Every space story worth its salt eventually reaches for lightspeed, the moment the engines catch and the stars streak. It is one of the oldest dreams in science fiction, so it is worth saying plainly what the physics actually allows, and what it flatly does not.

The blunt answer is that travelling at the speed of light is not merely difficult for anything with mass. It is impossible, and not in a way that a better engine will one day fix.

I am a writer with a long interest in this material, not a physicist, so treat this as a careful reading of settled science and clearly labelled speculation, kept apart.

Why light speed is a wall, not a target

The problem is built into relativity. The faster you push an object, the more energy each additional increment of speed demands, and the returns shrink as you approach the speed of light. To actually reach it, the energy required rises without limit. You would need an infinite amount, which is another way of saying it cannot be done.

Light itself gets to travel at light speed for one reason: photons have no mass. Massless things must move at that speed, and things with mass never can. The speed of light is not a speed limit that a clever enough spacecraft might one day break. It is closer to a feature of the shape of spacetime, the same for everyone, everywhere.

So the honest reply to “will we ever travel at the speed of light” is no, not us and not our machines, because we are made of mass.

How close could we get

The more interesting question is how near that wall you can press, and here the news is better, at least in principle.

There is no limit stopping you from approaching light speed, only from reaching it, and relativity throws in a strange gift on the way. As you travel faster, your own clock runs slow relative to the people you left behind. A crew moving close to light speed could in theory cross many light-years while ageing only a little, even as decades or centuries passed back on Earth. The distance does not shrink, but the time you personally spend crossing it can.

The gap between that principle and anything we can build is enormous. The fastest object we have ever launched, NASA’s Parker Solar Probe, travels at less than a tenth of one per cent of light speed. Even nature rarely gets close: a star whipped around the black hole at our galaxy’s centre reaches only about 3 per cent of light speed at its fastest, and that is one of the quickest large objects we know of.

The closest thing to a real plan

One concept comes nearer than the rest. Breakthrough Starshot, an initiative announced in 2016, proposes to skip heavy engines entirely and instead push a fleet of gram-scale probes with a ground-based laser, accelerating tiny light sails to around 20 per cent of the speed of light. At that pace a probe could reach the nearest star system, Alpha Centauri, in roughly twenty years rather than tens of thousands.

It is important to be clear about its status. This is a design and a research programme, not a spacecraft. The engineering problems, from a laser array of unprecedented power to a sail that will not vaporise, are unsolved. But it is the nearest thing to genuine near-light-speed travel that anyone has seriously put on paper.

The loopholes, and what they cost

If you cannot go faster than light through space, general relativity leaves a stranger door ajar: rearranging space itself.

In 1994 the physicist Miguel Alcubierre found a solution to Einstein’s equations describing a warp drive, a bubble that contracts spacetime in front of a ship and expands it behind, so the ship sits still while space does the moving. Wormholes, tunnels between distant points, are also valid solutions on paper. Neither would break the local speed limit, which is what makes them so tempting.

The catch is the same for both, and it is severe. They require what physicists call exotic matter, a form of negative energy that we have never observed and do not know how to make. Early estimates for a warp bubble needed more negative energy than the mass-energy of the entire observable universe. Later work trimmed that figure dramatically, but it remains vast, and the fundamental obstacle stands.

Recent designs have taken the opposite tack, dropping the exotic matter to stay within known physics, but the versions that need no negative energy are subluminal. They stay below light speed. As things stand, the maths permits shortcuts that the physics of building them cannot yet reach.

Where that leaves the dream

Put together, the picture is honest rather than romantic. At the speed of light, no, not for anything with mass. Close to it, physics allows what our engineering cannot presently manage, though concepts like Starshot show what trying would look like. Faster than it, only inside equations that call for a substance nobody has ever found.

None of this is likely to change at the level of the physics. What is worth watching is the near-lightspeed end, where a laser-driven sail or some successor might one day turn a fraction of the speed of light from a diagram into a departure.

The post Travelling at the speed of light is not just hard but impossible for anything that has mass, since it would take infinite energy, so the real question is how close we could get and whether the loopholes physicists talk about are more than mathematics appeared first on Space Daily.

In 2021 a team of paleontologists led by Charles Marshall at Berkeley did something clever: they estimated not how many T. rex we have dug up, but how many ever existed.

Their headline answer was about 2.5 billion, spread across the roughly 2.4 million years the species was around, although the uncertainty ranged from 140 million to 42 billion. At any given moment, the central estimate put about 20,000 adults on the continent at once, generation after generation, for longer than modern humans have existed. 

Now set that against how many we have found. The first partial skeleton recognized as T. rex was unearthed by Barnum Brown in Montana in 1902, and it became the name-bearing specimen when Henry Fairfield Osborn formally named the species in 1905.

By 2021, fewer than a hundred T. rex individuals had been found, many represented by a single fossilized bone. Only about 32 were relatively well-preserved post-juveniles held in public museums.

On Marshall’s estimate, that works out at roughly one recovered specimen for every 80 million post-juvenile animals that lived and died. Much of our physical knowledge of the animal rests on that extraordinarily narrow sample.

The math of what is missing

That fossil recovery rate that falls out is comically small.

However, for a T. rex to become a fossil you could visit, it had to die in the right place, get buried fast enough to escape scavengers and rot, survive tens of millions of years of erosion and geological change, and then happen to surface in a spot where a human being was looking. Almost nothing clears all of those hurdles.

The famous individuals bring this home. The great specimens have names, because there are few enough of them to name: Sue in Chicago, Stan, a short list of others that get written about again and again. When a single skeleton can anchor decades of research and a museum’s entire dinosaur hall, you are not looking at a well-stocked archive. You are looking at the handful of tickets that happened to win a very long lottery.

What we build on almost nothing

T. rex is not the poorly documented case. It is one of the better understood dinosaurs we have, a giant, sturdy-boned predator from rock we know how to read, hunted for over a century by people who badly wanted to find it.

If this is what good coverage looks like, roughly one relatively well-preserved post-juvenile in 80 million, then for most creatures that ever lived the record is not thin. It is blank. Whole species, whole families, came and went and left nothing a person will ever hold.

