Tag Archives: Geology

InSight maps Mars’ composition and chunky core for the first time

We are closer than ever before to understanding the composition of Mars thanks to the first observations of seismic activity on the planet made by the InSight lander. The NASA-led project, which landed on the surface of the Red Planet in November 2018 with the goal of probing beneath the Martian surface, observed several so-called ‘marsquakes’ which reveal details about its crust, mantle, and core.

Using seismic activity or ‘marsquakes’ researchers have detailed the composition of the Martian interior for the first time (Cottaar/ Science)

InSight’s primary findings which are detailed in three papers published today in the journal Science, represent the first time scientists have been able to produce a detailed picture of the interior of a planet other than Earth.

“We are seeking to understand the processes that govern planetary evolution and formation, to discover the factors that have led to Earth’s unique evolution,” says Amir Khan, ETH Zurich and the University of Zurich, whose team used direct and surface reflected seismic waves to reveal the structure of Mars’ mantle. “In this respect, the InSight mission fills a gap in the scientific exploration of the solar system by performing an in-situ investigation of a planet other than our own.”

The results from the ongoing NASA mission–with the full title ‘Interior Exploration using Seismic Investigations, Geodesy and Heat Transport’— could reveal key insights into the Red Planet‘s formation and evolution, as well as helping us understand the key differences between our planet and Mars.

“One big question we would like to understand is why Earth is the only planet with liquid oceans, plate tectonics, and abundant life?” adds Khan. “Mars is presently on the edge of the solar system’s habitable zone and may have been more hospitable in its early history. Whilst we don’t yet know the answers to these questions, we know they to be found are on Mars, most likely within its interior.”

The InSight Lander on the surface of Mars ((NASA/JPL-Caltech))

InSight first detected the presence of marsquakes from its position in Elysium Planitia near the Red Planet’s equator in 2019 and has since picked up more than 300 events–more than 2 a day–tracing many of them back to their source.

What is really impressive is what researchers can do with these quakes, using them as a diagnostic tool to ‘see’ deep into the planet’s interior.

“Studying the signals of marsquakes, we measured the thickness of the crust and the structure of the mantle, as well as the size of the Martian core,” Simon Stähler, a research seismologist at ETH Zurich, tells ZME Science. “This replicates what was done on Earth between 1900 and 1940 using the signals of earthquakes.”

From the Crust of Mars…

The observations made by InSight have allowed researchers to assess the structure of Mars’ crust, allowing them to determine its thickness and other properties in absolute numbers for the first time. The only values we previously had for the Martian crust were relative values that showed differences in thickness from area to area.

“As part of the bigger picture on the interior structure of Mars, we have determined the thickness and structure of the Martian crust,” Brigitte Knapmeyer-Endrun, a geophysicist at the University of Cologne’s Institute of Geology, tells ZME Science. “Previous estimates could only rely on orbital data–gravity and topography–that can accurately describe relative variations in crustal thickness, but no absolute values. These estimates also showed a wide variability.”

The Mars InSight lander’s seismometer consists of a protective dome that contains three extremely sensitive sensors. (NASA/JPL-Caltech)

With data collected regarding the crustal thickness at InSight’s landing area, new seismic measurements, and data collected by previous missions, the team could map the thickness across the entire Martian crust finding an average thickness of between 24 and 72 km.

Knapmeyer-Endrun explains that the data she and her team collected with InSight’s Seismic Experiment for Interior Structure (SEIS), particularly the very broad-band (VBB) seismometer–an instrument so sensitive it can record motion on an atomic scale–and information from the Marsquake Service (MQS) at ETH Zurich, suggest that the Red Planet’s crust is thinner than models have thus far predicted.

“We end up with two possible crustal thicknesses at the landing site–between 39 and 20 km– but both mean that the crust is thinner than some previous estimates and also less dense than what was postulated based on orbital measurements of the surface.”

Knapmeyer-Endrun continues by explaining that the InSight data also reveals the structure of the Martian crust as multi-layered with at least two interfaces that mark a change in composition. In addition to this, the team can’t rule out the presence of a third crustal layer before the mantle.

“The crust shows distinct layering, with a surficial layer of about 10 km thickness that has rather low velocities, implying that it probably consists of rather porous–fractured–rocks, which is not unexpected due to the repeated meteorite impacts,” says the geophysicist adding that we see something similar on the Moon, but the effect is more extreme due to that smaller body’s much thinner atmosphere.

The two largest quakes detected by NASA’s InSight appear to have originated in a region of Mars called Cerberus Fossae. Scientists previously spotted signs of tectonic activity here, including landslides. This image was taken by the HiRISE camera on NASA’s Mars Reconnaissance Orbiter (NASA/JPL-Caltech/University of Arizona)

Knapmeyer-Endrun is pleasantly surprised regarding just how much information InSight has been able to gather with just one seismometer.”It’s surprising we were really able to pull all of this information about the interior of Mars from the recordings of quakes with magnitudes of less than 4.0 from a single seismometer,” she explains. “On Earth, we would not be able to even detect those quakes at a comparable distance. We typically use 10s or even 100s of seismometers for similar studies.”

And the marsquake data collected by InSight has not just proven instrumental in assessing the thickness and composition of the planet’s crust, it has also allowed scientists to probe deeper, to the very core of Mars itself.

…To the Martian Mantle and Core

Using direct and surface reflected seismic waves from eight low-frequency marsquakes Khan and his team probed deeper beneath the surface of Mars to investigate the planet’s mantle. They found the possible presence of a thick lithosphere 500km beneath the Martian surface with an underlying low-velocity layer, similar to that found within Earth. Khan and his co-author’s study reveals that the crustal layer of Mars is likely to be enriched with radioactive elements. These elements heat this region with this warming reducing heat in lower layers.

It was these lower regions that Stähler and his colleagues investigated with the use of faint seismic signals reflected by the boundary between the Martian mantle and the planet’s core. What the team discovered is that the Red Planet’s core is actually larger than previously calculated, with a radius of around 1840 km rather than previous estimates of 1600km. This means the core begins roughly halfway between the planet’s surface and its centre.

From the new information, we can also determine the core’s density and extrapolate its composition.

A Comparison of Mars’ Earth’s interiors. The Martian core shown here is smaller than these new findings suggest. Whilst the crust shown is thicker.



“We now know for sure the size of the core and it’s significantly larger than it had been thought to be for a long time,” says Stähler. “Because we found that the core is quite large, we, therefore, know it is not very dense. This means that Mars must have accumulated a substantial quantity of light, volatile elements such as sulfur, carbon, oxygen, and hydrogen.”

This ratio of lighter elements is greater than that found within Earth’s denser core, and it could give us important hints about the differences in the formation of these neighbouring worlds.

“Somehow these light elements needed to get into the core. It may mean that the formation of Mars happened faster than Earth’s,” Stähler says. “These observations have fueled speculation that Mars might represent a stranded planetary embryo that depicts the chemical characteristics of the solar nebula located within the orbit of Mars.”

Thanks to NASA's InSight Mars mission we now have a good picture of the interior of another planet.
InSight captures an image of its landing site, which proved the ideal vantage point to observe marsquakes (NASA)

As just Knapmeyer-Endrun did, Stähler expresses some surprise regarding just how successful InSight has been in gathering seismological data, emphasising the role good fortune has played in the mission thus far.

“We were able to observe reflections of seismic waves from the core–like an echo–from relatively small quakes. And the quakes were just in the right distance from the lander. Had we landed in another location, it would not have worked out,” the seismologist says. “And the landing site was only selected because it was flat and had no rocks, so it was really pure luck.”

Stähler says that he and his team will now attempt to use seismic waves that have crossed the core of Mars to determine if the planet’s core possesses a solid-iron inner-core like Earth, or if it is entirely liquid. Just one of the lingering questions that Knapmeyer-Endrun says InSight will use marsquakes to tackle over the coming years.

“There are still multiple open questions that we’d like to tackle with seismology. For example, which geologic/tectonic features are the observed marsquakes linked to? At which depth do olivine phase transitions occur in the mantle? And Is there a solid inner core, like on Earth, or is the whole core of Mars liquid?” says the geophysicist.

And if we are to go by track record, the smart money is on InSight answering these questions and more. “Within just 2 years of recording data on Mars, this single seismometer has been able to tell us things about the crust, mantle and core of Mars that we’ve been speculating about for decades.”

Researchers want to use whale song for seismic imaging of the Earth’s crust

An innovative study suggests that songs of fin whales can be used for seismic studies of the oceanic subsurface. This could essentially open up a new avenue for geologic research and even reduce the need for seismic studies in the ocean, which is disturbing and even harmful to whales.

Image credits: Kuna and Nábelek.

