This mysterious space rock shouldn’t have a ring — but it does

Host: Nick Petrić Howe

Welcome back to the Nature Podcast. This week: a ring in space where there shouldn’t be one.

Host: Benjamin Thompson

And the hidden dangers of indoor air pollution. I’m Benjamin Thompson.

Host: Nick Petrić Howe

And I’m Nick Petrić Howe.

[Jingle]

Interviewer: Nick Petrić Howe

This week in Nature, there’s a paper about something very strange in the outer reaches of the Solar System – something that seems to defy our current understanding. Way up past Neptune in the Kuiper belt is a ball of rock about half the size of Pluto. Discovered in 2002, this object is known as Quaoar. There’s a lot researchers don’t know about it, so astronomer Bruno Morgado, from the Federal University of Rio de Janeiro, was trying to learn more.

Interviewee: Bruno Morgado

We are trying to get the physical parameters of this object, so we are trying to better understand this object. But something unexpected just appeared for us.

Interviewer: Nick Petrić Howe

With it being so small and far away, it’s quite hard to look at Quaoar directly, so Bruno has been observing it as it passes in front of stars. By measuring the dimming as it does so, he can get a sense of what the object is actually like. And back in 2021, he saw something quite unexpected.

Interviewee: Bruno Morgado

So, in fact, not only Quaoar itself passing in front of star, but something around Quaoar was existing there as well. And we were able to see that Quaoar, in fact, has a ring of material.

Interviewer: Nick Petrić Howe

But you might wonder why this is unexpected. After all, lots of things in the Solar System – Saturn, for example – have rings. But, well, Quaoar shouldn’t really have one like this.

Interviewee: Bruno Morgado

This ring should not be there. This ring should not exist.

Interviewer: Nick Petrić Howe

The reason for this is something known as the Roche limit, which essentially draws an imaginary line around an object in space. Inside this limit, there can be rings – no problem. But outside of this limit, the gravitational pull of the object isn’t strong enough to prevent the rings from coming together, so the chunks of rock, ice and dust that make them up are drawn to each other and should coalesce into moons or satellites, as astronomers often call them. But with Quaoar, its imaginary line is 1,780 kilometres from its centre. But its ring lies far, far outside that at 4,100 kilometres. So, really, that ring should be a moon.

Interviewee: Bruno Morgado

It's a very intriguing thing because we don't know exactly the physics of how this ring is there exactly. Why is it not a satellite? Why is it still a ring?

Interviewer: Nick Petrić Howe

So, what’s keeping this mysterious ring in place? Well, that’s a mystery on top of a mystery, but Bruno has come up with several ideas. For example, he may have just spotted the ring as it was becoming a moon.

Interviewee: Bruno Morgado

It is possible, but it's very unlikely because the timespan of this transformation from this to a moon is a few years. So, if you consider the history of the Solar System, it’s unlikely that we are in the exact moment in time to be able to see this evolution happening. And, of course, if this is true, this is also very interesting because we’ll be able to see first-hand the formation of a moon in a few years from now. But it’s also very unlikely.

Interviewer: Nick Petrić Howe

So, if it's unlikely to be a snapshot in the making of a moon, what else could it be? Well, Bruno's done some modelling which suggests that the ring could be maintained if the materials that make it up are a bit bouncier than they’re normally expected to be, which stops them coming together to become a moon. And this bounciness could be down to how cold it is all the way out around Quaoar. Alternatively, there are maybe other external forces at play. Keeping a ring spinning – keeping its velocity up – is important to prevent it from coalescing into a moon. Quaoar actually already had one moon that we know of –Weywot – and there may be others left to find. And this moon, or moons, could be interacting with the ring, stopping it from coalescing. Such things have been suggested before, like with Saturn’s F-ring – the outermost discrete ring – which is right at the Roche limit. At this point, moons can form, but the F-ring is still, well, a ring. So, some astronomers think this may be because the nearby moons are perturbing it, preventing it from becoming a moon itself.

Interviewee: Bruno Morgado

I think these are the main possibilities that we think right now. But we need a lot more studies to try to better understand this.

