Rajdeep Dasgupta and André Izidoro

Earth isn’t ‘super’ because the sun had rings before planets

‘Pressure bumps’ in sun’s protoplanetary disk explain many solar system features

HOUSTON – (Jan. 5, 2021) – Before the solar system had planets, the sun had rings — bands of dust and gas similar to Saturn’s rings — that likely played a role in Earth’s formation, according to a new study.


“In the solar system, something happened to prevent the Earth from growing to become a much larger type of terrestrial planet called a super-Earth,” said Rice University astrophysicist André Izidoro, referring to the massive rocky planets seen around at least 30% of sun-like stars in our galaxy.


Izidoro and colleagues used a supercomputer to simulate the solar system’s formation hundreds of times. Their model, which is described in a study published online in Nature Astronomy, produced rings like those seen around many distant, young stars. It also faithfully reproduced several features of the solar system missed by many previous models, including:

  • An asteroid belt between Mars and Jupiter containing objects from both the inner and outer solar system.
  • The locations and stable, almost circular orbits of Earth, Mars, Venus and Mercury.
  • The masses of the inner planets, including Mars, which many solar system models overestimate.
  • The dichotomy between the chemical makeup of objects in the inner and outer solar system.
  • A Kuiper belt region of comets, asteroids and small bodies beyond the orbit of Neptune.

The study by astronomers, astrophysicists and planetary scientists from Rice, the University of Bordeaux, Southwest Research Institute in Boulder, Colorado, and the Max Planck Institute for Astronomy in Heidelberg, Germany, draws on the latest astronomical research on infant star systems.

Their model assumes three bands of high pressure arose within the young sun’s disk of gas and dust. Such “pressure bumps” have been observed in ringed stellar disks around distant stars, and the study explains how pressure bumps and rings could account for the solar system’s architecture, said lead author Izidoro, a Rice postdoctoral researchers who received his Ph.D. training at Sao Paulo State University in Brazil.

“If super-Earths are super-common, why don’t we have one in the solar system?” Izidoro said. “We propose that pressure bumps produced disconnected reservoirs of disk material in the inner and outer solar system and regulated how much material was available to grow planets in the inner solar system.”

Pressure bumps

For decades, scientists believed gas and dust in protoplanetary disks gradually became less dense, dropping smoothly as a function of distance from the star. But computer simulations show planets are unlikely to form in smooth-disk scenarios.

“In a smooth disk, all solid particles — dust grains or boulders — should be drawn inward very quickly and lost in the star,” said astronomer and study co-author Andrea Isella, an associate professor of physics and astronomy at Rice. “One needs something to stop them in order to give them time to grow into planets.”

When particles move faster than the gas around them, they “feel a headwind and drift very quickly toward the star,” Izidoro explained. At pressure bumps, gas pressure increases, gas molecules move faster and solid particles stop feeling the headwind. “That’s what allows dust particles to accumulate at pressure bumps,”  he said.

Isella said astronomers have observed pressure bumps and protoplanetary disk rings with the Atacama Large Millimeter/submillimeter Array, or ALMA, an enormous 66-dish radio telescope that came online in Chile in 2013.

“ALMA is capable of taking very sharp images of young planetary systems that are still forming, and we have discovered that a lot of the protoplanetary disks in these systems are characterized by rings,” Isella said. “The effect of the pressure bump is that it collects dust particles, and that’s why we see rings. These rings are regions where you have more dust particles than in the gaps between rings.”

Ring formation

The model by Izidoro and colleagues assumed pressure bumps formed in the early solar system at three places where sunward-falling particles would have released large amounts of vaporized gas.

“It’s just a function of distance from the star, because temperature is going up as you get closer to the star,” said geochemist and study co-author Rajdeep Dasgupta, the Maurice Ewing Professor of Earth Systems Science at Rice. “The point where the temperature is high enough for ice to be vaporized, for example, is a sublimation line we call the snow line.”

In the Rice simulations, pressure bumps at the sublimation lines of silicate, water and carbon monoxide produced three distinct rings. At the silicate line, the basic ingredient of sand and glass, silicon dioxide, became vapor. This produced the sun’s nearest ring, where Mercury, Venus, Earth and Mars would later form. The middle ring appeared at the snow line and the farthest ring at the carbon monoxide line.