We are not usually reminded of that when we stand in front of the mounted skeleton. The display is confident. The posture, the coloring in the illustration beside it, the running speed on the little plaque, all of it reads as settled fact. A great deal of it is careful, honest extrapolation from a few bones and a lot of comparison with living animals, which is real science and often turns out right. But the certainty of the presentation and the scarcity of the evidence sit in an odd relationship, and I think it is worth holding both in mind at once.

None of this is a knock on paleontology. If anything it is the opposite. The impressive thing is not that our picture of T. rex has gaps. It is that anyone can say something reliable at all, starting from such a tiny fraction of the animals that lived and reasoning outward with that much care.

The wonder is not that we know so little. It is how much we have managed to reconstruct from so nearly nothing.

The post A 2021 estimate suggested that about 2.5 billion Tyrannosaurus rex lived, while only 32 relatively well-preserved post-juvenile specimens were then held in public museums — roughly one for every 80 million animals. And T. rex is one of the better represented large theropods appeared first on Space Daily.

Every few years asteroid mining returns to the headlines as a trillion-dollar gold rush waiting to happen, usually attached to a single staggering number about how much some metal-rich rock is theoretically worth. It is a genuinely exciting idea. It is also one where the economics tend to run in the opposite direction to the pitch.

I am a writer with a long interest in this beat, not an engineer or an economist, so take this as a careful reading of the material rather than expert testimony. The short version is that the case for asteroid mining is real, but almost nothing like the version that gets sold.

The graveyard of the first gold rush

This has been tried before, with serious money behind it. In the 2010s two well-funded companies, Planetary Resources and Deep Space Industries, set out to mine asteroids and drew backing from high-profile investors.

Neither mined anything. As CNBC reported, both ran short of the money needed to cover enormous development costs and were absorbed by other companies by 2018 and 2019, one of them pivoting to blockchain. The lesson was not that the resources are not there. It was that the timelines are long, the capital required is vast, and investors ran out of patience long before anyone reached an asteroid.

Why the trillion-dollar numbers mislead

The valuations that drive the headlines are the least useful part of the story. The metal asteroid 16 Psyche is often quoted as being worth something like ten quintillion dollars, a figure that dwarfs the entire world economy.

Two things are wrong with reading that as a business plan. The first is that the number assumes you could deliver all that metal to Earth at no cost, when the delivery is the entire problem. The second is more fundamental: if you actually did land that much platinum or gold, you would flood the market and collapse the price of the thing you came to sell. The markets for precious metals are small by weight, and they do not have room to absorb asteroid-scale quantities without the value evaporating.

It is worth adding that NASA’s Psyche mission, now on its way to the asteroid, is not a mining venture at all. It is a science mission to study a metal-rich world, which the agency now estimates is somewhere between 30 and 60 per cent metal. Nobody is going to mine Psyche, and there is no technology that could.

The prize that actually adds up is water

Strip out the gold-rush fantasy and a more sober case remains, and it is not about bringing anything home at all.

The expensive part of anything in space is lifting mass off the Earth against its gravity. A litre of water already in orbit is therefore worth far more than a litre sitting in a reservoir here, because you have not had to pay the enormous cost of launching it. Many asteroids, the dark carbonaceous ones, are thought to hold water ice, and water can be split into hydrogen and oxygen, which is rocket fuel, or used directly for life support.

So the version of asteroid mining that pencils out is not platinum sold on Earth. It is water and simple materials mined in space and used in space, to refuel spacecraft and supply habitats without hauling everything up from the ground. An analysis in the Harvard International Review makes this point plainly: the real economic logic points to servicing activity in orbit and beyond, not to enriching commodity markets back home.

This is a much less glamorous business than a space gold rush, and it is also the only one that currently makes physical sense.

The current attempt

A new generation is trying anyway, with more modest aims. The startup AstroForge is the most visible, and its record so far is a fair snapshot of how hard this is.

Its Odin spacecraft launched in February 2025 to scout a metallic near-Earth asteroid, but the company lost contact with it not long after deployment, ending the mission early. A follow-up probe, Vestri, is intended to actually dock with a small metallic asteroid, which would be a real first for a private spacecraft. It has not happened yet.

The targets, sensibly, are near-Earth asteroids, the ones whose orbits bring them close to us and make them reachable with reasonable amounts of fuel. These are the same objects we track for planetary defence, including ones like Apophis, which will pass close to Earth in 2029. Accessibility, not raw value, is what makes an asteroid worth visiting.

None of this is investment advice, and I have no idea whether any of these companies will succeed. What I can say is that the sober question worth watching is not which rock is worth the most on paper. It is whether anyone can mine water in space and sell it to the next spacecraft, because that, and not a platinum windfall, is the business that would actually change how we operate off the Earth.

The post Asteroid mining gets sold as a trillion-dollar gold rush, but the economics point the other way: hauling platinum back to Earth would crash its price, so the only prize that adds up is mining water and burning it as fuel in space appeared first on Space Daily.

Imagine placing two thermometers on Mars at noon. One lies flat against dark, sunlit soil near the equator. The other hangs roughly at the height of a standing person’s head.

The lower thermometer could read 24 degrees Celsius, a mild spring day by Earth standards. The upper one could remain at or below freezing. Nothing separates them except about two metres of the thinnest lower atmosphere any person in a spacesuit is likely to encounter.

NASA uses almost exactly this comparison in its Mars facts guide: spring at your feet and winter at your head. It sounds like a piece of planetary trivia, but it captures something fundamental about Martian weather. On Earth, the air is usually effective enough at moving heat that we treat the temperature of the ground and the temperature of the atmosphere as parts of the same experience. On Mars, they can behave like neighbouring but weakly connected systems.

The 24-degree figure is a plausible local surface temperature, not a promise about every equatorial noon. Season, dust, slope, colour, elevation and the material underfoot all matter. The real point is the vertical contrast. Sunlight can briefly warm the ground above freezing while the sparse gas above it stays bitterly cold.

The first trick is that ground temperature is not air temperature

A weather report on Earth normally gives air temperature measured in shade, not the temperature of sunlit concrete or beach sand. Those surfaces may be far hotter than the reported maximum. We know the distinction in daily life, but the atmosphere mixes enough heat through its lowest layers that a standing person does not ordinarily place their shoes in one season and their face in another.

Mars pushes the same distinction to an extreme. The ground absorbs sunlight and converts it to heat. A thermal infrared instrument can measure the energy radiated by that skin of dust and rock. A separate sensor measures the gas surrounding a rover. Both values are real, but they describe different material with very different capacities to absorb, store and transport energy.