Interviewer: Nick Petrić Howe

But what will solving the mystery of how Quaoar’s ring came to be achieve? Well, there’s lots for researchers to learn about how rings and moons form throughout the Solar System and beyond. This isn’t the only example of where a ring is present beyond the Roche limit. Saturn has some dusty and sparse rings outside this limit. But Quaoar’s ring is dense and well outside the Roche limit where such a ring should exist. And with the JWST providing better images of our own Solar System, we may just spot more unexpected rings where they’re not supposed to be. So, this strange exception to the rule could help us understand more about how rings and moons form.

Interviewee: Bruno Morgado

This changes a lot of things. Because at the end of the day, this Roche limit is also used in the context of moon formation and planetary formations. So, if there's more to it, we need to use it in all the systems that we know. All the other objects in our Solar System may have rings as well outside the Roche limit, so this is also something very interesting.

Interviewer: Nick Petrić Howe

That was Bruno Morgado from the Federal University of Rio de Janeiro in Brazil. To find out more about Quaoar and its strange ring, you can check out the paper and a News and Views article in the show notes.

Host: Benjamin Thompson

Coming up, we’ll be hearing about the serious health impacts of indoor air pollution and why research into it has been lagging behind. Right now, though, it’s time for the Research Highlights, read by Dan Fox.

[Jingle]

Dan Fox

A repurposed skin disease medication has been found to suppress alcohol consumption in people who drink excessively. Apremilast is licenced in the US to treat the skin disease psoriasis. It works by inhibiting an enzyme linked to alcohol dependence, so researchers looked into repurposing the drug. The team injected apremilast into mice that were bred to drink heavily and noticed the rodents had lower alcohol levels and did not binge drink as much as animals receiving a placebo. They also observed that activity in the region of the brain involved in controlling alcohol intake increased in the mice that received the drug. In humans, adults who have alcohol-use disorder who took the drug daily had fewer drinks per day over an 11-day period than those who took a placebo. With further studies, the drug could be used more widely for the treatment of alcohol-use disorders. Read that research in full in the Journal of Clinical Investigation.

[Jingle]

Dan Fox

Four volcanic eruptions between 168 and 158 BC disrupted the River Nile so severely that the changes probably contributed to social unrest during Egypt's Ptolemaic dynasty. Researchers don't know where these eruptions took place, but they know they occurred because the volcanoes left chemical fingerprints in polar ice cores. So, the team behind this work estimated where the volcanoes might have erupted and used the climate model to simulate how they affected rainfall over the Nile river basin. Particles from the eruption spread high into the atmosphere reflecting sunlight back into space and cooling parts of the Earth's surface. Temperatures dropped by roughly 1.5 °C after the first eruption and the cooling effect from this and other eruptions lasted more than 15 years. In the headwaters region of the Nile, weather patterns shifted and monsoon rains became significantly lighter, with the Nile’s flow dropping by as much as 38% as a result. Environmental changes from the four eruptions might have fed internal turmoil, including an agricultural crisis, leading to the widespread revolts of the time. Read that research in Climate of the Past.

[Jingle]

Interviewer: Benjamin Thompson

Around the world, billions of people are exposed to polluted air, and it’s been linked to millions of deaths each year. Now, we’re familiar with many of the sources of it. I walk down several extremely busy roads every morning, where the cars are often sitting nose-to-tail, for example. But while there have been concerted efforts to reduce outdoor air pollution like this, there’s another type which has received far less attention, and that’s indoor air pollution. This week, Nature has a Comment article written by a group of researchers arguing that the pollution people are exposed to within buildings represents an important health issue, and that more research needs to be done to understand how it originates and accumulates, and what can be done to mitigate it in order to inform future public health initiatives. One of the Comment’s authors is Ally Lewis, from the National Centre for Atmospheric Science and the University of York here in the UK. I gave him a call to find out more, and he told me about the difficulties involved in defining indoor air pollution.

