“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.

“The impacts of climate change and extreme weather events on the grid, mostly in the form of drought and heat waves, are going to get worse under climate change,” said Jordan Kern, assistant professor of forestry and environment resources at NC State. “Even as the West Coast grid moves away from fossil fuels toward wind and solar, these extreme weather events will still impact system reliability and the price of power.”

Published in the journal Earth’s Future, the two studies project future power supply and demand under separate scenarios. In the first study, researchers used computer models to simulate the impacts of climate change on the current power grid in California and the Pacific Northwest. They evaluated the grid’s price and reliability under 11 different climate scenarios between 2030 and 2060, drawing on multiple scientific models for how the climate would change under a “worst-case scenario” of fossil fuel emissions, and another less severe scenario.

“The worst-case scenario is worth looking at even if there’s some evidence that the world is going to reduce fossil fuel emissions enough to avoid it,” Kern said.

The researchers found greater risk of power blackouts in summer and early fall, largely driven by extreme heat in California that causes high demand for power as people cool their homes. They projected there would be shortfall events in all but one scenario where climate change affected power generation in both regions simultaneously.

However, they noted these power shortfalls would remain relatively rare. The maximum under the worst case was 72 hours of West Coast-wide power supply shortages across 31 years.

“As it gets hotter and hotter and hotter, and demand for electricity gets higher, we expect the grid to fail,” Kern said. “Those extreme heat events are going to become much more severe.”

Extreme heat in California would also affect the price and supply of power in the Pacific Northwest. Historically, the regions have shared power.

“If, and that’s a big ‘if,’ historic exchanges of electricity continue, and California has a high demand for electricity because of heat, it could cause the Pacific Northwest to run out of electricity, as they won’t be able to meet their own demand,” Kern said.

They also found climate change could impact the Pacific Northwest directly by limiting supplies of hydropower, which is electricity powered by water. Snow serves as stored power, so reductions in snow or changes in the timing of snowmelt reduce power available in summer.

The biggest effects of climate change on the Pacific Northwest would also be in the late summer or early fall, when the grid is already stressed. Even small decreases in streamflow in September caused by climate change, along with increases in summer demand for power, would be enough to cause more shortfall events in the Pacific Northwest. However, they also projected West Coast-wide shortfall events due to climate impacts on the Pacific Northwest alone to be rare.

In addition to issues of reliability, the researchers also found climate change would increase the price of power. Under the worst case where climate change impacts power supply and demand in both California and in the Pacific Northwest, they expected more hours in which the wholesale price of electricity reaches the cap of $1,000 megawatts per hour in California, especially in late summer. Climate change in California would also have significant impact on prices in the Pacific Northwest.

“When prices go up to $1,000 per megawatt hour, that’s the grid ringing the alarm bell,” Kern said. “They’re making electricity so expensive partly in order to incentivize people to consume less.”

In a second study, researchers evaluated the price of power through 2050 with more renewable energy sources added to the grid, while assuming natural gas power plants would still be in place as back-up. They compared five scenarios for each market: two scenarios that varied the mix of solar and wind by cost; one scenario with more batteries added to store power; a scenario in which many people are adopting electric vehicles; and the status quo trend. They assessed the cost of electricity in these different systems under 100 representative years of both normal and extreme weather events that could occur under historic climate conditions — without additional climate warming.

“With the West Coast grid now, we know certain things about how it will perform because it relies so much on hydropower — that a dry year is a bad and a wet year is good,” Kern said. “What we wanted to know is: as you decarbonize the grid out West, adding electric vehicles, batteries, solar and wind, does that shift at all?”

Even with renewables, they found extreme drought and heat would still drive the extremes in price — with “good” years of the lowest prices driven by mild temperatures and high streamflow, and the highest prices driven by extreme heat or drought.

“When you think about the very worst years, those conditions will still be driven by what drives those events today: lack of water or a heat wave in the middle of the summer,” Kern said. “Adding renewable energy does not change the very worst or best year, but it kind of shifts things around in the middle.”

In California, the future scenario with increased wind energy led to the lowest prices, followed by solar. In the Pacific Northwest, the scenarios with the highest amount of both wind and solar had the lowest prices. Supply shortfalls would be most frequent under the pathway with the greatest demand for electric vehicles.

“As the grid uses more wind and solar, the price goes down because it’s less expensive, and it pushes out natural gas,” Kern said. “The exception is that when you have high demand for power from electric vehicles, demand gets so high, it breaks the system. It’s pretty rare in our models, but it happens when there isn’t much water and there’s a heat wave.”