Rings birth planetesimals and planets

Protoplanetary disks cool with age, so sublimation lines would have migrated toward the sun. The study showed this process could allow dust to accumulate into asteroid-sized objects called planetesimals, which could then come together to form planets. Izidoro said previous studies assumed planetesimals could form if dust were sufficiently concentrated, but no model offered a convincing theoretical explanation of how dust might accumulate.

“Our model shows pressure bumps can concentrate dust, and moving pressure bumps can act as planetesimal factories,” Izidoro said. “We simulate planet formation starting with grains of dust and covering many different stages, from small millimeter-sized grains to planetesimals and then planets.”

Accounting for cosmochemical signatures, Mars’ mass and the asteroid belt

Many previous solar system simulations produced versions of Mars as much as 10 times more massive than Earth. The model correctly predicts Mars having about 10% of Earth’s mass because “Mars was born in a low-mass region of the disk,” Izidoro said.

Dasgupta said the model also provides a compelling explanation for two of the solar system’s cosmochemical mysteries: the marked difference between the chemical compositions of inner- and outer-solar system objects, and the presence of each of those objects in the asteroid belt between Mars and Jupiter.

Izidoro’s simulations showed the middle ring could account for the chemical dichotomy by preventing outer-system material from entering the inner system. The simulations also produced the asteroid belt in its correct location, and showed it was fed objects from both the inner and outer regions.

“The most common type of meteorites we get from the asteroid belt are isotopically similar to Mars,” Dasgupta said. “Andre explains why Mars and these ordinary meteorites should have a similar composition. He’s provided a nuanced answer to this question.”

Pressure-bump timing and super-Earths

Izidoro said the delayed appearance of the sun’s middle ring in some simulations led to the formation of super-Earths, which points to the importance of pressure-bump timing.

“By the time the pressure bump formed in those cases, a lot of mass had already invaded the inner system and was available to make super-Earths,” he said. “So the time when this middle pressure bump formed might be a key aspect of the solar system.”

Izidoro is a postdoctoral research associate in Rice’s Department of Earth, Environment and Planetary Sciences. Additional co-authors include Sean Raymond of the University of Bordeaux, Rogerio Deienno of Southwest Research Institute and Bertram Bitsch of the Max Planck Institute for Astronomy. The research was supported by NASA (80NSSC18K0828, 80NSSC21K0387), the European Research Council (757448-PAMDORA), the Brazilian Federal Agency for Support and Evaluation of Graduate Education (88887.310463/2018-00), the Welch Foundation (C-2035) and the French National Centre for Scientific Research’s National Planetology Program.


DOI: 10.1038/s41550-021-01557-z

Read the Nature Astronomy paper at: https://doi.org/10.1038/s41550-021-01557-z.

High-resolution IMAGES are available for download at:

CAPTION: The addition of false color to an image captured by the Atacama Large Millimeter/submillimeter Array, or ALMA, reveals a series of rings around a young star named HD163296. (Image courtesy of Andrea Isella/Rice University)

CAPTION: An illustration of three distinct, planetesimal-forming rings that could have produced the planets and other features of the solar system, according to a computational model from Rice University. The vaporization of solid silicates, water and carbon monoxide at “sublimation lines” (top) caused “pressure bumps” in the sun’s protoplanetary disk, trapping dust in three distinct rings. As the sun cooled, pressure bumps migrated sunward allowing trapped dust to accumulate into asteroid-sized planetesimals. The chemical composition of objects from the inner ring (NC) differs from the composition of middle- and outer-ring objects (CC). Inner-ring planetesimals produced the inner solar system’s planets (bottom), and planetesimals from the middle and outer rings produced the outer solar system planets and Kuiper Belt (not shown). The asteroid belt formed (top middle) from NC objects contributed by the inner ring (red arrows) and CC objects from the middle ring (white arrows). (Image courtesy of Rajdeep Dasgupta)

CAPTION: Rajdeep Dasgupta (left) and Andre Izidoro. (Photo by Jeff Fitlow/Rice University)

CAPTION: Andrea Isella (Photo by Jeff Fitlow/Rice University)

This release can be found online at news.rice.edu.

Air bubbles in Antarctic ice point to cause of oxygen decline

Glacial erosion likely caused atmospheric oxygen levels to dip over past 800,000 years


HOUSTON – (Dec. 20, 2021) – An unknown culprit has been removing oxygen from our atmosphere for at least 800,000 years, and an analysis of air bubbles preserved in Antarctic ice for up to 1.5 million years has revealed the likely suspect.