Interviewee: Ally Lewis

Well, this is one of the things that we tried to address in the article. And it's a very short thing to say – indoor air pollution – but it actually covers an incredibly broad range of different problem pollutants. And they come from obvious things like burning stuff, so if you have a stove in your home, or you cook, or you use solid fuel, that releases a lot of pollutants that look pretty similar to some of the ones that we see outside. But other things indoors can accumulate, things like carbon dioxide from our own respiration. And then there are unusual pollutants that are kind of concentrated indoors just because of the nature of where they're released, so things like volatile organic compounds that come from personal care or cleaning products, or radon that comes from the earth underneath our houses. So, they're sort of the chemical-type pollutants. And then the second class are biological pollutants, so these are things like spores that might emerge from damp and mould, or they might be respiratory viruses that we exhale. So, it's really diverse.

Interviewer: Benjamin Thompson

And I mean, I'm interested in what the scale of the problem is between indoor and outdoor pollution, I suppose. If we know that outdoor pollution causes potentially millions of deaths and heavy burden of disease, how does indoor pollution stack up, do you think?

Interviewee: Ally Lewis

If we look at a global scale, the World Health Organization, broadly speaking, attributes roughly the same number of deaths to inside as outside. It's sort of three-and-a-bit million to each of those. Now, a lot of that is associated with high indoor pollution in low- and middle-income countries – particularly the use of solid fuels for heating and cooking. But the effects spread all the way through to high-income countries as well. And very frequently now, we can find that some pollutants that we think a lot about outdoors are actually higher in homes, even in relatively wealthy countries.

Interviewer: Benjamin Thompson

And so, it potentially plays a role in millions of deaths. But despite the scale of the issue, in your Comment, you argue that scientists maybe know very little about it. Why is that?

Interviewee: Ally Lewis

Well, we do know quite a bit, but we're a long way behind in developing the science and the evidence base to help us take action. And typically, the priority for governments when they think about air pollution has been cleaning up outdoor air, so that's where most of the academic effort has gone. Thinking about indoors is something that's really only emerged in the last few decades. And so, we're trying to catch up on that.

Interviewer: Benjamin Thompson

And in your Comment, you lay out some of the things that need to be understood or considered when you're thinking about indoor air pollution. What are some of the key gaps in researchers’ knowledge that you think need to be addressed?

Interviewee: Ally Lewis

We need to really understand what are the most harmful components of that indoor pollution so that we can target our actions in the most effective places because with limited resources it's always most effective to try to target your efforts on the things that you think are causing the most damage. So, that's the starting point. But we also need to understand a little bit more about how pollutants actually accumulate and form and how they react indoors. So, the chemistry of indoors looks rather different to outdoors. There's less sunlight, for example. There are lots of unusual surfaces indoors that we don't really understand. Then we come to the real big problem, which is that indoors is so incredibly variable. Every home, every room, every business, every school is going to be slightly different. So, how do we provide good science-based advice to help get good indoor air quality when we've got such a wide range of different environments? So, the advice that we might provide in a high-income country in a cold climate could be very different to the advice that we might want to provide in a low- or a middle-income country in a really warm climate. So, there's a lot of stuff that we have to work on here.

Interviewer: Benjamin Thompson

And so, it's impossible to say that the way to alleviate it is as simple as opening a window and sticking a HEPA filter in the corner of each room then?

Interviewee: Ally Lewis

Well, this is one thing that I think we're trying to stress within the article is that there are some simple actions, but there's no single magic bullet. So, ventilation is a very straightforward intervention. But, of course, it also requires you to understand something about what the outdoor environment is like as well. So, on a wet, windy day, outdoor air pollution, particularly in Europe in the US, can be pretty good, so opening your window almost certainly improves the indoor air quality. But if you go to a very still, hot day in the middle of summer, opening your windows under those circumstances could well bring in large quantities of ozone, which is a photochemical pollutant produced through things like heat waves. So, it might not always be the most effective solution to open a window. And similarly, there are efforts, for example, to improve the monitoring of carbon dioxide within buildings, as a measure of how well respiration from people is being managed. Well, that might not tell you very much, for example, about whether that building has large emissions from chemicals in the fabric of the building. So, we're going to need to have a lot of different metrics to make sure that we capture this really broad range of effects indoors.