Earthquakes are some of nature’s most devastating processes, but in some ways, they can also be useful. Most of what we know about the Earth’s internal structure comes from earthquakes: researchers can analyze vibrations caused by seismic waves and draw conclusions about the Earth’s subsurface — from the near-surface crust to the depths of the mantle and the core.

But seismic waves are essentially just acoustic waves — they don’t need to be tectonic in nature. So researchers had a quirky idea: what if we could use the whales’ deep vocalizations as a ‘seismic’ source. John Nabelek, a professor at Oregon State University’s College of Earth, Ocean, and Atmospheric Sciences and a co-author of the paper explains:

“People in the past have used whale calls to track whales and study whale behavior. We thought maybe we can study the Earth using those calls,” Nabelek said. “What we discovered is that whale calls may serve as a complement to traditional passive seismic research methods.”

The study started as a bit of a chance occurrence. The study’s lead author is Vaclav M. Kuna, who worked on the project as a doctoral student at Oregon State and has since completed his Ph.D. Kuna and Nabelek were studying earthquakes from a network of 54 ocean-bottom seismometers about 1-200 miles from the coast of Oregon when they observed a strange signal. The signal turned out to correlate with whales’ presence in the area.

“After each whale call, if you look closely at the seismometer data, there is a response from the Earth,” Nabelek said.

Fin whales don’t actually “sing” — their calls are more like a series of clicks that go on for hours, two times louder than the loudest concert you’ve ever seen (although sound transmits differently in water). Turns out, the frequency of these clicks are within the range that can be picked up by seismographs. This is what researchers were picking up, so they figured that they could actually use these calls as signals for seismic studies.

It’s a complicated process. The sounds bounce between the surface of the water and the bottom of the ocean, with some of the waves’ energy going through the oceanic crust. Reconstructing this signal is a big challenge, but it can be done; this proof-of-concept study shows it. It’s not clear just how much information can be derived this way, but it could at least be a complement to more conventional seismic surveys.

The approach could also end up helping whales, as conventional seismic surveys can disturb whales.

Journal Reference: Václav M. Kuna et al, Seismic crustal imaging using fin whale songs, Science (2021). DOI: 10.1126/science.abf3962

NASA orbiter showcases the biggest canyon in the solar system — and it’s out of this world

It’s called Valles Marineris, and it would put any canyon on Earth to shame. It runs for 2,500 miles (4,000 km) along the equator of Mars — almost 10 times more than the Grand Canyon, and three times as deep. The awe-inspiring canyon was now showcased by NASA in unprecedented detail. Here’s a peek.

Image credits: NASA/JPL/UArizona.

Mars is host to some serious geology. Although the planet may not be all that active nowadays, whatever geological forces shaped Mars, they did some tremendous work — Mars is also home to Olympus Mons, the largest volcano in the Solar System, at a height of over 21 km, which may be connected to the canyon. Valles Marineris was imaged with the HiRISE (short for High Resolution Imaging Science Experiment) camera that’s aboard the Mars Reconnaissance Orbiter.

The HiRISE camera itself is pretty big: weighing 64 kilograms (143 pounds) and measuring roughly 0.6 x 1.5 meters (2 by 5 feet), the camera is perfectly equipped for imaging the surface of Mars in unprecedented detail. Its resolution can feature something the size of a desk in a shot that’s 6 km (3.7 miles) wide.

The image above features an area of the canyon called the Tithonium Chasma. If you look at it closely, you’ll see diagonal slashes on the slope — fissures of an unknown origin.

These fissures could be indicative of ancient cycles of freezing and thawing, some researchers believe.

In this top-down view, afternoon sunlight picks out subtle east-west trending ridges in the east-facing slope. Image credits: NASA/JPL/UArizona.

But it’s not clear just how the canyon was produced. According to NASA, Mars is too hot and too dry to have had a river big enough to create this type of canyon. However, it is possible that flowing water could have deepened and widened existing canyons — and we know that Mars likely had massive rivers that flowed for billions of years.

The European Space Agency put forth another theory: that a large portion of the canyon was cracked open billions of years ago, when a group of volcanoes started undergoing massive eruptions. After the original shape of the canyon was produced thusly, water could have come in and done the rest. Researchers from the University of Arizona have also suggested that landslides could have helped widen the canyon. The formation of the canyon is also thought to be connected to the Tharsis Bulge — a vast volcanic plateau in the vicinity of the canyon, home to the three largest volcanoes in the solar system.

A topographic map of the Tharsis region (shown in shades of red and brown) and the Valles Marineris canyon, in its eastern region. Image credits: NASA.

This type of high-resolution images is exactly what can help geologists fine-tune their theories of how the canyon was formed. To a geologist, minute details such as sedimentation patterns and fissure systems can be important clues regarding the evolution of the canyon system, and Mars itself.

Valles Marineris topographic view constructed from MOLA altimetry data. Image credits: NASA.

Scientists map the magma plume responsible for geothermal activity in the Arctic

A seismic station on the Greenland Ice Sheet installed by authors. Snow accumulation in one year is ~1.5 m (~5 ft), and the solar panels are buried in the snow. Snow removal and maintenance are done manually by several people. Image credits: Genti Toyokuni Full size

The North Atlantic region is awash with geothermal activity. Just think of Iceland’s volcanoes and hot springs, and you get a fairly good idea of what’s going on in some of these areas. It’s not just Iceland, either. Svalbard, a Norwegian archipelago in the Arctic, is another area with rich geothermal activity.

But we don’t know all that much about what’s causing this geothermal activity. Geologists are well aware that it’s a magma plume, but not much is known about the size and spread of this plume.

Now, in a new study, researchers have used seismic data to carry out a seismic tomography and analyze the area in unprecedented detail.

A schematic diagram showing the main tectonic features and mantle plumes beneath Greenland and the surrounding regions. Vp = P wave velocityCMB = the core-mantle boundary. Image credits: Tohoku University

It’s not an easy task. To conduct seismic tomography, you need measuring stations at various points which, in the Arctic, is quite the challenge. Researchers installed seismographs on the Greenland Ice Sheet in 2009, fitting them with solar panels to provide energy. The Greenland Ice Sheet Monitoring Network, a real-time array of 33 stations that monitors Greenland’s earthquakes and icequakes in real-time.

To generate the tomographic scan, you need numerous seismic waves. Researchers then calculate how long the fastest waves (called the P waves) take to reach the station and then calculate their speed. Seismic waves travel at a different speed through different materials — such as a plume, for instance. So you can map an area where waves travel at a plume-like speed and make the reasonable assumption that it is a plume. It’s kind of like how a CT scan works in the body.

In the end, it proved to be worth it. They were able to define such an area, finding that it rises from the core-mantle boundary, spreading to two branches that supply geothermal heat to Iceland and Svalbard.

In addition to helping geologists shed new light on one of the more mysterious parts of the Earth’s crust, this study could also help researchers understand how the volcanoes in the Arctic will be affected by processes such as ice melting and sea-level rise.

“Knowledge about the Greenland plume will bolster our understanding of volcanic activities in these regions and the problematic issue of global sea-level rising caused by the melting of the Greenland ice sheet,” said Dr. Genti Toyokuni, co-author of the studies.

Moving on Toyokuni wants to explore the thermal process in even more detail. “This study revealed the larger picture, so examining the plumes at a more localized level will reveal more information.”

Journal Reference: DOI: 10.1029/2020JB019837 / DOI: 10.1029/2020JB019839

Why is the ocean salty?

Every time you bathe in the sea, you have geology to thank for the extra buoyancy that salty water provides. Large-scale geological processes bring salt into the oceans and then recycle it deep into the planet. The short answer to ‘why is the ocean salty’ sounds something like this:

Salts eroded from rocks and soil are carried by rivers into the oceans, where salt accumulates. Another source of salts comes from hydrothermal vents, deep down on the surface of the ocean floor. We say “salts” — because the oceans carry several types of salts, not just what we call table salt.

But the longer answer (that follows below) is so much more interesting.

Image credits: Olia Nayda.

In the beginning there was saltiness

As it is so often the case in geology, our story begins with rocks and dirt, and we have to go back in time — a lot. Billions of years ago, during a period called the Archean, our planet was a very different environment than it is today. The atmosphere was different, the landscape was different, but as far as ocean saltiness goes, there may have been more similarities than differences.

Geologists look at ancient rocks that preserved ancient water (and therefore, its ancient salinity); one such study found that Earth’s Archean oceans may have been ~1.2 times saltier than they are today.

At first glance, this sounds pretty weird. Since salt in the seas and oceans is brought in by river runoff and erosion, the salts hadn’t yet had time to accumulate in Earth’s earliest days. So what’s going on?

