How Lula’s successes in Brazil may have paved the way for his presidential defeat

EXPLAINER

Brazil’s veteran leftist President Luiz Inacio "Lula" da Silva trailed Flavio Bolsonaro, the son of his far-right predecessor, in the first-round presidential vote on Sunday. Some analysts suggest that the sweeping anti-poverty measures Lula put in place over two decades may have helped give rise to a growing lower-middle class drawn to the far right’s promise to get the government out of people’s lives.


Issued on: 05/10/2026 

FRANCE24

By: Paul MILLAR

Brazilian President Luiz Inacio Lula da Silva, the Workers' Party (PT) candidate for presidential re-election, speaks to supporters in Sao Paulo, Brazil, October 4, 2026. © Brian Snyder, Reuters


As right-wing governments backed by Washington rise to power across Latin America, Brazil now looks like it will be the next domino to fall.

Far-right Senator Flavio Bolsonaro led the first round of Brazil’s presidential election on Sunday, with President Luiz Inacio Lula da Silva, a veteran left-wing leader and former trade unionist, trailing narrowly behind him. With neither candidate winning an outright majority, an October 25 run-off will determine who will lead the country of more than 214 million people over the next four years.

Bolsonaro’s father Jair is serving a 27-year sentence for having plotted a coup d’état after losing the 2022 presidential election to Lula. His eldest son, whom the former president anointed as his ideological successor a few scant months ago, has promised a pardon if he emerges triumphant in the second round.

While less than two percentage points separated the leading candidates, the results were a shock to supporters of Lula’s centre-left Workers' Party (PT); opinion polls had put Lula ahead of his rival in the days leading up to the vote. And with a handful of other right-wing candidates knocked out in the first round, the second round seems as though it’s Bolsonaro’s to lose.

Even if Lula does manage to mobilise enough of the more than one in five voters who abstained in the first round, the presidential palace of Planalto was not the only prize being contested in Sunday’s elections.

Across the country, congressional and gubernatorial elections have also seen the country lurch sharply to the right, with Bolsonaro’s far-right Liberal Party (PL) likely to emerge as the leading force in the lower-house Chamber of Deputies, as well as the Senate.

Despite his decades-long legacy of social-democratic policies that have lifted tens of millions of people out of poverty, Lula seems to have struggled to mobilise his base in the face of a far right that has succeeded in welding together a coalition of the country’s business elite and rising lower-middle classes.

READ MOREFlavio Bolsonaro: In the name of the father, sons, and holy ideology

Thomas Zicman de Barros, a fellow at the centre for political research at Sciences Po university in Paris, said the younger Bolsonaro has maintained his father’s appeal to voters frustrated by the status quo.

“Despite the fact that his father is now in prison, and the fact that Flavio Bolsonaro himself and the whole family are involved in many scandals in Brazil, they still succeed in embodying some kind of anti-establishment feeling,” he said.

“And Lula, despite the fact that he comes from a trade union background, and he was kind of a populist – and I don’t use the word in a pejorative sense – nowadays he embodies the establishment, and the very defence of a liberal democratic system that we have, that … has its flaws, its blind spots.”

Cover image: PERSPECTIVE © FRANCE 24
10:08

For some Brazilians, the man who previously served two terms as president from 2003 to 2011 remains deeply entrenched in the system, despite his leftist credentials.

Felipe Krause, a former Brazilian diplomat and the head of Oxford University’s Brazilian Studies Programme, said in an interview with FRANCE 24 television that the global cost-of-living crisis and mounting levels of household debt had eaten into the economic gains made under Lula’s most recent term in office.

“Interestingly, if you actually look at the economy, there’s kind of a mixed situation,” he said. “You do have relatively low unemployment and income is even rising to some extent, but prices are really high – and I think most of all, there’s a lack of a sense of hope for prosperity in the future.”

Krause said that Lula, who first won office in 2002 on a platform of social welfare reforms that earned him a strong following among Brazil’s poorest communities and organised working class, had failed to keep up with the social and economic changes sweeping the country.

“In my view, the Lula camp hasn’t really appreciated how the country has changed relative to Lula’s first two terms – and how the country in fact has changed due to the success of Lula’s own policies,” he said.

Brazil elections: Can Lula's anti-poverty record win over voters?

Cover image: © France 24
02:46

“You now have this rising middle class, which is far more interested in entrepreneurialism, a pro-market individualistic approach – and far less interested in the social protections, the formal employment, the labour unions and all those things that the Lula camp is used to offering.”

Zicman said that, for many people in Brazil’s lower-middle classes juggling more than one job in an expanding gig economy, Bolsonaro’s campaign pledge to lower taxes and – borrowing a phrase from Argentina’s far-right libertarian President Javier Milei – “take a chainsaw to bureaucracy”, may well have resonated.

“We’ve had transformations in labour relations all over the world, but notably in what we might call the Global South,” he said. “So nowadays, many precarious workers don’t even dream of having more stable jobs … They might sell some services or products [on] the internet.”

Zicman said a new sense of distrust is also permeating Brazil's politics. “There is this ‘self-made person’ spirit, that is, on one hand, individualistic – some might call it neoliberal subjectivity. That might explain why some people are now thinking, ‘I don’t trust the government anymore, I don’t think that the left, if it gets to power, [will] be capable of transforming my situation.’”

Whether or not the far right would be any more capable of doing so, he said, is a matter of sharply divided opinion.

