Tag Archives: earth

This rock fragment is over 4 billion years old. It may formed on Earth but ended up on the moon due to a massive asteroid impact. Credit: USRA/LPI.

Earth’s oldest rock was actually found on the moon and brought home by Apollo 14

In 1971, Apollo 14 astronauts brought home various minerals and rock samples from their brief lunar voyage. For decades, these lunar rocks have stayed in storage, occasionally being revisited by researchers curious to try out a new technique in order to learn more about the moon’s geochemistry. Imagine the surprise when scientists found in 2019 that one such rock was terrestrial in origin — to top it all off, it may very well be Earth’s oldest rock found thus far.

This rock fragment is over 4 billion years old. It may formed on Earth but ended up on the moon due to a massive asteroid impact. Credit: USRA/LPI.

This rock fragment is over 4 billion years old. It may have formed on Earth but ended up on the moon due to a massive asteroid impact. Credit: USRA/LPI.

This adventurous moon rock has quite the backstory. According to an international team of researchers, the two-gram piece of quartz, feldspar, and zircon was found embedded in a larger rock called Big Bertha. This combination of minerals shouldn’t be found on the moon but they’re quite common here on Earth. Quartz and zircon form in oxidized systems such as Earth, in high temperature and pressure environments experienced deep below the planet’s crust.

Since zircon contains uranium, whose half-life is predictable, the international team of researchers were able to confidently date the rock to about 4 to 4.1 billion years ago, corresponding to the Hadean Eon of Earth’s geological history. They also determined — based on the sample’s geochemical properties — that it must have formed at a depth of about 20 kilometers (12.4 miles) beneath Earth’s surface.

The Moon rock “Big Bertha”, collected during the 1971 Apollo 14 mission, contains an Earth meteorite that is 4 billion years old. Credit: Wikimedia Commons.

So, how did it end up on the moon? The most plausible explanation is that a massive asteroid impact hurled this traveling mineral into space and eventually crashed into Earth’s natural satellite, which happened to look a lot different than we know it.

For starters, the moon was about three times closer to Earth than it is today. Around 4 billion years ago, the planet was regularly bombarded by cosmic objects of all shapes and sizes, some responsible for producing craters thousands of kilometers in diameter on Earth — so the impactor hypothesis isn’t that far-fetched of an explanation at all. Once on the moon, the rock was further sculpted by new impacts which melted and altered it into a new kind of rock about 3.9 billion years ago. These forces also buried it deep below the lunar surface.

The Moon was much closer to the Earth than it is today when the rock fragment was produced and ejected from the Earth. Credit: LPI/David A. Kring.

The Moon was much closer to the Earth than it is today when the rock fragment was produced and ejected from the Earth. Credit: LPI/David A. Kring.

The rock probably stayed buried for eons until around 26 million years ago when another asteroid impact, this time on the moon, produced the 340-meter wide Cone Crater. Finally, Apollo 14 astronauts found the rock and reunited it with mother Earth.

“It is an extraordinary find that helps paint a better picture of early Earth and the bombardment that modified our planet during the dawn of life,” said Dr. David Kring, co-author of the new study and a researcher at the Lunar and Planetary Institute (LPI).

This may all sound a bit ridiculous, but this is the most plausible explanation. For the minerals to have formed on the moon, Science Alert writes that they must have formed 30 to 70 kilometers below the surface, in an “unusually oxidizing magmatic environment with oxygen levels much higher than those in the lunar mantle 4 billion years ago.” Theoretically, the fragment may have formed in weirdly water-rich pockets of magma deep within the ancient moon but it seems much more likely that the rock formed within our planet’s crust and later got jettisoned to the moon by one of the many daily meteor impacts that bombarded early Earth. 

Of course, there’s a lot of speculation involved in this scenario and the geological community at large is not so easily convinced. Researchers will have to verify this assumption by studying other lunar samples collected thus far. Hopefully, more new samples will be retrieved in the future now that NASA plans on returning humans to the moon.

The other candidate for the oldest material of terrestrial origin is a piece of zircon mineral dated from 4.4 billion years ago enclosed in a sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia. However, the dating has been disputed. Furthermore, the fragment is debris left over from that disintegrated long ago. By contrast, the Apollo 14 fragment is much better preserved since it didn’t endure millions of years of weathering. 

The oldest material of extraterrestrial origin found thus far are silicon carbide particles of the Murchison meteorite, which have been determined to be 7 billion years old, billions of years older than the 4.54 billion years age of Earth itself.

The findings appeared in the journal Earth and Planetary Science Letters.

Earth’s inner core may actually be mushy

In 1936, Danish seismologist Inge Lehmann performed a groundbreaking study showing that Earth’s iron-rich inner core is solid although it’s hotter than the sun’s surface. Since then, our understanding of the planet’s innermost layer has been constantly refined. Earlier this year, for instance, scientists in Australia showed that the inner core may be made of two distinct layers, which suggests perhaps two separate cooling events in Earth’s history. But that’s not all.

A new potentially textbook-altering study shows that the inner core may not be entirely solid — at least not in the sense that we image a solid material. Instead, scientists have found that the deepest layer of the Earth is made of a tangled bunch of solid surfaces that sit against melted or mushy iron.

Earth sounds more and more like a meat pie

Earthquake locations (red) and seismic stations (yellow). (Photo credit: Butler and Tsuboi, 2021.)

Although the inner core is obscured by more than 4,000 miles (6,300 km) of crust, mantle, and liquid outer core, scientists have a fairly clear picture of what goes inside the bowels of the Earth. How so?

Whenever a volcano erupts or an earthquake strikes, these events generate acoustic waves whose properties, such as direction, angle, and velocity, change predictably depending on the material they encounter.

There are multiple types of seismic waves, ignoring surface waves, which are responsible for the onslaught in the wake of some very powerful earthquakes. When studying the inner layers of Earth, geophysicists mainly focus on primary waves (P-waves) and shear waves (S-waves). P-waves travel through all types of mediums, whereas S-waves only travel through solid materials.

When seismic waves created by earthquakes hit the liquid outer core then travel through the inner core, seismic data gathered from stations across the world record an extra wave going off at right angles which can only be explained by a shear wave. This is how Lehmann showed that the inner core, which is about the size of the moon, is solid. It’s not all that different from how a doctor might use a CT scanner to image what’s inside your body without cutting it open.

Geophysicists are constantly learning new things about Earth’s inner layers as seismic data improves, helped by new tools such as machine learning algorithms and other AI machines. A new study led by Rhett Butler from the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology (SOEST), found that the inner core is not exactly solid. Instead, it’s a melange of liquid, soft, and hard structures. The heterogeneous composition is especially striking in the top 150 miles (240 km) of the inner core.

“In stark contrast to the homogeneous, soft-iron alloys considered in all Earth models of the inner core since the 1970s, our models suggest there are adjacent regions of hard, soft, and liquid or mushy iron alloys in the top 150 miles of the inner core,” said Butler. “This puts new constraints upon the composition, thermal history and evolution of Earth.”

The outer core is entirely liquid and much less controversial, with its molten iron in a constant churning movement, driven by convection as it steadily loses heat from the time Earth formed to the static mantle above. It’s this motion that generates our planet’s magnetic field like a dynamo, which cushions us from harmful radiation from the sun.

However, the outer core is influenced by the inner core. So having a better grasp of its true structure helps scientists form a better understanding of the dynamics between the inner and outer cores.

“Knowledge of this boundary condition from seismology may enable better, predictive models of the geomagnetic field which shields and protects life on our planet,” said Butler.

The findings appeared in the journal Science Advances.

Iconic photos of Earth taken by Apollo astronauts, digitally restored and in full glory

Earthrise, Apollo 8. Credit: NASA / Toby Ord.

In the late 1960s, humans caught the first good glimpse of our home planet from afar, thanks to the Apollo missions to the moon. During the first crewed voyage around the moon on Christmas Eve 1968, Bill Anders of the Apollo 8 mission took our planet’s most famous photo as his spacecraft rounded the dark side of the moon for the fourth time.

The picture, now known as Earthrise, is the first to show Earth rising above the moon’s barren and desolate landscape in perfect opposition to the vulnerable but life-teeming blue marble above.

The Blue Marble, Apollo 17. Credit: NASA / Toby Ord.