Kern said the reductions that they projected in greenhouse gas emissions under the five scenarios were “conservative;” their models chart up to 50% de-carbonization through 2050, while most West Coast states have set goals to make more substantial shifts sooner.

“Our key finding was that as the grid decarbonizes, you are still going to be left with that vulnerability to water and heat,” Kern said. “This is a system that can’t run away from that.”

The study, “The Effects of Climate Change on Interregional Electricity Market Dynamics on the U.S. West Coast,” was published online in Earth’s Future on Dec. 7, 2021. In addition to Kern, the other authors were Joy Hill, David E. Rupp, Nathalie Voisin and Gregory Characklis. The study was supported by the National Science Foundation INFEWS program under awards 1639268 T2 and 170082 T1.

The second study, “Technology pathways could help drive the U.S. West Coast grid’s exposure to hydrometerological uncertainty,” was published online in Earth’s Future on Dec. 28, 2022. In addition to Kern, the other authors include Jacob Wessel, Nathalie Voisin, Konstantinos Oikonomou and Jannik Haas. The study was funded by the U.S. Department of Energy Office of Science as part of research in the MultiSector Dynamics, Earth and Environmental System Modeling Program as well as the National Science Foundation INFEWS program award 1639268.

The study attempts to put to rest the debate over Stephen Hawking’s famous information paradox, the problem created by Hawking’s conclusion that any data that enters a black hole can never leave. This conclusion accorded with the laws of thermodynamics, but opposed the fundamental laws of quantum mechanics.

“What we found from string theory is that all the mass of a black hole is not getting sucked in to the center,” said Samir Mathur, lead author of the study and professor of physics at The Ohio State University. “The black hole tries to squeeze things to a point, but then the particles get stretched into these strings, and the strings start to stretch and expand and it becomes this fuzzball that expands to fill up the entirety of the black hole.”

The study, published Dec. 28 in the Turkish Journal of Physics, found that string theory almost certainly holds the answer to Hawking’s paradox, as the paper’s authors had originally believed. The physicists proved theorems to show that the fuzzball theory remains the most likely solution for Hawking’s information paradox. The researchers have also published an essay showing how this work may resolve longstanding puzzles in cosmology; the essay appeared in December in the International Journal of Modern Physics.

Mathur published a study in 2004 that theorized black holes were similar to very large, very messy balls of yarn — “fuzzballs” that become larger and messier as new objects get sucked in.

“The bigger the black hole, the more energy that goes in, and the bigger the fuzzball becomes,” Mathur said. The 2004 study found that string theory, the physics theory that holds that all particles in the universe are made of tiny vibrating strings, could be the solution to Hawking’s paradox. With this fuzzball structure, the hole radiates like any normal body, and there is no puzzle.

After Mathur’s 2004 study and other, similar works, “many people thought the problem was solved,” he said. “But in fact, a section of people in the string theory community itself thought they would look for a different solution to Hawking’s information paradox. They were bothered that, in physical terms, the whole structure of the black hole had changed.”

Studies in recent years attempted to reconcile Hawking’s conclusions with the old picture of the hole, where one can think of the black hole as being “empty space with all its mass in the center.” One theory, the wormhole paradigm, suggested that black holes might be one end of a bridge in the space-time continuum, meaning anything that entered a black hole might appear on the other end of the bridge — the other end of the wormhole — in a different place in space and time.

In order for the wormhole picture to work, though, some low-energy radiation would have to escape from the black hole at its edges.

This recent study proved a theorem — the “effective small corrections theorem” — to show that if that were to happen, black holes would not appear to radiate in the way that they do.

The researchers also examined physical properties from black holes, including topology change in quantum gravity, to determine whether the wormhole paradigm would work.

“In each of the versions that have been proposed for the wormhole approach, we found that the physics was not consistent,” Mathur said. “The wormhole paradigm tries to argue that, in some way, you could still think of the black hole as being effectively empty with all the mass in the center. And the theorems we prove show that such a picture of the hole is not a possibility.”

Other Ohio State researchers who worked on this study include Madhur Mehta, Marcel R. R. Hughes and Bin Guo.

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The study, which was published in Cell Metabolism on January 4, 2022, shows that a hormone called FGF1 regulates blood glucose by inhibiting fat breakdown (lipolysis). Like insulin, FGF1 controls blood glucose by inhibiting lipolysis, but the two hormones do so in different ways. Importantly, this difference could enable FGF1 to be used to safely and successfully lower blood glucose in people who suffer from insulin resistance.