“The far right is not necessarily lying to those people, because it is delivering what it promises: That is, ‘I will do nothing, and then you, by your own merit, you will succeed,’” he said.

“The lie – and this is my personal opinion – is that most people won’t succeed.”

Black Death hits Russia. It never really went away.

A case of plague was reported in Russia this week. An outbreak is unlikely, but the Black Death, which was born in Central Asia, never really went away. 

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By Ben Aris in Berlin October 5, 2026

Russia has quarantined and tested nearly 200 people following the mysterious death of a scientist at a Siberian anti-plague institute, triggering panic reporting that the Black Death has reappeared in Russia. The EU says it is “monitoring the situation very closely” and there have been calls to close the borders in case the illness spreads.

And the danger is real as the bubonic plague spores are still active in many of the former Soviet republics and there is usually an infection reported every year. Mongolia is particularly prone to outbreaks as locals hunt marmots, which are considered a delicacy, and have taken over from rats as the main carrier of the infection in modern times.

However, there is a great deal of confusion over what happened. Moscow has insisted that the victim, a labour worker at a medical institution, died from an unidentified form of pneumonia and there is no cause for alarm. But no one really trusts Moscow, especially when it comes to natural disasters. The Soviet government didn’t report the meltdown at Chernobyl for over 36 hours and hid the scale of the disaster from the public in 1986 and not much has changed since then.

Alarm bells began to ring after Darya Shipilova, a 28-year-old employee of the Irkutsk Anti-Plague Research Institute of Siberia and the Far East, was admitted to hospital in Shelekhov, near Irkutsk, with severe pneumonia in a just over a week ago and died days later.

Early reports claimed Shipilova had accidentally broken a test tube containing live plague bacteria while collecting samples. Russia keeps a number of deadly pathogens like Anthrax in storage in its medical institutes for research purposes, although it has signed off on the Chemical Weapons Convention (CWC) in 1993 and ratified it in 1997 that preclude their use by the military and has committed to destroy what remaining stockpiles of biohazardous agents it still had soon after.

Local media described the suspected infection as pneumonic plague, the most dangerous form of the disease because it attacks the lungs and, unlike the more familiar bubonic form, can spread directly between people through respiratory particles.

The reports triggered a rapid response. At least 197 people who had been in contact with Shipilova were placed under medical observation, including 189 who were hospitalised. Of those, 114 were reportedly held in one regional hospital, 63 in another and 12 at the anti-plague institute.

“All identified contact persons have been placed under medical observation. As of today, the contacts show no signs of illness, and their laboratory test results are negative,” Irkutsk Governor Igor Kobzev said. Typically, the illness has a 4-7 days incubation period before the first symptoms is detectable. It is extremely lethal if not immediately treated with antibiotics, killing 98% of its victims between 18-24 hours. However, it is not particularly infectious, spreading mainly through large respiratory droplets during close contact, with a low R0 rate of only 1.2-1.3 (one infected person typically infects one more person on average.)

The Shelekhov district hospital imposed quarantine restrictions, public events were postponed and Russia’s chief state sanitary doctor Anna Popova travelled to the region to oversee the response.

The nearby Irkutsk Aluminium Smelter, operated by Rusal (HKEX: 486; MOEX: RUAL), introduced mandatory masks for its 2,154 employees.

“We have introduced a mask protocol at the facility as a precaution. God protects the cautious, so follow safety measures. If symptoms appear, seek medical help immediately,” plant director Artyom Fominykh said.

But the official story then changed.

Russia’s consumer health watchdog Rospotrebnadzor said Shipilova did not die of plague and diagnosed her instead with “pneumonia of unknown aetiology”. Tests found no microorganisms associated with the dangerous pathogens she handled at work, according to the agency, while an investigation found no evidence that a laboratory accident had occurred.

Officials said subsequent testing of Shipilova’s contacts had found two cases of Covid-19 and two rhinovirus infections, but no plague.

Gennady Onishchenko, an epidemiologist and former head of Rospotrebnadzor, said the illness was “likely not plague”, while stressing that Russia had established treatment and prevention procedures should plague be confirmed.

Occasional outbreaks

Nevertheless, the scale of the precautions — quarantines, medical surveillance, masks and the personal intervention of Popova — has attracted attention as the former Soviet Union space does see occasional outbreaks of the bubonic plague, which killed a between a third and half of Europe’s population when it first appeared in the 14th century.

WHO has identified active natural plague foci across Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan, covering about 1.8mn square kilometres, with sporadic cases historically registered almost every year in the region.

The European Commission said it was monitoring the situation “very closely” and was in contact with the European Centre for Disease Prevention and Control.

“We are aware of the reports concerning the laboratory incident in Russia, seemingly involving a pathogen causing plague,” a Commission spokesperson said.

“Public health is always a priority for us, so we are in touch with our experts from the European Centre for Disease Prevention and Control,” the spokesperson added but saying it was not in contact with Russian officials since Russia's full-scale invasion of Ukraine.

“We are much better prepared for any pandemics” following the coronavirus crisis, the spokesperson said, during which significant antibiotic stocks were built up.

Washington is also monitoring events. US officials have urged Moscow to provide “accurate” information “quickly and openly”, while Brussels has called for “timely and transparent reporting”.

But for the moment there is no confirmed plague outbreak. No secondary plague cases have been reported and Russia says laboratory analysis does not support the theory that Shipilova contracted Yersinia pestis.