Another famous of Earth from way far away in outer space is Blue Marble, which shows our planet as seen by Apollo 17 astronauts in December 1972 about 30,000 kilometers into their journey towards the moon. A perfect combination of distance and timing allowed the astronauts to catch one of the few pictures showing an almost fully illuminated Earth, which from that far away resembles a spherical agate marble.

Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.

Alas, the photography gear available during the Apollo era didn’t do these sights enough justice. Toby Ord, a senior research fellow in philosophy at Oxford University in the UK, must have thought the same when he embarked on the Earth Restored project.

Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.

Earth Restored features a selection of photos captured on film that show the full Earth from space. These were taken with professional cameras specifically designed for the Apollo missions such as the Hasselblad 500EL with Zeiss Sonnar and Planar lenses. But although these photos are of good quality for the 1960s and 1970s, they nevertheless exhibit certain flaws in exposure and color casts.

For this series, Ord set out to do some cleanup work, adjusting white balances and black points, as well as dust and scratches on the camera lens, all while still preserving the look and feel of the original photos captured on film.

Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.

These pictures serve as a stark reminder that the world and all life are fragile. Ord is the founder of Giving What We Can, a movement that has so far pledged over $1.5 billion to the most effective charities across the world. He also recently published a new book called The Precipe, which concludes that “safeguarding our future is among the most pressing and neglected issues we face.”

Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.
Credit: NASA / Toby Ord.

For high-resolution images, visit Ord’s website.

Why don’t satellites fall down from the sky?

Image via Pixabay.

Satellites are able to stay in Earth’s orbit thanks to a perfect interplay of forces between gravity and their velocity. The satellite’s tendency to escape into space is canceled out by Earth’s gravitational pull so that it is in perfect balance. This is the same principle that explains how natural satellites, such as the moon, become locked in a planet’s orbit.

But some very smart people had to run some very complicated math to design the perfect satellite launch. If the satellite moves too fast, it escapes into space. Too slow and it is destined to crash into the atmosphere.

With the right distance, speed, and trajectory, an object can defy Earth’s gravitational pull for quite a long time. In fact, gravity — the same force that is trying to drag these down to the surface — is a vital force in keeping satellites orbiting around our planet.

And to make it entertaining, we’re going to start with rollercoasters.

Perpetually falling

If you’ve ever been on a rollercoaster, you’ll know that strange sensation you get in your gut around bends or hills. Physically speaking, that sensation is produced by inertia; although the cart is changing directions, your body is resisting this shift. You’re strapped in safely to the cart, but your internal organs have a bit more leeway to move. So, for a few moments, they essentially keep moving on the old trajectory, while the rest of your body is on a new one.

This process is summarized neatly in the first law of motion: an object, either moving in a straight line or at rest, will maintain that state until acted upon by an external force. “External force” here can mean a great many things, from air resistance to gravity to you hitting a flying ball with a bat.

Artificial and natural satellites rely on this law to stay above the clouds. Since there is no air resistance in space, once a body gets moving, there’s virtually nothing to slow it down. It doesn’t lose kinetic energy (momentum), so it can keep moving forever.

The satellites we build today get their energy from the rockets that bring them to orbit. They do have internal fuel supplies and thrusters, but these aren’t used to maintain speed. They’re for maneuvers such as avoiding debris or shifting orbits. Rockets impart the satellites they carry with quite a lot of energy, as they need to travel at speeds of at least 17,600 mph (28,330 km/h) to be able to escape Earth’s gravity. After separation from the satellite, this leaves enough energy to keep that satellite in orbit around the Earth for several decades, even a few centuries.

Still, the purpose of a satellite is to stay closeby (relatively speaking) so it can beam our social media posts all over the world. But from what we’ve seen so far, shouldn’t they just travel into space forever? Yes. But there’s one other force at play here — gravity. While momentum keeps satellites moving, gravity is what keeps them in our orbit.

If you fill a bucket with water and spin it really fast, you’ll see that the water won’t pour out of it. It’s being pushed against the bottom of the bucket by inertia (in this case, centrifugal force), but that bucket and your arm work against the force. They even out in the end: the water can’t move through the bucket’s bottom, it can’t escape over the lip, either, so it kind of stays in one place.

For satellites, the Earth’s gravity acts as the arm and bucket in the above example. One really simple way to understand the process is to visualize the satellite as a rocket that’s always going forward, tied with a very long chain to the center of our planet — it will just go around in circles.

What’s important here is to get the distance right. First off, you want your satellite to be outside of the planet’s atmosphere, so as to avoid air drag and keep a constant speed. But you don’t want to be too far away, because the force of gravity is inversely proportional to the squared distance between two objects. So if you double the distance between a satellite and the Earth, gravity would only pull on it one-quarter as strongly. If you triple it, it would only be one-ninth of the force. In other words, put a satellite too close to Earth and it will fall. Put it too far away, and it escapes into space.

In essence, what engineers try to do when putting a satellite in orbit is to make it fall forever. We put it up high enough that air friction is almost zero (ideally, zero). Then we push it really fast in one direction. Finally, we rely on the Earth’s gravity to pull it down while it is moving forward, so the resulting movement is a circle. Because it’s moving forward and the planet is round, it’s essentially gaining altitude constantly. But, since it’s also falling at the same time, it’s losing altitude constantly. The sweet spot is to have it escape into space just as fast as it’s falling down to Earth, all the time.

If the math is done just right and the deployment phase goes properly, these two cancel each other out, and we get an orbiting satellite. In practice, it never goes quite perfectly, which is why these devices are fitted with fuel and thrusters so they can perform tiny adjustments to their direction of motion or altitude and keep them in orbit.

A good example of what would happen in the absence of these thrusters is the Moon. Our trusty and distinctive nighttime companion is not on a stable orbit — it’s slowly escaping Earth’s gravitational pull. Due to the specifics of how the Earth’s gravitational field interacts with the Moon, our planet is ever-so-slowly accelerating it into a higher orbit. Continuing with the above example, it’s making the ‘escape into space’ force a tad more powerful than the ‘falling down to Earth’ force. As a consequence, the Moon will probably break out of orbit with Earth in the future, but we’re talking billions of years here.

Alternatively, we have (had?) the Mir space station as an example. This Russian installation ended its mission in March 2001 and was brought to a lower orbit — it was ‘deorbited‘. Here, air friction steadily slowed it down. Because of this, gravity started gaining the upper hand and Mir eventually burned up in the atmosphere while spinning around the globe, closer and closer to the surface.

The physics of how bodies in space interact is always fascinating, at least it is to me, and generally has a weird quirk to it that spices every scenario up. The idea that something can keep falling forever without actually coming closer to the ground certainly is quirky, and it fascinated me ever since I first came upon it. Later, sci-fi would bring me to concepts such as gravitational slingshots, which are very similar to what we’ve discussed here, but they actually help you go to space faster. Cool.

Our discussion so far makes this whole process sound simple, and in theory, it is. But very many bright people had to crunch some extremely complicated math to make it possible, and many still do that, in order to keep satellites orbiting over our heads. As much as falling forever sounds like magic, it’s built on countless hours of intellectual work and, in this day and age, on some very powerful computers running calculations around the clock. 

Several city- and state-sized asteroids impacted young Earth. Probably.

Early Earth might have caught some significantly larger asteroids than we assumed, a new paper reports. These could have ranged from a city to a small province in size, the authors explain. Still, in the end, these impacts could have helped to shape Earth into what it is today.

Rendering of Mars’ Victoria Crater. Image credits Alexander Antropov.

Take someone living today back to the days when our Earth was young, and they probably wouldn’t recognize it. Even after its crust cooled and solidified, the blue planet wasn’t particularly blue, but rather, a bit barren. It was also pockmarked by asteroid impacts and, occasionally, impacted by asteroids.

Most traces of this past have slowly been ground away by tectonics, erosion, and weathering. So we don’t have much in the way of direct evidence (i.e. craters) to study. Still, researchers are pretty confident that the Earth was hit by a significant number of large asteroids, rocks over 10 km (6.2 mi) in diameter, in the past, and that this helped shape its chemical properties, eventually culminating in the appearance of life. But new research presented at the 2021 Goldschmidt Geochemistry Conference proposes that these large asteroids were much larger than we believed.