That is why the warmest number quoted for Mars is usually a surface temperature. The air is much less willing to follow it. Even at the equator, a patch of ground that has crossed zero degrees does not imply a warm afternoon atmosphere.

There is almost no air available to carry the heat

The atmosphere at the Martian surface has less than one per cent of the pressure of Earth’s atmosphere at sea level. It is mostly carbon dioxide, but the abundance of a greenhouse gas by percentage is not enough to make a strong greenhouse blanket. The total quantity of gas overhead is small.

On Earth, molecules colliding with warm ground pick up energy. Convection, turbulence and wind then move that energy upward and sideways. Water vapour, clouds and oceans store and redistribute still more heat. Mars has weather, clouds and vigorous dust storms, but its near-surface gas contains far fewer molecules through which heat can travel.

This thinness has appeared repeatedly in the Mars machines I have written about. Ingenuity had to spin unusually large rotors at extraordinary speed to fly in air around one per cent as dense as Earth’s. MOXIE needed a pump to gather enough carbon dioxide before it could make oxygen. The same scarcity that makes lift and gas collection difficult also weakens the exchange of heat between soil and atmosphere.

The result is not zero heat transfer. The warmed surface drives turbulence and convective vortices, including dust devils. It simply cannot force the lowest two metres towards one uniform temperature as efficiently as Earth’s denser air usually does.

Perseverance measured the gradient directly

This is no longer only a thought experiment. The Mars Environmental Dynamics Analyzer, or MEDA, on Perseverance measures temperatures in and around Jezero Crater. Its sensors distinguish the surface from atmospheric layers at different heights.

NASA reported typical early MEDA observations in which the surface rose from about minus 83 degrees Celsius before dawn to 5 degrees at noon, while the air remained between about minus 83 and minus 23 degrees. Those particular days did not reproduce the 24-degree example, but they showed the same separation between a rapidly heated surface and colder air.

A 2023 analysis of MEDA measurements in the Journal of Geophysical Research: Planets quantified the vertical structure. For a set of repeatedly observed sols, the daytime temperature difference was concentrated in the first 1.45 metres above the ground. Near noon, the gradient reached about 26 degrees Celsius per metre.

The precise value changes with conditions, and it should not be applied to every place and season. Yet it gives physical substance to NASA’s spring-and-winter comparison. The lowest part of the Martian atmosphere can contain an enormous temperature change across the height of one human body.

Curiosity saw the distinction too. In one early sequence at Gale Crater, ground temperatures ranged from 3 to minus 91 degrees Celsius while air temperatures ranged from minus 2 to minus 75. The ground achieved both the warmer daytime peak and the colder nighttime minimum. It responded faster in both directions.

The kind of ground beneath the boots matters

Not every Martian surface heats at the same rate. Fine, loose dust has low thermal inertia. It changes temperature quickly when sunlight arrives and quickly loses that heat after sunset. Solid rock conducts and stores more energy, so it warms and cools more slowly. Particle size, cementation and material buried beneath the surface all affect the curve.

Planetary scientists use thermal inertia to interpret those differences from orbit. A region that remains relatively warm after sunset may contain rock, bedrock or coarser material. A dusty surface may produce a sharper afternoon peak and a steeper fall into night.

Colour and orientation matter as well. Darker ground generally absorbs more sunlight. A slope facing the Sun receives energy at a more direct angle than a shaded one. Airborne dust can reduce the sunlight reaching the surface while also changing how radiation moves through the atmosphere. Elevation changes the already low pressure.

There is therefore no single Martian noon temperature. I made a related point when writing about the immense, gently rising landscape of Olympus Mons: a global description can conceal what a person would encounter at ground level. On Mars, even two nearby patches of terrain can follow different thermal schedules.

A warm sole would not make a comfortable astronaut

The image of warm boots risks making an equatorial noon sound more hospitable than it is. An unprotected person could not stand there and compare sensations. The pressure is too low for the human body, the atmosphere contains almost no oxygen, ultraviolet and ionising radiation reach the surface, and liquid water is unstable under most present conditions.

A real astronaut would be separated from both ground and air by a pressure suit, insulation, boots and a controlled thermal system. The suit would manage heat generated by the body while limiting heat gained from sunlight and lost through radiation, contact and the surrounding gas. It would not simply transmit a pleasant 24 degrees from the soil to the foot.

There is another counterintuitive detail. Mars can have fast winds, but because the gas is so thin, those winds carry less force and exchange less heat than winds of the same speed on Earth. The cold air at head height would not feel like an ordinary terrestrial winter gale. Without a suit, the low pressure would be the immediate emergency. With one, thermal engineering determines the experience.

This is why my earlier look at the difficulty of building a home on Mars could not reduce the problem to an average temperature. A habitat must survive daily cycling, cold-soaked nights, sunlit surfaces, dust, radiation and a near-vacuum while maintaining one narrow indoor climate for people and equipment.

Mars loses the afternoon almost as quickly as it gains it

The warm ground is temporary. Once the Sun drops, a dusty surface radiates energy into the cold sky and has little atmosphere above it to return that energy. The same weak coupling that allows soil to become much warmer than the air at noon permits it to plunge below the air during the night.

That daily swing has shaped the history of Mars exploration. Solar-powered rovers conserve energy through cold periods and use heaters to keep critical components within operating limits. Batteries, lubricants, cameras and electronics experience a thermal environment that expands and contracts every sol. Opportunity ultimately endured far beyond its original design, but as I wrote in the account of its fourteen-and-a-half-year journey, sunlight remained both its power source and its final vulnerability.

The spring-underfoot image lasts only because sunlight is arriving faster than the particular ground can shed it. It says nothing about the night before, the night ahead or a shaded patch a few steps away.

One body can reveal a whole climate system

There is something useful about reducing Martian climate to the height of a person. Global averages tell us that Mars is cold. Pressure figures tell us that its atmosphere is thin. A vertical temperature profile shows what those statements mean together.

Sunlight crosses the sparse atmosphere and heats the soil. The soil tries to warm the gas touching it. There are too few molecules to distribute that energy efficiently, so a steep gradient forms just above the surface. Turbulence carries some heat upward, but the afternoon never becomes uniform. Then sunset removes the source and the ground rapidly gives back what it gained.