The Black Death never disappeared

Plague is caused by Yersinia pestis, a bacterium that survives naturally in populations of wild rodents and the fleas that live on them.

The disease still exists across parts of Asia, Africa and the Americas. Most recent cases reported to the WHO have been in the Democratic Republic of Congo and Madagascar, but natural plague reservoirs also persist across parts of Central Asia and Siberia.

Modern medicine has also radically changed the danger posed by the disease. When it first appeared, arriving on rats travelling with merchants along the Silk Road from Central Asia and merchant ships trading with Asia, it cut through Europe’s unprotected populations like a hot knife through butter. But since then the plague can be treated effectively with antibiotics if diagnosed quickly.

WHO says untreated bubonic plague has a fatality rate of roughly 30-60%, while untreated pneumonic and septicaemic plague are effectively invariably fatal. Pneumonic plague can kill within 18-24 hours of the onset of symptoms if treatment is not started, but recovery rates are high when antibiotics are administered early.

Over the years, Russia itself has recorded sporadic human infections. The last confirmed Russian case was in 2016, when a 10-year-old boy in the Altai Republic contracted bubonic plague after helping his grandfather skin a marmot. The boy reportedly cut himself while handling the animal. Seventeen contacts, including six children, were quarantined, and the boy survived after treatment.

Russian scientific literature records human cases in the same high-altitude Altai plague focus in 2014, 2015 and 2016, all associated with handling grey marmot carcasses.

But it is Mongolia which is most prone to infections and death. Marmots — large ground-dwelling rodents similar to ferrets — are a principal natural host for plague in Mongolia.

Mongolia's National Centre for Zoonotic Diseases says natural plague foci have been identified across 28.3% of the country's territory, covering 132 soums in 18 provinces. More than half of the roughly 3,000 plague strains isolated in Mongolia since 1928 have come from Mongolian marmots, while another 27% were isolated from ectoparasites including marmot fleas.

That creates a particular problem because hunting and eating marmots remains a tradition in parts of the country despite restrictions and the locals are so keen on the meat that they routinely ignore government warnings and continue to trap the rodents.

Research into Mongolian plague cases found 73 reported human infections between 1998 and 2020, of which 59% were associated with close contact with infected marmots and 7% with eating raw marmot organs.

In July 2020, two brothers aged 27 and 16 in western Mongolia's Khovd province contracted bubonic plague after hunting and eating marmot. Authorities quarantined their contacts and restricted travel while the pair were treated, who survived.

Later that month, a 15-year-old boy died in Govi-Altai province after contracting plague following the hunting and consumption of a marmot. Fifteen people who had been in contact with him were isolated and given antibiotic treatment.

A year earlier, two people died again after consuming raw marmot organs in Mongolia.

Marmot hunting has been banned, but enforcement is difficult and the animals remain a prized food in some rural communities. Parts of the animal are also traditionally believed to possess health-giving properties.

In Mongolia the disease is often referred to colloquially as the “Marmot Plague”, a name that obscures the fact that it is caused by exactly the same bacterium associated with history's most notorious pandemic.

The connection between Central Asia and plague goes much deeper than today's occasional outbreaks.

A landmark genetic study published in Nature in 2022 traced the probable source of the plague strain behind the 14th-century Black Death to the Tian Shan region around modern Kyrgyzstan.

Researchers examined human remains from the Kara-Djigach and Burana cemeteries near Lake Issyk-Kul, the smaller sister lake to Baikal in Siberia, where an unusually large number of tombstones dating from 1338 and 1339 explicitly referred to deaths from “pestilence”.

Ancient DNA recovered from seven individuals revealed Yersinia pestis in three of them. Researchers reconstructed two plague genomes which they identified as ancestors of the enormous diversification of plague strains associated with the Black Death that swept through western Eurasia beginning several years later.

“It is like finding the place where all the strains come together, like with coronavirus where we have Alpha, Delta, Omicron all coming from this strain in Wuhan, [China],” Johannes Krause, a palaeogeneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig and one of the study's leaders, said at the time. “It was like a big bang of plague,” Krause said.

SPACE/COSMOS

A look inside stars and planets

Experiment confirms prediction about turbulence in rapidly rotating celestial bodies

Helmholtz-Zentrum Dresden-Rossendorf

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Complex flow patterns develop in the interiors of rapidly rotating stars. An international research team has now experimentally demonstrated for the first time a flow state characteristic of such celestial bodies. The artistic visualization shows a star characterized by turbulent structures.

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Credit: B. Schröder/HZDR

Since we cannot look into the interiors of stars and planets, we rely on lab experiments to replicate the physical processes that occur there. Led by the University of California, Los Angeles (UCLA), an international research team has now produced the first experimental verification of a theoretically predicted flow state that is deemed characteristic of the interiors of rapidly rotating celestial bodies. The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) also participated in the study, which has been published in Physical Review Letters (DOI: 10.1103/pc8y-j7g8). The results provide a robust experimental basis for testing theoretical models of the processes that occur inside these celestial bodies.

Inside stars and planets, heat is transported by convection: Hot material rises while cooler material sinks. This generates turbulent flows that drive the Earth’s magnetic field and shape the dynamics of stars. According to theoretical predictions, these flows attain a special state inside rapidly rotating celestial bodies. The scientific community calls this ultimate state the diffusivity-free regime, in which large flows are determined almost exclusively by buoyancy and rotation while fluid properties such as viscosity or thermal conductivity become almost negligible. Many models of the interiors of stars and planets are based on the assumption that convection operates precisely within this ultimate regime.

