What if Earth is a Really Atypical Abode for Life?

Recent space missions have raised some interesting ideas about exobiology for me. The Galileo and Cassini results on Europa and Enceladus, respectively have revealed evidence for liquid water oceans under their surface ice, providing a remarkably clement environment for life to originate and evolve, perhaps. And exoplanet surveys have found a lot of terrestrial worlds larger than the Earth that may well possess habitable atmospheres, while smaller worlds might have such thin atmospheres that they couldn’t very well have life on them.

It raises an interesting speculative thought for me: what if there really is something very odd about the Earth?

Near Side of the Moon

Near Side of the Moon (a rendered CG Moon from our “Lunatics!” project).

Astronomically, the Earth has one really weird feature, which is our large Moon. This was created by a bizarre collision during the Earth’s formation. And it has probably influenced the evolution of the Earth, through tidal effects. Planets with such large and influential moons are probably very rare.

Some people have suggested that the reason the modern Earth has as thin an atmosphere as it does is because of the Moon.

Sometimes this theory is used to suggest that the Earth is the only (or one of the VERY few) worlds to produce life. Maybe that’s the “great filter”, they argue (that explains “Fermi’s Paradox” — or “why hasn’t anyone visited us already?”).

But what if it turns out that most worlds with life fall into a few categories of worlds very different from the Earth?

For example:

  • Earth-size to Super-Earth-size worlds with THICK atmospheres and heavy cloud decks, large greenhouse effect — but further from the star, so that the effect balances out.
  • Ice-ball moons like Europa and Enceladus where tidal heating maintains a clement liquid ocean under the ice.

We know the latter kind of world must be very common, just from the fact that there’s more than one in our own star system. The former sounds a bit like some of the worlds that have shown up in the Kepler survey.

Both kinds of worlds have interesting problems for development of spaceflight, let alone interstellar flight or even communications.

The heavy gravity of super-earths makes developing launch vehicles (a task we barely succeeded at) very VERY hard.

For the moon-ocean-dwellers, the problem is that they have to get through the ice to reach space.

Woodcut from Flammarion's "The Atmosphere" / PD

Perhaps this image of a solid sky (adapted from an illustration in Camille Flammarion’s “The Atmosphere”) is more literal for species on other worlds? How would that change us?

But more importantly, neither of these worlds even allow their inhabitants to SEE space.

For thousands of years, humans believed the world was flat and even when they became convinced it was round, they believed it was the whole universe, with the sky some kind of dome or sphere attached to it (and very close).

It was the behavior of the stars and planets in the sky (and the Moon) that clued ancient humans in that something more interesting was going on and that the universe was a lot bigger than they had imagined.

Basically, we had the cheatbook staring us right in the face.

That gave us the ambition. And eventually we developed the technology to follow it.

Even there, though, the universe was very kind to us — providing us with a very tantalizing target in the Moon. And beyond that, Mars is a beckoning, earthlike world, compared to most of the worlds we know.

Biologically, also — we are adapted to live in a thin atmosphere. We have senses that don’t depend on the presence of air and use light, which travels just fine through a vacuum. The ocean-dwellers might well be echo-locators, since they presumably live in a very dark ocean. Even if they were to get through the ice and emerge into the vacuum on the other side, what would they make of it? They couldn’t naturally see the stars — and what would give them the idea to build instruments to see them?

What would give them the idea that the universe had anything to offer above the ice sheet (except a quick death)?

Imagine that someday humans make contact with such species. What would they think of us? We’d seem like being peculiarly-blessed with an affinity for life in space — adapted to a thin light air supply, able to withstand both strong gee forces and microgravity, with senses capable of perceiving other star systems and worlds at EXTREME distances, ranging from millions of kilometers to light years.

We’d seem like creatures bizarrely adapted for life in space.

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Nearest Star Has a Potentially Habitable Planet!

The “Pale Red Dot” campaign at ESO has just announced a discovery that is truly extraordinary!  This would have been my dream discovery as an astronomer! I feel really lucky (and a little giddy) to have gone from simply wondering if there really were planets around other stars to finding this in my lifetime! I hope we will find out more about it in the years to come, and that someday our descendants will get to see it up close.