It is believed that while the very first primeval oceans were less salty than they are today, our oceans have had a significant salinity for billions of years. Although rivers hadn’t had sufficient time to dissolve salts and carry them to oceans, this salinity was driven by the oceanic melting of briny rocks called evaporites, and potentially volcanic activity. It is in this water that the first life forms on Earth emerged and started evolving.

“The ions that were put there long ago have managed to stick around,” says Galen McKinley, a UW-Madison professor of atmospheric and oceanic sciences. “There is geologic evidence that the saltiness of the water has been the way that it is for at least a billion years.”

The ancient salinity of oceans is still an area of active research with many unknowns. But while we don’t fully understand what’s going on with the ancient oceans, we have a much better understanding of what drives salinity today.

So how do the oceans get salty today?

Salinity map of the world’s oceans. Scale is in parts per thousand. Image credits: NASA.

Oceans today have an average of 3.5% salinity. In other words, 3.5% of the ocean’s weight is made of dissolved salts. Most, but not all of that is sodium chloride (what we call ‘salt‘ in day to day life). Around 10% of the salt ions come from different minerals.

At first glance, 3.5% may not seem that much, but we forget that around 70% of our planet is covered in oceans. If we took all the salt in the ocean and spread it evenly over the land surface, it would form a layer over 500 feet (166 meters) thick — a whopping 40-story building’s height of salt covering the entire planet’s landmass. That’s how much 3.5% means in this particular case.

All these salts come from rocks. Rocks are laden with ionic elements such as sodium, chlorine, and potassium. Much of this material was spewed as magma by massive volcanic eruptions and can form salts under the right conditions.

Because it is slightly acidic, rainwater can slowly dissolve, erode rocks. As it does so, it gathers ions that make up salts and transfers them to streams and rivers. We consider rivers to be “freshwater”, but that’s not technically true: all rivers have some salt dissolved in them, but because they flow, they don’t really accumulate it. Rivers are agents for carrying salts, but they don’t store salts themselves.

The main culprit for why oceans are salty: rivers. Image credits: Jon Flobrant.

Rivers constantly gather more salts, but they constantly push it downstream. Influx from precipitation also ensures that the salt concentration doesn’t increase over time.

Meanwhile, the oceans have no outlet, and while they also have currents and are still dynamic, they have nowhere to send the salts to, so they just accumulate more and more salt. Which leads us to an interesting question.

So, are the oceans getting saltier?

Bodies of water can be classified by their salt content.

No, not really. Although it’s hard to say whether oceans will get saltier in geologic time (ie millions of years), ocean salinity remains generally constant, despite the constant influx of salt.

“Ions aren’t being removed or supplied in an appreciable amount,” says McKinley. “The removal and sources that do exist are so small and the reservoir is so large that those ions just stay in the water.” For example, she says, “Each year, runoff from the land adds only 0.00005 percent of total ocean salts.”

A part of the minerals is used by animals and plants in the water and another part of salts becomes sediment on the ocean floor and is not dissolved. However, the main reason why oceans aren’t getting saltier is once more geological.

The surface of our planet is in a constant state of movement — we call this plate tectonics. Essentially, the Earth’s crust is split into rigid plates that move around at a speed of a few centimeters per year. Some are buried through the process of subduction, taking with them the minerals and salts into the mantle, where they are recycled. The movement of tectonic plates constantly recirculates material from and into the mantle.

Schematic of subduction (and some other associated processes). Image credits: K. D. Schroeder.

With these processes, along with the flow of freshwater, precipitation, and a number of other processes, the salinity of the Earth’s oceans remains relatively stable — the oceans have a stable input and output of salts.

But isolated bodies of water, however, can become extra salty.

Why some lakes are freshwater, and some are *very* salty

Lakes are temporary storage areas for water, and most lakes tend to be freshwater. Rivers and streams bring water to lakes just like they do to oceans, so then why don’t lakes get salty?

Well, lakes are usually only wide depressions in a river channel — there is a water input and a water output, water flows in and it flows out. This is called an open lake, and open lakes are essentially a buffer for rivers, where water accumulates, but it still flows in and out, without salts accumulating. Many lakes are also the result of chaotic drainage patterns left over from the last Ice Age, which makes them very recent in geologic time and salts have not had the time to accumulate.

Beautiful glacial lakes such as this one are the remains of Ice Age melting. Image credits: K. D. Schroeder.

But when a lake has no water output and it has had enough time to accumulate salts, it can become very salty. This is called a closed lake, and closed lakes (and seas) can be very salty, much more so than the planetary oceans. They accumulate salts and lose water through evaporation, which increases the concentration of salts. Closed lakes are pretty much always saline.

We mentioned that world oceans are 3.5% salt on average. The Mediterranean Sea has a salinity of 3.8%. The Red Sea has some areas with salinity over 4%, and Mono Lake in California can have a salinity of 8.8%. But even that isn’t close to the saltiest lakes on Earth. Great Salt Lake in Utah has a whopping salinity of 31.7%, and the pink lake Retba in Senegal, where people have mined salt for centuries, has a salinity that reaches 40% in some points. The saltiest lake we know of is called Gaet’ale Pond — a small, hot pond with a salinity of 43% — a testament to just how saline these isolated bodies of water can get.

Worker digging the salt in Lake Retba. Image in public domain.

It’s important to note that lakes are not stable geologically, and many tend to not last in geologic time. Some of the world’s biggest lakes are drying up, both as a natural process and due to rising temperatures, drought, and agricultural irrigation.

Salt can also come from below

Hydrothermal vent. Image credits: NOAA.

We’ve mentioned that rock weathering and dissolving makes oceans salty, but there is another process: hydrothermal vents.

A part of the ocean water seeps deeper into the crust, becomes hotter, dissolves some minerals, and then flows back into the ocean through these vents. The hot water brings large amounts of minerals and salts. It’s not a one-way process — some of the salts react with the rocks and are removed from seawater, but this process also contributes to salinization.

Lastly, underwater volcanic eruptions can also bring salts from the deeper parts to the surface, affecting the salt content of oceans.

First geological map of Titan reveals varied, intriguing geology

Different infrared views of Titan. Image credits: NASA / JPL.

Titan’s atmosphere is dense and hazy, just like Earth’s. The satellite also features intricate, stable bodies of liquid on its surface. But that’s where the similarities with the Earth end. Titan’s liquid isn’t water, but hydrocarbon (mostly methane). It’s atmosphere — 97% nitrogen, the rest methane and hydrogen.

Titan’s remarkable features make it extremely interesting for astronomers and geologists alike. It may not have water or oxygen, but aside from Earth, Titan is still the only body in the solar system to have an atmosphere and hydrologic system, which has a significant impact on its surface and evolution. However, its hazy atmosphere hinders our view of the surface, and it has been difficult to obtain a global vision of Titan’s geology.

Even after Titan was examined by both Voyager 1 and 2 in 1980 and 1981, respectively, it remained a mysterious object — a large satellite shrouded in an atmosphere too thick to enable observation.

All that changed with the Cassini mission. Armed with state of the art technology and perfectly equipped to deal with the planet’s rough conditions, Cassini revealed Titan in unprecedented detail.

Rosaly Lopes from NASA’s Jet Propulsion Laboratory and colleagues used data gathered with infrared and radar instruments aboard Cassini to reconstruct and map Titan’s surface, including its poles. They identified six major geological forms, describing their approximate age and distribution around the globe. While Titan’s geology has been mapped before, this is the most comprehensive map of its kind.

Titan’s main geological features. Image credits: Lopes et al.

Titan’s geology depends strongly on latitude. Most of the satellite is covered by featured organic plains, which are widespread at mid-latitudes. But around the equator, young dune fields and hydrocarbon lakes dominate the landscape. These dunes, most of which measure 80-130 meters high, are the second-most extensive unit on Titan. Another important feature is the hummocky landscape — rocky mounds that are exposed as isolated peaks or ranges, gently undulating from mid to high latitudes, generally aligned east-west. These structures may have formed through tectonic activity, early in Titan’s history.

Titan also features lakes and seas, either dry or liquid-filled. The polar regions alone contain over 650 lakes, the majority being in the northern polar region.

Titan isn’t a static environment. Its surface has been changed by several geological processes, including impact cratering, precipitation, tectonism, as well as erosion. Given its hydrocarbon-rich surface, Titan is also riddled in organic material. This material is constantly eroded, shifted, deposited, and transported. All these interactions make Titan’s geology much more difficult to understand — which is why a geological map comes in handy.

These observations demonstrate the extent to which Titan is shaped by its methane cycle — just like the Earth is shaped by the water cycle. The polar areas are humid enough to keep liquid bodies of methane, whereas the arid equatorial climate keeps wind-shaped dunes intact.

