the sand and clay curves, about an order of magnitude removed from each. We used it as a compromise between pure sand muds and pure clay/silt muds. In our simulations, the highest initial value of c is 0.625. Flow rates and shear rates are very low, and shearing effects are therefore neglected. Viscosity can be affected by other factors not included explicitly in our viscosity model, such as the shape of particles and the particle size distribution; these can also affect the lock-up concentration [for example, see the studies of Delaney et al. (46) and Stickel and Powell (47)]. Once coarse particles reach the core region and the 50% packing density is reached, the core bed structure becomes immobile, and its viscosity is effectively infinite. However, the remaining mud phase (water plus fines) can flow through the core bed's pores, given sufficient driving force. In the larger bodies, settling rates are faster but convection is also stronger, so the picture remains qualitatively the same.
Core formation and evolution of mud. The core formation process is not instantaneous; it occurs gradually over a period of at least 3 × 104 years and as much as 105 years for some cases. As particles are released at the melting front and fall, their trajectories can be modified by the mud flow occurring around and below them. Mud does not have the same constitution everywhere; in some places, the particulate load is high, and in other areas, it is low, depending on settling history through each grid node.
Convection in the core. When the coarse particles settle into the core and reach their packing density, they are no longer considered part of the mud and cannot move; their effective viscosity is infinite. We then have an essentially two-phase domain. The locked-up coarse particles form a porous, permeable bed that grows in depth until the melt front has reached its limit near the surface. The mud in the pores of the core bed then consists of water plus the fine particles. This mud can still flow through the pores of the core bed, if there is sufficient driving force. The driving force is provided by the energy released during serpentinization and from decay of short-lived radioisotopes. The structure of the core itself, formed by the coarse particles, does not convect (although coarse particles on the topmost layer of the core may still be loftable, until buried by continued raining down of particles from the melt front). Convection through the pores of the core will depend on the permeability of the core bed, in part. Permeability of the core bed is determined from the coarse particle sizes present at each node in the core and the porosity at that point. The mud in the mantle layer consists of water plus fines plus coarse particles that have not yet reached the core region and locked up. Eventually, after the melt process has ended, the mantle mud will also consist essentially of just water plus fines. It can flow given sufficient driving force, but eventually, after several million years for the smaller bodies, the asteroid will freeze completely.
Clustering of particles in the core. There is a burst of convection when serpentinization occurs, very soon after thawing. This energy is being released and drives convection even as particles are flowing down, so there is an opportunity for the flow to change the trajectory of falling coarse particles, especially the smaller ones. Convection will strengthen as the thawed region expands (convection varies with the cube of the domain depth). Upwelling mud currents will entrain and push against the falling coarse particles to varying degrees, imparting to them a horizontal velocity component. As long as the coarse particles are free to move, their trajectories will tend to reflect the convective flow pattern. This results in the clustering of particles seen in the images in Fig. 1. After the serpentinization phase ends (short time frame), and short-lived radionuclides are mostly spent, convection diminishes and the clustering process ends. In Fig. 1, the clustering is most pronounced at slightly more than mid-depth in the core region. This corresponds to the time of maximal convection strength.
Crustal stability. The numerical simulations described in the main text produce density structures that include a frozen crust of variable thickness, generally 2 to 10 km in thickness, during the duration of a few million years of the simulations. The density structure generally shows that the mantle, if it develops, has a lower density than the crust. In that event, questions naturally arise as to the stability of the crust. Formisano et al. (48) recently analyzed the stability of the crust of Ceres for a variety of conditions. We do not believe that crustal stability is an issue in our study for the following several reasons: (i) Formisano et al. (48) considered long-term crustal stability for Ceres, after core formation and after short-lived radionuclides have decayed. We are concerned with early-time behavior, in the first few million years, when most particle sorting would likely occur. Even for a Ceres-sized case, they found that crustal stability holds for at least 100 My in all the cases they included. (ii) The mantle density in all cases that we have examined is greater than or equal to the 1440 kg/m3 used in the stability analysis of Formisano et al. (48), meaning that the density difference between crust and mantle would be no more than in their cases. (iii) In the smaller cases we consider, the crustal thickness diminishes for a short period of time to only 1 to 2 km, especially for the non–core-forming cases. During that time interval, flow would mix the near-surface environment. (iv) According to Formisano et al. (48), crustal stability holds as long as viscosity exceeds a critical viscosity value. For the smaller bodies that we are considering, the stability criterion will be weaker, because critical viscosity of Formisano et al. (48) varies directly with gravity. For our 50- and 100-km-sized bodies, the critical viscosity is roughly 10 and 5 times lower than that for Ceres, respectively, meaning it is more likely that these smaller bodies will have a stable crust. (v) Desiccation of the surface will reduce the density of the crust, further dampening the Rayleigh-Taylor instability mechanism. In 100 My, for example, a crust several kilometers in thickness could likely lose a significant amount of its H2O ice through sublimation and diffusion through the crust. (vi) In the Rayleigh-Taylor stability analysis, the basis for the Formisano et al. (48) analysis, perturbations grow at a rate that is proportional to exp(√g) so that, for the smaller bodies, the rate of growth of any crustal perturbation will be very much slower than that for a Ceres-sized body.
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Acknowledgments: Funding: This work was funded by the Australian Research Council via their Laureate Fellowship program. Author contributions: P.A.B. and B.J.T. contributed equally to this work. Competing interests: The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.