Proxima Centauri

The Pale Red Dot campaign was set up to search for possible planets around the nearest star, Proxima Centauri (a.k.a. Alpha Centauri C). (Image Credit: ESO / CC By 4.0).

They report three rather stunning things which, together, make for a highly coincidental and lucky find for us:
  1. This is the nearest star to our solar system, meaning the easiest for us to reach with an interstellar spaceprobe. It could be done with technology that would take only a decade or so to develop in about a 50-100 year flight. Actually, it’s a perfect target for something like the “100 Year Starship” project, currently led by Mae Jemison‘s Foundation which was set up to explore the problem of maintaining a support organization for such long-term projects and develop the necessary technologies.
  2. The planet is about 1.3 Earth masses in size (actually it could be a bit more, because this is a radial velocity measurement without a confirmed inclination angle, but it’s unlikely to be more than twice that mass). Based on our understanding of planetary science, that almost certainly makes it a terrestrial planet, and one which would easily be able to hold onto a thick atmosphere. It might also have a significant magnetosphere, though that’s a much more complicated issue to work out (a slow rotation rate might argue against that).
  3. The planet lies within the habitability zone, meaning that liquid water could exist in significant quantities on its surface — it could have oceans, for example.
Proxima Centauri is a very small star — an M-class red dwarf. So it’s really more like the size of Jupiter than the Sun (although quite a bit heavier), and it’s dim and reddish (although not as deep-red as sometimes depicted in illustrations — they often exaggerate the color). The habitability zone of such a star is very small — this planet orbits much closer than Mercury around our Sun, with a period of only 11.2 days.
Perhaps surprisingly, it’s actually on the cold side of the band.
Because the orbit is small compared to the diameters of both the star and the planet, the planet is likely to have become tidally-locked (like our Moon is around the Earth, so that the face of the Moon we see does not change). A second possibility is that it has settled into a 3:2 resonance, the way Mercury rotates in our solar system.
Bear in mind that these are all “model-based projections”. All we really know is orbit and mass information. But we know the properties of the star and we can extrapolate from what we know about terrestrial planets in our solar system (meaning Mercury, Venus, Earth, and Mars). Moons may be nearly as relevant, since such small orbits resemble the orbits of moons around the large gas-giant planets in their dimensions.
The Earth is, however, the largest terrestrial planet we have been able to study up close.
If we make some assumptions — namely that the planet has an atmosphere just like Earth’s and the surface is an ocean (not a bad approximation for the Earth, which is about 70% ocean), then we can project a map of what the surface temperature would be like. The researchers did this with an existing climate model developed for Earth, running two separate simulations — one with the 1:1 rotation/orbit assumption (“tidally locked” like the Moon) and the 3:2 rotation/orbit assumption (“3:2 resonance” like Mercury).
Under either of these assumptions, more than half of the planet would persist at temperatures between -15 C and +30 C, well within the range of active ecosystems on Earth. Unlike Earth, the temperature would not change much over time. The weather would be very stable, with conditions more dependent on geography than time — life forms might migrate inwards or outwards to find habitats more suited for them (or to escape predators that couldn’t stand the conditions).
About the only “weather” I would expect would be due to flare activity from Proxima, which would probably cause some atmospheric disturbances by extra heating and X-radiation.
The tidally-locked case is actually the more habitable case, with the “hot pole” hovering at +30 C, and the freeze-line lying most of the way to the terminator. The coldest point in this model is around -75 C, which is pretty cold, but not colder than the coldest record temperatures on Earth (parts of Antarctica can get below -80 C occasionally).
Video turn-around of the tidally-locked model:


In the 3:2 model, the warm region is just above freezing, but covers a large equatorial band.

Video turn-around of the 3:2 model:


Of course, the atmosphere is likely different than Earth’s, and that expands the range of possibilities considerably. For example, a thicker atmosphere might both warm the planet by additional greenhouse warming and distribute the heat more evenly. A surface not covered by oceans would, on the other hand, probably show more temperature extremes.

It is easy to imagine this place having evolved life forms. In fact, it’s kind of hard not to. 😉

From an exo-biological perspective, the worst property of this planet is that it probably gets bathed in quite a bit of X-ray emission from Proxima, which is an active flare star. Any life to evolve in such an environment, would have to have very high natural resistance to them.

