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Moonquakes and marsquakes: How we peer inside other worlds – Horizon magazine

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On Earth, we can feel and see the often terrifying results of the tectonic plates shifting beneath our feet. As they grind together, they generate earthquakes that produce seismic waves that reverberate through layers of rock, magma and metal deep inside our planet.

Scientists can monitor these seismic waves using a variety of instruments that pick up even faint vibrations passing through the Earth’s crust and core. Studying how the behaviour of these waves changes as they pass through our planet’s interior, reveals details about what lies deep inside the Earth, far out of our sight.

But Earth is not the only place in our solar system that experiences seismic activity. Both Mars and the moon also experience quakes – although for different reasons than here on Earth. Seismometers deployed on the moon and – more recently – on Mars, are allowing researchers to probe the interiors of both of these distant worlds.

The results show that while on the surface Earth, Mars and the moon are not alike, beneath it they have more in common than might be suspected, but with some striking differences.

Moonquakes

Moonquakes – as they are known on the moon – are produced as a result of meteoroids hitting the surface or by the gravitational pull of the Earth squeezing and stretching the moon’s interior, in a similar way to the moon’s tidal pull on Earth’s oceans. As the lunar interior cools, it is also causing the moon to shrink and shrivel like a raisin, causing other quakes as the crust buckles and breaks. Heat from the sun can also produce thermal quakes due to the temperature difference in the lunar crust as the moon emerges from its night.

Five seismometers have been deployed on the moon, left by astronauts during the Apollo missions between 1969 to 1972. The first lunar seismometer was set up by Neil Armstrong and Buzz Aldrin on the Apollo 11 mission. After deploying the instrument, Aldrin stamped on the lunar surface to check it was working – with the instrument picking up the waves produced by his foot.

The other four seismometers were left by subsequent missions and they were operated until 1977, five years after the final Apollo astronauts set foot on the lunar surface. But some 43 years later, their data is still being pored over by scientists.

SeisMo is one project that recently re-analysed the data. ‘We were trying to apply a technique which is used quite commonly on Earth,’ said Dr Ceri Nunn, from NASA’s Jet Propulsion Laboratory in California, US, the lead scientist on the project. ‘If you cross-correlate the noise between stations, you can actually see waves travelling between them. The first station is a source, and the second station is a receiver.’

Unfortunately, Dr Nunn was unable to pick up similar patterns in the data from the moon. But that failure revealed something else about the moon – namely that it doesn’t appear to have surface waves, which get trapped in the upper layers of rock and bounce around. ‘That wave doesn’t seem to exist on the moon,’ said Dr Nunn.

This suggests the upper layer of the moon’s surface is likely highly fractured, and up to 100 kilometres thick, both of which disturb the movement of seismic waves across the surface. ‘This highly fractured layer is changing the way that seismic waves behave,’ said Dr Nunn.

Currently there are no active seismometers on the moon. But there are proposals to send new seismometers back to the lunar surface in future missions.

‘We’re interested in using much smaller seismometers, possibly being delivered by penetrators, which are almost like missile-shaped objects,’ said Dr Nunn. ‘You put a very small seismometer in the back and then launch them either from a descending lander or directly from Earth.’

Questions

Putting new seismometers on the moon could answer several outstanding questions, such as why there are large structural differences between the near side of the moon that points towards us and the far side that points away.

‘(That could be) related to the internal structure,’ said Dr Nunn. ‘There’s a theory (the moon) was hit again after it formed by another moon, and that’s why you get this strange asymmetry. Exploring the internal structure would be interesting. And on top of that we’d like to constrain how thick the core is.’

Understanding this could help to prove theories about how these early, cataclysmic impacts around the time the Earth and moon were forming helped to determine the structures they have today.

On Mars, however, things are a bit different. Marsquakes are produced not by tidal interactions, but by the planet cooling and contracting, producing deep stresses. Meteoroid impacts are believed to play a part too, just like on the moon, sending seismic waves around the planet.

The existence of marsquakes had never been proven until researchers landed a seismometer on the red planet in 2018 as part of NASA’s InSight mission. The InSight Mars lander detected the first-ever definitive marsquake on 6 April 2019 using its Seismic Experiment for Interior Structure (SEIS) instrument, which had been gently placed on the surface by the lander’s robotic arm shortly after it touched down on 26 November 2018. Since then about 500 subsequent events have also been detected.

Volcanic activity

While most of the marsquakes have been relatively small, some of these have been large enough – almost equivalent to a magnitude 4 earthquake – to be traced back to their source, an area known as Cerberus Fossae, about 1,600 kilometres east of InSight. It is thought the quakes there are being caused by the build-up of stress as fractures in the Martian crust are stretched, possibly by volcanic activity.

While the larger quakes appear to originate from the mantle beneath the Martian crust, the smaller marsquakes are thought to begin in the crust itself. The velocity of seismic waves in the upper Martian crust, however, in the first eight to 11 kilometres, seems to be about 50% lower than in similar rocks on Earth.

Researchers who are part of the GeoInSight project have been studying the geology of the surface around the InSight landing site to understand more about what might be going on. They used images and data from NASA’s Mars Reconnaissance Orbiter (MRO) to study the Elysium Planitia area before InSight arrived.

The images revealed that there are lava flows 200 to 300 metres beneath the lander, according to Dr Lu Pan from the University of Copenhagen, Denmark, the project coordinator on GeoInsight. ‘But beneath those lava flows, we have sedimentary rocks and clay-bearing rocks a few kilometres in depth,’ she said.

This layering is one explanation for the lower velocity of the seismic waves, says Dr Pan, because sedimentary rocks have a high porosity that could slow the waves down. Another possibility is that the upper crust has been heavily damaged and fractured by meteorite impacts and other processes, producing more resistance for the waves.

The findings also have implications for some of InSight’s other results, noted Dr Pan. ‘For example, one of the exciting discoveries of InSight was the magnetic field, (which was) ten times more than we observed from orbit,’ she said. ‘Having established the stratigraphy (the layering of the rocks), we could help put some constraints on where the magnetic field came from – stratigraphy from before 3.9 billion years (ago).’

Humming

While InSight will continue to probe the interior of Mars with its SEIS instrument, scientists are keen to also unravel the mystery of a strange reading it has been picking up.

‘There’s this humming at a specific frequency that occurs when there’s another event,’ said Dr Pan. ‘We don’t really understand what it is. Sometimes when there’s a quake, we see that humming come afterwards. We don’t really have a good analogue on Earth.’

As InSight and its instruments listen into to the inner workings of the red planet, it might help reveal the source of this hum and reveal what really lies deep inside this alien world.

The research in this article was funded by the EU. If you liked this article, please consider sharing it on social media.

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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