The Nile is 30 million years old — and held together by movements in the Earth’s mantle

The River Nile over Cairo, Egypt. Image credits: Fakharany / Wikipedia.

It’s harder to imagine a more imposing river than the Nile. Stretching over 6,650 km (4130 miles) long and serving as an essential water source since time immemorial, the Nile is a lifeline across northern Africa. Ancient Egyptians considered the Nile river to be the source of all life, and believed the river to be eternal.

Recent research seemed to back that idea up — well, maybe the Nile wasn’t eternal, but it was around for a few million years — which is eternal by humanity’s standards.

The Nile has a surprisingly steady path, nourishing the valleys of Africa for millions of years and shaping the course of civilizations. But for geologists, that was weird.

Why is the Nile so steady when rivers (particularly larger rivers in flat areas) tend to meander so much?

Now, researchers at the University of Texas at Austin believed they’ve cracked that mystery, and it has a lot to do with movement inside the Earth’s mantle.

“One of the big questions about the Nile is when it originated and why it has persisted for so long,” said lead author Claudio Faccenna, a professor at the UT Jackson School of Geosciences. “Our solution is actually quite exciting.”

Convection belts in the mantle.

The team traced the geologic history of the Nile, correlating it with information from volcanic rocks and sedimentary deposits under the Nile Delta. They also carried out computer simulations that recreated tectonic activity in the area over the past 40 million years.

They linked the Nile’s behavior to a mantle conveyor belt.

“We propose that the drainage of one of the longest rivers on Earth, the Nile, is indeed controlled by topography related to mantle dynamics (that is, dynamic topography).”

The Earth’s interior is dominated by the mantle, and the mantle is not static. Large swaths of the mantle are moved around by convection. Sometimes, parts of that are pushed towards the surface. This upwelling magma has been pushing up the Ethiopian Highlands, helping to keep the river flowing straight to the north instead of wending its way sideways. This uplift, researchers conclude, is responsible for the gentle and steady gradient that keeps the Nile on a consistent course.

The Nile famously flows steadily to the North. Image credits: NASA.

Getting to this conclusion, however, was not straightforward — and it wouldn’t have been possible without state-of-the-art geophysical modeling. This proved to be the glue that pieced the entire theory together.

“I think this technique gives us something we didn’t have in the past,” said Jackson School scientists Petar Glisovic, one of the authors who is now a research collaborator at the University of Quebec.

As a consequence of this study, the researchers also showed that the Nile must be at least as old as the Ethiopian highlands — so this puts its age at 30 million years, which is several times more than previous estimates.

The study was published in Nature.

The ‘Age of Man’ is upon us — Anthropocene period close to becoming official

Mankind is having such a profound impact on the planet that we’ve kickstarted a new geological era: the Anthropocene. A panel of scientists has now taken an important step towards defining this new age, and having it start with the ‘Atomic Age’.

Geologists love to classify things — and they especially love to classify time. The geologic time scale covers the entire 4.5-billion-year history of our Earth, splitting it neatly based on decisive environmental characteristics. You’ve probably heard about Jurassic Park — the Jurassic spans from 201.3 million years ago to 145 million years ago. Before the Jurassic, there was the Triassic, and after it, there was the Cretaceous. The Jurassic itself, like the periods before and after it, is split into smaller subdivisions.

We are currently living in a period of time called the Quaternary, which started 2.6 million years ago and loosely represents the period where recognizable hominids have existed. The Quaternary is also split into several smaller periods, and the current one is called the Holocene.

The Holocene began approximately 11,650 years ago, and includes the development of all written human history, as well as most if not all of our species’ major civilizations. Although it’s a mere blink in the grand scheme of geological time, it is the period when mankind rose to become the dominant species on the planet. Right now, however, the Holocene is coming to an end.

The impact of mankind on planet Earth has become so large that most scientists agree that we should designate a new geological period called the ‘Anthropocene’ — the Age of Man (from the Greek ‘anthropos’ which means”man/human being”). Although the term has not become official just yet, it represents the reality which we are all seeing: the environment, both above and beneath the ground, is heavily affected by mankind. We have produced nuclear explosions which left behind chemical marks that will be visible for millions of years. The plastic we are producing (and dumping into landfills or oceans) takes millennia to decompose. The chemistry of the atmosphere and the oceans has also been substantially altered, and even the bones of the animals we eat are a sign that we are having a dominant impact on the planet — it’s time for all this to get its own period. It is a clearly distinguishable and unprecedented period in Earth’s geological history.

With this in mind, the 34-member Anthropocene Working Group (AWG) voted to establish the Anthropocene as a new type of age. It wasn’t a unanimous vote, but 29 out of the 34 members supported it. The AWG, which works under the tutelage of the International Commission on Stratigraphy (which oversees the official time periods), is now considering what the best starting point of the Anthropocene would be. The first atomic-bomb seems like the most plausible place to start.

The AWG is now looking for the best sites with sufficient sedimentary evidence to support the start of the Anthropocene.

 

Huge underwater eruption created giant volcano off the coast of Africa

The beautiful island of Mayotte was shaken by numerous volcanic temblors. Image credits: Yane Mainard.

Volcanic shake

About half a year ago, seismologists noticed something unusual off the coast of Mayotte, an overseas French territory between Africa’s eastern coast and Madagascar. Sensors all around the world picked up seismic waves coming from around the island, but the source was largely unknown.

The locals felt it too. Almost every day, they felt small rumbles, stressing out about what the source might be, and authorities had little answers. French researchers had a hunch what the source might be, but without an on-site expedition, it was impossible to confirm. In February, such an expedition was launched. Nathalie Feuillet of the Institute of Geophysics in Paris (IPGP) and colleagues installed six seismometers on the seafloor, 3.5 kilometers beneath the surface, to monitor the seismic activity.

They pinpointed the seismic area, triangulating a region some 20-50 km deep — but this was only the first step. After the area was identified, researchers mapped it using sonar, finding evidence of a tall volcanic mountain formed underwater, and a huge quantity of solidified lava around it.

The outline of the volcano (in red) was excellently outlined by the sonar beams. The 800-meter (half a mile) volcano was built from nothing in just six months. The eruption was so dramatic that the island of Mayotte sank by about 13 centimeters (5 inches) and moved eastwards about 10 centimeters (4 inches). The sonar also revealed 5 cubic km (1.2 cubic miles) of magma on the seafloor Image credits: MAYOBS TEAM (CNRS/IPGP-UNIVERSITÉ DE PARIS/IFREMER/BRGM).

Competing theories

Mayotte is part of the Comoros archipelago, an archipelago formed through volcanic eruptions. However, although some areas of the Comoros are still very active, the last eruption around Mayotte took place about 7,000 years ago. It’s not just the location of this new volcano that’s a bit puzzling, its nature is also a mystery.

There are several competing theories regarding the nature of this volcanic range. Most volcanoes are found along mid-ocean ridges — underwater mountain ranges formed where the Earth’s tectonic plates are pulling apart, and where convection currents from the mantle are bringing magma closer to the surface. However, this isn’t really the case in the Comoros.

Another possibility is that of a hotspot. A volcanic hotspot is an area where a rising mantle plume comes really close to the surface, producing volcanic activity. The classic example is Hawaii, although the nearby island of Reunion was also formed this way. Hot spots aren’t affected by plate tectonics, and they stay in place while tectonic plates move about, typically leaving a “trail” of volcanoes on the surface. This is consistent with the fairly deep earthquakes observed around Mayotte, which would also suggest that the volcanic magma chamber is also very deep. But the evidence isn’t convincing enough to definitively say that there’s a hotspot there.

Depiction of a rift breaking down into multiple rigid blocks. Image credits: Italian Institute for Geosciences.

Another likely culprit is the geological process of rifting. East Africa is one of the world’s most active rift zones, with the African tectonic plate splitting into two separate plates. The rifting area isn’t exactly close to Mayotte, but rifting tends to break large areas into rigid blocks, and this might be responsible for the volcanic events.

Most intriguingly, it could be a combination of some (or all) of the above, making Mayotte one of the most exciting volcanic areas to study.

As for the island’s inhabitants, they still have reason to worry. The volcano is probably too deep to threaten the island in any way — the eruptions are too deep to affect the surface and even a potential collapse of one of its flanks would likely be too deep to generate a tsunami. However, the earthquakes seem to be slowly migrating towards the island, which could potentially lead to a collapse of the island’s flank itself — which would, of course, be much more dangerous. Given this turn of events, Feuillet wants to extend the mission for a few months and get a much better view of what’s happening with this volcanic activity in order to assess the potential risk to the locals. After this is done, results will also be published in a journal, Feuillet says.

