Telescopes In Space For Even Sharper Images Of Black Holes

Astronomers have just managed to take the first image of a black hole, and now the next challenge facing them is how to take even sharper images, so that Einstein’s Theory of General Relativity can be tested. Radboud University astronomers, along with the European Space Agency (ESA) and others, are putting forward a concept for achieving this by launching radio telescopes into space. They publish their plans in the scientific journal Astronomy & Astrophysics.

The idea is to place two or three satellites in circular orbit around the Earth to observe black holes. The concept goes by the name Event Horizon Imager (EHI). In their new study, the scientists present simulations of what images of the black hole Sagittarius A* would look if they were taken by satellites like these.

More than five times as sharp

“There are lots of advantages to using satellites instead of permanent radio telescopes on Earth, as with the Event Horizon Telescope (EHT),” says Freek Roelofs, a PhD candidate at Radboud University and the lead author of the article. “In space, you can make observations at higher radio frequencies, because the frequencies from Earth are filtered out by the atmosphere. The distances between the telescopes in space are also larger. This allows us to take a big step forward. We would be able to take images with a resolution more than five times what is possible with the EHT.”

Sharper images of a black hole will lead to better information that could be used to test Einstein’s Theory of General Relativity in greater detail. “The fact that the satellites are moving round the Earth makes for considerable advantages,” Radio Astronomy Professor Heino Falcke says. “With them, you can take near perfect images to see the real details of black holes. If small deviations from Einstein’s theory occur, we should be able to see them.”

The EHI will also be able to image about five additional black holes that are smaller than the black holes that the EHT is currently focussing on. The latter are Sagittarius A* at the centre of our Milky Way and M87* at the centre of Messier 87, a massive galaxy in the Virgo Cluster.

Technological challenges

The researchers have simulated what they would be able to see with different versions of the technology under different circumstances. For this they made use of models of plasma behaviour around the black hole and the resulting radiation. “The simulations look promising from a scientific aspect, but there are difficulties to overcome at a technical level,” Roelofs says.

The astronomers collaborated with scientists from ESA/ESTEC to investigate the technical feasibility of the project. “The concept demands that you must be able to ascertain the position and speed of the satellites very accurately,” according to Volodymyr Kudriashov, a researcher at the Radboud Radio Lab who also works at ESA/ESTEC. “But we really believe that the project is feasible.”

Consideration also has to be given to how the satellites exchange data. “With the EHT, hard drives with data are transported to the processing centre by airplane. That’s of course not possible in space.” In this concept, the satellites will exchange data via a laser link, with the data being partially processed on board before being sent back to Earth for further analysis. “There are already laser links in space,” Kudriashov notes.

Hybrid system

The idea is that the satellites will initially function independently of the EHT telescopes. But consideration is also being given to a hybrid system, with the orbiting telescopes combined with the ones on Earth. Falcke: “Using a hybrid like this could provide the possibility of creating moving images of a black hole, and you might be able to observe even more and also weaker sources.”

The research is part of the BlackHoleCam project, which is an ERC Synergy Grant awarded in 2013 to a team of European astrophysicists to image, measure and understand black holes. BlackHoleCam is an active partner of the Event Horizon Telescope collaboration.

At Least 15 Dead As Cyclone Fani Moves Toward Bangladesh

Dhaka, Bangladesh — A mammoth preparation exercise that included the evacuation of more than 1 million people appears to have spared India a devastating death toll from Cyclone Fani, one of the biggest storms in decades. However, the full extent of the damage was yet to be known, officials said Saturday.

The cyclone packed winds of 155 miles per hour when it made landfall in eastern Odisha state on Friday, equivalent in strength to a Category 4 hurricane, said Mohammad Heidarzadei, an expert on cyclones at Brunel University of London.

As of late Saturday, India’s National Disaster Response Force director S.N. Pradhan said three people had been killed, though the storm smashed thatched-roof huts, uprooted trees and power lines, ripped the roof off a medical college and sprayed the emptied coastline with debris. “The precautions that have been taken should be continued,” Pradhan said.

Officials cautioned that the death toll could rise as communications were restored.

Fani crossed over India’s West Bengal state and moved northeast toward Bangladesh on Saturday, weakening from a severe cyclonic storm to a cyclonic storm.