Big Rock

While our planet slowly grinds away traces of asteroid impacts unlike, say, the Moon or Mars, we can still find evidence of them happening in the shape of spherules. These are round, glassy beads that are produced by super-heated material ejected during an asteroid impact. As they’re propelled away from the impact through the air, they cool to form a spherical shape and eventually land back on the surface. Over geological time, they become encased by rocks. The greater the impact, the more of these particles it would produce, and the wider they would spread around the crater.

A large enough impact could even spread spherules across the world.

The team developed a statistical model to analyze our records of spherule layers so far. Their model suggests that the number of known impacts in the past “severely underestimates” the real number of impacts. According to the results, there were likely 10 times more impacts between 3.5 and 2.5 billion years ago than we assumed. That’s equivalent to one Chicxulub-sized impact (the one that wiped out the dinosaurs) once every 15 million years.

The authors add that although we have very little information regarding their number and magnitude, these impacts had a profound effect on how the Earth’s surface and atmosphere evolved throughout the ages. For example, they explain that atmospheric levels of oxygen likely varied significantly during these impacts. They could help account for the dips we see in oxygen levels throughout history, before they stabilized around 2.5 billion years ago, for example.

Given how important oxygen eventually became for the evolution of both the Earth and the life upon it, a better understanding of ancient impacts could help us better understand how we came to be here.

Naturally, the impacts also caused widespread disruption and destruction, but we don’t really have enough evidence to estimate their true effect; very few rocks survive from that period. This lack of direct data is what prompted the team to develop a statistical model to study these impacts in the first place.

How many Earths can you fit inside the sun?

From the vantage point of a human, our world truly is huge. However, in the grand, cosmic scheme of things, the Earth is but a drop in the solar bucket.

The sun is a star at the center of the solar system, a sphere made up of hot plasma and magnetic fields. Its diameter is about 1,392,000 km (864,000 miles), nearly 109 times larger than the Earth, and its mass is 330,000 times that of the Earth. In fact, by mass, the sun makes up over 99.86% of the solar system, whereas gas giants like Jupiter and Saturn comprise most of the remaining 0.14%.

In order to comprehend the sheer scale of the sun, it’s worth asking the question: how many Earth-sized planets can you fit inside the sun?

Volume-wise, you could fit nearly 1.3 million Earths into the sun (1.412 x 1018 km3). That’s assuming all those millions of Earths are squished together with no empty space in between. But the Earth’s shape is spherical not a cube, so only about 960,000 Earths would fit inside the volume of the sun.

Here’s how it would look like (approximately) if the Earth was a tiny blue marble:

The sun is just an average-sized star, though. For instance, the red giant Betelgeuse has a radius 936 times that of the sun, making it billions of times larger in volume than the Earth.

And that’s nothing. VY Canis Majoris is thought to have between 1,800 and 2,100 times the radius of the sun. Therefore, you could fit dozens of billions of Earths in some of the largest stars in the universe.

This illustration shows the approximate sizes of the planets relative to each other. Credit: Wikimedia Commons / NASA/ A. Simon.

Earth is neither the largest nor the smallest planet in the solar system. Mercury (0.055 times Earth’s volume), Venus (0.85 times Eath’s volume), and Mars (0.151 times Earth’s volume) are all smaller than Earth. It would take 17.45 million Mercury-sized planets, 1.12 million Venus-sized planets, and 6.3 million Mars-sized planets to fill the sun, gaps not included.

On the opposite end, you could fit 726 Jupiter-sized planets (1,321 times the volume of Earth) and 1,256 Saturn-sized planets (764 times the volume of Earth) inside a hollow sun, gaps not included.

In the future, you could cram even more Earths or Jupiters into the sun. As it drags closer to the end of its lifecycle, the sun gets both hotter and larger as it continues to fuse hydrogen into helium at its core. When it runs out of fuel, the core will collapse and heat up ferociously, causing the sun’s outer layers to expand.

By astronomers’ calculations, the sun is already 20% larger than at the time of its formation roughly five billion years ago. In another five billion years, when it will reach its helium-burning phase, the sun will turn into a red giant. It will be so large at this time that it will completely engulf the planets Mercury, Venus, and perhaps even Earth.

Mars is also a wobbly planet like Earth, and we don’t know why

Mars becomes the second planet after Earth that we know is wobbling around its axis. As to why — we’re yet unsure.

Digital rendering of Mars. Image via Pixabay.

As the Red Planet spins during its day, it also wobbles and bobbles gently around its own axis, a new paper reports. Astronomers have no idea why this is happening, but the fact that Mars is the second planet we know of to do this (after Earth) could help us understand it better.

The Chandler wobble

This type of motion — a planet’s wobble around its own axis as it spins — is known as the Chandler wobble. Earth shows some 30 feet (9 meters) of amplitude in this wobble: its poles move in a circle with a 9-meter diameter around its axis, with a period of around 430 days.

Mars seems to be doing the same, albeit the diameter it spins on is way smaller: 4 inches (10 centimeters) off-center, with a period of around 200 days, according to Eos.org, the news blog of the American Geophysical Union (AGU).

The Chandler wobble is produced when a rotating body’s mass isn’t distributed evenly. Things like differences in density throughout its body or in its shape will lead to such a wobble. In Earth’s case, it is caused by its shape, which isn’t perfectly round. Although Earth’s is much more pronounced than that of Mars, it’s possible that the source of the wobble is the same for both planets.

Still, here’s where the mystery begins. Over time, we know that this wobble should fade out. It’s been calculated that for Earth, any Chandler wobbling should disappear within a century of it starting. However, we know that this isn’t the case — Earth has been wobbling for much longer than that.

Given that our planet is both geologically and biologically active, our running assumption so far is that shifts in atmospheric and ocean pressures (i.e. the movement of large bodies of water and gas) are constantly fueling this wobble, which is why it didn’t die out when our calculations said it would.

But Mars is neither geologically nor biologically active, as far as we know. It has no oceans and only a thin coating of an atmosphere. And yet it wobbles.

The movement was detected using 18 years’ worth of data collected by satellites around Mars: Mars Odyssey, Mars Reconnaissance Orbiter and, Mars Global Surveyor. Crunching the math leads to the same conclusion as it does on Earth: this wobble should end naturally, but so far, it hasn’t.

Our only guess so far is that, in Mars’ case, the Chandler wobble is fueled by atmospheric motions alone; this would fit with the much lower amplitude of motion compared to Earth’s own wobble. However, more data is needed before we can be certain.

However, we do know one thing for sure: if we’ve found two planets which wobble, we’re likely to see more in the future doing the same. Maybe we can understand what’s happening before we run into the third.

A Big Blue Marble. A History of Earth from Space

“As the Sun came up I was absolutely blown away by how incredibly beautiful our planet Earth is. Absolutely breathtaking. Like someone took the most brilliant blue paint and painted a mural right in front of my eyes. I knew right then and there that I would never, ever see anything as beautiful as planet Earth again.”

Scott Kelly, Former NASA Astronaut
The Blue Marble. Taken by the crew of Apollo 17 in 1972 at a distance of 29,000 km above the planet. (NASA/Apollo 17 crew)

There is a common experience shared by human beings who visit that edge of space when they turn back and look upon their home planet. In that most fleeting of moments, they see the beauty and delicacy of our homeworld. It’s clearly not a view that many of us will get to experience in person, certainly not for the foreseeable future at least.

Despite that, thanks to some incredible photography and imaging techniques we too can view Earth from space and get a sense of our place in the solar system and the wider universe. 

The term ‘Big Blue Marble’ as it applies to Earth refers to an image captured of our planet by the Apollo 17 astronauts in December 1972. The image — officially designated as AS17–148–22727 by NASA— was taken at 29 thousand kilometres above the Earth by the crew of the spacecraft as it headed to the Moon.

Turning their view back on our planet, the astronomers caught a stunning image of the Mediterranean Sea to Antarctica. The image shows the south hemisphere heavily shrouded by clouds and represents the first time that an Apollo craft had been able to capture the southern polar ice caps.

The original uncropped AS17–148–22727 from which 'the Blue Marble' is taken. (NASA/Apollo 17 crew)
The original uncropped AS17–148–22727 from which ‘the Blue Marble’ is taken. (NASA/Apollo 17 crew)

Perhaps the most extraordinary thing about AS17-148-22727 is that it wasn’t supposed to exist. The crew weren’t scheduled to take an image at that point in their journey.