Yuzhen Yan in Antarctica
Yuzhen Yan in Antarctica in December 2015. (Photo courtesy of Yuzhen Yan)

“We know atmospheric oxygen levels began declining slightly in the late Pleistocene, and it looks like glaciers might have something to do with that,” said Rice University’s Yuzhen Yan, corresponding author of the geochemistry study published in Science Advances. “Glaciation became more expansive and more intense about the same time, and the simple fact that there is glacial grinding increases weathering.”

Weathering refers to the physical and chemical processes that break down rocks and minerals, and the oxidation of metals is among the most important. The rusting of iron is an example. Reddish iron oxide forms quickly on iron surfaces exposed to atmospheric oxygen, or O2.

“When you expose fresh crystalline surfaces from the sedimentary reservoir to O2, you get weathering that consumes oxygen,” said Yan, a postdoctoral research associate in Rice’s Department of Earth, Environmental and Planetary Sciences.

Another way glaciers could promote the consumption of atmospheric oxygen is by exposing organic carbon that had been buried for millions of years, Yan said.

During Yan’s Ph.D. studies in the labs of Princeton University’s Michael Bender and John Higgins, Yan worked on a 2016 study led by Daniel Stolper, now an assistant professor at the University of California, Berkeley, that used air bubbles in ice cores to show the proportion of oxygen in Earth’s atmosphere had declined by about 0.2% in the past 800,000 years.

air bubbles visible in disk of Antarctic ice
Researchers studied Earth’s ancient atmosphere by capturing tiny bubbles of air that were preserved in Antarctic ice for up to 1.5 million years. (Photo by Yuzhen Yan)

In the Science Advances study, Yan, Higgins and colleagues from Oregon State University, the University of Maine and the University of California, San Diego, analyzed bubbles in older ice cores to show the O2 dip began after the length of Earth’s glacial cycles more than doubled around 1 million years ago.

The ice age Earth is in today began about 2.7 million years ago. Dozens of glacial cycles followed. In each, ice caps alternately grew, covering up to a third of the planet, and then retreated toward the poles. Each cycle lasted around 40,000 years until about 1 million years ago. At roughly the same time atmospheric oxygen began to decline, glacial cycles began lasting about 100,000 years.

“The reason for the decline is the rate of O2 being produced is lower than the rate of O2 being consumed,” Yan said. “That’s what we call the source and the sink. The source is what produces O2, and the sink is what consumes or drags on O2. In the study, we interpret the decline to be a stronger drag on O2, meaning more is being consumed.”

Yan said Earth’s biosphere didn’t contribute to the decline because it is balanced, drawing as much O2 from the atmosphere as it produces. Weathering, on a global scale, is the most likely geological process capable of consuming enough excess O2 to account for the decline, and Yan and colleagues considered two scenarios for increased weathering.

drilled ice core in Allan Hills, East Antarctica
A scientific drilling mission to Allan Hills, East Antarctica, in 2015-16 yielded ice cores with trapped bubbles of ancient air, including some that predated the ice age that began 2.7 million years ago. (Photo by Yuzhen Yan)

Global sea level falls when glaciers are advancing and rises when they retreat. When the length of glacial cycles more than doubled, so did the magnitude of swings in sea level. As coastlines advanced, land previously covered by water would have been exposed to the oxidizing power of atmospheric O2.

“We did some calculations to see how much oxygen that might consume and found it could only account for about a quarter of the observed decrease,” Yan said.

Because the extent of ice coverage isn’t precisely known for each glacial cycle, there’s a wider range of uncertainty about the magnitude of chemical weathering from glacial erosion. But Yan said the evidence suggests it could draw enough oxygen to account for the decline.

“On a global scale, it’s very hard to pinpoint,” he said. “But we did some tests about how much additional weathering would be needed to account for the O2 decline, and it’s not unreasonable. Theoretically, it could account for the magnitude of what’s been observed.”

Additional co-authors include Edward Brook of Oregon State, Andrei Kurbatov of the University of Maine and Jeffrey Severinghaus of UC San Diego. The research was supported by the National Science Foundation (1443263, 1443276, 1443306, 0538630, 0944343, 1043681 and 1559691) and a Poh-Hsi Pan Postdoctoral Fellowship from Rice University.