On Earth, weather surrounds us. On Mars, the most dramatic piece of weather may fit between the soles of a pair of boots and the top of a helmet.

NASA’s comparison is memorable because it compresses an alien climate into human proportions. Spring and winter can occupy the same standing person, not because Mars has found a loophole in temperature, but because it lacks the thick, mixing atmosphere that quietly makes our own experience of temperature feel coherent.

The post Mars has such thin air that around noon near the equator, sunlit ground beneath your boots could reach 24 degrees Celsius while the air around your head remained below freezing — allowing one standing person to span temperatures resembling spring and winter at the same time. appeared first on Space Daily.

Picture the den in early summer. Some of the adult wolves have left to hunt, which can mean being gone for the better part of a day or longer and covering ground a person would struggle to walk.

The new pups are too small to follow and too helpless to leave truly alone. So they are not left alone. A pack member often stays behind, and that wolf may be an older brother or sister from a previous litter, on babysitting duty.

Wolves are one of a fairly small number of animals where the raising of the young is a group effort rather than a job for two. Biologists call it alloparenting, care given by animals other than the mother and father. In a wolf family it often falls to yearlings and other nonbreeding wolves that have not yet left to start families of their own. The Wolf Conservation Center describes them babysitting the pups, regurgitating food for them and playing with them. 

The most striking part, to me, is the food. A yearling that has fed at a kill will travel back to the den and regurgitate meat for the pups, delivering a meal it carried home inside itself. It is not glamorous. It is also a genuinely generous act by an animal that could simply have eaten and kept walking. The parents do it too, but research on wild wolves found that all adult pack members, including yearlings, regurgitated food, so the pups can be fed from several directions at once.

There is a quiet division of labor worth noticing. In one Idaho study, nonbreeding females attended dens and rendezvous sites about twice as often as nonbreeding males, suggesting that older sisters may take a closer hand in caring for the new pups.

The younger wolves may also be gaining practical experience. By the time a yearling leaves to raise its own litter, it may already have spent a season or two feeding, guarding, and minding pups. It has, in the most practical way, learned the job before it needs it.

All of this can have a hard payoff. Spreading the care across the pack means the pups can be watched, fed, and defended while other wolves hunt, part of what makes a pack so resilient. In a long-term study of reintroduced red wolves, helpers were associated with higher pup mass and survival at low population density, although the survival benefit disappeared at high density. Gray-wolf research likewise shows that the relationship between pack size and surviving pups varies with ecological conditions. Extra hands are not automatically better in every place and every year, but they let a wolf family divide the essential work of guarding and provisioning.

What I like about it is how unfamiliar it makes a familiar animal look. We are used to thinking of wolves through the language of dominance and the lone hunter. The reality on the ground, in early summer, is a young pack member staying home to mind the babies while others hunt, and then bringing dinner back for everyone.

It is closer to the cooperative way humans have raised children across much of our history, with older children and other relatives helping to care for and provision the young.

The pups will grow, and in a year or two some of the babysitters will leave to become parents themselves, carrying the whole routine somewhere new. It is a small, well-run system, repeated from one generation to the next

The post In a wolf pack, older brothers and sisters often help with the babysitting. While some adults are away hunting, wolves from previous litters guard the new pups and carry food back for them — an all-hands approach to raising the young that can improve a pup’s chances of surviving appeared first on Space Daily.

Calling Ganymede a moon is correct, but it does very little to prepare us for what the object actually is.

It is the largest moon in the Solar System, with a diameter of about 5,262 kilometres. It has an iron-rich core, a rocky mantle, an immense layer of water and ice, an old and geologically complicated surface, a thin atmosphere, auroras and a magnetic field generated inside the moon itself. If it travelled around the Sun rather than Jupiter, nobody encountering it for the first time would mistake it for a minor piece of debris.

That does not mean Ganymede has been misclassified. A moon is defined by what it orbits, not by how geologically accomplished it appears. But Ganymede is a useful reminder that the word describes an orbital relationship, not a level of complexity. This is a full-sized world living as one component of the Jupiter system.

Larger than Mercury does not mean heavier

The cleanest comparison begins with size. JPL lists Ganymede’s mean radius as 2,631.2 kilometres. Mercury’s mean radius is 2,439.4 kilometres. Ganymede is therefore almost 8 per cent wider than the smallest planet.

It is not, however, more massive. Ganymede has only about 45 per cent of Mercury’s mass. The difference is composition. Mercury is an unusually dense, metal-rich planet, while Ganymede is a much lighter mixture of rock and water ice. Mercury’s average density is about 5.43 grams per cubic centimetre; Ganymede’s is about 1.94.

This distinction matters because the familiar sentence, “Ganymede is bigger than Mercury,” can accidentally create the wrong mental image. The moon has a larger volume, but much less material packed inside it. Its surface gravity is only around 15 per cent of Earth’s, lower even than the Moon’s.

The comparison also exposes why size alone cannot decide whether something is a planet. Mercury independently circles the Sun. Ganymede completes an orbit around Jupiter every 7.15 days. Its status follows that architecture, even though its body is more planet-like than the word moon tends to imply.

Under the crust is a differentiated world

Small Solar System bodies are often imagined as frozen mixtures that never became warm enough to organise themselves internally. Ganymede did. NASA’s current overview describes a deep metallic core, a surrounding rock shell and an outer system of water and ice. In other words, the moon differentiated into layers, as the rocky planets did.

The surface keeps part of that history. Dark, heavily cratered terrain records very old ground. Brighter regions are crossed by long grooves and ridges, evidence that the crust was stretched, fractured and resurfaced. Ganymede is no longer as visibly active as neighbouring Io, but it is not a featureless ball that simply froze in place.

The contrast with its parent planet is almost comic. As I explored in an earlier article about why there is no solid surface on Jupiter to land on, the giant planet becomes progressively denser with depth until hydrogen behaves like an electrically conducting metal. Ganymede, despite orbiting that enormous fluid world, offers recognisable ground, internal layers and geological provinces. The moon is the place with the planetary surface; the planet is not.

The water claim is large, but easy to misunderstand

The statement that Ganymede may contain more water than Earth does not describe an open sea. No camera has looked through the crust, and no probe has sampled the liquid. The evidence comes from several indirect measurements, including how Ganymede responds to Jupiter’s changing magnetic environment.