The fact that the photo was snapped very much during a ‘stolen moment’ aboard the craft and during a mission that was tightly scheduled down to the minute, makes the fleeting beauty it presents even more striking, as too does the fact that no human since has travelled far enough away from the surface of the planet to take such an image.

Since being taken ‘the Blue Marble’ has rightfully become one of the most reproduced images in human history. Though the most famous image of Earth from a space-based vantage point and a rare example of the glimpse of a fully illuminated globe, AS17–148–22727 is just one of a cavalcade of stunning images of our planet taken over seven decades.

The very first of these images were captured in perhaps the most unusual and ironic of circumstances. 

The Early days of Earth Photography: Recovering from War

“Consider again that dot [Earth]. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every ‘superstar,’ every ‘supreme leader,’ every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.”

Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space
The first image of Earth taken from space in 1946 (White Sands Missile Range / Applied Physics Laboratory)

During the Second World War German V2s caused untold amounts of damage upon the cities of Europe, raining death from the skies and bringing profound fear and sorrow. It’s somewhat ironic then that the scientific marvel of the first image of Earth from space was delivered by one of these fearsome rockets.

Several V2s– Vergeltungswaffe 2, the world’s first long-range guided ballistic missiles–had been reclaimed by the United States as part of Operation Paperclip. The aim, however, was to use their incredible supersonic speed not to escape radar detection, as had been the case during the war, but to escape the confines of the atmosphere.

The rockets had their explosive payloads removed from their nosecones and replaced with scientific equipment.

On 24th October 1946, experiments with the V2s would result in a tangible benefit and a legitimate scientific breakthrough. A rocket launched from the White Sands Missile Range in New Mexico, USA, would capture an image of the Earth from an altitude of 105km. Up until this point in time, the highest an image of earth that had been taken was 22km by equipment aboard a high-altitude balloon.

The image was captured by a 35mm camera in the device’s nosecone which was set to capture a picture every 1.5 seconds. These images were then dropped back to earth in a steel canister and developed.

(White Sands Missile Range / Applied Physics Laboratory)

The V2 program and the series of experiments that it birthed would help US scientists lay the groundwork for future space exploration and was reflected by similar experiments in the Soviet Union at the time. These programs and the reclamation of German technology and the scientists behind it was responsible for launching the space race of the 1950s and 1960s. And no goal or aspiration would encompass this heated scientific battle more than the desire to put a human on the Moon.

The Earth and the Moon: Picturing a Perfect Partnership

“Orbiting Earth in the spaceship, I saw how beautiful our planet is. People, let us preserve and increase this beauty, not destroy it!”

Yuri Gagarin, the first human in space (12 April 1961)
A view of the Earth from the Moon taken by NASA’s Lunar Orbiter 1 in 1966 (NASA/ LOIRP).

By 1966 when the image above was captured the space race was in full swing. The USSR had launched both Sputnik 1 & 2 into orbit in October and November 1957 respectively, with the first becoming the original Earth-orbiting satellite and the second carrying a dog named Laika into space.

This would quickly be followed by US satellites Explorer 1 carrying experimental equipment that would lead to the discovery of the Van Allen radiation belt, and the world’s first communications satellite SCORE, both in 1958. In the same year, the National Aeronautics and Space Administration (NASA) would be created to replace the National Advisory Committee on Aeronautics (NACA).

Earth rises above the Moon’s horizon as seen by Apollo 11 (NASA/ JSC)


Most significantly, in 1961 the Soviets would put the first human being into orbit. Cosmonaut Yuri Gagarin made a single orbit around the Earth at a speed of over 27 thousand kilometres per hour during his 108-minute stay in space.

Yet, it wasn’t the Soviets that captured the stunning image above of earth from the vicinity of the Moon’s surface. That honour belongs to the US craft Lunar Orbiter 1 (LU-A). The NASA spacecraft was the first US mission to orbit the Moon, its primary task was to photograph not the Earth but rather potential landing sites on the Moon for the upcoming Apollo missions.

Again, as was the case with Apollo 17’s ‘Blue Marble’, the image of Earth from space taken by Lu-A taken on August 28th 1966 by the onboard Eastman Kodak imaging system was completely unplanned.

In 1969 many of the Apollo missions themselves would capture stunning and evocative images of the Earth rising above the crest of the Moon’s surface–including the above image captured by Apollo 11 and the one below taken by Apollo 8. These ‘Earthrise’ photographs would become a popular expression of Earth’s relative isolation and vulnerability.

NASA’s Lunar Reconnaissance Orbiter (LRO) captured a unique view of Earth from the spacecraft’s vantage point in orbit around the moon on October 12, 2015. (NASA/ Goddard/ Arizona State University).

The Earth From the Surface of an Alien World

“The vast loneliness is awe-inspiring and it makes you realize just what you have back there on Earth.” 

Jim Lovell, Apollo 8 Command Module Pilot, during a live broadcast from the Moon on Christmas Eve 1968.

It’s no great surprise given our advancing exploration of space that our attention has turned to the view of Earth from other alien worlds. Even though we are still capturing amazing images from that vantage point such as the one above taken by NASA’s Lunar Reconnaissance Orbiter mission in 2015, our horizons have also broadened to a view of our homeworld from the surface of more distant worlds.

The first image ever taken of Earth from the surface of a planet beyond the Moon. It was taken by the Mars Exploration Rover Spirit (NASA/JPL/Cornell/Texas A&M)

The first image of earth taken from another planet (above) was captured by the Mars Exploration Rover Spirit on the 63rd Martian day of its mission in 2004. Earth was only visible in the image–comprised from images taken by the now silent robotic rover’s four panoramic cameras–after all the colour filters were removed.

This was followed up in January 2014 by NASA’s Curiosity Rover when it captured its first glimpse of Earth from the surface of Mars.

NASA’s Mars rover Curiosity took this photo of Earth from the surface of Mars on Jan. 31, 2014, 40 minutes after local sunset, using the left-eye camera on its mast. Inset: A zoomed-in view of the Earth and moon in the image. (NASA/JPL-Caltech/MSSS/TAMU)

Whilst Mars Exploration Rover Spirit and the Curiosity Rover images may not be the most visually spectacular in the catalogue built during seven decades of space exploration, it stands as a testament to man’s determination to explore other worlds. a determination that nows carries us beyond the solar system.


This composite image of Earth and its moon, as seen from Mars, combines the best Earth image with the best moon image from four sets of images acquired on Nov. 20, 2016, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter. (NASA/JPL-Caltech/Univ. of Arizona)

A View on the Future

“You develop an instant global consciousness, a people orientation, an intense dissatisfaction with the state of the world, and a compulsion to do something about it. From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, ‘Look at that, you son of a bitch!’ “

Edgar Mitchell, Apollo 14 astronaut and the sixth person to walk on the Moon.
Deep Space Climate Observatory (DSCOVR)

As we continue to expand our view of the Universe studying cosmic bodies further and further from our own solar system, the history of space photography reminds us that it is vital we keep a view on our own planet, too. It’s a testament to our scientific progress that the hardest element about putting together a brief article about images of Earth from space that it involved sifting through thousands of incredible pictures.

Currently, NASA’s fleet of satellites consists of many craft devoted to the observation of Earth from space. Often this observation from a cosmic vantage point has the benefit of providing perspective on the damage we are doing to our world. Not only this but NASA’s continued observation of our world allows us to better understand weather patterns and mitigate potential disasters.

Humanity has never been in a better position to understand our world and its place within the wider Universe. The view of our planet from space has shown us its fragility, vulnerability, and the lengths we must go to preserve this beautiful blue marble.

“It is crystal clear from up here that everything is finite on this little blue marble in a black space, and there is no planet B.”

Alexander Gerst, European Space Agency astronaut, to world leaders live from the ISS, December 17th 2018.

Sea turtles are amazing navigators — but they only use crude maps

: A Green Turtle that was returning to sea, the morning after she laid her eggs on Ascension Island. They lay on average 120 eggs in a clutch and may lay 6 clutches in a season. Credit: Wikimedia Commons.

Sea turtles are migratory species from the moment they are ready to come into this world. After they’ve hatched out of their nesting grounds on the beaches of Florida, Yucatan, or other eastern coasts of the Americas, they immediately embark on a frenzied race towards the sea.

On their journeys, these younglings can end up traveling more than 10,000 miles across the entire North Atlantic, before returning to their original breeding grounds.