Interviewer: Benjamin Thompson

And in terms of public health, you mentioned respiratory diseases earlier. And of course, we're still living through a pandemic where ventilation was shown to be of key importance to respiratory health. Have you and your co-authors’ experiences of the past few years influenced your thoughts on air pollution, do you think?

Interviewee: Ally Lewis

Well, I think the last few years have really brought it home just how complicated the indoor environment is, and possibly that many of us that work on issues to do with indoor air have been, to a degree, siloed thinking about only our own definition of what good indoor air quality means. I sit within a chemistry department. I typically think of indoor pollutants as things from chemical processes. And I think what we've learned is that of course we're all dealing with the same problem but just with our own subset of problem materials, and there is a lot that we can then share, I think, between those to try to deal with the issue in a more holistic sense. And, say, it's slightly strange to talk about some of the issues associated with respiratory viruses as pollutants. But, in a way, that's how we will have to treat them if we want to manage them.

Interviewer: Benjamin Thompson

And one thing that comes across reading your article is that there's so many potential sources of indoor pollution and that trends are changing in some things. Smoking is going down in many cases, while the use of personal care products is increasing. Combining all of that with the potential variability between, on a small scale, rooms in an individual house, let alone between types of building. And obviously, construction materials here in the UK differ from in other parts of the world. And there's cultural differences in how indoor spaces are used, and all the rest of it. So, is there a risk that because things are so nuanced, Ally, it would be impossible to ultimately create any public health policies because it's all about context?

Interviewee: Ally Lewis

I think it's hard, but I don't think it's impossible. We've made great strides with outdoor air pollution by understanding how much is emitted from particular processes and particular activities. So, there's really good characterization, for example, for how much pollution comes out of a particular sort of diesel car driven for so many miles per year. We haven't really started to try to characterise those emissions indoors, but that is a thing that can be done. And from that, begin to establish what the major sources are, and therefore which ones would be the best ones to provide advice on.

Interviewer: Benjamin Thompson

And once you've got a handle on what the source of this pollution is and ways to maybe reduce it or mitigate it, what difference ultimately could this make sort of on a broad scale?

Interviewee: Ally Lewis

So, I think it could be very, very significant globally, and the range of effects are very broad. We still get, for example, tragic cases of deaths indoors from carbon monoxide poisoning or deaths from poisoning from butane and propane. They're the extreme cases that happen through acute effects. But at the population level, we have effects that accumulate over time, for example, issues associated with respiration or cardiovascular disease or cancer or even dementia.

Interviewer: Benjamin Thompson

In your Comment, you do mention that there are, of course, disparities in pollution levels. What can be done to ensure that any public health efforts to improve indoor air quality are equitable and can benefit the most amount of people?

Interviewee: Ally Lewis

So, air pollution globally has always been an unequally distributed problem. And so, poorer countries have significantly larger issues associated with air pollution impacts. But even if you look within a country, whether it's a poor one, a middle one or a rich one, you almost always find inequality in exposure – that the most deprived in those societies are exposed to more pollution. So, it's an issue that we have to tackle globally through targeting action, particularly at the removal of solid fuels in low-income countries. But we also need to think about how we will reduce those disparities even within, for example, high-income countries. And you've mentioned around changes to things like appliances, and this is where we consider that decarbonisation could play a really major role here. As we decarbonise buildings, it does give us the opportunity to remove some of those sources that release pollution, and not all of them are hugely expensive. For example, changing a gas hob for an electric hob is a relatively reasonable amount of expenditure that someone might have to undertake, but it would have a pretty substantial impact on their indoor air quality. So, I think it's important to remember that not all of these interventions that we might need to do in people's homes are necessarily ripping out the heating system. There may be things that are a bit more affordable that could be recommended as well.

Interviewer: Benjamin Thompson

That was Ally Lewis from the National Centre for Atmospheric Science and the University of York. To read his co-authored Comment, look out for a link in the show notes.

[Jingle]

Host: Benjamin Thompson

Finally on the show, it’s time for the Briefing chat, where we chat about a couple of articles that have been featured in the Nature Briefing. And this week, I am joined by none other than Flora Graham, senior editor of the Nature Briefing. Flora, thank you so much for joining me today.

Flora Graham

Thank you so much for having me.

