Using a technique called ‘seismic noise interferometry’ combined with geophysical measurements, the researchers measured the energy moving through a volcano. They found that there is a good correlation between the speed at which the energy travelled and the amount of bulging and shrinking observed in the rock. The technique could be used to predict more accurately when a volcano will erupt. Their results are reported in the journal Science Advances.

Data was collected by the US Geological Survey across Kīlauea in Hawaii, a very active volcano with a lake of bubbling lava just beneath its summit. During a four-year period, the researchers used sensors to measure relative changes in the velocity of seismic waves moving through the volcano over time. They then compared their results with a second set of data which measured tiny changes in the angle of the volcano over the same time period.

As Kīlauea is such an active volcano, it is constantly bulging and shrinking as pressure in the magma chamber beneath the summit increases and decreases. Kīlauea’s current eruption started in 1983, and it spews and sputters lava almost constantly. Earlier this year, a large part of the volcano fell away and it opened up a huge ‘waterfall’ of lava into the ocean below. Due to this high volume of activity, Kīlauea is also one of the most-studied volcanoes on Earth.

The Cambridge researchers used seismic noise to detect what was controlling Kīlauea’s movement. Seismic noise is a persistent low-level vibration in the Earth, caused by everything from earthquakes to waves in the ocean, and can often be read on a single sensor as random noise. But by pairing sensors together, the researchers were able to observe energy passing between the two, therefore allowing them to isolate the seismic noise that was coming from the volcano.

“We were interested in how the energy travelling between the sensors changes, whether it’s getting faster or slower,” said Clare Donaldson, a PhD student in Cambridge’s Department of Earth Sciences, and the paper’s first author. “We want to know whether the seismic velocity changes reflect increasing pressure in the volcano, as volcanoes bulge out before an eruption. This is crucial for eruption forecasting.”

One to two kilometres below Kīlauea’s lava lake, there is a reservoir of magma. As the amount of magma changes in this underground reservoir, the whole summit of the volcano bulges and shrinks. At the same time, the seismic velocity changes. As the magma chamber fills up, it causes an increase in pressure, which leads to cracks closing in the surrounding rock and producing faster seismic waves — and vice versa.

“This is the first time that we’ve been able to compare seismic noise with deformation over such a long period, and the strong correlation between the two shows that this could be a new way of predicting volcanic eruptions,” said Donaldson.

Volcano seismology has traditionally measured small earthquakes at volcanoes. When magma moves underground, it often sets off tiny earthquakes, as it cracks its way through solid rock. Detecting these earthquakes is therefore very useful for eruption prediction. But sometimes magma can flow silently, through pre-existing pathways, and no earthquakes may occur. This new technique will still detect the changes caused by the magma flow.

Seismic noise occurs continuously, and is sensitive to changes that would otherwise have been missed. The researchers anticipate that this new research will allow the method to be used at the hundreds of active volcanoes around the world.

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The new findings, published in Science Advances, show that less cloud cover and more summer sunshine allows increased solar radiation to reach the surface providing more energy for melting.

Using data from earth-observing satellites and high-resolution climate models, the authors found a consistent decrease in summer cloud cover since 1995.

The research shows that a one percent reduction in summer cloud cover is equivalent to 27 gigatons of extra ice melt on the Greenland ice sheet — this is roughly equivalent to the annual domestic water supply of the USA or 180 million times the weight of a blue whale.

Since 1995, researchers found that Greenland has lost a total of about 4,000 gigatons of ice, which has become the biggest single contributor to the rise in global sea levels. PhD student, Stefan Hofer, from the University’s School of Geographical Sciences and member of the Black and Bloom and GlobalMass projects is the lead author of the study.

He said: “The impact of increased sunshine during summer is large, it explains about two-thirds of Greenland’s melting signal in recent decades.

“Until now we thought that the recent Greenland melt is caused almost exclusively by higher temperatures and the resulting feedbacks.

“Our study shows that there is more to the story than the local increase in temperatures and the change in cloud cover isn’t just a blip, it’s been happening for the last two decades. That was a big surprise.”

The team also reported that climate change has found a second pathway to increase melt over Greenland, adding to the effect of higher temperatures:

Co-author Professor Jonathan Bamber, based at the University of Bristol, and President of the European Geoscience Union (EGU), added: “We are seeing changes in the large-scale circulation patterns, which leads to more frequent sunshine and higher amounts of solar energy reaching the surface of the ice sheet.

“These changes in large-scale circulation patterns during summer are especially pronounced over the Arctic and the North Atlantic.

“The state shift in atmospheric circulation is unprecedented in the observational record, which goes back as far as 1850.

“This highly unusual state of the atmosphere has been linked to record low sea ice cover during summer over the Arctic Ocean. This highlights the coupled nature of the climate system and the consequences of changes in one component on another.”

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What makes tidying up especially challenging is that the debris exists in space. Suction cups don’t work in a vacuum. Traditional sticky substances, like tape, are largely useless because the chemicals they rely on can’t withstand the extreme temperature swings. Magnets only work on objects that are magnetic. Most proposed solutions, including debris harpoons, either require or cause forceful interaction with the debris, which could push those objects in unintended, unpredictable directions.