Clearly, sea turtles are amazing navigators, likely using the earth’s geomagnetic field to pinpoint their position and orientate. However, don’t imagine that their internal GPS is very accurate.

According to a new study, sea turtles often miss their mark, sometimes by hundreds of miles. This can add thousands of extra miles to their migrations as they take less straightforward paths to their destination. So, instead of Google Maps, think of the sea turtle’s positioning system more like a very crude map — it’s far from perfect, but it gets the job done.

“By satellite tracking turtles travelling to small, isolated oceanic islands, we show that turtles do not arrive at their targets with pinpoint accuracy,” says Graeme Hays of Australia’s Deakin University.

“While their navigation is not perfect, we showed that turtles can make course corrections in the open ocean when they are heading off-route. These findings support the suggestion, from previous laboratory work, that turtles use a crude true navigation system in the open ocean, possibly using the earth’s geomagnetic field.”

Hays and colleagues attached satellite tags to 33 nesting green turtles (Chelonia mydas). Originally, the researchers wanted to find out more about the extent of the animals’ movements in order to identify key areas for conservation efforts.

But as the researchers tracked the turtles, they noticed that they were traveling to isolated islands and submerged banks — and they did so rather awkwardly.

The turtles were tracked from the moment they left their nesting beaches on the island of Diego Garcia in the Indian Ocean, from which they embark on a journey towards their foraging grounds across the western Indian Ocean.

According to the satellite data, 28 out of 33 turtles didn’t reorient themselves daily or at a fine scale. As a result, the turtle would often travel hundreds of miles out of their way before correcting their course. This confusion most often occurred in the open ocean.

So, instead of reaching their small island destination with pinpoint accuracy, the turtles more often than not overshot their targets or wasted time searching for their favorite remote islands during the final stages of their migration.

“We were surprised that turtles had such difficulties in finding their way to small targets,” Hays says. “Often they swam well off course and sometimes they spent many weeks searching for isolated islands.

“We were also surprised at the distance that some turtles migrated. Six tracked turtles travelled more than 4,000 kilometers to the east African coast, from Mozambique in the south, to as far north as Somalia. So, these turtles complete round-trip migrations of more than 8,000 kilometers to and from their nesting beaches in the Chagos Archipelago.”

Although this study shows that highly accurate turtle navigation is a myth, the findings do not subtract from their impressive migrating abilities. After all, this is the first study that showed that sea turtles are capable of reorienting themselves in the open ocean, which implies they actually have a mental map of some sort.

The study also has important applications for sea turtle conservation. Once their nesting season is done, turtles travel extensively across the open ocean. As such, conservation efforts have to be coordinated across large spatial scales, covering many countries.

In the future, the researchers would like to employ novel tag technology that will enable them to not only determine their location but also the turtles’ compass heading.

“Then we can directly assess how ocean currents carry turtles off-course and gain further insight into the mechanisms that allow turtles to complete such prodigious feats of navigation,” Hays says.

The findings were reported in the journal Current Biology.

Jupiter will be very bright and visible tonight, as it comes closest to Earth

The largest planet in our Solar System will be shining bright tonight and in the early hours of Tuesday morning.

Jupiter, seen by the Juno spacecraft.
Image via Wikimedia.

According to NASA, the orange giant will be in ‘opposition’ to Earth — at its closest point to our home in its orbit. Its size and proximity should make it very easy to spot during this time, with only the Moon and Venus likely to out-do it in terms of shine.

The best time to spot it should be between midnight and 2 in the morning. Light-drenched environments such as big cities aren’t going to be the best viewing spots (although Jupiter, which will outshine stars, should still be visible from here).

Your local weather conditions will obviously also impact visibility. Most of the US is forecasted to see clear night skies on Monday. The forecast for Europe is a bit more uncertain, with central and Eastern Europe likely to see rain.

“When a planet is at opposition, it is the best time to look for it in the night sky. This is the point in its orbit when it’s closest to the Earth, making it appear brighter than other times of the year,” AccuWeather explains.

The term ‘opposition’ refers to two celestial bodies being on opposite sides of a third one, usually the star they orbit (in this case, the Sun).

If you like star (planet?) gazing, this isn’t the only treat you’re getting this month. Jupiter, the yellow slightly-smaller giant behind Jupiter, will also reach opposition on July 20. Comet Neowise, discovered in late March, will be putting on “Earth’s greatest cometary show in 13 years”. It will become visible starting with 12-13 July and be most visible on the 23rd, according to Forbes.

Neowise is brighter than Halley’s Comet was in 1986 at the moment, and will only get brighter as it nears the Sun.

So make sure to keep your eyes on the skies this month, and not miss the show that nature is putting on.

Seismic waves reveal surprisingly widespread blobs near the Earth’s core

Our planet’s core might be pockmarked with hot blobs. We don’t know what they are, we don’t know where they’re from, but according to a new study, they’re there.

The blobs in the core. Image credits: Doyeon Kim/University of Maryland.

Ever stopped and wondered just how we know so much about the Earth’s interior? Since we’re kids, we’re told that the Earth has a crust, a mantle, and a core, but how do we know this? The Earth’s radius measures thousands of kilometers, and the deepest hole mankind has ever dug only goes down to 10 km, so it’s not like we actually went there and saw what was going on.

Most of the information we have about the Earth’s structure comes from earthquakes.

When an earthquake takes place, it sends out seismic waves in all directions. These waves are essentially acoustic waves, propagating throughout the planet’s interior. Seismologists detect these waves using specialized stations placed all around the world, and by analyzing these waves, they can understand some of the properties of the planet’s structure, similar to an ultrasound. This is exactly what happened here.

Researchers looked at echoes generated by a specific type of wave. This particular type of wave travels along the core-mantle boundary and is called a shear wave. But looking for a single wave on a seismogram is very challenging — the wave from your earthquake needs to travel to the planet’s core and then back to the surface, where we can detect it. So instead, researchers tried a different approach.

Seismogram example from the 1906 San Francisco earthquake.

Using a machine-learning algorithm, they analyzed 7,000 seismograms from hundreds of big earthquakes around the Pacific Ocean from 1990 to 2018, looking for similarities and patterns in the data. A smudge in the seismograph might be a coincidence, but the same smudge in hundreds of seismograms has meaning — and in this case, researchers found quite a few smudges.

Correlation in smudges on different seismographs. Image credits: Doyeon Kim

The findings suggest that there are widespread areas around the Earth’s core where seismic waves travel at a lower-than-normal velocity. These low-velocity areas are thought to represent hot, molten blobs — and according to this study, the core is much more blobby than we thought.

In particular, the team found a lot of these hot blobs under the Marquesas Islands, a group of volcanic islands about halfway between South American and Australia.

“We were surprised to find such a big feature beneath the Marquesas Islands that we didn’t even know existed before,” said geologist Vedran Lekić of the University of Maryland.

“This is really exciting, because it shows how the algorithm can help us to contextualise seismogram data across the globe in a way we couldn’t before.”

The algorithm itself shows great promise. It’s called Sequencer and was designed to run through large astronomical datasets looking for patterns. Now that researchers have adapted it to different types of data, and this first find is already exciting.

“We were surprised to find such a big feature beneath the Marquesas Islands that we didn’t even know existed before,” said Vedran Lekić, an associate professor of geology at UMD and a co-author of the study. “This is really exciting, because it shows how the Sequencer algorithm can help us to contextualize seismogram data across the globe in a way we couldn’t before.”

Researchers knew that some of these can exist, but they turned out to be much more common than expected — potentially hinting that they may also be present in other areas of the planet’s interior.

“We found echoes on about 40% of all seismic wave paths,” Lekić said . “That was surprising because we were expecting them to be more rare, and what that means is the anomalous structures at the core-mantle boundary are much more widespread than previously thought.”

In addition, since the Sequencer algorithm has already proven to be quite robust, researchers say that it could potentially be adapted to other types of research as well.

“Exploring a large dataset with the Sequencer enables a data-driven analysis of seismic waveforms without any prior expectations. We anticipate this approach to be useful for many types of datasets beyond seismograms,” the researchers conclude.