“Finding a second hormone that suppresses lipolysis and lowers glucose is a scientific breakthrough,” says co-senior author and Professor Ronald Evans, holder of the March of Dimes Chair in Molecular and Developmental Biology. “We have identified a new player in regulating fat lipolysis that will help us understand how energy stores are managed in the body.”

When we eat, energy-rich fats and glucose enter the bloodstream. Insulin normally shuttles these nutrients to cells in muscles and fat tissue, where they are either used immediately or stored for later use. In people with insulin resistance, glucose is not efficiently removed from the blood, and higher lipolysis increases the fatty acid levels. These extra fatty acids accelerate glucose production from the liver, compounding the already high glucose levels. Moreover, fatty acids accumulate in organs, exacerbating the insulin resistance — characteristics of diabetes and obesity.

Previously, the lab showed that injecting FGF1 dramatically lowered blood glucose in mice and that chronic FGF1 treatment relieved insulin resistance. But how it worked remained a mystery.

In the current work, the team investigated the mechanisms behind these phenomena and how they were linked. First, they showed that FGF1 suppresses lipolysis, as insulin does. Then they showed that FGF1 regulates the production of glucose in the liver, as insulin does. These similarities led the group to wonder if FGF1 and insulin use the same signaling (communication) pathways to regulate blood glucose.

It was already known that insulin suppresses lipolysis through PDE3B, an enzyme that initiates a signaling pathway, so the team tested a full array of similar enzymes, with PDE3B at the top of their list. They were surprised to find that FGF1 uses a different pathway — PDE4.

“This mechanism is basically a second loop, with all the advantages of a parallel pathway. In insulin resistance, insulin signaling is impaired. However, with a different signaling cascade, if one is not working, the other can. That way you still have the control of lipolysis and blood glucose regulation,” says first author Gencer Sancar, a postdoctoral researcher in the Evans lab.

Finding the PDE4 pathway opens new opportunities for drug discovery and basic research focused on high blood glucose (hyperglycemia) and insulin resistance. The scientists are eager to investigate the possibility of modifying FGF1 to improve PDE4 activity. Another route is targeting multiple points in the signaling pathway before PDE4 is activated.

“The unique ability of FGF1 to induce sustained glucose lowering in insulin-resistant diabetic mice is a promising therapeutic route for diabetic patients. We hope that understanding this pathway will lead to better treatments for diabetic patients,” says co-senior author Michael Downes, a senior staff scientist in the Evans lab. “Now that we’ve got a new pathway, we can figure out its role in energy homeostasis in the body and how to manipulate it.”

Other authors included Sihao Liu, Emanuel Gasser, Jacqueline G. Alvarez, Christopher Moutos, Kyeongkyu Kim, Yuhao Wang, Timothy F. Huddy, Brittany Ross, Yang Dai, David Zepeda, Brett Collins, Emma Tilley, Matthew J. Kolar, Ruth T. Yu, Annette R. Atkins and Alan Saghatelian of Salk; Tim van Zutphen, Theo H. van Dijk and Johan W. Jonker of the University of Groningen, in the Netherlands.

The research was supported by the National Institutes of Health, the Nomis Foundation, the March of Dimes, Deutsche Forschungsgemeinschaft (DFG), Netherlands Organization for Scientific Research, the European Foundation for the Study of Diabetes and the Swiss National Science Foundation.

“The nanoparticle we developed is a powerful new delivery system for genome editing in vascular endothelial cells, and could be used to treat many diseases, including acute respiratory distress syndrome from severe COVID-19,” said senior author Dr. Zhao from Lurie Children’s. “With this nanoparticle we can introduce genes to inhibit vascular injury and/or promote vascular repair, correct gene mutations and turn genes on or off to restore normal function. It also allows us to edit multiple genes at the same time. This is an important advance for treating any disease caused by endothelial dysfunction.”

Endothelial dysfunction is at the root of many diseases, such as coronary artery disease, stroke, bronchopulmonary dysplasia and pulmonary artery hypertension. Dr. Zhao explained that genome editing in endothelial cells could even treat cancers by cutting off the blood supply to the tumor or blocking cancer metastasis.

At this stage, Dr. Zhao and colleagues achieved excellent results in a mouse model. The nanoparticle carrying CRISPR/Cas9 plasmid DNA was introduced via a one-time IV injection and required a few days to be effective. Preclinical testing will be necessary before clinical trials can begin.

“Our nanoparticle delivery system for genome editing and transgene expression also is a huge advance for cardiovascular research,” added Dr. Zhao.

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