Outcrop.

Rock-solid geology puns that will have you erupting in laughter

Outcrop.

Some of these rocks are also the schist.
Image via Pixabay.

Ahhhh, geology. The noble art of hiking to rock, hitting rock with hammer, and then establishing its particular rockiness.

It’s quite the fun career, if occasionally physically-intensive, but it’s peppered with long stretches where not much happens. Whether you’re hiking to an outcrop or hitching a ride to a nice formation, you have to pass the time somehow. Drinks are therefore much appreciated in the field of geology, but puns are a close second — especially when you need to stay productive.

I’m also a big fan of puns. So, today, I invite you to join in on the fun with a few geology puns that I find quite funny. Audible groaning and eye-rolling aren’t only acceptable, they’re encouraged. Just give me a minute to dig some good ones up. I’ll make sure they’re all clastics.

To begin with:

Let’s whet your apatite

Apatite.

Calcium ions give apatite a blue hue. The yellowish mineral is calcite.
Image credits Géry Parent / Flickr.

Apatite is a group of minerals rich in phosphorus and ions of other compounds and elements, such as fluorine, chlorine, or hydrogen-oxygen. While it can be very pretty, most apatites end up being crushed and processed into fertilizers. Sad.

One really geeky reason I love this pun is that apatite itself is a bit of a meta-pun. Apatite crystals aren’t particularly distinctive, so the mineral gets confused for other geological species quite frequently. In fact, its very name comes from ‘apatein’, an ancient Greek for ‘deceive’ or ‘dupe’.

Moving on swiftly, let’s talk about what motivates us to study geology in the first place:

We come for the cleavage and stay for the joints

So it’s pretty much like college!

Joints.

Don’t get excited too fast. These are the joints we’re talking about.
Image via Wikimedia.

Unlike college (again, sad), ‘cleavage’ refers either to features in rock generated by pressure and heat if you’re a geologist, or to the tendency of crystals to split across certain planes if you’re more of a mineralogist. ‘Joints’ are fractures in rock, separating blocks that move relative to one another. They tend to form under tensile, rather than shearing, stress.

However, some of us never get into geology. And I get it. It may appear like there’s no need for new students, for new ideas, because

So many geologists are out standing in the field

Ehehehehe. Maybe they’re really busy with

Thrusting in orogenous zones

Thrust faults are tears in rock formations whereby older strata are pushed above more recent ones. Orogenies, being mountain-building events, will definitely create such faults.

But not everything is borne of orogeny; sometimes

Igneous is bliss

Volcanic rock.

A volcanic rock.
Image credits Angela Thomas.

I love my job.

Igneous rocks form from the cooling of magma deep inside the earth. They’re also known as magmatic or volcanic rocks (if they form from magma oozing out of a volcano). Still,

Studying volcanoes can be tuff

Tuff is basically rock-ified volcanic ash. Volcanoes spew out a lot of volcanic ash (and burning magma)!

Always name your WiFi “Yellowstone”

Because it’s a hotspot.

Puns — they’ll always be there when you hit rock bottom. Some people won’t like them, and they’ll smack you over the head if you try to make puns. They’re what geologists call karst holes.

If you know any good geology puns, don’t be afraid to share in the comments below.

This graphic shows how the ancient land masses of Laurentia, Avalonia and Armorica would have collided to create the countries of England, Scotland and Wales. Credit: University of Plymouth

The British mainland was formed by three continental collisions

The British mainland was formed by the collision of three — not two — ancient continental land masses, geologists say.

This graphic shows how the ancient land masses of Laurentia, Avalonia and Armorica would have collided to create the countries of England, Scotland and Wales. Credit: University of Plymouth

This graphic shows how the ancient land masses of Laurentia, Avalonia and Armorica would have collided to create the countries of England, Scotland and Wales. Credit: University of Plymouth

The findings follow an extensive mineralogy study of exposed rock features across Devon and Cornwall. The two counties are separated by a clear geological boundary, with the north sharing properties with the rest of England and Wales while the southern part has an identical geological makeup to France and mainland Europe.

Up until now, the leading theory was that England, Wales and Scotland formed due to the merger of Avalonia and Laurentia more than 400 million years ago. The new study, carried out by scientists at the University of Plymouth, suggests that a third land mass — Armorica — was also involved in the process.

“This is a completely new way of thinking about how Britain was formed. It has always been presumed that the border of Avalonia and Armorica was beneath what would seem to be the natural boundary of the English Channel,” says lead researcher Dr. Arjan Dijkstra, who is a lecturer in Igneous Petrology at the University of Plymouth, UK.

“But our findings suggest that although there is no physical line on the surface, there is a clear geological boundary which separates Cornwall and south Devon from the rest of the UK.”

The team visited 22 sites in Devon and Cornwall where they sampled solidified magma that welled up long ago from a depth of 100km, as a result of underground volcanic eruptions or other geological events. Rocks from each site were subjected to a detailed chemical analysis in the lab using X-ray fluorescence (XRF) spectrometry. An isotopic analysis of the rocks — which involved comparing levels of strontium and neodymium elements — enabled the researchers to paint a fuller picture of the rocks’ history.

Finally, the results were compared to studies performed elsewhere in the UK or mainland Europe. The comparison shows there’s a clear boundary running from the Exe estuary in the East to Camelford in the west.

The new findings published in the journal Nature Communications mean that we have to rethink how the British Isles formed. The researchers say that the process looked very much like a three-way car crash — first, Avalonia and Laurentia collided forming much of Britain; later Armorica crashed into Avalonia from the south, only to back away, leaving behind a bumper-like formation. Later on, the landmass advanced again, crushing into Avalonia once more.

“We always knew that around 10,000 years ago you would have been able to walk from England to France,” Dr. Dijkstra added. “But our findings show that millions of years before that, the bonds between the two countries would have been even stronger.”

“It explains the immense mineral wealth of South West England, which had previously been something of a mystery, and provides a fascinating new insight into the geological history of the UK.”

Unique fossils show how early bird beaks developed

New fossils show that the transition from dinosaur to bird beaks was much more complex than we previously believed.

CT-scan-based skull restoration and life reconstruction of the toothed stem bird Ichthyornis dispar, showing that the first form of the avian beak was a precision pincer-tip probably used for fine manipulation. Image Credits: Michael Hanson and Bhart-Anjan S. Bhullar.

The main perk of being a geologist is that you get to make silly jokes. For instance, every time someone makes a comment about dinosaurs being extinct, you can just chime in and say that dinosaurs aren’t gone — they’re all around us. After a few moments of confusion, you can explain that birds are actually dinosaurs, and slowly retreat after seeing the annoyed gazes directed at you. In all seriousness though, the current scientific consensus is that birds are a group of theropod dinosaurs that originated during the Mesozoic Era, and through successive adaptations, developed into the incredibly diverse group we see today.

There are, of course, dramatic differences between birds and dinosaurs. Aside from the obvious flying wings, there’s also the beak. The skulls of modern birds are dramatically different from those of dinosaurs, featuring several adaptations: an enlarged and toothless beak, bigger braincases, weaker jaw-closing muscles and more articulated skulls with mobile palates and suspended jaws.

However, researchers don’t really know which of these features came first and which followed — this is where the new fossils come in.

“The distinctive features of birds, from beaks to feathers, provide a stark separation between avians and other animal groups. But how did the features of the bird skull evolve? On page 96, Field et al. present a computerized reconstruction of the skull of a pivotal early bird that brings avian evolution into sharper focus,” writes Kevin Padian, Professor of Integrative Biology at the University of California, Berkeley, in an accompanying News & Views article.

Bhart-Anjan Bhullar and colleagues describe four new fossils of the early bird Ichthyornis dispar. Ichtyornis had a 60-centimeter wingspan and a toothy, tern-like beak. It lived some 100–66 million years ago, and it fills a somewhat unique spot in the fossil record: it’s new enough to resemble modern birds, but it also maintains many of its archaic features.

Skull of the bird Ichthyornis dispar. Image credits: Michael Hanson and Bhart-Anjan S. Bhullar.

Paleontologists have known about this species for more than a century. It was first discovered in 1870, but the first fossils were incomplete and damaged — and no new fossils had been found until now. The newly discovered fossils are complete and 3D (as opposed to flattened), offering a much better look into what the species look like. The research team carried out complete CT scans, reconstructing the bird’s skull.

They found that, like dinosaurs, Ichthyornis sports holes in its skull for large jaw-closing muscles. However, unlike them, the bird also has a largely modern, articulated skull, which features a small, primitive beak on its jaw tips. This unusual mix of features would have enabled preening and object manipulation after arms became wings, and goes to show that the feeding apparatus of living birds evolved earlier than previously thought.