At least a dozen people had been confirmed killed in Bangladesh as the cyclone hovered over the country’s southwestern coast early Saturday, delivering battering rain storms. Lightning killed at least six people, local newspapers and TV reported. However, the death toll had not increased by Saturday afternoon, suggesting effective preparedness in Bangladesh as well.

Bad weather from the storm system was projected to affect around 100 million people in South Asia, from India’s distant Andaman Islands to Mount Everest in Nepal.

The relatively low casualty count demonstrates much improved disaster readiness in India since 1999, when a “super” cyclone killed around 10,000 people and devastated large parts of Odisha.

“In the event of such a major calamity like this — where Odisha was hit by close to a super-cyclone — instead of being a tragedy of humongous proportion, we are in the process of restoring critical infrastructure. That is the transformation that Odisha has had,” the state’s top government official, Naveen Patnaik, said in a statement.

India’s disaster response agency said authorities were working “on war footing” to restore power and communications, and clear roads of debris. Widespread power outages, damaged water supplies and roads blocked by fallen trees and power lines made transport around the affected area difficult, officials said.

Pravat Ranjan Mohapatra, the deputy relief commissioner at Odisha’s emergency center, said his phone line and internet were down for most of Saturday.

“Earlier we were not able to connect with authorities for infrastructure damage, how many houses are damaged or how many people have died or were injured,” he said.

According to the Press Trust of India, one victim was a teenager killed by a falling tree in the district of Puri, a popular tourist area in Odisha. Another woman was killed while fetching water when she was struck by flying debris loosened from a concrete structure. Another woman, age 65, died after a suspected heart attack at a cyclone shelter, PTI reported.

Water Found In Samples From Asteroid Itokawa

Two cosmochemists at Arizona State University have made the first-ever measurements of water contained in samples from the surface of an asteroid. The samples came from asteroid Itokawa and were collected by the Japanese space probe Hayabusa.

The team’s findings suggest that impacts early in Earth’s history by similar asteroids could have delivered as much as half of our planet’s ocean water.

“We found the samples we examined were enriched in water compared to the average for inner solar system objects,” says Ziliang Jin. A postdoctoral scholar in ASU’s School of Earth and Space Exploration, he is the lead author on the paper published May 1 in Science Advances reporting the results. His co-author is Maitrayee Bose, assistant professor in the School.

“It was a privilege that the Japanese space agency JAXA was willing to share five particles from Itokawa with a U.S. investigator,” Bose says. “It also reflects well on our School.”

The team’s idea of looking for water in the Itokawa samples came as a surprise for the Hayabusa project.

“Until we proposed it, no one thought to look for water,” says Bose. “I’m happy to report that our hunch paid off.”

In two of the five particles, the team identified the mineral pyroxene. In terrestrial samples, pyroxenes have water in their crystal structure. Bose and Jin suspected that the Itokawa particles might also have traces of water, but they wanted to know exactly how much. Itokawa has had a rough history involving heating, multiple impacts, shocks, and fragmentation. These would raise the temperature of the minerals and drive off water.

To study the samples, each about half the thickness of a human hair, the team used ASU’s Nanoscale Secondary Ion Mass Spectrometer (NanoSIMS), which can measure such tiny mineral grains with great sensitivity.

The NanoSIMS measurements revealed the samples were unexpectedly rich in water. They also suggest that even nominally dry asteroids such as Itokawa may in fact harbor more water than scientists have assumed.

Fragmented world

Itokawa is a peanut-shaped asteroid about 1,800 feet long and 700 to 1,000 feet wide. It circles the Sun every 18 months at an average distance of 1.3 times the Earth-Sun distance. Part of Itokawa’s path brings it inside Earth’s orbit and at farthest, it sweeps out a little beyond that of Mars.

Based on Itokawa’s spectrum in Earth-based telescopes, planetary scientists place it in the S class. This links it with the stony meteorites, which are thought to be fragments from S-type asteroids broken off in collisions.

“S-type asteroids are one of the most common objects in the asteroid belt,” says Bose. “They originally formed at a distance from the Sun of one-third to three times Earth’s distance.” She adds that although they are small, these asteroids have kept whatever water and other volatile materials they formed with.

In structure, Itokawa resembles a pair of rubble piles crunched together. It has two main lobes, each studded with boulders but having different overall densities, while between the lobes is a narrower section.