Of course, there are all kinds of caveats. We know absolutely zip about this planet from direct observation. We only have “M sin i” (meaning the minimum mass it can have) and orbital parameters (except for i — the inclination). This is the usual case with radial velocity discoveries of extrasolar planets, unless you just happen to be lucky enough to catch a planet that is aligned so that it passes in front of the star (in which case, i is pretty nearly 90 degrees).  In this case we know it doesn’t, so i is a bit less than 90 degrees. It could be a more massive planet seen practically pole-on, but that’s just very unlikely geometrically. There are also some indirect indicators that favor a high inclination — a second detected planet apparently does transit the star, which puts its inclination near 90 degrees. We think planets in a planetary system will tend to lie in the same plane as they do in our solar system, so it’s likely that this planet is not anywhere near pole-on.We only presume from the mass that the planet is terrestrial. We’ve never seen a gas-giant (or “ice-giant” as some people call Uranus and Neptune) which is this light, but then we haven’t seen many planets directly. Direct observations of extrasolar planets are extraordinarily hard, not only because they are dim, but because they are right next to the much brighter light source of the star. It may be quite some time before we hear about any direct observations, although for such observations, the distance is really important, and this is the absolute closest star system to our own (On the other hand, the orbit is also very close, which makes it harder).

ESO has also published an interview with the Pale Red Dot project scientists, Pedro Amado, Guillem Anglada-Escudé and Ansgar Reiners:



THIS is a reason to build a starship! I know I want a closer look!



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Review: Zardoz

I have been seeing stills and even a few clips from “Zardoz” since way back in the 1980s, with the general impression that it was a cheesy B-grade sci-fi movie. And while I appreciate that Sean Connery in a red thong is probably a plus for a significant part of the audience, it’s not doing much for me. So I put off watching this one for quite a few years.

However, “Zardoz” was a much better movie than I expected. Now I’m somewhat disappointed I hadn’t seen it years ago. Interesting philosophical and social issues. Also not a bad SF presentation of things that are starting to happen now, such as this collective mind we call the “Internet”.

I was expecting something much more simplistic, but this was pretty serious art.

Of course, there is plenty to laugh at, if that’s what you’re in it for — the costumes and effects are cheesy, and some of the sexual themes will no doubt inspire some giggles. But since the film is ultimately about sex and death, the link between them, and the problems that removing them would create, they really are necessary to the story.

It is visually challenging, frequently surrealistic, and occasionally stagey. It also requires the audience to do some thinking to keep up with what is going on, as actions are not always explained, even though I never felt lost, so I wouldn’t describe it as incoherent.

In fact, I’m somewhat reminded of the level of the better original “Star Trek” episodes, or perhaps Doctor Who — the demise of a questionable utopia, although neither series would be able to deal head-on with the adult themes this film does, due to broadcast restrictions and propriety (you could probably skirt around these issues with a less explicit version, but it would be a weaker film for it).

Pretty trippy stuff. I recommend it if you, like me, have been overlooking this film because of its reputation. Not for younger viewers, I think — as much for the “death wish” theme as much as the sexuality (which while occasionally explicit, is neither particularly erotic nor prurient).

Zardoz on IMDB

Zardoz Poster

Zardoz Poster (IMDB)