The brain was also relatively modern, but the temporal region was unexpectedly dinosaurian. This combination of features documents that important attributes of the avian brain and palate evolved before the reduction of jaw musculature and the full transformation of the beak, researchers write in the study.

“Moreover, ‘bird brain’ is not the insult you might think. Bird brains are larger relative to their body size than is the case for reptiles, and the relative size of bird brains is comparable to that of placental mammals. As birds evolved from their dinosaur ancestors, the bones that protect the brain enlarged to keep pace with the changes in brain size,” Padian continues.

But, aside from providing some answers, this study raises even more questions. For instance, how did the biological transition from dinosaur to bird change the animal’s diet, and what ecological habits are associated with the loss of teeth from the upper jaw and the evolution of the horny beak that covers it? While we still don’t know all those things, this beautiful reconstruction provides a valuable stepping stone for future studies, and will undoubtedly serve as a resource for future paleontological studies.

The study “Complete Ichthyornis skull illuminates mosaic assembly of the avian head” has been published in Nature.

Researchers have figured out how the Giant’s Causeway came to be

A new study by University of Liverpool geologists has uncovered the secrets of one of the planet’s most impressive geological features: columnar basalts, such as those at the Giant’s Causeway in Northern Ireland.

Hexagonal columnar basalts at the Giant’s Causeway. Image credits: Chmee2 / Wikipedia.

The Giant’s Causeway is an area of 40,000 interlocking geometrical basalt columns which were created after a volcanic eruption some 60 million years ago, during a period called the Tertiary. The resulting columns have regular, hexagonal shapes, which have inspired myths, legends, and most recently, geologists.

When a thick lava flows and starts to solidify and cool down, it compresses and starts to fracture. If it cools down very fast, the compressional forces that act on the lava are very strong and can create a regular, cellular system of fractures. These fractures often create hexagonal structures, though shapes with a different number of sides can also be created. If the conditions are right, the resulting columns have smooth geometric shapes.

Researchers have known about this process for quite a while but the temperature at which this process takes place was still a question mark. Now, University of Liverpool researchers have designed a new type of experiment to show how as magma cools, it contracts and accumulates stress, until it cracks.

They recreated the formation of columnar basalts, finding that they fracture when they cool from around 90 to 140˚C below the temperature at which magma crystallizes into rock — which is about 980˚C for basalts. This means that basalts such as those at the Giant’s Causeway were formed at temperatures of around 840-890 ˚C.

Yan Lavallée, Professor of Volcanology, who headed the research, explains:

“The temperature at which magma cools to form these columnar joints is a question that has fascinated the world of geology for a very long time. We have been wanting to know whether the temperature of the lava that causes the fractures was hot, warm or cold.

“I have spent over a decade pondering how to address this question and construct the right experiment to find the answer to this question. Now, with this study, we have found that the answer is hot, but after it solidified.”

Stuðlaberg (Columnar basalt) in Breiðafjörður, Iceland. Image credits: Zinneke / Wikipedia.

Understanding the thermal constraints of this process is not only important for solving a geological mystery, it could also be useful for geothermal energy harnessing — the point at which magma starts to fracture is also the point at which it initiates fluid circulation in the fracture network.

“Fluid flow controls heat transfer in volcanic systems, which can be harnessed for geothermal energy production. So the findings have tremendous applications for both volcanology and geothermal research,” says Dr Jackie Kendrick, a post-doctoral researcher in the group.

 

Journal Reference: Anthony Lamur et al. Disclosing the temperature of columnar jointing in lavas. doi:10.1038/s41467-018-03842-4

Mars render.

NASA’s next mission to Mars will map the planet’s interior, scheduled for May 5th

NASA’s next mission will provide InSight into the workings of Mars’ interior — and find out whether there is such a thing as a Marsquake.

Mars render.

Mars rendered in Autodesk Maya.
Image credits Kevin Gill / Flickr.

No, that’s not a typo — NASA’s InSight mission, short for Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport, leaves little room for doubt as to what it will entail — except that it will do it on Mars. There’s a lot of interest among planetary scientists about what secrets the red planet’s interior hides, and the mission aims to bring many of those to light. As part of this mission, the eponymous lander will blast off from the Vandenberg Air Force Base in California as early as May 5, according to a news release.

Red to the core?

The InSight mission will be the first in many regards: it’s the first launch to another planet from the West Coast — usually, that’s a role reserved for Cape Canaveral, Florida. It’s also the first mission dedicated to studying Mars’ deep interior, the product of 25 years of planning and effort, says the mission’s lead investigator Bruce Banerdt.

Although the launch is scheduled for the 5th of May, it will still take the lander about six months to make the 301-million-mile treck to Mars, according to NASA estimates. Another 2-3 months will be needed to get the instruments all nicely calibrated and humming at peak accuracy; all in all, the mission should last about two Earth years, which is a little over one Martian year.

According to Banerdt, InSight will collect seismic data and chart heat flows beneath the planet’s crust, all while keeping a highly-accurate eye on Mars’ north pole. He’s confident that by the mission’s end, researchers will have enough data on hand to map out the interior structure of Mars — a feat that could finally tell us what turned the planet so barren. The craft will be beaming data back since day one, however, so maybe we’ll piece things together a bit faster.

InSight’s observations extend farther than Mars alone, though. Data gleaned from the lander will help scientists better understand how rocky bodies or planets form and evolve; Banerdt described the mission as a “scientific time machine that will bring back information about the early stages of Mars’ formation four-and-a-half-billion years ago”.

Having access to this story will even help scientists better understand how Earth and our moon came to be. Down here, because our planet is still keeping active (isn’t it making us all so proud?), the same clues InSight will be looking for just aren’t available anymore; they’ve been destroyed by millions of years of erosion, mantle convection, plate tectonics, and other geological processes. Mars, luckily for us, hasn’t been active enough to cover up the traces left by its formation and early processes, according to Banerdt.

“What InSight is going to do is, it is going to sort of fill in the last big hole in our understanding of Mars. We’ve sent orbiters to Mars which have studied the entire surface, [but e]verything more than just a few feet below the surface is completely unknown territory,” he explains.

“And InSight is going to fill in the gap in our knowledge of Mars and sort of finish the reconnaissance of the exploration of Mars.”

InSight’s launch is scheduled for May 5; if anything should interfere with that date and the mission needs to be delayed, its launch window is open until June 8.

Mars.

Water may, ironically, be the root of Mars’ dreariness — it could have sabotaged its magnetic field

Mars’ lack of water and of a magnetic field could be linked, new research proposes.

Mars.

Image via Pixabay.

Despite being a pretty inhospitable place today, Mars used to have liquid water aplenty and an atmosphere. Taken together, these likely made the red planet not that unlike our own Earth — which is to say, ‘comfortable’. Sometime in the past, however, both the water and the air vanished. Our working theory is that it was caused by Mars’s magnetic field, which waned then disappeared roughly 4 billion years ago. Without it to insulate the planet, solar winds flayed it of its atmosphere, slowly turning it into the dry ball of dust and rock we see today.

Magnet..Oh…

It’s a compelling story, but there is one especially frustrating piece missing from it: what killed off the magnetic field? Last week, at the at the Lunar and Planetary Science Conference held in Texas, planetary scientist Joseph O’Rourke presented a new theory which could fill in this missing piece. He believes that the disappearance of the planet’s magnetic field is connected to its missing surface water.

To the best of our knowledge, planets produce their magnetic fields through the churning of their molten, ferrous cores. Convection — where the heated part of a molten material rises to the top, to be replaced by the denser, colder part on top — keeps this metal moving. And just like a dynamo, where you have moving iron, you get a magnetic field.

O’Rourke’s theory is that an influx of hydrogen, sourced by the splitting of water molecules deeper into the Martian mantle, could have stalled this dynamo — and with it, Mars’ magnetic field. Convection relies on differences in density to keep material (in our case, molten iron) moving. But if a lighter material — and it’s hard to get lighter than hydrogen — settles relatively close to the bottom of the convection cell, it can block denser material from sinking back down. It clogs the system.

 “Too much hydrogen and you can shut down convection entirely,” he said. “Hydrogen is a heartless killer.”

O’Rourke, from the Arizona State University in Tempe, worked together with Dan Shim, a colleague at the University, to determine where all this hydrogen could have come from. They believe it was sourced from water that was chemically locked in Martial minerals. While it would remain stable in the upper layers of the mantle, the incredible heat and pressures closer to the core could pull these water molecules out of their minerals, and then break them apart. The oxygen atom, being highly reactive, would go on to form new compounds — while the hydrogen atoms would build up near the core and stall convection.