Host: Benjamin Thompson

So, a couple of stories that we’re going to talk about then, Flora. Let’s start with this one, and I will say, for listeners at home, you messaged me on Friday saying, ‘We need to talk about a new sort of ice.’

Flora Graham

That’s right. This is the kind of story that I have to call everyone I know. This is the one at the dinner table. I said, ‘Guys, I can’t even wait until you read the Briefing. You need to hear this. There’s a new kind of ice discovered.’

Host: Benjamin Thompson

Well, okay, let’s get into it then. This was reported on in Nature and based on a paper in Science. And specifically, it’s talking about medium-density amorphous ice, which is, well, I mean, it seems like quite a descriptive name, but can you tell me more about it?

Flora Graham

Well, I have to be honest. Before I read this paper, I was not aware that there are 20 different kinds of ice already known – a little more than 20 actually – and they have different structures. The vast majority of them are crystalline, so the kind of ice that you or I might be familiar with in a cocktail, say, made up of a hexagonal structure. There’s also already known two types of ice that don’t have this ordered structure, and they’re known as amorphous ice. Now, they don’t tend to exist on Earth. It’s something that’s more plentiful in space. Like comets, for example, are made up mostly of amorphous ice. But what this new type of amorphous ice is it’s not much lower density than water, it’s not much higher density than water. It seems to actually be about the same density as water. And this is really exciting because there’s the potential for this ice to actually possibly have some of the same properties as water. And water, although being everywhere in part of our daily lives and part of who we are, is actually really mysterious and has a lot of weird features.

Host: Benjamin Thompson

So, it’s more than low density, amorphous, it’s less than high density. It’s that sort of Goldilocks spot in between. And I think we need to talk about how the researchers behind this work made it because it seems like some sort of super high-tech physics going on, but maybe that’s not the case.

Flora Graham

Well, that’s why I had cocktails on my mind because basically what they did was put this in a cocktail shaker. It’s a special metal container made up of steel balls, they popped them in some ice, they shook it all around, and what they believe is that the steel balls kind of smashed and crashed and disrupted the molecular structure of the ice, and what they ended up with was this white kind of granular powder on the metal balls, and this is the medium-density amorphous ice. Now, it remains to be seen all of the properties that this stuff is actually going to have, but just finding it for the first time and seeing it for the first time is exciting enough.

Host: Benjamin Thompson

And so, we’ve gone then from this sort of rigid hexagonal structure, which is the ice that I think about, that I learnt about at school then, to this kind of structure that has no obvious pattern. Is it actually like liquid water but also ice at the same time?

Flora Graham

I mean, that’s the kind of tantalising possibility. This might be a form of ice that maybe reflects in a solid state the kind of interesting and unusual properties that water has. Now, I should add that when this ice was produced, it was at extremely low temperatures. This is around -200 °C. So, when we’re thinking about where this ice might actually form naturally, we’re thinking about maybe like the icy moons of Jupiter where we might want to know how this ice might behave under the kind of shears of gravitational forces and how that might actually affect how these icy moons evolve and change.

Host: Benjamin Thompson

Cool, so we’ve got this new type of ice then. What have the researchers said about this?

Flora Graham

Well, one way that this ice is really interestingly linked to water is, I mean, you may have already known there’s 24 different kinds of ice, but did you know there’s 2 different kinds of water? So, scientists actually think that water is made up of two different kind of forms of water, which are low density and high density kind of mixed together. It’s not like there’s half a glass of low- and then half a glass of high-density water sitting on top of it. This kind of matched up very well with the idea that, okay, there’s high-density amorphous ice and there’s low-density amorphous ice. Now, the discovery of a medium-density amorphous ice could challenge this understanding of liquid water. It would imply that this model of high-density and low-density water mixed together is incorrect and scientists say it could actually open up a whole new chapter in research into ice and water.

Host: Benjamin Thompson

Well, a super interesting one there, Flora. But let’s move on to our second topic to chat about today. And you’ve talked about one sort of essential liquid to life, there, of course – water. Let’s talk about a second one, and that is coffee.