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Living with Risk

One of the most messed-up things in modern American culture is that we don’t cope well with risk — or at least the knowledge of risk.
The risk of terrorism, police violence, crime, car accidents, and falling into a pit with an animal that can kill you (the most recent shocking terror as I write this, apparently). These are all real things that CAN happen to you or your kids. And you can’t do anything that will eliminate that risk entirely.
In a country of over 300,000,000 people, there are going to be very weird accidents and crimes in the news. And that’s scary, because you feel like it’s more real when you can see it happening. But it was always a real risk. And it is still a very small risk.
You have to learn to accept that risk is just part of life. We’re all going to die sooner or later. And some of us are going to die sooner. What’s more, we really can’t predict it.
It’s one thing to take rational precautions to reduce risk. It’s quite another to fall into a neurotic heap because you can’t cope with the knowledge of all the million-to-one risks that, while so rare you might as well ignore them, are nevertheless real. And it’s more bizarre still to self-righteously blame the people who had the misfortune to have their number come up in the Really Bad Things lottery.
People have these weird ideas that society is more dangerous today than it was in the past. Statistics, though, tell a completely different story. Crime and violent crime rates are lower than they have been since we started recording the statistics. The world is full of carefully-engineered safety devices, and car accidents kill a smaller fraction of the people involved in them, because cars have gotten safer (because engineers have put a lot of hard work into making them safer).
You are safer today leaving your front door unlocked than you would have been 60 years ago when a lot of people felt safe to do so. But the thing is, they felt safe because they lived in a tiny little world, with only the most abstract knowledge of faraway places. So in their little world, there weren’t a lot of reports of crime. Even in the 1970s, when I grew up, the news rarely reported any crime outside of my city. It was pretty rare to hear about crimes in other states, let alone other countries. So my information world had a MUCH smaller population. Now I get information from perhaps 100X as many people, and so naturally, I hear about 100X less-likely things happening.
It’s not the world going to hell in a handbasket. It’s just math.

Urban caver standing in storm tunnel junction.

Living with Risk: An urban caver, exploring a section of underground storm tunnel. (CC By 3 / DarkDay@Flickr).

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Pluto’s Place in the Solar System

When New Horizons​ launched, its mission in the public imagination was to complete the set of the nine planets. No doubt this helped the mission get funded, and I respect that.

Nine Planets with Pluto

“Nine Planets” Collection with new image of Pluto, created by Ben Gross ( bhgross144@twitter ).

By the time it arrived, though, we had accumulated enough evidence to establish that Pluto is not best thought of as one of the “major planets” of our star system. We now think there are only 8 of those, or as I prefer to think of them, 4 “terrestrial planets” and 4 “gas giant planets” (with their accompanying moon-systems, containing more than a dozen major worlds among them):

Solar System Worlds

Worlds of the solar system to same scale, dominated by four gas giant planets, but also showing the four terrestrial planets and many of the larger moons. I think this picture also shows adequately why I think it’s a little silly to lump the “terrestrial planets” (Mercury, Venus, Earth, and Mars) with the “gas giant planets” (Jupiter, Saturn, Uranus, and Neptune) — they are entirely different types of objects!

Now, Pluto is better seen as the first Kuiper Belt Object to be explored. And thus it is the beginning of a whole NEW set of objects in our solar system. There are a lot of small worlds out there in the space beyond Neptune. The Kuiper Belt is like a second, icier asteroid belt around our Sun. And there are scattered worlds beyond those (collectively called “Trans-Neptunian Objects”, which include Kuiper Belt Objects, Scattered Kuiper Belt Objects, and more — we’re just beginning to learn about this part of the solar system, because we’re only now getting sensitive enough telescopes to see these objects).

8 TNOs

The eight largest Trans-Neptunian Objects in the solar system, including Pluto, Eris, and Sedna. ( Credit: Lexicon@Wikipedia / CC By-SA )

Eris is almost exactly the same diameter as Pluto and quite a bit heavier. It is currently about three-times further from the Sun, though in the middle of the 23rd century it will swing back to a distance similar to Pluto’s in its 558 year orbit.

Eris and Dysnomia

Eris and its moon, Dysnomia seen in a Hubble Space Telescope image from Earth orbit.


Orbit of Eris

Eris is currently just past its 1977 aphelion (furthest point from the Sun), and thus is about 95 AU from the Sun. Its next perihelion (closest point) is in about 2256.

The highly elliptical orbit of Sedna

Sedna’s orbit carries it far out into the dark on an orbit with a period of more than 11,000 years, which takes it out to nearly 1000 AU.

Sedna is currently just a little bit closer, and will be making its closest approach late in this century — only to swing back out into the dark for over 11,000 years, in a ellipse that carries it nearly to 1000 AU, where it spends most of its time.

Artist's Concept of Sedna

For now, Sedna is only a tiny blip in our best telescopic images, so we have to imagine what it might look like.

There may be other worlds out there. Some may even be larger than these. Certainly there are many smaller ones.

There will always be more to explore.

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What might it mean if Pluto is geologically active?