Journal Reference: D. Kim, V. Lekić, B. Ménard, D. Baron and M. Taghizadeh-Popp. Sequencing Seismograms: A Panoptic View of Scattering in the Core-Mantle Boundary Region. Science, 2020 DOI: 10.1126/science.aba8972

Scientists have new evidence that Earth’s inner core may be rotating

A new study of Earth’s inner core used seismic data from repeating earthquakes, called doublets, to find that refracted waves, blue, rather than reflected waves, purple, change over time – providing the best evidence yet that Earth’s inner core is rotating. Credit: Michael Vincent.

Geologists have been debating for decades whether the planet’s inner core is rotating or not. New evidence obtained by Chinese researchers seems to hint towards the former, according to seismic data.

The motion of molten iron alloys in the Earth’s outer core acts as a planetary dynamo, generating a massive magnetic field called the magnetosphere. It extends for several tens of thousands of kilometers into space, well above the atmosphere, sheltering the planet from the charged particles of the solar wind and cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects life from harmful ultraviolet radiation.

However, there is still much we don’t know about how the planet’s core interacts with complex physics to generate magnetic fields. For instance, the north and south poles have “wandered” and flipped periodically over Earth’s geological history, and these behaviors aren’t completely understood.

For decades, the motion of the inner core has been the realm of theoreticians. But in 1996, Xiaodong Song, now a geology professor at Peking University in China, detected seismic waves passing through the inner core that suggested differential rotation of the inner core relative to Earth’s surface.

These initial findings were rather quickly dismissed, with other studies pointing towards the reflection of seismic waves off the ununiform inner core boundary, which can act like canyons or mountains.

For their new study, Song and colleagues — including researchers at the University of Illinois at Urbana-Champaign — reviewed seismic data from a range of geographical locations across the world. The data also included repeating earthquakes, known as doublets, that occur in the same spot over time.

These doublets proved essential because they offer the separating factor enabling scientists to distinguish changes due to variation in relief from changes due to movement and rotation of the planet’s core.

According to the findings, some of the earthquake-generated seismic waves penetrated the iron layer right below the inner core boundary and changed over time. This shouldn’t have happened if the inner core were stationary, the researchers wrote in the journal Earth and Planetary Science Letters.

“Importantly, we are seeing that these refracted waves change before the reflected waves bounce off the inner core boundary, implying that the changes are coming from inside the inner core,” Song said.

“This work confirms that the temporal changes come mostly, if not all, from the body of the inner core, and the idea that inner core surface changes are the sole source of the signal changes can now be ruled out,” he added.

In a previous study while he was a professor at Columbia University, Song and colleagues estimated that the inner core rotates in the same direction as the Earth and slightly faster, completing its once-a-day rotation about two-thirds of a second faster than the entire Earth.

While that might not seem like a lot, it’s still some 100,000 times faster than the drift of continents — and over time it adds up. Over the past 100 years that extra speed has gained the core a quarter-turn on the planet as a whole, the scientists found. 

Splendid animation shows the Earth without water — it’s stunning

What would the Earth look like without its oceans? Surprisingly mountainous, a new animation reveals.

Image credits James O’Donoghue via Youtube.

The clip was produced by planetary scientist James O’Donoghue, formerly at NASA and currently working for the Japanese space agency (JAXA). O’Donoghue worked from a video created by NASA physicist and animator Horace Mitchell back in 2008, editing its timing and adding in a tracker to showcase how much water was drained throughout the animation.

All in all, the video is a great way to showcase Earth’s underwater mountain ranges — the longest ones in the world — and the now-submerged paths that took humanity across the continents.

Sans water

“I slowed down the start since, rather surprisingly, there’s a lot of undersea landscape instantly revealed in the first tens of meters,” O’Donoghue told Business Insider.

The landscapes O’Donoghue mentions here are the continental shelves and undersea edges of each continent. These are swathes of land with higher average altitudes than the rest of the ocean floor which surround the continents — they represent the transitional landscape between dry land and the deep abyss.

The land bridges that early humans used to migrate from continent to continent are part of these raised areas. They’re submerged right now but tens of thousands of years ago, when ocean levels were much lower due to an ice age that created huge volumes of ice at the poles, they were raised enough to walk across. In those days, you could just walk from Europe to the UK, to Alaska from Siberia, or from Australia to the many islands surrounding the land down under.

“Each of these links enabled humans to migrate, and when the ice age ended, the water sort of sealed them in,” O’Donoghue adds.

But the oceans are hiding more than the movements of our ancestors. Earth’s longest chains of mountains appear in the video once sea levels have dropped by 2,000 to 3,000 meters. These sunken mountains are known as mid-ocean ridges, and form in the areas where tectonic plates butt heads. Earth’s deepest areas also make an appearance — once all the water is taken away, understandably. These deep-ocean trenches form where tectonic plates move away from one another, creating deep gorges where magma pushes up from the Earth’s interior to generate fresh crust. To give you an idea of just how deep these gorges are, the Mariana Trench first pops up after 6,000 meters of water are removed in the video; however, its bottom only becomes visible after another 5,000-or-so meters.

“I like how this animation reveals that the ocean floor is just as variable and interesting in its geology as the continents,” O’Donoghue concludes.

Around two-thirds of the planet is covered by water. Since we don’t really have many opportunities to see the ocean floor, it is commonly imagined as a vast, flat, featureless expanse. But O’Donoghue’s work showcases the richness of underwater landscapes, and reminds us that the bottom of the ocean isn’t a boring place — it’s one of the most spectacular and untouched frontiers left on Earth.

In the Earth’s core, it’s snowing iron

Christmas is just around the corner, and with it, inevitably, come songs of “let it snow”. This particular carol is also relevant at the Earth’s core, a new study shows. According to the findings, iron snow blankets our planet’s internal core year-round.

Image credits Hendrik Kueck / Flickr.

Extreme pressure and heat don’t rule out snow, it seems, but it does make it more metal. Particles of iron that form in the Earth’s outer core ‘snow down’ on top of the inner core, a new study reports, and pile up in layers up to 200 miles thick.

The Earth’s inner core is hot, under immense pressure and snow-capped, according to new research that could help scientists better understand forces that affect the entire planet.

The snow is made of tiny particles of iron — much heavier than any snowflake on Earth’s surface — that fall from the molten outer core and pile on top of the inner core, creating piles up to 200 miles thick that cover the inner core. The findings could help explain anomalies seen in geophysical systems and improve our understanding of the processes taking place in the heart of our planet.

Inside knowledge

“The Earth’s metallic core works like a magma chamber that we know better of in the crust,” said Jung-Fu Lin, a professor in the Jackson School of Geosciences at The University of Texas at Austin and a co-author of the study.

Since the Earth’s interior is a tad inaccessible to us, researchers use seismic waves to investigate its structure and behavior. We know how seismic waves act in different contexts from experiments done on the surface, so we can estimate how they will behave inside the planet based on our current models of Earth’s structure. Whenever we see something that doesn’t go according to our predictions, it’s a good sign that our model was wrong — and we update it to fit the results.

One area where our predictions didn’t match results is at the boundary between the outer and inner core. Seismic waves move more slowly through this area than we expected, and move faster than we thought they would through the eastern hemisphere of the topmost inner core.

The study proposes that the layers of ‘iron snow’ that form on the core can explain the results. The existence of this slurry-like layer has been suggested since the early 1960s, but the data needed to support this view proved elusive.

In the study, Zhang and his team explain that crystallization was possible in this layer of the Earth and that about 15% of the lowermost outer core could be made up of iron-based crystals. It’s these crystals that fall down and settle onto the liquid inner core like a blanket of snow. This build-up is the cause of the anomalous seismic readings in the area, they add.

“It’s sort of a bizarre thing to think about,” said Nick Dygert, an assistant professor at the University of Tennessee who co-authored the study. “You have crystals within the outer core snowing down onto the inner core over a distance of several hundred kilometers.”

Seismic waves move faster through denser material — and the slurry-like coating of iron crystals slows them down. Because there is a variation in the thickness of these deposits around the inner core, with the eastern hemisphere showing thinner packs, seismic wave speed isn’t constant throughout the boundary.

“The inner-core boundary is not a simple and smooth surface, which may affect the thermal conduction and the convections of the core,” Zhang said.

The Earth’s core is the lynchpin in phenomena that affect the planet as a whole, from supplying the heat that drives plate tectonics to the generation of its magnetic field. Better understanding its structure and properties can help us make better sense of the processes it partakes in — and of other planets as well.