Read the Science Advances paper, “Ice core evidence for atmospheric oxygen decline since the mid-Pleistocene transition,” at https://doi.org/10.1126/sciadv.abj9341 .

High-resolution IMAGES are available for download at:

CAPTION: Yuzhen Yan in Antarctica in December 2015. (Photo courtesy of Yuzhen Yan)

CAPTION: Researchers studied Earth’s ancient atmosphere by capturing tiny bubbles of air that were preserved in Antarctic ice for up to 1.5 million years. (Photo by Yuzhen Yan)

CAPTION: A scientific drilling mission to Allan Hills, East Antarctica, in 2015-16 yielded ice cores with trapped bubbles of ancient air, including some that predated the ice age that began 2.7 million years ago. (Photo by Yuzhen Yan)

EEPS Omer Alpak honored by the Society of Petroleum Engineers 2021 International Award

Sylvia Dee

Sylvia Dee wins fellowship to launch Gulf of Mexico study

– SEPTEMBER 28, 2021

National Academies back ‘bold’ research projects by early-career scientists

Sylvia Dee, an assistant professor of Earth, environmental and planetary sciences at Rice University, has won one of eight national early-career fellowships to pursue research that relates to the changing ecosystem of the Gulf of Mexico.

Sylvia Dee

Sylvia Dee

Dee was selected for the environmental protection and stewardship track of the 2021 Early-Career Research Fellowship (ECRF), announced by the Gulf Research Program (GRP) of the National Academies of Sciences, Engineering and Medicine. 

The Gulf is home to a wide variety of ecosystems including estuaries, oyster reefs, beaches and dunes, mangroves and offshore shoals and banks. Dee and her students focus their study on coral reefs, which are critically threatened in the Gulf. These fragile ecosystems continue to shift with climate change, urbanization and increased demand for food, water and energy. Predicting and anticipating these changes is essential to allocating natural resources in an equitable way while protecting the environment, according to the GHP.

The fellows will investigate specific issues related to Gulf ecosystems and produce research that helps enhance environmental protection and stewardship.

“This fellowship will be critical for supporting research in coral reef risk forecasting and mitigation,” Dee said. “Since moving to Texas, I’ve increasingly focused on local issues, and our coral reefs are critical to the ecosystem services we rely on in Houston. The grant will help us build capacity to predict, map and work with our collaborators at the Flower Garden Banks National Marine Sanctuary to protect the unique coral reefs in the Gulf of Mexico.”

The ECRF award is not attached to a specific project, which allows fellows to take on bold research they might not otherwise be able to pursue. All of the fellows are investigators, faculty members, clinician scientists or scientific team leads at colleges, universities and research institutions. Each of them will receive a $76,000 award, mentoring support and a built-in community of current and past cohorts.

“The opportunity to collaborate and interact with other early-career fellows is really exciting,” Dee said. “Our meetings provide us time to branch off into teams to identify research solutions by reaching across disciplines to work on a common problem. The mentoring component spans everything from work-life balance to networking. And in that way, the program really is designed to help us not only launch critical research, but also develop and grow as scientists and scholars.”

“Research that enhances environmental protection and stewardship requires both multidisciplinary thinking and the ability to build strong relationships with decision-makers,” said Karena Mary Mothershed, senior program manager for the GRP’s Board on Gulf Education and Engagement. “These exceptional fellows embody those qualities through their perseverance, creativity and inventiveness. One of the most unique aspects of the ECRF is that it supports people, not projects — and we’re excited to be a part of our fellows’ continued success and professional growth.”

The National Academies’ Gulf Research Program is an independent, science-based program founded in 2013 as part of legal settlements with the companies involved in the 2010 Deepwater Horizon disaster. Its goal is to enhance offshore energy system safety and protect human health and the environment by catalyzing advances in science, practice and capacity, generating long-term benefits for the Gulf of Mexico region and the nation.

Nature’s archive reveals Atlantic tempests through time

– SEPTEMBER 7, 2021

Paleo storm hunters at Rice need data to refine the record of history’s hurricanes

Atlantic hurricanes don’t just come and go. They leave clues to their passage through the landscape that last centuries or more. Rice University scientists are using these natural archives to find signs of storms hundreds of years before satellites allowed us to watch them in real time.