Jin and Bose point out that today’s Itokawa is the remnant of a parent body at least 12 miles wide that at some point was heated between 1,000 and 1,500 degrees Fahrenheit. The parent body suffered several large shocks from impacts, with one final shattering event that broke it apart. In the aftermath two of the fragments merged and formed today’s Itokawa, which reached its current size and shape about 8 million years ago.

“The particles we analyzed came from a part of Itokawa called the Muses Sea,” says Bose. “It’s an area on the asteroid that’s smooth and dust-covered.”

Jin adds, “Although the samples were collected at the surface, we don’t know where these grains were in the original parent body. But our best guess is that they were buried more than 100 meters deep within it.”

He adds that despite the catastrophic breakup of the parent body, and the sample grains being exposed to radiation and impacts by micrometeorites at the surface, the minerals still show evidence of water that has not been lost to space.

In addition, says Jin, “The minerals have hydrogen isotopic compositions that are indistinguishable from Earth.”

Bose explains, “This means S-type asteroids and the parent bodies of ordinary chondrites are likely a critical source of water and several other elements for the terrestrial planets.”

She adds, “And we can say this only because of in-situ isotopic measurements on returned samples of asteroid regolith — their surface dust and rocks.

“That makes these asteroids high-priority targets for exploration.”

Scouting for samples

Bose notes that she is building a clean-lab facility at ASU, which along with the NanoSIMS (partially funded by National Science Foundation) would be the first such facility at a public university capable of analyzing dust grains from other solar system bodies.

Another Japanese mission, Hayabusa 2, is currently at an asteroid named Ryugu, where it will collect samples, bringing them back to Earth in December 2020. The director of ASU’s Center for Meteorite Studies, professor Meenakshi Wadhwa, is a member of the Initial Analysis team for Chemistry for the Hayabusa 2 mission.

ASU is also on board NASA’s OSIRIS-REx sample-return mission, which is orbiting a near-Earth asteroid named Bennu. Among other instruments, the spacecraft carries the OSIRIS-REx Thermal Emission Spectrometer (OTES), designed by ASU Regents’ Professor Philip Christensen and built at the School. OSIRIS-REx is scheduled to collect samples from Bennu in summer 2020 and bring them back to Earth in September 2023.

For planetary scientists and cosmochemists who are drawing a picture of how the solar system formed, asteroids are a great resource. As leftover building blocks for the planetary system, they vary greatly among themselves while preserving materials from early in solar system history.

Says Bose, “Sample-return missions are mandatory if we really want to do an in-depth study of planetary objects.”

And she adds, “The Hayabusa mission to Itokawa has expanded our knowledge of the volatile contents of the bodies that helped form Earth. It would not be surprising if a similar mechanism of water production is common for rocky exoplanets around other stars.”

Hubble Astronomers Assemble Wide View Of The Evolving Universe

Astronomers have put together the largest and most comprehensive “history book” of galaxies into one single image, using 16 years’ worth of observations from NASA’s Hubble Space Telescope.

The deep-sky mosaic, created from nearly 7,500 individual exposures, provides a wide portrait of the distant universe, containing 265,000 galaxies that stretch back through 13.3 billion years of time to just 500 million years after the big bang. The faintest and farthest galaxies are just one ten-billionth the brightness of what the human eye can see. The universe’s evolutionary history is also chronicled in this one sweeping view. The portrait shows how galaxies change over time, building themselves up to become the giant galaxies seen in the nearby universe.

This ambitious endeavor, called the Hubble Legacy Field, also combines observations taken by several Hubble deep-field surveys, including the eXtreme Deep Field (XDF), the deepest view of the universe. The wavelength range stretches from ultraviolet to near-infrared light, capturing the key features of galaxy assembly over time.

“Now that we have gone wider than in previous surveys, we are harvesting many more distant galaxies in the largest such dataset ever produced by Hubble,” said Garth Illingworth of the University of California, Santa Cruz, leader of the team that assembled the image. “This one image contains the full history of the growth of galaxies in the universe, from their time as ‘infants’ to when they grew into fully fledged ‘adults.'”

No image will surpass this one until future space telescopes are launched. “We’ve put together this mosaic as a tool to be used by us and by other astronomers,” Illingworth added. “The expectation is that this survey will lead to an even more coherent, in-depth and greater understanding of the universe’s evolution in the coming years.”