This meddling hydrogen

So, was there enough water in Mars’ mantle for the job? The authors note that Mars’ crust is rich in olivine, a material that doesn’t bond very well with water, and so it remains relatively dry. At deeper levels, where there’s more pressure, this olivine transforms into the minerals wadsleyite and ringwoodite, which do hold more water. Deeper still, the mineral turns into bridgmanite and becomes dry again. According to the team, this bridgmanite layer should act as a buffer, keeping water away and insulating the convection cell. So far, the situation on (in?) Mars is very similar to that on Earth — the same minerals are involved,  and there’s no reason to believe that they would behave differently on Mars.

However, there is one important distinction between the two planets — Mars’ mantle cooled down significantly, while Earth’s remains hot. Temperature plays a key role here because it’s the combination of high pressure at high temperatures that prompts the transition to bridgmanite and later keeps it stable. In a progressively cool mantle, like Mars’, the bridgmanite layer would shrink and eventually disappear altogether.

Whether or not this mineral survived in Mars’ interior depends on how large the planet’s core is. We don’t yet know how large it is, but NASA’s InSight Mars lander, scheduled for launch on May 5th, may find out.

One interesting implication of O’Rourke’s theory is that if hydrogen did clog up the magnetic field, it did so surprisingly fast — previous research suggests that Mars’ magnetic field disappeared quite rapidly, over 100 million years’ time.

For now, we’ll have to wait for InSight to launch, and see if the theory stands up to measurements taken in the field. Whatever the results may be, one thing is certain: Mars’ stubborn lack of a magnetic field is bad for business. Hopefully, this research will offer some insight as to how we can fix it.

The paper “Suppressing the Martian Dynamo with Ongoing Hydrogenation of the Core by Hydrated Mantle Minerals” has been presented at the 49th  Lunar and Planetary Science Conference, The Woodlands, Texas, on March 21, 2018.

For the first time, researchers record a volcanic thunder

A group of scientists achieved what many believed was impossible: recording a volcano’s thunder.

This satellite image shows Bogoslof volcano erupting on May 28, 2017. The eruption began about 18 minutes prior to this image and the cloud rose to an altitude greater than 12 kilometers (40,000 feet) above sea level. Image credits: Dave Schneider / Alaska Volcano Observatory & U.S. Geological Survey.

Not all volcanoes are made equal, and not all eruptions are the same. Depending on the chemistry and temperature of the lava, some eruptions are essentially a neat lava fountain, while others are more explosive, ejecting clouds of hot rock and ash that can reach the stratosphere. As they do so, these charged particles can create loud thunders, but these thunders tend to get lost in the overall cacophony of tumbles and rumbles in the eruption.

Now, for the first time, geoscientists have managed to isolate that thunder boom, digitally disentangling it from other sounds in the background.

“It’s something that people who’ve been at eruptions have certainly seen and heard before, but this is the first time we’ve definitively caught it and identified it in scientific data,” said Matt Haney, a seismologist at the Alaska Volcano Observatory in Anchorage and lead author of the new study set to be published in Geophysical Research Letters.

You can listen to the sound here:

This audio file contains 20 minutes of microphone data recorded during the March 8, 2017 Bogoslof eruption, sped up 60 times. Credit: Matt Haney / Alaska Volcano Observatory & U.S. Geological Survey.

Isolating the sound isn’t just interesting as a technical achievement, it can be used as a proxy for volcanic lightning (the stronger the lightning is, the stronger the thunder is). Then, the lightning itself can be used to assess how big the volcanic plume is — and how hazardous it is.

“Understanding where lightning is occurring in the plume tells us about how much ash has been erupted, and that’s something that’s notoriously difficult to measure,” Johnson said. “So if you’re locating thunder over a long area, you could potentially say something about how extensive the plume is.”

Bogoslof Volcano erupting on June 5, 2017. Image credits: NASA Earth Observatory.

The team was able to record the rumbling and thunder using a microphone array, a tool which is becoming more and more common in volcano monitoring. Although zoning in on the thunder alone was considered impossible by some geoscientists, Haney believes the technique might become more and more common (and useful) in the near future.

“If people had been observing the eruption in person, they would have heard this thunder,” Haney said. “I expect that going forward, other researchers are going to be excited and motivated to look in their datasets to see if they can pick up the thunder signal.”

Journal Reference: ‘Volcanic thunder from explosive eruptions at Bogoslof volcano, Alaska’. Geophysical Research Lettersonlinelibrary.wiley.com/doi/10 … 017GL076911/abstract

Geologists discover ancient meteorite on the Isle of Skye, in Scotland

Geologists exploring the Isle of Skye have uncovered something out of this world: evidence of a meteorite which bombarded Scotland 60 million years ago.

A thin section of the meteoritic rock seen through a microscope. Image credits: Simon Drake.

By now, we have a pretty good idea of our planet’s geological make-up. So when Simon Drake, an associate lecturer in geology at the Birkbeck University of London, came across a meter-thick layer at the base of a 60.0 million-year-old lava flow, he thought it was an ignimbrite — pumice-dominated pyroclastic flow deposits. But when he analyzed it more closely with an electron microscope, he quickly understood that the rock wasn’t what he thought.

The key to this understanding it is a mineral called osbornite. Osbornite is a strange beast, hard to really put in a mineralogical class. It’s also not from Earth — it was only observed in meteorites and comets. The fact that osbornite was found unmelted indicates that it was an original piece of the meteorite. This wasn’t the only smoking gun; geologists also found reidite, an extremely high-pressure form of zircon which is only associated with strong impacts.

“The most compelling evidence really is the presence of vanadium-rich and niobium-rich osbornite. Neither of these have ever been found on Earth before. We have these mineral totally enclosed in native iron, which itself is not of this planet,” Drake says.

They managed to date the layer to sometime between 60 million and 61.4 million years ago and confirmed the initial finding in another place. Dr. Drake said:

“We have found evidence of the impact at two sites and at another potential two sites on the Isle of Skye, at the moment.”

The finding helps put Skye’s rich geological history into context. Even though the isle was studied extensively, the structures were buried beneath a murky swamp which likely dissuaded previous efforts.

“One of the things that is really interesting here is that the volcanological evolution of the Isle of Skye has always been considered to have been started with what’s called a volcanic plume, an enormously large bulk of magma which has come up under what then was the crust that Skye was on,” according to Drake.

“We are now suggesting that this may well have been assisted by a meteorite impact.”

However, there’s still much work to be done. The team still doesn’t know exactly where the meteorite hit, and how it affected local volcanism. It’s unclear if it the meteorite helped trigger volcanism or if the two events are completely unrelated. Hopefully, future studies can help clear out these mysteries and add another piece to the geological puzzle.

Journal Reference: Simon M. Drake et al. Discovery of a meteoritic ejecta layer containing unmelted impactor fragments at the base of Paleocene lavas, Isle of Skye, Scotland. Geology, 2017; DOI: 10.1130/G39452.1

Gullies Mars.

Boiling water shapes Mars’ landscape, experiment reveals

Researchers at The Open University (OU) could finally put the mystery regarding the formation of Mars’ land features to rest. The red planet’s landscapes, they report, is formed by small amounts of water boiling in the thin atmosphere.

Gullies Mars.

Gullies on Mars’ surface are likely formed through this process.
Image credits NASA / Mars Reconnaissance Orbiter.

There’s a good reason why Mars doesn’t make it very high on the ‘best spots for watersports’ lists for — it’s quite dry. There are no oceans, no rivers, no lakes here. There’s also the issue of its whispy-thin but the decidedly deadly atmosphere.

This dryness has also puzzled researchers trying to understand the planet’s landscapes for a long time now. On Earth, water has a central role to play in shaping landscapes. It provides sediment mobility (i.e. it moves particles of soil and rocks around), chisels and polishes through erosion, and adds the final details through chemical alteration. Mars, however, showcases some breathtaking features despite its relative absence of water. The mystery only compounds when you factor in its atmosphere, which is far less able than Earth’s to influence landscapes.

Make do

To get to the bottom of things, a group of scientists from the OU used the university’s Mars Simulation Chamber to re-create conditions on Mars and see how they influence land feature formation. Their work revealed that because of our neighbor’s thin atmosphere (about 0.7% as thick as Earth’s, at roughly 7 mbar) water will spontaneously, and violently, boil on its surface. During periods when Mars’ surface is relatively warm, even a small quantity of water flowing to the surface can move large amounts of sand or other sediments. The team describes the process as material or pellets of material “levitating” on the cushion of vapor released by boiling waters.

Compared to what we’re used to seeing on Earth, even small amounts of liquid water running across Mars’ surface could thus form the large dune flows, gullies, and other characteristic features. Here you can see the difference in sediment flow on the simulated Martian surface during a “cold” (no boil) and “warm” (boil) run. These runs would correspond to mean temperatures on Mars’ surface during cold seasons and warmer ones (i.e. Martian summer.)