To tackle the mess, researchers from Stanford University and NASA’s Jet Propulsion Laboratory (JPL) have designed a new kind of robotic gripper to grab and dispose of the debris, featured in the June 27 issue of Science Robotics.

“What we’ve developed is a gripper that uses gecko-inspired adhesives,” said Mark Cutkosky, professor of mechanical engineering and senior author of the paper. “It’s an outgrowth of work we started about 10 years ago on climbing robots that used adhesives inspired by how geckos stick to walls.”

The group tested their gripper, and smaller versions, in their lab and in multiple zero gravity experimental spaces, including the International Space Station. Promising results from those early tests have led the researchers to wonder how their grippers would fare outside the station, a likely next step.

“There are many missions that would benefit from this, like rendezvous and docking and orbital debris mitigation,” said Aaron Parness, MS ’06, PhD ’10, group leader of the Extreme Environment Robotics Group at JPL. “We could also eventually develop a climbing robot assistant that could crawl around on the spacecraft, doing repairs, filming and checking for defects.”

Creating a gecko gripper

The adhesives developed by the Cutkosky lab have previously been used in climbing robots and even a system that allowed humans to climb up certain surfaces. They were inspired by geckos, which can climb walls because their feet have microscopic flaps that, when in full contact with a surface, create a Van der Waals force between the feet and the surface. These are weak intermolecular forces that result from subtle differences in the positions of electrons on the outsides of molecules.

The gripper is not as intricate as a gecko’s foot — the flaps of the adhesive are about 40 micrometers across while a gecko’s are 200 about nanometers — but the gecko-inspired adhesive works in much the same way. Like a gecko’s foot, it is only sticky if the flaps are pushed in a specific direction but making it stick only requires a light push in the right direction. This is a helpful feature for the kinds of tasks a space gripper would perform.

“If I came in and tried to push a pressure-sensitive adhesive onto a floating object, it would drift away,” said Elliot Hawkes, MS ’11, PhD ’15, a visiting assistant professor from the University of California, Santa Barbara and co-author of the paper. “Instead, I can touch the adhesive pads very gently to a floating object, squeeze the pads toward each other so that they’re locked and then I’m able to move the object around.”

The pads unlock with the same gentle movement, creating very little force against the object.

The gripper the researchers created has a grid of adhesive squares on the front and arms with thin adhesive strips that can fold out and move toward the middle of the robot from either side, as though it’s offering a hug. The grid can stick to flat objects, like a solar panel, and the arms can grab curved objects, like a rocket body.

One of the biggest challenges of the work was to make sure the load on the adhesives was evenly distributed, which the researchers achieved by connecting the small squares through a pulley system that also serves to lock and unlock the pads. Without this system, uneven stress would cause the squares to unstick one by one, until the entire gripper let go. This load-sharing system also allows the gripper to work on surfaces with defects that prevent some of the squares from sticking.

The group also designed the gripper to switch between a relaxed and rigid state.

“Imagining that you are trying to grasp a floating object, you want to conform to that object while being as flexible as possible, so that you don’t push that object away,” explained Hao Jiang, a graduate student in the Cutkosky lab and lead author of the paper. “After grasping, you want your manipulation to be very stiff, very precise, so that you don’t feel delays or slack between your arm and your object.”

Gecko-inspired adhesive in zero-G

The group first tested the gripper in the Cutkosky lab. They closely measured how much load the gripper could handle, what happened when different forces and torques were applied and how many times it could be stuck and unstuck. Through their partnership with JPL, the researchers also tested the gripper in zero gravity environments.

In JPL’s Robodome, they attached small rectangular arms with the adhesive to a large robot, then placed that modified robot on a floor that resembled a giant air-hockey table to simulate a 2D zero gravity environment. They then tried to get their robot to scoot around the frictionless floor and capture and move a similar robot.

“We had one robot chase the other, catch it and then pull it back toward where we wanted it to go,” said Hawkes. “I think that was definitely an eye-opener, to see how a relatively small patch of our adhesive could pull around a 300 kilogram robot.”

Next, Jiang and Parness went on a parabolic airplane flight to test the gripper in zero gravity. Over two days, they flew a series of 80 ascents and dives, which created an alternating experience of about 20 seconds of 2G and 20 seconds of zero-G conditions in the cabin. The gripper successfully grasped and let go of a cube and a large beach ball with a gentle enough touch that the objects barely moved when released.

Lastly, Parness’s lab developed a small gripper that went up in the International Space Station (ISS), where they tested how well the grippers worked inside the station.

Next steps for the gripper involve readying it for testing outside the space station, including creating a version made of longer lasting materials able to hold up to high levels of radiation and extreme temperatures. The current prototype is made of laser-cut plywood and includes rubber bands, which would become brittle in space. The researchers will have to make something sturdier for testing outside the ISS, likely designed to attach to the end of a robot arm.

Back on Earth, Cutkosky also hopes that they can manufacture larger quantities of the adhesive at a lower cost. He imagines that someday gecko-inspired adhesive could be as common as Velcro.