Postdoctoral fellow Elizabeth Wallace, a paleotempestologist who joined the lab of Rice climate scientist Sylvia Dee this year, is building upon techniques that reveal the frequency of hurricanes in the Atlantic basin over millennia.

The North Atlantic network of sites that preserve records of hurricanes stretches along the coast from Canada to Central America, but with significant gaps. A new study led by scientists at Rice University shows filling those gaps with data from the mid-Atlantic states will help improve the historical record of storms over the past several thousand years and could aid in predictions of future storms in a time of climate change. Illustration by Elizabeth Wallace

The North Atlantic network of sites that preserve records of hurricanes stretches along the coast from Canada to Central America, but with significant gaps. A new study led by scientists at Rice University shows filling those gaps with data from the mid-Atlantic states will help improve the historical record of storms over the past several thousand years and could aid in predictions of future storms in a time of climate change. Illustration by Elizabeth Wallace

Paleoclimate hurricane data (or ‘proxy’ data) is found in archives like tree rings that retain signs of short-term flooding, sediments in blue holes (marine caverns) and coastal ponds that preserve evidence of sand washed inland by storm surges. These natural archives give researchers a rough idea of when and where hurricanes have come ashore.

In a new paper in Geophysical Research Letters, Wallace, Dee and co-author Kerry Emanuel, a climate scientist at the Massachusetts Institute of Technology, take hundreds of thousands of “synthetic” storms spun up from global climate model simulations of the past 1,000 years and examine whether or not they are captured by the vast network of Atlantic paleohurricane proxies.

Reconstructing the past will help scientists understand the ebb and flow of Atlantic hurricanes over time. Previous studies by Wallace and others have demonstrated that a single site capturing past storms cannot be used to reconstruct hurricane climate changes; however, a network of proxies might help refine models of how these storms are likely to be affected by climate change going forward.

Elizabeth Wallace

Elizabeth Wallace

“These paleo hurricane proxies allow us to reconstruct storms into the past, and we’re using them  to figure out how basin-wide storm activity has changed,” said Wallace, a Virginia native who earned her doctorate at MIT and the Woods Hole Oceanographic Institution last year and connected with Dee when the professor spoke there in 2017.

“If I have a sediment core from Florida, it’s only capturing storms that hit Florida,” she said. “I wanted to see if we can use the full collection of records collected from the Bahamas, the East Coast and the Gulf of Mexico over the past few decades to accurately reconstruct basin-wide storm activity over the last few centuries.”

The synthetic storms they built helped illustrate what Wallace already knew: There’s a bias toward the Caribbean and Gulf of Mexico, and a need for more proxies along the east coasts of North and Central America. The Rice team’s quest going forward will be to refine their climate simulations and add more sites to the networks to better reconstruct past hurricane activity.

“In particular, there aren’t really any sites from the Southeast U.S., places like the Carolinas,” she said. “One of the goals of this work is to highlight where scientists should go to core next.”

Wallace has first-hand experience drilling cores. “During a storm event, you get high winds and waves that take the sand from the beach and essentially just throw it back into a coastal pond,” she said. “Only during storm events do these sand layers get deposited in the pond, and in the sediment cores you can see them interspersed with the fine mud that’s typically there. We can date these sand layers and know when a hurricane struck the site.”

She noted there has not yet been an “intensive” effort to compare sediment and tree ring records. “The tree record is still an uncertain proxy,” Wallace said. “We’re looking for tree ring records with rainfall signatures that correspond to storms going over the past 200 or 300 years that match the sediment records for that same interval.”

Sylvia Dee

Sylvia Dee

Dee said the work is fundamentally different from the paleoclimate models she most often studies. “Here we’re taking climate models and generating hundreds of pseudo-tropical storms,” she said. “We’re ‘playing Gaia’ by making a plausible version of reality and combining it with our knowledge of available proxy sites.

“This tells us how many records from how many places we realistically need to capture a climate signal,” Dee said. “It’s really expensive to go out and drill cores, and this helps give us a way to prioritize where to drill.

“This research is crucial as we accelerate into a climate mean state with ever-warmer Atlantic Ocean temperatures,” she said. “Understanding how these storms have evolved over time provides a baseline against which to evaluate tropical cyclones with and without human impacts on the climate system.”