Mars leviflow.

Image, map, and elevation data recorded at the end of experiments.
A, d, photographs of the “cold” and “warm” experiments respectively.
D, e, hillshaded relief digital elevation models (DEM) overlain by process-zone maps giving the spatial extent of the different transport types (blue = overland flow, green = percolation, red = pellets, yellow = dry avalanches/saltation) for “cold” (b) and “warm” (e) experiments.
C, F, elevation differences between the start and end of the experiment for “cold” and “warm” runs respectively.
Flow direction is from top to bottom and the same scale is used for all images.
Image credits Jan Raack et al., 2018, N.Comm.

“Whilst planetary scientists already know that the surface of Mars has ‘mass-wasting’ features — such as dune flows, gullies, and recurring slope lineae — which occur as a result of sediment transportation down a slope, the debate about what is forming them continues,” according to Dr Jan Raack, Marie Skłodowska-Curie Research Fellow at The Open University and lead author of the paper.

“Our research has discovered that this levitation effect caused by boiling water under low pressure enables the rapid transport of sand and sediment across the surface. This is a new geological phenomenon, which doesn’t happen on Earth, and could be vital to understanding similar processes on other planetary surfaces.”

The team reports that levitation processes can increase sediment transport nine-fold (as compared to ‘cold’ runs with no boiling and ‘warm’ runs), reducing the amount of water needed to move a given volume of material “by nearly an order of magnitude.” Finally, they calculate that Mars’ reduced gravitational pull would allow these processes to persist up to 48 times longer. While the team admits that this number “is likely to be an overestimation,” even a 10-times longer persistence of the levitation processes “would result in a decameter-extent of sediment disturbance, which should be visible in remote sensing images”. The sediment pellets themselves would likely not be visible in remote-sensing images.

Overall, the team says that levitation processes associated with small water flows on Mars’ surface features have been “widely underestimated”, and call for more observational studies on the matter.

“We need to carry out more research into how water levitates on Mars, and missions such as the ESA ExoMars 2020 Rover will provide vital insight to help us better understand our closest neighbour.”

Sediment transport where this mechanism is active is about nine times greater than without this effect, reducing the amount of water required to transport comparable sediment volumes by nearly an order of magnitude. Our calculations show that the effect of levitation could persist up to ~48 times longer under reduced Martian gravity.

The paper “Water induced sediment levitation enhances downslope transport on Mars” has been published in the journal Nature Communications.

New evidence indicates that life on Earth emerged almost 4 billion years ago

Earth had life since its infancy — new evidence indicates that primordial life emerged at least 3.95 billion years ago. The Earth is only 4.54 billion years old.

Traces of graphite in ancient Canadian rocks were produced by microorganisms 3.95 billion years ago, according to new research. Credits: Tsuyoshi Komiya, University of Tokyo.

Life, uh, finds a way

The Torngat Mountains in the Labrador Peninsula in Canada are no strangers to life. These days, Caribou munch on the lichen and lush grass, while polar bears roam the shore in search of other animals to hunt. But back in the day, things were a bit different, and I mean back in the day. Four billion years ago, the Earth — let alone the Torngat Mountains — was a very different place. We’re talking about the very end of the Hadean Era, a geological time named after the ancient Greek God of the underworld, and it’s easy to understand why. Earth was initially molten due to extreme volcanism and frequent collisions with other bodies, but it ultimately formed a solid crust. The atmosphere was only starting to form, still leaving the planet vulnerable to catastrophic impacts. The oceans were also just forming, from condensing water vapor, augmented by ice delivered from comets.

Yet through all this, life somehow managed to emerge.

Yuji Sano and Tsuyoshi Komiya from the University of Tokyo analyzed graphite particles in rocks from the mountains. They found evidence of stromatolites, layered structures created by bacteria, thanks to an analysis of carbon isotopes. Carbon comes in two stable isotopes: carbon-12, which is the most common, and carbon-13, which is rarer and slightly heavier. Life prefers carbon-12 because it is more reactive. So by looking at the carbon-12 to carbon-13 ratio, researchers can deduce (to some degree of accuracy) whether or not life was there. This ratio did indicate the existence of life, though there are still some question marks around this approach.

Then even if this is the case, there’s also the matter of whether or not the life is as old as the surrounding rocks. The rocks they found the samples in are metamorphic, meaning they’ve been subjected to a lot of pressure and heat these past four billion years, and it’s not impossible for external graphite to have sneaked in from different, more recent rocks. So before we get overly excited there are still matters which need to be cleared about this study.

As far back as we can look

But if the findings are confirmed, then it would be an incredible testament to life’s resilience. Not only going back to an ungodly time in our planet’s history but going back pretty much as far as we can look for.

A microscopic image of the globular shape produced by the graphite grains. (Image: Tsuyoshi Komiya, The University of Tokyo).

“The emerging picture from the ancient-rock record is that life was everywhere,” says Vickie Bennett from Australian National University, who was not involved in the latest study, according to The Atlantic. “As far back as the rock record extends—that is, as far back as we can look for direct evidence of early life, we are finding it. Earth has been a biotic, life-sustaining planet since close to its beginning.”

Prior to this, the earliest discovered life was dated to 3.7 billion years ago. While the difference might not seem that large, it’s quite significant. The reason is that 3.95 billion years ago is during the so-called Late Heavy Bombardment, during which a disproportionately large number of asteroids colliding with Earth, whereas 3.7 is not.

“It may be difficult to create life before 3.8bn years ago due to the bombardment, which may destroy early life,” he said. “But now it is 4bn years. Life started on Earth during the heavy bombardment of meteorites, which is amazing.”

Journal Reference: Takayuki Tashiro et al. Early trace of life from 3.95 Ga sedimentary rocks in Labrador, Canadadoi:10.1038/nature24019

 

Surtsey Island.

Researchers will drill into one of Earth’s youngest islands to understand how land forms

 One of the world’s youngest islands will be drilled in an effort to understand how land forms on Earth.

Surtsey Island.

Surtsey island, as seen in 2001.
Image credits ICDP.

The tiny island of Surtsey wasn’t even there 50 years ago. This 1.3 square kilometer island was formed off Iceland’s southwestern coast somewhere between 1963 and 1967 by a series of volcanic eruptions. And next month, a team of scientists will drill two holes into the depths of this young land. Supported in part by the International Continental Scientific Drilling Program, this will be the most detailed look at newly-formed land, which researchers hope will help them understand how molten rock, cold seawater, and the underground biosphere interact.

Why here

Being so new, Surtsey could probably boast some of the wildest, most untouched environments currently on the planet. It’s a UNESCO World Heritage site, earmarked for scientific observation — mainly regarding the biogeographic evolution of new land as it’s being colonized by plants and wildlife.

One particular point of interest is to see how hydrothermal minerals fit into the island’s rocks. These are believed to be at the root of Surtsey’s resilience against the North Atlantic Ocean’s waves and could help engineers design stronger blends of concrete. Another is to see how underground flora feeds on the minerals contained in rocks and hot fluids — helping us understand the role of the deep crustal biosphere in the environments we see topside.

The first of the drill holes will run parallel to an 181-meter deep hole drilled in 1979, which the scientists will use to see how microbes on the island evolved over time. This has been monitored since it was first drilled and is now likely teeming with micro-organisms indigenous to Surtsey. The team plans to place five incubation chambers in the new hole, at different depths, let them stay for a year, then checking them for microbes that have moved in.

The landscape on Surtsey (Wikipedia).

A second drill will be set at an angle and will investigate the hot fluids percolating (flowing) through the volcanic cracks and craters that formed Surtsey. Information gleaned here will help geologists reconstruct the sub surface volcano system that built Surtsey. In the initial contact between seawater and hot magma, hydrothermal vents formed in the rock. It made them less porous and helped reinforce Surtsey’s shores against erosion. This places it in stark contrast to other volcanic islands, which get ground down by the waves pretty rapidly after formation. Getting a better idea of how these minerals evolved over time could help engineers create better, more resilient types of concrete.

If all goes according to plan, both holes will pass through the original 1960s ocean floor, at about 190m below sea level.

Iceland’s Coast Guard will start shuttling in the required 60 tonnes of equipment and supplies drillers will need on Surtsey, which they estimate will take around 100 helicopter flights. In accordance with UNESCO regulations, all waste will be removed from the island, including the sterilized seawater to be used as drilling fluid. Drilling will be performed 24 hours a day to keep the operation as short as possible, and only 12 people will be allowed on the island at a time. The rest of the team will stay on the neighboring island of Heimæy.