The image yields a huge catalog of distant galaxies. “Such exquisite high-resolution measurements of the numerous galaxies in this catalog enable a wide swath of extragalactic study,” said catalog lead researcher Katherine Whitaker of the University of Connecticut, in Storrs. “Often, these kinds of surveys have yielded unanticipated discoveries which have had the greatest impact on our understanding of galaxy evolution.”

Galaxies are the “markers of space,” as astronomer Edwin Hubble once described them a century ago. Galaxies allow astronomers to trace the expansion of the universe, offer clues to the underlying physics of the cosmos, show when the chemical elements originated, and enable the conditions that eventually led to the appearance of our solar system and life.

This wider view contains about 30 times as many galaxies as in the previous deep fields. The new portrait, a mosaic of multiple snapshots, covers almost the width of the full Moon. The XDF, which penetrated deeper into space than this wider view, lies in this region, but it covers less than one-tenth of the full Moon’s diameter. The Legacy Field also uncovers a zoo of unusual objects. Many of them are the remnants of galactic “train wrecks,” a time in the early universe when small, young galaxies collided and merged with other galaxies.

Assembling all of the observations was an immense task. The image comprises the collective work of 31 Hubble programs by different teams of astronomers. Hubble has spent more time on this tiny area than on any other region of the sky, totaling more than 250 days, representing nearly three-quarters of a year.

“Our goal was to assemble all 16 years of exposures into a legacy image,” explained Dan Magee, of the University of California, Santa Cruz, the team’s data processing lead. “Previously, most of these exposures had not been put together in a consistent way that can be used by any researcher. Astronomers can select the data in the Legacy Field they want and work with it immediately, as opposed to having to perform a huge amount of data reduction before conducting scientific analysis.”

The image, along with the individual exposures that make up the new view, is available to the worldwide astronomical community through the Mikulski Archive for Space Telescopes (MAST). MAST, an online database of astronomical data from Hubble and other NASA missions, is located at the Space Telescope Science Institute in Baltimore, Maryland.

The Hubble Space Telescope has come a long way in taking ever deeper “core samples” of the distant universe. After Hubble’s launch in 1990, astronomers debated if it was worth spending a chunk of the telescope’s time to go on a “fishing expedition” to take a very long exposure of a small, seemingly blank piece of sky. The resulting Hubble Deep Field image in 1995 captured several thousand unseen galaxies in one pointing. The bold effort was a landmark demonstration and a defining proof-of-concept that set the stage for future deep field images. In 2002, Hubble’s Advanced Camera for Surveys went even deeper to uncover 10,000 galaxies in a single snapshot. Astronomers used exposures taken by Hubble’s Wide Field Camera 3 (WFC3), installed in 2009, to assemble the eXtreme Deep Field snapshot in 2012. Unlike previous Hubble cameras, the telescope’s WFC3 covers a broader wavelength range, from ultraviolet to near-infrared.

This new image mosaic is the first in a series of Hubble Legacy Field images. The team is working on a second set of images, totaling more than 5,200 Hubble exposures, in another area of the sky. In the future, astronomers hope to broaden the multiwavelength range in the legacy images to include longer-wavelength infrared data and high-energy X-ray observations from two other NASA Great Observatories, the Spitzer Space Telescope and Chandra X-ray Observatory.

The vast number of galaxies in the Legacy Field image are also prime targets for future telescopes. “This will really set the stage for NASA’s planned Wide Field Infrared Survey Telescope (WFIRST),” Illingworth said. “The Legacy Field is a pathfinder for WFIRST, which will capture an image that is 100 times larger than a typical Hubble photo. In just three weeks’ worth of observations by WFIRST, astronomers will be able to assemble a field that is much deeper and more than twice as large as the Hubble Legacy Field.”

In addition, NASA’s upcoming James Webb Space Telescope will allow astronomers to push much deeper into the legacy field to reveal how the infant galaxies actually grew. Webb’s infrared coverage will go beyond the limits of Hubble and Spitzer to help astronomers identify the first galaxies in the universe.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

The Space Rock That Hit The Moon At 61,000 Kilometers An Hour

Observers watching January’s total eclipse of the Moon saw a rare event, a short-lived flash as a meteorite hit the lunar surface. Spanish astronomers now think the space rock collided with the Moon at 61,000 kilometres an hour, excavating a crater 10 to 15 metres across. Prof Jose Maria Madiedo of the University of Huelva, and Dr Jose L. Ortiz of the Institute of Astrophysics of Andalusia, publish their results in a new paper in Monthly Notices of the Royal Astronomical Society.