The paper “Fe Alloy Slurry and a Compacting Cumulate Pile Across Earth’s Inner‐Core Boundary” has been published in the Journal of Geophysical Research: Solid Earth.

Exoplanets could have better conditions for life than Earth, study finds

Some exoplanets could have better conditions for life to thrive than Earth itself, according to a new study that used computer modeling to explore the conditions that could exist on different types of exoplanets.

Credit: Flickr

“This is a surprising conclusion,” said lead researcher Dr. Stephanie Olson, “it shows us that conditions on some exoplanets with favorable ocean circulation patterns could be better suited to support life that is more abundant or more active than life on Earth.”

The search for life outside the solar system has been accelerated by the discovery of exoplanets. As they can’t be explored by space probes because of the distances involved, scientists are working with remote tools such as telescope to understand conditions there.

With her team, Olson used software called ROCKE-3D developed by NASA’s Goddard Institute for Space Studies to model rocky exoplanets. They modeled a range of different exoplanets to explore which would be the most likely to develop and sustain life, based on ocean circulation.

They found that thicker atmospheres combined with slower rotation rates and the presence of continents all produced higher upwelling rates. The research was presented at the Goldschmidt Geochemistry Congress in Barcelona.

“NASA’s search for life in the Universe is focused on the so-called ‘habitable zone’ planets, which are worlds that have the potential for liquid water oceans. But not all oceans are equally hospitable—and some oceans will be better places to live than others due to their global circulation patterns,” Olson said.

Previous research has shown that salty oceans are likely to exist beyond the Solar System. In addition to Earth, Mars was once rather watery for example and there are moons that appear to harbor liquid oceans. But these nearby worlds don’t meet the criteria laid out by the research, though.

Mars is dry and has a thin whisper of an atmosphere, and the moons so far researched have barely any atmospheres as well; we’re also currently unsure of their continental status. But there are a lot more exoplanets out there in the galaxy than there are moons in the Solar System.

The first criterion that has so far been used in the search for habitable exoplanets has been whether a planet is in the “habitable zone” — where temperatures are not so hot that liquid oceans would boil, nor so cold that they would freeze. This new research adds some parameters that could be employed in future searches.

“In our search for life in the Universe, we should target the subset of habitable planets that will be most favorable to large, globally active biospheres,” Olson said, “because those are the planets where life will be easiest to detect – and where non-detections will be most meaningful.”

Earth’s history gets rewritten by a single drop of water

Using just the remaining of a single microscopic drop of ancient water, a group of researchers was able to rewrite the history of the Earth’s evolution and change the time when plate tectonics actually started on the planet.

Credit: Flickr

Plate tectonics is a continuous recycling process that directly or indirectly controls almost every function of the planet, such as atmospheric conditions, mountain building, natural hazards, the formation of mineral deposits and the maintenance of the oceans.

The large continental plates of the planet continuously move thanks to this process, while the top layers of the Earth are recycled into the mantle and replaced by new layers through processes such as volcanic activity.

The plate tectonics was initially thought to have started about 2.7 billion years, but that has now changed. A team of researchers used the microscopic leftovers of a drop of water that was transported into the Earth’s deep mantle to show this process actually started 600 million years before that.

“Plate tectonics constantly recycles the planet’s matter, and without it, the planet would look like Mars,” says Professor Allan Wilson, who was part of the research team. “Our research shows that plate tectonics started 3.3 billion years ago now coincides with the period that life started on Earth. It tells us where the planet came from and how it evolved.”

For their research, published in the journal Nature, the team analyzed a piece of rock melt, called komatiite – named after the Komati river near Barberton in Mpumalanga where it most commonly occurs – that are the leftovers from the hottest magma ever produced in the first quarter of Earth’s existence.

Despite most of the komatiites were obscured by later alteration and exposure to the atmosphere, small droplets of the molten rock were preserved in a mineral called olivine. This allowed the team to study a perfectly preserved piece of ancient lava as part of their research.

“We examined a piece of melt that was 0.01mm in diameter, and analyzed its chemical indicators such as H2O content, chlorine, and deuterium/hydrogen ratio, and found that Earth’s recycling process started about 600 million years earlier than originally thought,” said Wilson. “We found that seawater was transported deep into the mantle and then re-emerged through volcanic plumes from the core-mantle boundary.”

Earth is the only planet in our solar system that is shaped by plate tectonics and without it the planet would be uninhabitable. The research offers insight into the first stages of plate tectonics and the start of a stable continental crust.

“What is exciting is that this discovery comes at the 50th anniversary of the discovery of komatiites in the Barberton Mountain Land by Wits Professors, the brothers Morris and Richard Viljoen,” said Wilson.

Humanity has already spent all of Earth’s environmental budget for 2019

Starting today, humanity will consume more resources through the end of 2019 than the planet can sustainably regenerate for the year. This year is the earliest we’ve ever spent these resources, according to the Global Footprint Network (GFN), which has been calculating Earth Overshoot Day since 1986.

Shifting from fossil fuels to renewables can help reduce consumption. Credit: Christian Dembowski

 

“The day falling on July 29 means that humanity is currently using nature 1.75 times faster than our planet’s ecosystems can regenerate. This is akin to using 1.75 Earths,” the environmental group said in a statement.

Annual ecological deficits began in the 1970s, according to the GFN, compromising the planet’s future regenerative capacity.

In 1993, Earth Overshoot fell on October 21. In 2003 it happened on September 22, and in 2017 it fell on August 2.

The Earth is so large and its resources are so plentiful that it almost seems infinite — but it’s not. Our planet has a finite regeneration capacity, and we’ve heavily overtaxing it.

The GFN totals usage of food, timber, fibers, carbon sequestration and more. Currently, carbon emissions from fossil fuel constitute 60% of humanity’s ecological footprint, according to the environmental group.

“We have only got one Earth this is the ultimately defining context for human existence. We can’t use 1.75 (earths) without destructive consequences,” said Mathis Wackernagel, founder of GFN.

Some countries reach their own overshoot days much more quickly than others, the report said. Qatar and Luxembourg overshoot the mark less than 50 days into the year, while the United Arab Emirates, Kuwait, the US, Canada, Denmark, and Australia burned through their allotted resources before the end of March.

Overshoot Day is a good way to see how sustainably we are faring. If it were moved back five days annually, we could life sustainably (that is, use the resources available to a single planet) 2050. But things are moving backward instead of forward, and any improvement will require massive changes. For instance, replacing 50% of meat consumption with vegetarian food would move the date of Overshoot Day 15 days

The organization has identified several areas in which we can reduce consumption — and it’s an all too familiar picture. We need:

  • a shift away from fossil fuels, which make up the biggest share of our overall footprint;
  • more efficient and low-carbon city design;
  • a fix of our the food system;
  • protecting nature through regenerative agriculture and large-scale conservation.

Overpopulation is also a key point, Wackernagel said; one of the best solutions is to provide women and girls with the same educational and economic opportunities offered to men.

“The costs of this global ecological overspending are becoming increasingly evident in the form of deforestation, soil erosion, biodiversity loss or the buildup of carbon dioxide in the atmosphere,” according to the GFN. “The latter leads to climate change and more frequent extreme weather events.”

To help mankind decrease consumption to sustainable levels, GFN offers its ecological footprint calculator in Hindi, English, Chinese, French, German, Portuguese, Spanish and Italian.

Planet hands.

Climate warming is definitely, for sure, no doubt about it, our fault, says new study

University of Oxford researchers have confirmation: we’re causing climate change, natural factors have very little to do with it.

Planet hands.

Image via Pixabay.

Human activity and other external factors are responsible for climate warming, the paper reports. This, in itself, isn’t exactly news; there has been consensus around the issue in the scientific community for a long time now. One piece of the puzzle, however, remained unclear — what effect natural ocean currents had on climate patterns over the course of multiple decades. This lack of understanding has been leveraged by some to throw the whole thing into question.

The new paper, however, is clear: natural ocean-cycles have very little to no effect on global warming.

Man-made climate change

“We can now say with confidence that human factors like greenhouse gas emissions and particulate pollution, along with year-to-year changes brought on by natural phenomenon like volcanic eruptions or the El Niño, are sufficient to explain virtually all of the long-term changes in temperature,” says study lead author Dr Karsten Haustein.