A question that has been unanswered for decades
Yet until now, this had precisely been the issue: In classical lab experiments, thermal boundary layers form on the walls of the test vessels, affecting the flow to the point that its state remained hidden. For a long time, it was therefore unclear whether it was even possible to verify the theoretical predictions in an experimental setting.

The international research team achieved the decisive breakthrough with a rotating liquid-metal experiment using liquid gallium as the test medium and a special oscillating flow mode that occurs exclusively in liquid metals instead of the usual stationary convection. Unlike classical convection flows, this mode is not determined by the thermal boundary layers on the vessel walls, but by the temperature gradient inside the liquid, making it possible to create the conditions that models have long predicted.

“Our experiment demonstrated this theoretically predicted state in the lab for the first time, which greatly strengthens our confidence in the models we use to describe processes inside stars and planets,” says Dr. Jewel Abbate of UCLA, who conducted this research as part of her PhD studies.

A new pathway into the interior of stars
Dr. Tobias Vogt from HZDR’s Institute of Fluid Dynamics also participated in the experiments and measurements during two research stays at UCLA. To validate the experimental results, the researchers compared three independent metrics with the theoretical predictions: heat transport, flow velocity, and temperature fluctuations within the fluid. All three matched the models quantitatively. High-resolution numerical simulations further confirmed the results.

“What makes our work particularly compelling is the fact that theory, experiment, and numerical simulations now agree quantitatively, allowing us to confirm experimentally that the underlying physical models describe the observed heat transport very accurately. This gives us far greater confidence to apply these models to the interiors of planets and stars,” Vogt summarizes.

The results close a decades-old gap between theory and experiment, opening up new possibilities for investigating the dynamics inside stars and planets in lab experiments – for more reliable models of these fundamental processes in the universe.

Publication:
J. A. Abbate, Y. Xu, T. Vogt, S. Horn, K. Julien, J. M. Aurnou, “Diffusivity-Free Turbulence in Liquid Metal Rotating Rayleigh-Bénard Convection Experiments” in Physical Review Letters (2026) (DOI: 10.1103/pc8y-j7g8)

Further information:
Dr. Tobias Vogt
Institute of Fluid Dynamics at HZDR
Phone: +49 351 260 2451 | Email: t.vogt@hzdr.de

Prof. Jonathan M. Aurnou
Department of Earth, Planetary, and Space Sciences (EPSS)
University of California, Los Angeles (UCLA)
Email: aurnou@g.ucla.edu

Media contact:
Simon Schmitt | Head
Communications and Media Relations at HZDR
Phone: +49 351 260 3400 | Mobile: +49 175 874 2865 | Email: s.schmitt@hzdr.de

The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) performs – as an independent German research center – research in the fields of energy, health, and matter. We focus on answering the following questions:
•    How can energy and resources be utilized in an efficient, safe, and sustainable way?
•    How can malignant tumors be more precisely visualized, characterized, and more effectively treated?
•    How do matter and materials behave under the influence of strong fields and in smallest dimensions?
To help answer these research questions, HZDR operates large-scale facilities, which are also used by visiting researchers: the Ion Beam Center, the Dresden High Magnetic Field Laboratory and the ELBE Center for High-Power Radiation Sources.
HZDR is a member of the Helmholtz Association and has seven sites (Dresden, Freiberg, Görlitz, Grenoble, Leipzig, Rostock and Schenefeld near Hamburg) with almost 1,500 members of staff, of whom about 700 are scientists, including 200 Ph.D. candidates.

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Journal

Physical Review Letters

DOI

10.1103/pc8y-j7g8 

Roman Space Telescope equipped with technology from Heidelberg set for launch

Beyond probing the history of the universe, the NASA space telescope will test a new technique for examining exoplanets.

Max Planck Institute for Astronomy

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The NASA space telescope “Nancy Grace Roman” (or Roman for short) is scheduled to launch into space from the Kennedy Space Center in the US aboard a SpaceX Falcon Heavy rocket at 13:26 (1:26 p.m.) CEST on 30 August 2026, following a construction period of around ten years.

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Credit: NASA/SVS

The NASA space telescope “Nancy Grace Roman” (or Roman for short) is scheduled to launch into space from the Kennedy Space Center in the US aboard a SpaceX Falcon Heavy rocket at 13:26 (1:26 p.m.) CEST on 30 August 2026, following a construction period of around ten years. One of the telescope’s primary missions during its operational lifespan of at least five years will be to investigate the history of the universe and the contributions of dark matter and dark energy to its expansion and the formation of the cosmic large-scale structure. In doing so, its measurements will complement those of the European Space Agency’s (ESA) Euclid space telescope, which has been pursuing similar objectives since 2023.

MPIA in Heidelberg makes important contributions

Additionally, Roman will discover a multitude of new exoplanets, utilizing among other equipment the Coronagraph Instrument (CGI). The Max Planck Institute for Astronomy (MPIA) in Heidelberg, NASA’s sole direct German partner, has played a key role in developing and constructing this instrument. Under the leadership of Oliver Krause, engineers and scientists at MPIA designed, developed, manufactured, and tested central optical elements for the CGI, known as the Precision Alignment Mechanisms (PAMs). The company von Hoerner & Sulger, based in the neighbouring town of Schwetzingen, supported the construction process.