Total lunar eclipses take place when the Moon moves completely into the shadow of the Earth. The Moon takes on a red colour — the result of scattered sunlight refracted through the Earth’s atmosphere — but is much darker than normal. These spectacular events are regularly observed by astronomers and the wider public alike.

The most recent lunar eclipse took place on 21 January 2019, with observers in North and South America and Western Europe enjoying the best view. At 0441 GMT, just after the total phase of the eclipse began, a flash was seen on the lunar surface. Widespread reports from amateur astronomers indicated the flash — attributed to a meteorite impact — was bright enough to be seen with the naked eye.

Madiedo and Ortiz operate the Moon Impacts Detection and Analysis System (MIDAS), using eight telescopes in south of Spain to monitor the lunar surface. The impact flash lasted 0.28 seconds and is the first ever filmed during a lunar eclipse, despite a number of earlier attempts.

“Something inside of me told me that this time would be the time,” said Madiedo, who was impressed when he observed the event, as it was brighter than most of the events regularly detected by the survey.

Unlike the Earth, the Moon has no atmosphere to protect it and so even small rocks can hit its surface. Since these impacts take place at huge speeds, the rocks are instantaneously vaporised at the impact site, producing an expanding plume of debris whose glow can be detected from our planet as short-duration flashes.

MIDAS telescopes observed the impact flash at multiple wavelengths (different colours of light), improving the analysis of the event. Madiedo and Ortiz conclude that the incoming rock had a mass of 45kg, measured 30 to 60 centimetres across, and hit the surface at 61,000 kilometres an hour. The impact site is close to the crater Lagrange H, near the west-south-west portion of the lunar limb.

The two scientists assess the impact energy as equivalent to 1.5 tonnes of TNT, enough to create a crater up to 15 metres across, or about the size of two double decker buses side by side. The debris ejected is estimated to have reached a peak temperature of 5400 degrees Celsius, roughly the same as the surface of the Sun.

Madiedo comments: “It would be impossible to reproduce these high-speed collisions in a lab on Earth. Observing flashes is a great way to test our ideas on exactly what happens when a meteorite collides with the Moon.”

The team plan to continue monitoring meteorite impacts on the lunar surface, not least to understand the risk they present to astronauts, set to return to the Moon in the next decade.

Magma Is The Key To The Moon’s Makeup

For more than a century, scientists have squabbled over how Earth’s moon formed. But researchers at Yale and in Japan say they may have the answer.

Many theorists believe a Mars-sized object slammed into the early Earth, and material dislodged from that collision formed the basis of the moon. When this idea was tested in computer simulations, it turned out that the moon would be made primarily from the impacting object. Yet the opposite is true; we know from analyzing rocks brought back from Apollo missions that the moon consists mainly of material from Earth.

A new study published April 29 in Nature Geoscience, co-authored by Yale geophysicist Shun-ichiro Karato, offers an explanation.

The key, Karato says, is that the early, proto-Earth — about 50 million years after the formation of the Sun — was covered by a sea of hot magma, while the impacting object was likely made of solid material. Karato and his collaborators set out to test a new model, based on the collision of a proto-Earth covered with an ocean of magma and a solid impacting object.

The model showed that after the collision, the magma is heated much more than solids from the impacting object. The magma then expands in volume and goes into orbit to form the moon, the researchers say. This explains why there is much more Earth material in the moon’s makeup. Previous models did not account for the different degree of heating between the proto-Earth silicate and the impactor.

“In our model, about 80% of the moon is made of proto-Earth materials,” said Karato, who has conducted extensive research on the chemical properties of proto-Earth magma. “In most of the previous models, about 80% of the moon is made of the impactor. This is a big difference.”

Karato said the new model confirms previous theories about how the moon formed, without the need to propose unconventional collision conditions — something theorists have had to do until now.

For the study, Karato led the research into the compression of molten silicate. A group from the Tokyo Institute of Technology and the RIKEN Center for Computational Science developed a computational model to predict how material from the collision became the moon.