This week, we saw this on Pluto:

Pluto Mountains

First close-up surface image of Pluto.

This surface has no yet-identified impact craters in it. Instead, there are very tall mountains of unknown geology, some weird puffy deposits near the limb, obscuring underlying geology, a rille I cannot explain, except maybe it’s a fault or an escarpment. Some isolated mountains with what might be calderas in them, and a bunch of smooth terrain. All of that is evidence for active geology on a world which according to (prior) conventional planetological wisdom, just shouldn’t be able to do that.

What does it mean if Pluto has active geology driven by a subsurface mantle/ocean? Why is that so exciting? There are many reasons, but let me explain why it gives me a chill.

Caution: the following is wild speculation, not any kind of solid science!

In bioastronomical terms, it might be a bombshell.

Sometime back, we realized that, underneath the ice, Europa may have an ocean very much like Earth’s oceans. It may even have a geothermal power source in terms of subsurface vents that might have replaced the energy from sunlight as a means of bringing about the origin and evolution of life.

There may be fishes in that sea.

Since then, we’ve looked at other icier worlds, like Enceladus, and… WOW: we see similar stuff! Enceladus probably has a sub-surface ocean, too, even though it is much smaller and lighter than Europa. Whether it has the other chemistry needed to support life is unknown, but it may — such bodies generally are expected to have silicate cores and impurities throughout the water ice. They also have even larger inventories of basic organic compounds than does the Earth (as a fraction, I mean — they’re smaller worlds).

Several of the icy moons in the outer solar system probably have a water mantle or “ocean” like this at some depth — although some will be a lot deeper.

It is possible not only that these places are abodes for life, but that they may be the primary abode of life forms in the universe, and that “Earth-like” planets are more of an exceptional case. (Because icy little worlds like Enceladus are probably a lot more common than “Earths”).

Until recently, we thought we understood where the energy to power these geologically-active icy moons came from — we thought it was tidal forces from the giant planets they orbit.

However… remember (the largest belt asteroid) Ceres, with the bright spots that are probably new surface deposits of either water or salt? Well, Ceres doesn’t have a giant planet warping it with tidal stress either, so some kind of power source is driving that.

And something like Ceres lives inside of icy worlds like Enceladus or Triton, or Pluto. Because they generally have some silicate core deep under the icy mantle and crust. If whatever drives the activity on Ceres is driving activity in the core of Pluto, then it could be melting the ice above it and creating a water ocean/mantle on Pluto, like the ones we theorize are inside of the icy moons of Saturn or inside Triton.

Pluto gets very little sunlight.

If it’s got that kind of power, it’s not coming from the Sun, and that means that if it can happen at Pluto, it can happen at Eris or Sedna or in large objects in the Oort cloud — or even drifting through interstellar space.  (And remember also — Eris is much denser than Pluto. It may have a larger and thus more powerful core).

Data from Kepler suggest that there is quite a large population of rogue planets in the galaxy, even of large jovian-sized planets. Presumably little icy planetoids would be even more common.

There is probably a HUGE population of tiny little icy worlds in the universe, in a wide variety of different sizes, densities, and dynamical environments.

So, it’s possible that there are little icy, enclosed life incubators strewn throughout the galaxy. That might raise the possible locations for life to originate by a couple of orders of magnitude!

Of course, we might question whether such life would ever manage to escape its tightly-enclosed, hermetically-sealed universe into the larger universe outside? Would they ever even wonder what is above the solid icy dome of “heaven” through which no night sky can be seen? Who knows? It’s probably not impossible anymore than spaceflight is impossible for us, though it may take them a long time to discover it.

Final caveat:

This is big, long line of speculation with lots of ifs. It’s a bit like Sagan’s “Observation: I can’t see a thing. Conclusion: Dinosaurs” regarding Venus. So keep that grain (or bucket) of salt at hand.

It’s not worthy of being called a “theory”. Maybe a “hypothesis” or as I call it “wild speculation”.

Because of that, working scientists are very hesitant to come out and say stuff like this. It’s too wild, and with the low-quality of science journalism, “it might lead us to wildly speculate” is likely to be shortened to “scientists say…” removing all nuance and doubt, which could make us all feel very foolish someday.