“The CGI aboard the Roman Space Telescope is the most technically sophisticated device for optical observations ever operated in space for scientific research,” says Oliver Krause, head of the Infrared Space Astronomy Research Group at MPIA.

Furthermore, MPIA is participating in the development of software to process both technical and scientific data, as well as in preparing the observations. The measurements are coordinated by a NASA panel, the Community Participation Program (CPP), whose core team includes Oliver Krause as the local project lead. On behalf of MPIA, Wolfgang Brandner is responsible within the CPP for observations aimed at detecting gas giants in visible light, while Gaël Chauvin is involved in observation preparations.

Shortly after launch, CPP members will work around the clock on data evaluation during the telescope's commissioning. “However, thanks to the CPP's global distribution, with members in the US, Japan, and Europe, our data analysts can carry out their tasks during normal office hours,” says Wolfgang Brandner. During routine operations, all data will be made available to the public immediately following processing at the Roman Science Support Center.

New camera design for a scientific breakthrough

CGI is an innovative instrument design that will be tested to enable direct imaging and spectroscopy of exoplanets in tight orbits around distant stars. Its optical elements—masks, deformable mirrors, and sensors—will suppress interfering starlight, making the faint light reflected by the planets visible for research.

The objective of CGI is to image planets and circumstellar discs around nearby stars in visible light. This will allow the study of gas giants that are older, cooler, and orbit their host stars at closer distances than the hot, young planets previously discovered through direct imaging.

To this end, CGI combines two established observation techniques for the first time in space: coronagraphs and adaptive optics. Coronagraphs block out bright objects using specialized masks, revealing fainter celestial bodies nearby. However, the masks employed usually cause strong image artefacts around the masked stars. Therefore, astronomers using this method almost exclusively find gas giants similar to Jupiter that orbit at relatively large distances from their host stars.

For smaller planets in tighter orbits, these unwanted effects must be reduced. For this reason, CGI additionally features an adaptive optics system, enabling a higher brightness contrast between stars and planets. This technology is typically found in ground-based telescopes, where it helps eliminate image degradation caused by atmospheric turbulence. For space-based cameras, however, the required processing power presents a new challenge.

Technology of maximum precision

The CGI’s design aims to detect a planet whose nearby host star is a billion times brighter—roughly corresponding to the contrast ratio between Jupiter and the Sun. Compared with current capabilities, this represents up to a thousandfold improvement. An integrated spectrograph will then enable researchers to analyze the atmospheric composition of these planets.

These goals require the PAMs, manufactured by MPIA, to guarantee exceptionally high precision and stability in the positioning of optical elements, such as filters, coronagraphs, and mirrors, over a period of several hours. During operation, the PAMs must not tilt by more than 40 milliarcseconds over an eight-hour timeframe (3.6 million milliarcseconds correspond to one degree). This is equivalent to the angular size of a human being in Los Angeles when viewed from Heidelberg.

Following a successful CGI mission, this technology could be further refined for future space observatories like the Habitable Worlds Observatory. Directly imaging an Earth analogue would then be within reach.

Background information

The Nancy Grace Roman Space Telescope (formerly WFIRST: Wide-Field Infrared Survey Telescope) was developed under NASA leadership. The telescope is named after astronomer Nancy Grace Roman, who directed NASA’s astronomical research programmes for decades. Among other achievements, she was responsible for the scientific planning of the Hubble Space Telescope. The 2.4-metre primary mirror is similar to the one used in the Hubble Space Telescope. For one of the two scientific instruments, the Coronagraph Instrument (CGI), the Max Planck Institute for Astronomy (MPIA) in Heidelberg constructed central optomechanical components.

For the translation from the German original, a language model was utilized in an intermediate step, with the output being editorially reviewed and corrected.

One of six flight models of the Precision Alignment Mechanisms (PAMs) for the Coronagraph Instrument (CGI), a camera aboard the Nancy Grace Roman Space Telescope. The PAMs position and stabilize the optical elements of the CGI during observations.

Credit

O. Krause / MPIA

The impact of thermocapillary convection on phase-change material melting process under varying gravity conditions

Beijing Institute of Technology Press Co., Ltd

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Fig. 1. Sketch of the simulation domain with (A) aspect ratio (AR) = 2 and (B) AR = 10.

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Credit: Space: Science & Technology

With the accelerated advancement of lunar and Mars exploration programs, long-term human habitation on extraterrestrial bodies faces the severe challenge of extreme diurnal temperature variations. Phase change materials (PCMs), owing to their ability to store or release substantial latent heat during solid–liquid phase transitions while maintaining a nearly constant temperature, have become an ideal solution for space thermal control systems. However, in the microgravity environment of space, the ground-dominant natural convection tends to disappear, and thermocapillary convection may become the prevailing heat transfer mechanism; in low-gravity environments such as those on the Moon and Mars, the coexistence and competition between these two convective regimes remain unclear. Existing studies have predominantly focused on either Earth's gravity or pure microgravity conditions, with a notable scarcity of research on the coupled effects of thermocapillary and natural convection at intermediate gravity levels. The melting dynamics of two typical organic PCMs, succinonitrile and n-octadecane, under low-gravity conditions have not yet been systematically elucidated. Therefore, clarifying the roles of thermocapillary convection under varying gravity levels and container geometries holds significant engineering guidance for the design of efficient space thermal control systems.