The first author of the study is Natsuki Hosono of RIKEN. Additional co-authors are Junichiro Makino and Takayuki Saitoh.

New Fallout From ‘The Collision That Changed The World’

When the landmass that is now the Indian subcontinent slammed into Asia about 50 million years ago, the collision changed the configuration of the continents, the landscape, global climate and more. Now a team of Princeton University scientists has identified one more effect: the oxygen in the world’s oceans increased, altering the conditions for life.

“These results are different from anything people have previously seen,” said Emma Kast, a graduate student in geosciences and the lead author on a paper coming out in Science on April 26. “The magnitude of the reconstructed change took us by surprise.”

Kast used microscopic seashells to create a record of ocean nitrogen over a period from 70 million years ago — shortly before the extinction of the dinosaurs — until 30 million years ago. This record is an enormous contribution to the field of global climate studies, said John Higgins, an associate professor of geosciences at Princeton and a co-author on the paper.

“In our field, there are records that you look at as fundamental, that need to be explained by any sort of hypothesis that wants to make biogeochemical connections,” Higgins said. “Those are few and far between, in part because it’s very hard to create records that go far back in time. Fifty-million-year-old rocks don’t willingly give up their secrets. I would certainly consider Emma’s record to be one of those fundamental records. From now on, people who want to engage with how the Earth has changed over the last 70 million years will have to engage with Emma’s data.”

In addition to being the most abundant gas in the atmosphere, nitrogen is key to all life on Earth. “I study nitrogen so that I can study the global environment,” said Daniel Sigman, Princeton’s Dusenbury Professor of Geological and Geophysical Sciences and the senior author on the paper. Sigman initiated this project with Higgins and then-Princeton postdoctoral researcher Daniel Stolper, who is now an assistant professor of Earth and planetary science at the University of California-Berkeley.

Every organism on Earth requires “fixed” nitrogen — sometimes called “biologically available nitrogen.” Nitrogen makes up 78% of our planet’s atmosphere, but few organisms can “fix” it by converting the gas into a biologically useful form. In the oceans, cyanobacteria in surface waters fix nitrogen for all other ocean life. As the cyanobacteria and other creatures die and sink downward, they decompose.

Nitrogen has two stable isotopes, 15N and 14N. In oxygen-poor waters, decomposition uses up “fixed” nitrogen. This occurs with a slight preference for the lighter nitrogen isotope, 14N, so the ocean’s 15N-to-14N ratio reflects its oxygen levels.

That ratio is incorporated into tiny sea creatures called foraminifera during their lives, and then preserved in their shells when they die. By analyzing their fossils — collected by the Ocean Drilling Program from the North Atlantic, North Pacific, and South Atlantic — Kast and her colleagues were able to reconstruct the 15N-to-14N ratio of the ancient ocean, and therefore identify past changes in oxygen levels.

Oxygen controls the distribution of marine organisms, with oxygen-poor waters being bad for most ocean life. Many past climate warming events caused decreases in ocean oxygen that limited the habitats of sea creatures, from microscopic plankton to the fish and whales that feed on them. Scientists trying to predict the impact of current and future global warming have warned that low levels of ocean oxygen could decimate marine ecosystems, including important fish populations.

When the researchers assembled their unprecedented geologic record of ocean nitrogen, they found that in the 10 million years after dinosaurs went extinct, the 15N-to-14N ratio was high, suggesting that ocean oxygen levels were low. They first thought that the warm climate of the time was responsible, as oxygen is less soluble in warmer water. But the timing told another story: the change to higher ocean oxygen occurred around 55 million years ago, during a time of continuously warm climate.

“Contrary to our first expectations, global climate was not the primary cause of this change in ocean oxygen and nitrogen cycling,” Kast said. The more likely culprit? Plate tectonics. The collision of India with Asia — dubbed “the collision that changed the world” by legendary geoscientist Wally Broecker, a founder of modern climate research — closed off an ancient sea called the Tethys, disturbing the continental shelves and their connections with the open ocean.

“Over millions of years, tectonic changes have the potential to have massive effects on ocean circulation,” said Sigman. But that doesn’t mean climate change can be discounted, he added. “On timescales of years to millenia, climate has the upper hand.”