A Pan Postdoctoral Research Fellowship and Rice Academy Fellowship to Wallace and a Gulf Research Program grant to Dee supported the study. Dee is an assistant professor of Earth, environmental and planetary sciences. Emanuel is the Cecil & Ida Green Professor of Atmospheric Science and co-director of the Lorenz Center at MIT.

Helge Gonnermann in EOS article about the impacts of volcanic eruptions on climate

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Featured image credit:  NASA

Sylvia Dee highlights the accomplishments of 19th Century scientist Eunice Foote

Sylvia Dee, assistant professor of Earth, environmental and planetary sciences, authored an article about the work of American scientist  Eunice Foote, who published a paper that documented the underlying cause of today’s climate change crisis.

(This article originally appeared in The Conversation and was included in a previous edition of Dateline. It has also appeared in more than 10 other media outlets since then and was in the July 23 print edition of the Houston Chronicle.)



Seismic study will help keep carbon underground

– JUNE 17, 2021

Department of Energy grant backs development of Jonathan Ajo-Franklin’s fiber-optic monitors

Rice University geoscientists and their colleagues will develop sophisticated fiber-optic sensors and seismic sources to find and evaluate small faults deep underground at sites that store carbon dioxide (CO2) to keep it out of the atmosphere.

Rice University graduate student Valeriia Sobolevskaia at the on-campus well site being developed to help geoscientists continue development of fiber-optic sensors to find and evaluate small faults at underground carbon dioxide storage reservoirs. Courtesy of the Ajo-Franklin Lab

The Department of Energy has awarded Rice geoscientist Jonathan Ajo-Franklin $1.2 million to adapt his lab’s distributed acoustic sensing (DAS) method to monitor storage sites where reactivation of small faults could allow leakage into adjacent groundwater or the atmosphere. The project is part of $4 million in grants announced in late May to enhance the safety and security of CO2 storage.

Capturing CO2 and sequestering it underground, often in former oil and gas reservoirs, is seen as a way to bring the nation closer to its goal of net-zero carbon emissions by 2050.

“Moving forward, we need to focus on reducing emissions, even while fossil fuels are still part of the mix,” Ajo-Franklin said. “Geologic carbon storage has always been viewed as a stopgap solution during the energy transition, but if we can delay emissions for hundreds to thousands of years by keeping it underground, that’s a win.”

The Rice project, with collaborators at Pennsylvania State University and the Lawrence Berkeley National Laboratory, aims to enhance Department of Energy-funded technologies known collectively as “continuous active source seismic monitoring” with DAS, which employs fiber-optic sensors permanently installed in boreholes at storage sites.

The sensors would provide better resolution of seismic property changes at a lower cost than current techniques, Ajo-Franklin said. Distributing multiple sensors at an installation would enable the detection of mechanical changes in the rock that could impact a reservoir.


Jonathan Ajo-Franklin.

Jonathan Ajo-Franklin

“Surface seismology is actually pretty good at finding faults in sedimentary systems,” he said. “That’s what a lot of oil and gas exploration is built around. We’re trying to understand what it looks like if you pressurize a small fault and cause flow along it. To do a good study, we need to reactivate a fault.”

The Rice team is well ahead of the game, with plans to test the ability of DAS to detect small seismic ruptures at an underground geological laboratory in Switzerland. “Mont Terri has an easily accessible fault within a shale formation that we can pressurize with CO2 and image a rupturing fault patch as it slips in a controlled way.”

Building on his research at the Lawrence Berkeley National Laboratory, where researchers employed undersea telecommunication cable to measure earthquakes for a study in Science, Ajo-Franklin and his group have also drilled three instrumented wells in an out-of-the-way spot on the Rice campus for long-duration tests of their instruments and how they compare to more traditional seismic sensors called geophones.

Ajo-Franklin said federal tax credits enacted in recent years have made carbon sequestration more viable, especially at sites with what he called “clean CO2 streams” that need little processing before injecting back into the ground.

Rice University geoscientist Jonathan Ajo-Franklin and his group have drilled three wells in an out-of-the-way spot on campus for long-duration tests of their fiber-optic instruments. Ajo-Franklin is leading a project funded by the Department of Energy to find and evaluate small faults deep underground at sites that store carbon dioxide (CO2) to keep it out of the atmosphere. Photo by Jeff Fitlow

“Until very recently, there wasn’t a reasonable tax or other monetary incentive for companies to do capture and injection,” he said. “They’re not going to do it for free, because the capital investments are very large.”