In a recent study published in Space: Science & Technology, the research team led by Ruiz from the Universitat Rovira i Virgili in Spain systematically investigated the influence of thermocapillary convection on the melting process of PCMs through numerical simulations. The study focuses on succinonitrile and n-octadecane as model PCMs, subjecting them to a temperature difference of 40 K in two rectangular cavities of different aspect ratios to drive melting, while simulating four gravity environments: microgravity on the International Space Station, lunar gravity, Martian gravity, and Earth's gravity. The results indicate that the aspect ratio is the key factor determining the dominant convective regime. In a flat cavity with an aspect ratio of 10, thermocapillary effects dominate the melting process at all gravity levels, significantly accelerating melting and generating multi-cellular oscillatory flows. In contrast, in a cavity with an aspect ratio of 2, natural convection is substantially enhanced and, at higher gravity levels, can counteract thermocapillary effects and even reduce the melting rate. Succinonitrile exhibits a markedly faster melting rate than n-octadecane owing to its higher thermal conductivity; nevertheless, the two materials show consistent trends in the competition between thermocapillary and natural convection. The study points out that in low-gravity environments such as those on the Moon and Mars, the rational selection of cavities with a large aspect ratio allows thermocapillary and natural convection to act synergistically, significantly enhancing the melting rate of PCMs. This research provides important theoretical foundations and optimization directions for the design of thermal management systems for future lunar and Martian bases, as well as for space-based PCM experiments in orbit, offering significant engineering application value for supporting the development of thermal control technologies for long-term extraterrestrial habitation.

 

First, this study focuses on the melting behavior of phase change materials (PCMs) under different gravity environments, with particular attention to the coupled effects of thermocapillary and natural convection. With the advancement of lunar and Mars exploration programs, the extreme diurnal temperature variations on extraterrestrial bodies pose severe challenges to thermal control systems, and phase change materials, owing to their constant-temperature heat storage and release characteristics, have become an ideal solution. However, under microgravity conditions, natural convection is weakened or even eliminated, and thermocapillary convection may become the dominant heat transfer mechanism; yet the competition between these two convection modes in low-gravity environments such as those on the Moon and Mars remains unclear. The study selects two typical organic PCMs—succinonitrile (Pr=23) and n-octadecane (Pr=56)—the former possessing higher thermal conductivity and faster melting, while the latter serves as the working fluid for the MarPCM experiment on the International Space Station. Simulations are conducted in rectangular cavities with a fixed length of 8 cm and aspect ratios of 2 and 10, respectively; a temperature difference of 40 K is imposed on the left and right walls to drive melting, and the upper surface is set as a free boundary to apply thermocapillary forces (as shown in the computational domain setup of Fig. 1). The accuracy of the numerical method is validated by comparison with published results; the comparison shows that the flow field structure obtained in this study is in excellent agreement with that in the literature under identical conditions, confirming the reliability of the solver.

Second, the study reveals the significant influence of gravity level and container aspect ratio on the melting dynamics. The liquid fraction evolution curves (Fig. 2) show that succinonitrile consistently melts faster than n-octadecane owing to its higher thermal conductivity, and thermocapillary effects serve to accelerate or modulate the melting process in both materials. In the flat cavity with an aspect ratio of 10, thermocapillary effects accelerate melting at all gravity levels, enabling the solid–liquid interface to reach the cold wall more rapidly, while the characteristic time for the liquid fraction to reach 95% is also substantially shortened. In the cavity with an aspect ratio of 2, the situation is more complex: in the early stages of melting, thermocapillary flow accelerates interface advancement; however, as the melt grows, natural convection progressively strengthens and flows in the direction opposite to the surface flow, thereby reducing the melting rate in the later stages at higher gravity levels. Fig. 3 summarizes the specific values of the two characteristic times under the four gravity scenarios, clearly demonstrating that thermocapillary effects are most pronounced under microgravity and low-gravity conditions, with their relative contribution gradually diminishing as gravity increases.

Finally, the study provides an in-depth elucidation of the melting mechanisms under different conditions through visualization of the flow and temperature fields, as well as the temporal evolution of the convective contribution factor. In the cavity with an aspect ratio of 2, pure natural convection gives rise to stable single-vortex or double-vortex structures; pure thermocapillary convection, in contrast, generates complex multi-cellular flows; when both mechanisms coexist, a distinctive three-zone structure emerges—comprising a bottom natural-convection vortex, a surface thermocapillary vortex, and an intermediate transition zone—with natural convection gradually becoming dominant as gravity increases (Fig. 4). In the flat cavity with an aspect ratio of 10, natural convection is significantly weakened due to the restricted height, and thermocapillary effects still dominate in the mixed convection regime, resulting in substantial deformation of the melting front and sustained oscillations under low-gravity conditions (Fig. 5). Fig. 6 presents the temporal evolution of the thermocapillary factor, which reaches a peak rapidly in the early stage of melting and then gradually declines, with its value decreasing as gravity increases. The study concludes that in low-gravity environments such as those on the Moon and Mars, a rational choice of containers with a large aspect ratio enables thermocapillary and natural convection to act synergistically in accelerating melting. This finding offers important engineering guidance for the design of thermal management systems for future lunar and Martian bases, as well as for space-based phase-change material experiments in orbit.