One especially elegant test used the moon’s auroras. Jupiter’s magnetic field should make those glowing bands rock back and forth by about six degrees. In Hubble observations, they moved by only about two degrees. A conductive, salty ocean beneath the crust provided the best explanation, because electrical currents in the water generate a secondary magnetic response that damps the motion.

The 2015 model associated with those observations placed an ocean roughly 100 kilometres thick beneath about 150 kilometres of mostly ice. Those figures are estimates, not a sonar reading. Other models allow a layered arrangement in which liquid water is separated by different phases of high-pressure ice, closer to a club sandwich than one unbroken sea.

Even with that uncertainty, Ganymede’s total water inventory may exceed all the water on Earth’s surface. The careful wording matters. Earth also stores water inside its mantle, and Ganymede’s water is not necessarily all liquid at once. The comparison concerns the moon’s enormous combined water layer and the oceans, ice and surface water visible on Earth.

This is part of the larger change I wrote about in the expansion of the habitable-zone idea beyond sunlight. It also explains why the list of credible hidden-ocean moons keeps growing. Yet water volume alone does not make Ganymede habitable. If high-pressure ice separates the ocean from rock below, the chemical exchange available at a rocky seafloor may be limited. The depth that protects the water also makes it extraordinarily difficult to investigate.

The moon carries a magnetosphere inside a magnetosphere

Ganymede’s most unusual property is not its size or even its water. It is the only moon known to generate its own intrinsic magnetic field. NASA’s Galileo spacecraft detected the field during close encounters beginning in 1996. The leading explanation is a dynamo operating in a liquid, electrically conducting part of the metallic core, broadly the same physical mechanism that sustains Earth’s global field.

The distinction between intrinsic and induced fields is important. The buried saltwater ocean appears to develop an induced response as Jupiter’s external field changes around it. The stronger, permanent field comes from much deeper inside Ganymede. Measurements and modelling describe a small Ganymede magnetosphere nested within Jupiter’s much larger one.

That arrangement produces auroras near the moon’s poles, but it should not be confused with an Earth-like protective cocoon. Ganymede has only a very tenuous atmosphere, and it remains immersed in Jupiter’s radiation and plasma environment. A magnetic field can organise the charged particles around the moon without turning its surface into a safe refuge.

There is still an active question about how such a small world has retained the fluid motions needed for a dynamo. Space Daily recently examined the proposal that Ganymede’s core may still be evolving. The details are not settled, but the field is direct evidence that the moon is not internally inert.

Ganymede is a world, but not an isolated one

It is tempting to describe Ganymede as a planet that happens to have been captured by Jupiter. That would go too far. Ganymede’s history and present behaviour are inseparable from the system it inhabits.

Its orbit participates in the Laplace resonance with Europa and Io. For every orbit Ganymede completes, Europa completes about two and Io about four. Their recurring gravitational tugs prevent the orbits from becoming perfectly circular and help redistribute energy through the moons. I described the same mechanism in an article about Europa’s place in Jupiter’s three-moon gravitational machine.

Past tidal heating may have helped Ganymede separate into its present layers, and Jupiter controls the magnetic environment in which its ocean signal is measured. The moon is also tidally locked, keeping the same face towards Jupiter as it travels around the planet. Its planet-like qualities therefore do not make it independent. They show how elaborate a satellite can become while remaining physically bound to a larger system.

This is the more interesting lesson than a debate over labels. A moon can have the diameter of a planet, the interior architecture of a planet and a dynamo usually associated with planets, while its geology and energy budget remain shaped by a relationship no solitary planet has.

JUICE is going there because Ganymede requires an orbiter

Most of what we know about Ganymede comes from fly-bys, remote observations and measurements made during brief passages. ESA’s Jupiter Icy Moons Explorer, or JUICE, is designed to change the scale of the investigation.

JUICE launched in April 2023 and is scheduled to reach Jupiter in July 2031. After a tour of the Jovian system, the mission plan calls for insertion into orbit around Ganymede in December 2034. If successful, it will become the first spacecraft to orbit a moon beyond Earth’s own.

Its instruments are meant to treat Ganymede as a system rather than a single target. Radar will probe the icy shell. Magnetic measurements will separate signals from the core, ocean and Jupiter. Laser altimetry, radio science and cameras will examine the moon’s shape, gravity, surface and response to tides. Together, those observations should constrain how thick the ice is, how the water is arranged and how the deep interior keeps its field alive.

Ganymede does not need to be promoted from moon to planet for any of this to count. “Moon” tells us that it goes around Jupiter. “World” tells us that it has a history, structure and physical identity worth studying on its own terms. Ganymede is both, and the tension between those descriptions is exactly what makes it so revealing.

The post Ganymede is a moon, yet it is larger than the planet Mercury, may contain more water than exists on Earth’s surface, and even generates its own magnetic field, making it less like a conventional moon than a full-sized world that happens to orbit Jupiter. appeared first on Space Daily.

There is something difficult to grasp about the number of lakes in Canada. A few thousand would already seem excessive. Tens of thousands would be hard to picture. Canada has more than two million by federal estimates, scattered across a landscape shaped by ice.

The number is so large that it almost stops meaning anything. You could visit a different Canadian lake every day for an entire lifetime and still see only a small fraction of them. On a map they appear as blue flecks, crowded together across the north, but each one is a real body of water with its own shoreline, islands, depths and surrounding ecosystem.

What does “60 per cent of the world’s lakes” mean?

The often repeated claim that Canada holds around 60 per cent of the world’s lakes needs some qualification. There is no universally agreed count of every lake on Earth, because the result depends on what size of body is included and how lakes are distinguished from ponds, reservoirs and seasonal water.

One of the most widely used global databases, HydroLAKES, maps about 1.4 million lakes and reservoirs with a surface area of at least ten hectares. According to research describing the database, roughly 62 per cent of those water bodies are in Canada.

That does not mean Canada contains 62 per cent of the world’s freshwater. It means that nearly two-thirds of the lakes included in that particular global dataset lie inside Canada. The country nevertheless holds an enormous amount of water, and fresh water covers about eight per cent of its surface area.

What the ice left behind

The explanation lies largely in the Ice Ages. During repeated periods of glaciation, much of Canada was covered by continental ice sheets several kilometres thick. These were not static blocks of ice. They moved slowly across the land, grinding against the bedrock beneath them.