He noted CO2 storage could become big business in Texas, where tapped-out reservoirs abound. “Luckily, there are plenty of reservoirs on the Gulf Coast that have already been explored for oil and gas production and are very permeable,” he said.

How planets form controls elements essential for life


Rice scientists attribute Earth’s nitrogen to rapid growth of moon- to Mars-sized bodies
The prospects for life on a given planet depend not only on where it forms but also how, according to Rice University scientists.

Planets like Earth that orbit within a solar system’s Goldilocks zone, with conditions supporting liquid water and a rich atmosphere, are more likely to harbor life. As it turns out, how that planet came together also determines whether it captured and retained certain volatile elements and compounds, including nitrogen, carbon and water, that give rise to life.

In a study published in Nature Geoscience, Rice graduate student and lead author Damanveer Grewal and Professor Rajdeep Dasgupta show the competition between the time it takes for material to accrete into a protoplanet and the time the protoplanet takes to separate into its distinct layers — a metallic core, a shell of silicate mantle and an atmospheric envelope in a process called planetary differentiation — is critical in determining what volatile elements the rocky planet retains.

Nitrogen-bearing, Earth-like planets can be formed if their feedstock material grows quickly to around moon- and Mars-sized planetary embryos before separating into core-mantle-crust-atmosphere, according to Rice University scientists. If metal-silicate differentiation is faster than the growth of planetary embryo-sized bodies, then solid reservoirs fail to retain much nitrogen and planets growing from such feedstock become extremely nitrogen-poor. (Credit: Illustration by Amrita P. Vyas/Rice University)


Using nitrogen as proxy for volatiles, the researchers showed most of the nitrogen escapes into the atmosphere of protoplanets during differentiation. This nitrogen is subsequently lost to space as the protoplanet either cools down or collides with other protoplanets or cosmic bodies during the next stage of its growth.

This process depletes nitrogen in the atmosphere and mantle of rocky planets, but if the metallic core retains enough, it could still be a significant source of nitrogen during the formation of Earth-like planets.

Dasgupta’s high-pressure lab at Rice captured protoplanetary differentiation in action to show the affinity of nitrogen toward metallic cores.

“We simulated high pressure-temperature conditions by subjecting a mixture of nitrogen-bearing metal and silicate powders to nearly 30,000 times the atmospheric pressure and heating them beyond their melting points,” Grewal said. “Small metallic blobs embedded in the silicate glasses of the recovered samples were the respective analogs of protoplanetary cores and mantles.”

Rice University graduate student Damanveer Grewal, left, and geochemist Rajdeep Dasgupta discuss their experiments in the lab, where they compress complex mixtures of elements to simulate conditions deep in protoplanets and planets. In a new study, they determined that how a planet comes together has implications for whether it captures and retains the volatile elements, including nitrogen, carbon and water, essential to life. (Credit: Tommy LaVergne/Rice University)


Using this experimental data, the researchers modeled the thermodynamic relationships to show how nitrogen distributes between the atmosphere, molten silicate and core.

“We realized that fractionation of nitrogen between all these reservoirs is very sensitive to the size of the body,” Grewal said. “Using this idea, we could calculate how nitrogen would have separated between different reservoirs of protoplanetary bodies through time to finally build a habitable planet like Earth.”

Their theory suggests that feedstock materials for Earth grew quickly to around moon- and Mars-sized planetary embryos before they completed the process of differentiating into the familiar metal-silicate-gas vapor arrangement.

In general, they estimate the embryos formed within 1-2 million years of the beginning of the solar system, far sooner than the time it took for them to completely differentiate. If the rate of differentiation was faster than the rate of accretion for these embryos, the rocky planets forming from them could not have accreted enough nitrogen, and likely other volatiles, critical to developing conditions that support life.

“Our calculations show that forming an Earth-size planet via planetary embryos that grew extremely quickly before undergoing metal-silicate differentiation sets a unique pathway to satisfy Earth’s nitrogen budget,” said Dasgupta, the principal investigator of CLEVER Planets, a NASA-funded collaborative project exploring how life-essential elements might have come together on rocky planets in our solar system or on distant, rocky exoplanets.