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Journal

Space: Science & Technology

DOI

10.34133/space.0516 

Article Title

The Impact of Thermocapillary Convection on Phase-Change Material Melting Process under Varying Gravity Conditions

 

Media tip sheet: Wildlife ecology at ESA’s 2026 Annual Meeting

Ecological Society of America

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The 2026 Annual Meeting of the Ecological Society of America will take place in Salt Lake City, Utah, July 26-31. Members of the press are invited to apply for complimentary press registration.

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Credit: Ecological Society of America

Featured presentations at the 111th Annual Meeting of the Ecological Society of America in Salt Lake City, Utah

Wildlife populations are responding to rapid environmental change in ways that can reshape ecosystems and inform conservation efforts. At this year’s Ecological Society of America (ESA) Annual Meeting (July 26–31) in Salt Lake City, Utah, researchers will present new findings on the ecological relationships between animals, their habitats and the growing influence of human activities across terrestrial, freshwater and marine ecosystems.

Highlighted presentations explore topics including predator recovery, species declines, rewilding, wildlife disease, animal behavior and human-wildlife interactions. Studies examine organisms ranging from elephants, pangolins and bottlenose dolphins to loons, seabirds, suckers and urban mammals, while also addressing issues such as road mortality, habitat development, anthropogenic noise and community-based conservation. The research highlights how wildlife ecology is informing conservation strategies and improving our understanding of how animals respond to environmental change.

ESA invites staff journalists, freelance journalists, student journalists and press officers to register for free as media attendees up to and throughout the week of the Annual Meeting. For eligibility information, please visit ESA’s press registration credential policy page.

Members of the media will have access to all scientific sessions at the conference and to a press room where they can enjoy refreshments, internet access, a printer and an interview area.

Monday, July 27

1:30 PM – 3:00 PM MT	Elephant carcasses restructure soil chemistry and resistance, woody plant physiology, seedling recruitment, and herbivory across a savanna landscape Presenters: Ryan Helcoski, Utah State University; Ndzalama Mkansi, Scientific Services; Courtney G. Reed, UC Santa Barbara; Dave I. Thompson, South African Environmental Observation Network; Joshua Schimel, UC Santa Barbara; Izak Smit, Nelson Mandela University; Tercia Strydom, Scientific Services; Aimee G. Tallia, Utah State University; Deron E. Burkepile, UC Santa Barbara; Nathan P. Lemoine, Marquette University; Michelle Budny, Marquette University; Edd Hammill, Utah State University; Johan T. du Toit, Utah State University Contributed Oral Presentation
1:30 PM – 3:00 PM MT	Persistent landscape-scale aspen decline following large carnivore restoration in northern Yellowstone National Park Presenters: Dan MacNulty, Utah State University; Nicholas Bergeron, Utah State University; James A. Lutz, Utah State University; Douglas Ramsey, Utah State University; Eric Larsen, University of Wisconsin, Stevens Point Contributed Oral Presentation
3:30 PM – 5:00 PM MT	Endangered suckers nearing extirpation in Upper Klamath Lake Presenters: Jacob Krause, U.S. Geological Survey; Brian Hayes, U.S. Geological Survey; Rachael Paul-Wilson, Pacific States Marine Fisheries Commission; Maria Dzul, U.S. Geological Survey Contributed Oral Presentation
5:00 PM – 6:30 PM MT	Six decades of monitoring provide critical context for an avian influenza outbreak in marine mammals Presenters: Esin Ickin, UC Santa Cruz; Molly H. McEntee, UC Santa Cruz; Marm Kilpatrick, UC Santa Cruz; Patrick W. Robinson, UC Santa Cruz; Zabe Premo, UC Santa Cruz; Conner M. Hale, UC Santa Cruz; Madison J. Pfau, UC Santa Cruz; Elizabeth Ashley, UC Davis; Frankie Gerraty, UC Santa Cruz; Madeline Cheu, UC Santa Cruz; Natalie A. Storm, UC Santa Cruz; Sebastian Caamaño, Moss Landing Marine Laboratories, California State University; Aditi M. Jacob, UC Santa Cruz; Ali White, UC Santa Cruz; Stella Cardenas, UC Santa Cruz; Honour Dufresne, UC Santa Cruz; Amaya Espardinez, UC Santa Cruz; Hailey Hacker, UC Santa Cruz; Beatrice Hawkins, UC Santa Cruz; Madison Kranker, UC Santa Cruz; Violet Lemley, UC Santa Cruz; Kevin O’Connor, UC Santa Cruz; Sean Quigley, UC Santa Cruz; Lucas Romano, UC Santa Cruz; Isabelle Santiago, UC Santa Cruz; Brandon States, UC Santa Cruz; Kate Wang, UC Santa Cruz; Daniel P. Costa, UC Santa Cruz; Christine Johnson, UC Davis; Roxanne S. Beltran, UC Santa Cruz Contributed Poster Presentation