As the glaciers advanced and retreated, they scraped away soil and rock, deepened existing valleys and gouged countless depressions into the surface. When the climate warmed and the ice melted, water collected in those hollows.

The glaciers also carried enormous quantities of stone, sand and clay. As they withdrew, they left behind ridges and irregular piles of debris that blocked rivers and trapped meltwater. Some lakes formed in basins carved directly into rock. Others developed behind natural dams of glacial sediment.

This process happened across an immense area. The Canadian Shield, which stretches around Hudson Bay and across much of central and eastern Canada, is particularly full of exposed rock, shallow soil and water-filled depressions. From the air, much of the region looks less like solid land dotted with lakes than a broken mixture of rock, forest and water.

A landscape made of water

Some Canadian lakes are among the largest in the world. The Great Bear Lake and Great Slave Lake dominate the Northwest Territories, while parts of four of the five Great Lakes lie within Canada. But the extraordinary total comes mainly from the vast number of smaller lakes scattered across the country.

Many are remote enough to have no roads, settlements or permanent names. Some can be reached only by aircraft, canoe or long journeys through forest and tundra. Others sit within sight of towns and cities, forming part of ordinary Canadian life through fishing, swimming, transport, tourism and hydroelectric power.

The abundance of lakes also creates problems. Water may appear limitless, but it is unevenly distributed, often far from the country’s largest population centres. Pollution, warming temperatures, invasive species and changing rainfall patterns can still damage individual lakes, no matter how much water exists elsewhere.

Closing thoughts

Standing beside one cold lake in the Canadian bush, there would be no way to sense that it was one of more than two million. That is the odd thing about scale. From the shore, the lake is simply a place: water against rock, trees reflected on the surface, perhaps an island in the distance. Only from the level of a map or a database does it become part of something almost impossible to imagine. 

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Most ocean worlds present the same brutal engineering problem. The water may be scientifically irresistible, but it is buried beneath an ice shell that no spacecraft has yet drilled through.

Enceladus is different. Saturn’s small icy moon pushes water vapour and frozen droplets through fractures near its south pole, accelerating the material into space. A spacecraft can cross that plume with its instruments open and analyse ocean-linked material without touching the surface.

NASA once described these eruptions as “free samples” from the moon’s global ocean. That phrase captures the extraordinary advantage, but it can also make the measurement sound cleaner than it is. The plume offers access, not a perfectly preserved jar of seawater. Understanding what happened between ocean and instrument is part of the science.

I find that distinction almost as interesting as the plume itself. Enceladus has removed the largest physical barrier for us. It has not removed the need to interpret what comes through.

The moon brings its ocean to the spacecraft

Enceladus is about 500 kilometres across. Beneath its bright crust is a global salty ocean in contact with a rocky core, while four long south-polar fractures, nicknamed the tiger stripes, vent water vapour and ice grains.

Some grains fall back onto the surface. Others escape the moon’s weak gravity and supply Saturn’s broad E ring. NASA estimates that water leaves the fractures at about 1,300 kilometres per hour, carrying salts, ammonia, methane, silica particles and organic material into a region a spacecraft can reach.

This matters because drilling through an alien ice shell is not simply a matter of attaching a longer bit. A lander would need to descend safely, generate substantial power, operate autonomously, prevent terrestrial microbes from being carried downwards and communicate through or around the ice. The deeper it travelled, the harder every one of those problems would become.

A plume fly-through replaces that entire descent with navigation and mass spectrometry. The moon has already done the lifting.

Cassini sampled gas and grains separately

NASA’s Cassini spacecraft was not built to investigate an Enceladus ocean because nobody knew the ocean or plume existed when it launched in 1997. Once the jets were discovered, mission planners redirected later encounters around the opportunity.

Cassini ultimately completed 23 targeted fly-bys of Enceladus. Its Ion and Neutral Mass Spectrometer measured gases, while its Cosmic Dust Analyzer recorded tiny solid particles that struck its target plate and produced clouds of ions. The masses and arrival times of those ions created chemical fingerprints of individual grains.

During the E21 encounter in October 2015, Cassini passed only 49 kilometres above the surface. NASA stated in its fly-by briefing that the pass would sample material from the ocean but could not detect life. The spacecraft simply did not carry the right instruments for a definitive biological test.

What it could do was establish a chain of evidence for habitability. In my earlier article on Enceladus’s salts, molecular hydrogen and phosphorus, I followed the separate measurements that point to liquid water touching rock, a possible source of chemical energy and a nutrient used by all known terrestrial life. Those findings came from material available above the moon, not from a probe lowered into its sea.

The plume is an ocean sample after processing

The word “direct” needs care. Material in the plume is linked to the subsurface ocean, but it has travelled upwards through long, cold fractures and changed phase along the way.

Ocean water can form droplets that freeze into ice grains. Dissolved gases leave the liquid at different rates. Water vapour condenses on the fissure walls as the mixture rises into colder ice. Some compounds become concentrated in the escaping gas, while others are depleted. Gas and solid grains can therefore tell different parts of the ocean’s story.

A 2022 paper by Lucas Fifer, David Catling and Jonathan Toner in The Planetary Science Journal modelled this chemical fractionation between ocean and plume. One earlier model discussed in the paper estimated that more than 99 per cent of the water vapour could condense onto the fissure walls during eruption. Because the other gases do not condense in the same way, their measured proportions above the surface cannot simply be copied into a table and labelled “ocean composition”.

The ice grains are especially valuable because salt-rich particles appear to begin as ocean droplets. Even they are not identical. Cassini found that only about 1 to 4 per cent of plume grains carried organics at high concentrations. A bulk average could dilute the rare, chemically interesting grains until their signals nearly disappeared.

Space Daily’s editorial team has already covered the plume’s water, phosphate, hydrogen and varied organic chemistry. The measurement lesson beneath that list is that a future spacecraft should analyse many grains individually and record where and when each one was collected.

A grain hitting a spacecraft becomes the experiment

There is no scoop dipping gently into the plume. At fly-by speed, an ice particle slams into an instrument, vaporises and ionises. The collision destroys the original grain, but the ions produced by the impact reveal what it contained.

Speed changes the spectrum. In October 2008, Cassini crossed fresh plume material at about 17.7 kilometres per second. A 2025 study led by Nozair Khawaja in Nature Astronomy reanalysed 1,519 spectra collected during roughly six minutes of that encounter and identified several families of organic fragments, including signals consistent with aromatic and oxygen-bearing chemistry.