Rice University geochemists analyzed experimental samples of coexisting metals and silicates to learn how they would chemically interact when placed under pressures and temperatures similar to those experienced by differentiating protoplanets. Using nitrogen as a proxy, they theorize that how a planet comes together has implications for whether it captures and retains volatile elements essential to life. (Credit: Tommy LaVergne/Rice University)


“This work shows there’s much greater affinity of nitrogen toward core-forming metallic liquid than previously thought,” he said.

The study follows earlier works, one showing how the impact by a moon-forming body could have given Earth much of its volatile content, and another suggesting that the planet gained more of its nitrogen from local sources in the solar system than once believed.

In the latter study, Grewal said, “We showed that protoplanets growing in both inner and outer regions of the solar system accreted nitrogen, and Earth sourced its nitrogen by accreting protoplanets from both of these regions. However, it was unknown as to how the nitrogen budget of Earth was established.”

“We are making a big claim that will go beyond just the topic of the origin of volatile elements and nitrogen, and will impact a cross-section of the scientific community interested in planet formation and growth,” Dasgupta said.

Rice undergraduate intern Taylor Hough and research intern Alexandra Farnell, then a student at St. John’s School in Houston and now an undergraduate at Dartmouth College, are co-authors of the study.

NASA grants, including one via the FINESST program, and a Lodieska Stockbridge Vaughn Fellowship at Rice supported the research.

EEPS joint faculty and Clever Planets scientist Pedram Hassanzadeh wins NSF CAREER Award

– APRIL 21, 2021

Grant will push study of atmospheric ‘blocking events’ that cause extreme weather

Remember Hurricane Harvey? Look west and there was an atmospheric block. Remember the Great Freeze of 2021? Look north and there was a block.

Atmospheric blocking is known to cause or exacerbate extreme weather events, but much about them remains a mystery. Rice University fluid dynamicist Pedram Hassanzadeh has won a prestigious National Science Foundation CAREER Award to study these events with an eye toward better understanding the physics behind their complex mechanics.

Pedram Hassanzadeh

Pedram Hassanzadeh

CAREER grants are awarded to fewer than 400 early career engineers and scientists each year who are expected to make significant impact in their disciplines.

The five-year, $735,000 award will allow Hassanzadeh and his lab to study blocks, which are large-scale, quasi-stationary, high-pressure systems that persist from five days to a few weeks in the middle latitudes between 40 and 60 degrees. In the northern hemisphere, this includes most of the United States and Canada.

“The main component of the middle latitude atmosphere is the jet stream of strong, turbulent winds in the first 10 kilometers of the atmosphere that generally go from west to east,” said Hassanzadeh, an assistant professor of mechanical engineering at Rice’s Brown School of Engineering. “They can be pretty fast, about 100 miles per hour on average, and you see them as wavy lines on the weather.

“The news also shows you high- and low-pressure systems, and generally these systems move and local weather changes daily,” he said. “But sometimes these high-pressure systems stop moving. They get stuck. And when that happens for more than five days, they’re called blocking events.”

They can wreak havoc, prompting heat waves and cold spells. “In 2010, there was a heatwave over Russia that lasted for a month and killed thousands,” Hassanzadeh said. “In 2003, there was one in France. And specifically for Houston, one reason Harvey didn’t move was because a blocking event over the western U.S., with clockwise circulation, prevented it from moving up. This year, during the cold snap, there was a blocking event over Canada.

“These events show up a lot in association with extreme weather but their dynamics are still not well-understood, even though people have been looking at them since the 1940s,” Hassanzadeh said. Poor understanding of the dynamics of blocks has hindered decades of effort focused on improving the prediction of extreme events and projecting how these events might change in the future, he said.

Blocks are thought to involve complex interactions between small and large turbulent swirling flows, and understanding them requires novel methods and approaches, Hassanzadeh said. His group has been developing such methods for atmospheric turbulence and extreme events.

An earlier study from his group used climate models to suggest blocking events in the northern hemisphere will become as much as 17% larger due to anthropogenic climate change.

Hassanzadeh also won one of 26 grants from the Office of Naval Research Young Investigator Program in 2020 to pursue improved weather/climate modeling capabilities using deep learning.

The CAREER grant includes funds for a Research Experiences for Teachers program with research positions and workshops for high-school science teachers. The grant will also facilitate the development of materials to teach climate science and a course to introduce college students to climate science and applications of math, advanced computing and artificial intelligence to climate research.