“The idea that oceans could have been driving the climate in a colder or warmer direction for multiple decades in the past, and therefore will do so in the future, is unlikely to be correct.”

For the study, the team of researchers at the Environmental Change Institute looked at ocean and land surface temperature measurements since 1850. Apart from human-induced factors such as greenhouse gas concentrations, the analysis also looked at other occurrences such as volcanic eruptions, solar activity, and air pollution (both natural and anthropic).

The key finding that the authors report on is that slow-acting ocean cycles don’t explain changes in global temperatures, including several decades of accelerated or slowed warming. The paper shows that the ‘early warming’ period (1915 — 1945) was also caused by external factors. Formerly, this period of warming had been largely attributed to natural ocean temperature changes, which fueled uncertainty around the effect of unpredictable natural factors on climate.

“Our study showed that there are no hidden drivers of global mean temperature,” says co-author Dr Friederike Otto. “The temperature change we observe is due to the drivers we know.”

“This sounds boring, but sometimes boring results are really important. In this case, it means we will not see any surprises when these drivers — such as gas emissions — change. In good news, this means when greenhouse gas concentrations go down, temperatures will do so as predicted; the bad news is there is nothing that saves us from temperatures going up as forecasted if we fail to drastically cut greenhouse gas emissions.”

The paper “A limited role for unforced internal variability in 20th century warming” has been published in the Journal of Climate.

Earth’s core is a lot like oil and vinegar — in a way

What does salad dressing have to do with the core of our planet? Quite a bit, according to a new study, and it’s got a lot to do with the Earth’s magnetic field.

A laser-heated diamond anvil cell is used to simulate the pressure and temperature conditions of Earth’s core. Top right inset shows a scanning electron microscope image of a quenched melt spot with immiscible liquids. Image credits: Sarah M. Arveson / Yale University.

Earth’s magnetic field, produced near the center of the planet, is essential to the survival of all life on the planet, acting as a protective shield from the harmful radiation of solar winds emanating from the Sun. However, our knowledge of Earth’s magnetic field and its evolution is incomplete. A new study finds that this evolution might have a lot to do with a process called immiscibility.

Miscibility is the property of two substances to mix, forming a homogeneous solution. When two substances are immiscible, they don’t mix — think of oil and water or oil and vinegar, for instance. Yale associate professor Kanani K.M. Lee and her team published a new study which suggests that molten iron alloys containing silicon and oxygen form two distinct liquids in the Earth’s core — two immiscible fluids, which just don’t mix together.

“We observe liquid immiscibility often in everyday life, like when oil and vinegar separate in salad dressing. It is surprising that liquid phase separation can occur when atoms are being forced very close together under the immense pressures of Earth’s core,” said Yale graduate student Sarah Arveson, the study’s lead author.

We’ve known for quite a while that the outer core has two major layers. Seismic waves traveling through the outer part of the outer core move slower than in the inner parts. Scientists have several theories explaining what is causing this slower layer, including immiscible fluid. However, until now, there was no experimental evidence to support this idea. In the new study, Lee and colleagues used laser-heated, diamond-anvil cell experiments to generate high pressures and temperatures, mimicking the conditions of the outer core. They found that under these conditions, two distinct, molten fluid layers are formed: an oxygen-poor, iron-silicon fluid and an iron-silicon-oxygen fluid. Because the iron-silicon-oxygen layer is less dense, it rises to the top, forming an oxygen-rich layer of fluid.

“Our study presents the first observation of immiscible molten metal alloys at such extreme conditions, hinting that immiscibility in metallic melts may be prevalent at high pressures,” said Lee.

This is important for the Earth’s magnetic field because most of it is believed to be generated in this outer core as the hot fluid in this layer roils vigorously as it convects.

This still doesn’t completely solve the puzzle of our planet’s magnetic field, but it offers an important puzzle piece.

The study has been published in the Proceedings of the National Academy of Sciences

Half of all water in the oceans may have come from ancient asteroid collisions

Water is essential for life on Earth and is one of our most precious natural resources. But considering how our planet formed, it is quite surprising how much water we still have. The Earth aggregated from a cloud of gas and dust – a protoplanetary disk – and was incandescently hot for the first few million years. Its surface was kept molten by impacts from comets and asteroids. Earth’s interior was also (and still is) kept liquid by a combination of gravitational heating and the decay of radioactive isotopes.

That means that if there were any initial water (and organic compounds) on the Earth, it should have boiled off quickly. So how come there’s plenty of water on our planet today – where did it actually come from? A surprising new study, published in Science Advances, suggests that a type of asteroid we didn’t think contained very much water could be responsible – simultaneously demonstrating that the solar system is probably a lot wetter than had previously been thought.

Scientists have long debated exactly where the Earth’s water comes from. One theory suggests that it might have been captured from the asteroids and comets that collided with it. Another argues that water was always present in the rocks of the Earth’s mantle and was gradually released to the surface through volcanoes.


itokawa. Credit: NASA/JPL.

Thanks to the Japanese Hayabusa mission we now have fresh evidence. The spacecraft brought back a precious cargo of grains retrieved from the surface of asteroid 25143 Itokawa in 2010. The researchers behind the new study were able to analyse the water content of two grains. They used a sophisticated piece of kit called an ion microprobe, which bombards a sample with a beam of ions (charged atoms) in order to probe the composition of its surface.

The experiment was not easy – the grains are tiny, less than 40 microns (one millionth of a metre) across, and each grain was made up of several different minerals. The ion microprobe had to be focused on one specific mineral within each grain so that the authors could gather the required data. The species of mineral that they analysed was an iron and magnesium-bearing silicate known as a pyroxene, which is almost entirely free of calcium.

This type of substance is not usually associated with water – indeed, it is regarded as a Nominally Anhydrous Mineral (NAM). The lattice of a pyroxene crystal does not contain vacant sites for water molecules in the same way that, for example, a clay mineral does – so its structure is not necessarily conducive to taking up water. However, the sensitivity of the technique that the authors used was such that they could detect and measure tiny quantities of water.

The results were surprising: the grains contained up to 1,000 parts per million of water. Knowing the composition of Itokawa, the researchers could then estimate the water content of the entire asteroid, which translated to between 160 and 510 parts per million of water. This is more than had been anticipated – remote measurements of two similar bodies (also S-type asteroids) found that one contained 30 and the other 300 parts per million water.

Unlikely source

Water is made from hydrogen and oxygen. But those elements occur as different isotopes – meaning they can have a different number of neutrons in their atomic nucleus (neutrons are particles that make up the nucleus together with protons). The researchers looked at the hydrogen isotopic composition of the water and discovered it was very close to that of Earth, suggesting the water on Earth has the same source as that of the Hayabusa grains.

The results raise several interesting questions, the first of which is how so much water came to be in nominally anhydrous minerals? The authors suggest that, during their formation, the grains absorbed hydrogen from the protoplanetary disk, which, at the high temperatures and pressures of the solar nebula, combined with oxygen in the minerals to produce water.


Original morphology of the two studied Itokawa particles. Credit: Japan Aerospace Exploration Agency (JAXA), edited by Z. Jin

So far, so reasonable. But how is it possible that the water has remained in the minerals? They after all came from an S-type asteroid – one that forms in the inner and hotter part of the solar system. Itokawa has had a complex history of thermal metamorphism and collision, reaching temperatures at least as high as 900°C. But the researchers used computer models to predict how much water would be lost in these processes – and it turned out to be less than 10% of the total.

Earth’s water

But how does all this relate to Earth’s water? The researchers speculate that following the grains’ uptake of water from the protoplanetary disk, the minerals aggregated and stuck together to form pebbles and eventually larger bodies such as asteroids.

If this mechanism worked for asteroids, it could also hold true for the Earth – maybe its original water came from these minerals coming together to help form the Earth. While water was then lost during the Earth’s early history, it was added again during collisions by the numerous S-type asteroids – as implied by the similarity in hydrogen isotopic composition between Earth and Itokawa.

This fresh look at an old problem – the origin of Earth’s water – has produced a surprising conclusion, one that suggests a large population of inner solar system asteroids might contain a lot more water than had been realised.

So while there is water everywhere in the solar system, the fact that it is hidden away inside minerals means that there is not always a drop to drink.

Monica Grady, Professor of Planetary and Space Sciences, The Open University

This article is republished from The Conversation under a Creative Commons license. Read the original article.