Flora Graham

Absolutely, I mean, I’m drinking a coffee right now. Let’s be honest, coffee kind of powers Nature as it does many other workplaces, and we were very interested to see that food scientist Emma Beckett has bought together some of the current research into coffee and the news is that coffee might make you feel perky and alert but you are just borrowing, and you are going to have to pay the piper, and you will actually feel more tired later, and that’s because of the way caffeine actually functions in the brain.

Host: Benjamin Thompson

Sigh, I knew it. But let’s talk about it then, Flora. So, this is an article in The Conversation then. So, let’s talk about how the books need to be balanced then. What’s going on with caffeine then, the main stimulant in coffee, of course.

Flora Graham

Well, the main way caffeine works is it blocks a receptor in the brain. So, there is a compound called adenosine, which kind of lets our cells know that we’re getting tired. It builds up and it binds to these receptors, and our cells slow down and it is sleepy time. Now, caffeine doesn’t perform the same job as this compound, but what it does is it blocks that receptor and binds to that receptor instead. So, you think, okay, I’m not tired. This is great. But meanwhile, especially if it’s already late in the day, you’ve got a certain level of adenosine building up in your body, and so when the caffeine eventually degrades, depending on the person, maybe around five hours later, that’s when the crash comes. Now, the best way to recover from that is, no surprise, get a good night’s sleep. There’s no shortcut to that.

Host: Benjamin Thompson

And I think in the article, yes, it does say that different people metabolise at different rates. I used to work with a guy who couldn’t go to bed unless he had a double espresso, which I thought was wild. But for me, I’d be bouncing of the walls until 5 o’clock in the morning.

Flora Graham

Wow, and that could be because the more you drink coffee, the more that system of binding to the receptor, you get kind of inured to it, so your body will adapt and try to get back into the balance of the system of tiredness. So, there are those people who can have a double espresso after dinner. For me, absolutely no caffeine after 3pm.

Host: Benjamin Thompson

It’s not necessarily just adenosine then. There are other factors at play as well.

Flora Graham

It’s interesting, of course, to note that coffee is not the only source of caffeine. So, you might be getting your caffeine from energy drinks or tea or other beverages. And all of those can have different compounds that are in there as well as caffeine. So, they can have additional stimulant effects depending on what you’re drinking. Or they can interact with the caffeine to change its impacts slightly. So, each caffeinated beverage kind of has its own profile of how it affects you. And there’s more to the effect of caffeine in your body than just adenosine. It can also raise levels of cortisol, which is a stress hormone. It can make you feel more alert. Apparently, for some people, this means that caffeine feels more effective later in the morning because you already do have a natural rise in cortisol as you wake up. And also, there’s less adenosine built up in your body, so when you first wake up and you have a coffee, maybe you don’t feel the same kind of jolt. Whereas later in the afternoon, maybe you have a bit of sugar, which ramps up the energy level in your body, and also can ramp up that feeling of a crash later on.

Host: Benjamin Thompson

I mean, it seems like caffeine is maybe not the wonder drug that we thought it was, and yet I’m not sure I’m ready to give it up just yet, Flora.

Flora Graham

There’s another great article in The Conversation this month about the carbon impact of coffee, and we all know that it’s got quite high impact. So, it can be a little bit tough of your body and it can be a little bit tough of the environment, so make sure that you use it when you really need it, I guess, which is for me, right now, as I record this podcast.

Host: Benjamin Thompson

Wonderful, well, let’s leave it there then, Flora. Thank you so much for joining me on this week’s Briefing Chat. But before you go, maybe you could tell our listeners where they could get more stories like this but delivered, let’s say, in email form directly to their inbox.

Flora Graham

That’s right. If you go to nature.com/briefing and sign up for our newsletter, I will email stories like this, and others, straight to your inbox.

Host: Benjamin Thompson

Flora Graham there. And head over to the show notes where you can find links to the stories we chatted about today.

Host: Nick Petrić Howe

That’s all this week. Don’t forget that you can keep in touch with us on Twitter. We’re @NaturePodcast. Or you can send an email to podcast@nature.com. I’m Nick Petrić Howe.

Host: Benjamin Thompson

And I’m Benjamin Thompson. Thanks for listening.