The speed was both helpful and limiting. It broke water clusters apart, exposing signals that were obscured at slower impacts, but it also fragmented larger molecules so severely that their original structures could not always be reconstructed. The authors explicitly said the conditions did not allow quantitative analysis. They could identify possible chemical groups, not measure the precise concentration of every original compound in the ocean.

A purpose-built spacecraft could approach more slowly, use instruments with a wider mass range and repeat its passes through different parts of the plume. It could combine grain measurements with gas analysis, imaging and observations of how plume output changes as Enceladus moves around Saturn.

A future instrument may be able to read part of a cell

The most striking laboratory result I found came from a 2024 Science Advances paper led by Fabian Klenner. The team placed cells of a cold-water bacterium into droplets, froze them and simulated the impact-ionisation spectra that a modern spacecraft instrument might record at four to six kilometres per second.

In those experiments, characteristic signals remained identifiable even when an ice grain contained less than one whole cell’s worth of material. The work supports analysing individual grains rather than mixing billions of particles into a bulk sample, because any biological material might be concentrated in a very small minority of them.

It does not show that Enceladus contains cells, or guarantee that alien biology would resemble the organism used in the laboratory. It demonstrates instrument sensitivity under a controlled analogue. A convincing claim of life would still require several independent signals and careful exclusion of non-biological chemistry and contamination.

That caution is not a minor footnote. As Space Daily’s editorial team argued in its article on what a null result at Enceladus could mean, a habitable environment and an inhabited one are different scientific claims.

No drilling does not mean an easy mission

Enceladus orbits roughly 1.4 billion kilometres from the Sun. Reaching Saturn takes years, sunlight is weak, communications are slow and entering an orbit that permits repeated low-speed plume crossings requires substantial propulsion and careful navigation.

The spacecraft itself must also be kept clean enough that a trace of amino acid, lipid or terrestrial cell does not masquerade as evidence from the moon. In my article on Cassini’s deliberate destruction in Saturn, I looked at the same contamination problem from the other direction. Cassini was disposed of before loss of control could create a future impact risk at Enceladus.

Europe has now placed the moon at the centre of its long-range planning. In 2024, ESA identified Enceladus as the top target for its first large-class Voyage 2050 mission. The concept could launch in the early 2040s, arrive around a decade later, conduct a Saturn-system tour and eventually collect ejected material close to the surface, potentially combining plume sampling with a landing. It remains a future programme rather than a spacecraft ready to fly.

The long timetable is frustrating, but the destination offers an unusual bargain. Other ocean worlds ask us to infer chemistry through magnetic fields, surface deposits or radar echoes. Enceladus places newly erupted material in the path of an instrument.

We do not need to build a machine that crosses kilometres of ice before we can ask whether the ocean contains useful energy, complex chemistry or possible biological patterns. We need a clean spacecraft, the right mass spectrometers and enough careful passes through a plume that the moon keeps providing.

The ocean remains hidden. Its samples do not.

The post Enceladus hides a salty ocean beneath its ice but also blasts that ocean directly into space, which means a spacecraft can test water from a potentially habitable sea simply by flying through the plume — no landing, drilling, or journey through kilometres of frozen crust required. appeared first on Space Daily.

In the middle of the nineteenth century, a Dutch army recruit stood on average around five feet five inches. That was short even for the time, shorter than many of his European and American contemporaries, and nobody looking at the Netherlands then would have picked it as the future home of some of the tallest people on Earth. Yet that is exactly what happened. Young Dutch men born in the Netherlands now measure nearly 1.84 metres on average, almost exactly six feet, and the country consistently ranks among the world’s tallest. In the space of about 150 years, one of the shortest populations became one of the tallest.

Twenty centimetres in a century and a half

The scale of the change is easy to say and hard to feel. Dutch men gained roughly 20 centimetres, close to eight inches, between the mid-nineteenth century and the modern era. That is not the kind of drift you expect from a stable population. It is a population visibly rebuilding itself, generation by generation, each cohort of children arriving taller than their parents for decade after decade until the whole nation had grown into a different shape.

Height works this way because it is only partly written in your genes. Your genes strongly influence the range of height you might reach. Where you fall within that range depends heavily on the years between birth and adulthood: whether you got enough good food, whether illness kept interrupting your growth, and whether the conditions around you let a body spend energy on getting tall rather than just getting through. A child who is well fed and rarely sick is more likely to grow toward the top of that range. A child who is not, may not. Multiply that across millions of children and stature becomes a kind of national report card.

Milk, money and doctors, not evolution

So what changed in the Netherlands? The answer is less dramatic than the transformation, and I think that is part of what makes it interesting.

The country got richer, and it got healthier. As researchers behind a Dutch Growth Study concluded, “Main contributors to the increase in height may be improved nutrition, child health, and hygiene, and a reduction of family size.” Prosperity, diet, healthcare and hygiene pulled in the same direction for generations, and the population climbed.

There was, for a while, a more exciting theory. In 2015 a study in a Royal Society journal suggested the Dutch might also be evolving taller, because taller Dutch men appeared to be having slightly more children, which could nudge the genes associated with height upward over time. It is a genuinely appealing idea, natural selection caught in the act in a modern European country. But it is worth being careful here, because the same lead researcher later put numbers on it. A 2023 simulation estimated that natural selection could account for only 0.07 to 0.36 centimetres of the change between 1850 and 2000. Against a gain of nearly 20 centimetres, that is a rounding error. The dramatic explanation turns out to be a footnote, and the dull one, better food and better health, did nearly all the work.

What a body remembers

I keep coming back to the idea that a population’s height is a physical record of its recent past. You cannot easily fake it or rush it, and it does not respond to a single good year. It responds to conditions sustained across a childhood, and then across many childhoods in a row.

When a country gets taller the way the Netherlands did, the bodies of its people are, in a real sense, remembering decades of enough food and decent medicine. The change is written into skeletons before it shows up in any history book.

It cuts the other way too. When researchers see average height stall or fall in a population, it can point to something going wrong in childhood: nutrition slipping, healthcare thinning out, or hard years landing on the young. 

The Dutch story is often told as a curiosity, a fun fact about a nation of unusually tall people ducking under doorframes. I think it is better read as evidence of something quietly hopeful. Give children enough to eat and keep them healthy, reliably, for long enough, and you can watch the result stand up in a crowd a century later. The Netherlands did not stumble into being tall. It fed and cared for a very long line of children, and the height is what that looks like from the outside.