But if you’re pondering why scientists get excited about this kind of information — this is one reason why. It could be shattering to our view of how the universe (and life in it) works.  And I just wanted to connect those dots for you.

How to answer the question?

Someday, I hope we’ll have solid evidence one way or the other. Lander or subsurface missions to Europa or Enceladus might tell us a lot more. A flyby of Eris or even Sedna might show us an active surface there, too, and that would be even more stunning (we also see some geological activity on Charon, which is even smaller than Sedna!). Perhaps Dawn will be able to tell us what’s going on with Ceres, and give us a good theory for how the power is generated (there are some theories, ranging from latent heat storage mechanisms, to radioisotope heating, to very slow geochemical processes that might generate heat).

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Three Kinds of Poverty

I’ve seen a number of nonsensical conflations of different poverty issues go by in various social media feeds today. I think a major problem is that people seem to think that poverty is just one issue — and they keep fighting over what that issue is. But it’s not one issue.

As I see it, there are three distinct issues with respect to “poverty”:

(1) There are still parts of the world with what the UN calls “extreme poverty”, which means people are literally on the verge of starving to death or dying from easily treatable diseases. This has to do with people’s basic physical needs being met.

(2) There is “first-world poverty” which is the waste of human potential that occurs when people who would otherwise live productive and meaningful lives are forced to live below the poverty line by poor labor policies, low wages, unemployment, and high costs of health care, housing, and other necessities. This has to do with what we as a society are comfortable with allowing as the minimum to show a decent respect for human beings.

(3) There is “inequality”, where wealth is so highly concentrated in the upper 0.01% of the population that something like half the population is barely getting by and thus a great deal of potential is wasted that could otherwise be developed, while those at the top essentially sit on the cash and do little with it of value. This has to do with the way that wealth is distributed, and the relative income and net-worth gaps between lower, middle, and upper classes.

Each has different kinds of urgency, different impact, and calls for different kinds of solutions. Conflating any of these with the others only muddles the issue, and is done to promote political agendas of denial and fatalism — particularly the do-nothing agenda that is based on the idea that these problems are unavoidable and should be blamed primarily on the people who are experiencing them.

Globally, #1 is the most critical, but it’s hardly an issue at all within the bounds of the USA, and thus within the area over which we have administrative control. Thus, for the most part, although it’s an important problem to address in foreign policy, it isn’t really our responsibility to solve it. In doing so, we would often be interfering with the principles of self-determination and national sovereignty in foreign countries. Therefore, there is not a lot we can do about it — and that is why the do-nothings want to dismiss the other kinds of poverty and focus on this.

Problem #2 is a serious problem for the well-being of citizens of the USA, and is the proper concern of domestic policy at federal, state, and local levels. It is a root cause of crime, drug abuse, domestic violence, and many other social ills that conservatives claim to be concerned about stopping — and yet they consistently avoid addressing this number one root cause of those problems, preferring instead to blame it on some vague and generalized “decline in moral fiber” of the poor themselves. Worst of all, many of the people in this situation are either already working full time, or are trying very hard to get work or retrain for new work — exactly what the critics claim they wish would happen.

Problem #3 is primarily an ECONOMIC issue, and represents an enormous inefficiency for our nation as a whole. It’s not primarily about basic human rights, because it’s not about some minimum that people need — it’s about the relative distribution of resources. But it IS about the ethic of maximizing the potential of individuals. And it is an issue of great concern if you think that a thriving, healthy economy is worthwhile. Because when people have more disposable income, they spend it on things, they become customers. And customers is what businesses need to make jobs. Most jobs don’t come from big multi-national corporations, they come from small local businesses serving the interests of customers in their community. And that only happens if those customers have some money to spend.

We need to recognize that these issues are distinct. It is not constructive to dismiss first-world poverty as unimportant, simply because more severe poverty exists in the world. The first duty of a government is to its own citizens.

Likewise, inequality is not something to be solved primarily out of concern for the poor, but rather for the health of the entire society. It’s about lost opportunity. Resolving issues of inequality is a way to make the economy as a whole more robust and ultimately more productive. Greater equality will not only make the pie more reasonably distributed, but it will also make the pie bigger.

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