The post In the mid-nineteenth century, the Dutch were among the shortest people in Europe. Today they remain among the tallest on the planet, with young men standing about 1.83 metres on average. Rising prosperity, better nutrition and improved healthcare added nearly 20 centimetres in roughly 150 years appeared first on Space Daily.

Somewhere in Tokyo in the mid-1980s, a Norwegian marketing strategist stood in front of a room of Japanese seafood executives, served them raw salmon, and watched the room politely fall apart. The colour was wrong, they told him. Its smell, they said, had a river-like quality. Someone objected to the shape of the fish’s head.

I think about that meeting every time I sit at a conveyor belt and watch the orange slabs go past. Salmon nigiri has the settled look of something that was always there, parked next to the tuna and looking as venerable as a prawn tempura. It has been on Japanese menus for about thirty years.

What Japan actually ate before

Japanese cooks have used salmon for centuries. They grilled it, salted it, flaked it into rice balls and packed it into lunchboxes. Nippon.com describes grilled salmon and salmon flakes as fixtures of home cooking, with a hard line drawn between that cooked fare and anything sliced raw. The domestic workhorse was chum salmon: lean, firm, nobody’s idea of sashimi.

So the fish was there. The appetite for raw fish was very obviously there. Those two facts never met.

The parasite question, answered properly

There was a real reason for the line, and fussiness was not it.

Wild Pacific salmon carry Anisakis simplex, a nematode larva that causes a thoroughly miserable illness called anisakiasis if you swallow it alive. Heat kills it. Deep freezing kills it. Slicing the fish fresh and eating it does not, which is why generations of Japanese cooks treated raw salmon as a hazard to be cooked out.

Farmed Atlantic salmon raised on heat-treated pellets is a different animal. The Norwegian Food Safety Authority exempts farmed salmon and rainbow trout from the freezing rule that otherwise applies to fish destined to be eaten raw, on the grounds that the fish eat nothing but dry feed containing no viable parasites and barely graze on wild organisms in the pen. That exemption tracks a 2010 European Food Safety Authority opinion and its 2024 re-evaluation.

A survey published in the Italian Journal of Food Safety put numbers on it: 270 slices of smoked farmed Atlantic salmon examined, zero anisakids found, against ten positives out of thirteen slices of wild sockeye. One paper on one processed product, not a settled literature, but it points the same way the regulators do.

Norway had too much fish

Norway started farming salmon commercially in the 1970s, then watched its own population drift towards chicken and red meat.

Freezers filled up.

The Norwegian Seafood Council, which has every commercial reason to tell this story well, dates the campaign to 1985, when a delegation led by former fisheries minister Thor Listau flew to Tokyo. Their figures: two tonnes of Norwegian salmon went to Japan in 1980, and twenty years later the annual number was above 45,000 tonnes.

Underneath all of it sat one piece of arithmetic. Fish sold for the grill competes on price with every other cheap protein, while fish accepted for sashimi could fetch up to ten times more, as Bjørn Eirik Olsen, who ran market research for the project, later told The Japan Times.

A name change, then a decade of nothing

“We couldn’t just say that our fish doesn’t have parasites,” Olsen said in that interview. Walking into a foreign industry and announcing that its national fish is wormy tends to close doors rather than open them.

So he went after the word instead. The Japanese for salmon is sake, and sake carried every association he was trying to escape: grilled, salted, cheap, the thing in the lunchbox. Olsen borrowed the English word and pushed the katakana sāmon, the term still stamped on essentially every sushi menu in the country. Same animal, different shelf.

Then came the advertising, all clean fjords and clear arctic water, and it achieved almost nothing for years. Olsen told NPR that pressure from home to abandon the sushi idea and dump the stock into the grill market was relentless.

The deal that broke it open

In 1992, Olsen offered the frozen food giant Nichirei 5,000 tonnes of salmon at close to giveaway prices, with one condition written into it: the fish could only be sold as sushi. Nichirei said yes.

That was the crack in the wall. Through the 1990s, Iron Chef and celebrity chefs including Yutaka Ishinabe put Norwegian salmon onto national television, and appetite did the rest. Olsen has said he knew the campaign had landed when he started noticing plastic salmon nigiri in restaurant window displays.

Where salmon sits now

Salmon has topped Japan’s biggest conveyor-belt sushi survey for fifteen consecutive years. In the 2026 round, run by Umios (the company known as Maruha Nichiro until March), 47.7 per cent of respondents named it as the topping they eat most often, more than eleven points clear of lean tuna in second place. The split runs along age lines: older diners tend to open with lean white fish and work up to tuna, while younger ones go straight for the orange.

Norway built something very large on the back of it. The seafood council reckons roughly 30 per cent of all Norwegian salmon now ends up raw in sushi, and that Norway supplies a little over half the global salmon market across 113 countries.

The high end went too. That’s the part I still find slightly hard to credit. Iwasa-zushi in Toyosu used to turn away customers who asked for salmon back when the market was at Tsukiji, and now has it on the board. Yamagata Tadashi, whose family has run a Nihonbashi sushi restaurant since 1887 and who chairs the Japan Sushi Environmental Health Federation, expects salmon to become a staple of Edomae sushi, arguing that clinging to wild domestic fish alone will empty the sea.

What a tradition is made of

The reasoning that lost for a decade turned out to be correct. Cold water, controlled feed, negligible parasite risk, safe raw. Olsen simply had no way to prove it to a room that had already decided, and no vocabulary that did not sound like an insult.

The argument never won anyone over. A discount and a shipping container did.

What gets me is how completely the seam has vanished. A teenager ordering sāmon at a kaiten place in Osaka is not participating in a trade negotiation or performing globalisation, any more than an Indian cook reaching for a chilli is. Thirty years is apparently long enough for a foreign product, sold under an English name at a loss by a government agency with a warehouse problem, to become simply what people like. Every cuisine anybody calls ancient is carrying a few of these, quietly, with the receipts thrown out.

The post That salmon on your sushi plate feels like an ancient Japanese tradition, but it isn’t — until the 1990s the Japanese didn’t eat raw salmon at all, and the reason they do now traces back to a Norwegian marketing campaign appeared first on Space Daily.