Tuesday, July 28

10:00 AM – 11:30 AM MT	Advancing the ecological knowledge of a soft tick vector to inform the U.S. surveillance and response plan to African swine fever emergence Presenters: Sebastian Botero-Cañola, University of Florida; Carson Torhorst, University of Florida; Nicholas Canino, University of Florida; Kathleen C. O’Hara, USDA Animal and Plant Health Inspection Service; Angela M. James, USDA Animal and Plant Health Inspection Service; Samantha Wisely, University of Florida Contributed Oral Presentation
10:00 AM – 11:30 AM MT	Pronounced post-COVID-19 decline in sale and usage of medicinal pangolin products in China Presenters: Timothy C. Bonebrake, University of Hong Kong; Yifu Wang, The Chinese University of Hong Kong Shenzhen Contributed Oral Presentation
1:30 PM – 3:00 PM MT	Responses of African savanna trees to large herbivore extinction and rewilding Presenters: Tyler C. Coverdale, University of Notre Dame; Mahesh Sankaran, National Centre for Biological Sciences; Andrew Davies, Harvard University, Jayashree Ratnam, National Centre for Biological Sciences; Benjamin Wigley, University of Bayreuth; David J. Augustine, USDA-ARS Rangeland Resources and Systems Research Unit Contributed Oral Presentation
3:30 PM – 5:00 PM MT	Cat(ch) ‘meow’tside how ’bout that: The impacts of domestic cats and dogs on urban mammal spatiotemporal behavior Presenters: Austin M. Green, University of Utah; Chloe Horn, University of Utah; Kent Wu, Central Wasatch Commission; Rachael Berghahn, University of Utah Contributed Oral Presentation
5:00 PM – 6:30 PM MT	Marine-derived nitrogen deposition from salmon carcasses in coastal temperate rainforests shapes soil microbial community composition Presenter: Caroline Daws, Outer Coast Contributed Poster Presentation

Wednesday, July 29

8:00 AM – 9:30 AM MT	Estimating Annual Large Mammal Roadkill for California Presenters: Lorna Haworth, UC Davis; Alice Michel, UC Davis; Benjamin Hodgson, UC Davis; Fraser Shilling, UC Davis Contributed Oral Presentation
10:00 AM – 11:30 AM MT	Accelerometry and animal-borne video reveals the importance of aerial capture of flying fish and predator facilitation interactions to red-footed boobies. Presenters: Abigail Schiffmiller, University of Alaska, Fairbanks; Greg Breed, University of Alaska, Fairbanks; Hillary Young, UC Santa Barbara; Scott Shaffer, San Jose State University; Sara Maxwell, University of Washington Bothell Contributed Oral Presentation
10:00 AM – 11:30 AM MT	Functional Roles of the World’s Recovered Predators Presenters: Ishana Shukla, UC Davis; Julia D. Monk, New York University; Justine Smith, UC Davis Contributed Oral Presentation
3:30 PM – 5:00 PM MT	From the Ground Up: Community-Powered Wildlife Conservation in Utah and Abroad Presenters: Austin Green, University of Utah; Julie Young, Utah State University; Gaby Karakcheyeva, University of Utah; Ilina Mocuta, University of Utah; Emmanuel Santa Martinez, Salt Lake Community College; Frances Ngo, Sageland Collaborative; Kaylee Meyers, University of Utah       Symposium
5:00 PM – 6:30 PM MT	Evaluating Camera Traps and Field Surveys for Monitoring Herpetofauna in the Civilian Control Zone, South Korea Presenters: Jiyeon Cheon, Transboundary Ecological Research Institute; Jihu Koo, DMZ Ecology Research Institute; Chloe Jun, DMZ Ecology Research Institute; Yune Hur, DMZ Ecology Research Institute; Jason Chung, DMZ Ecology Research Institute; Hailey Cho, DMZ Ecology Research Institute; Zoe Chang, DMZ Ecology Research Institute; Jae Hyun Kim, Transboundary Ecological Research Institute; Seung Ho Kim, DMZ Ecology Research Institute Contributed Poster Presentation
5:00 PM – 6:30 PM MT	Global Patterns of Decline in the World’s Avian Functional Guilds Presenters: Nikolas D. Orton, University of Utah; Cagan H. Sekercioglu, University of Utah Contributed Poster Presentation
5:00 PM – 6:30 PM MT	Some like it hot: Miami’s urban heat island aids the spread of its most prolific non-native lizards Presenters: Elizabeth A. Afkhami Searcy, University of Miami; Dishane Hewavithana, Florida International University; Kathryn A. Afkhami Searcy, Miami Dade School District; Michelle E. Afkhami, University of Miami; Christopher A. Searcy, University of Miami Contributed Poster Presentation

Thursday, July 30

10:00 AM – 11:30 AM MT	Common loons breed on lakes with shoreline development similar to where they were born Presenters: Emily F. Renkey, UC Los Angeles; Katie A. Adler, UC Los Angeles; Daniel T. Blumstein, UC Los Angeles; Walter Piper, Chapman University Contributed Oral Presentation
1:30 PM – 3:00 PM MT	Cascading effects of anthropogenic noise and heat on avian foraging and parenting behavior in California vineyards Presenters: Karen V. Gallardo Cruz, UC Davis; Gail L. Patricelli, UC Davis; Tara Robey, UC Davis; Erin Wilson-Rankin, UC Riverside; Houston Wilson, UC Riverside; Matthew Johnson, Cal Poly Humboldt; Daniel S. Karp, UC Davis Contributed Oral Presentation
3:30 PM – 5:00 PM MT	A quarter century on the edge: Spatiotemporal dynamics, risk patterns, and impacts of human-wildlife conflict in Chitwan National Park, Nepal Presenters: Abhinaya Pathak, UC San Diego Contributed Oral Presentation
5:00 PM – 6:30 PM MT	Shipside Feeding in Bottlenose Dolphins: Quantifying the Behavioral Mechanisms of a Novel Foraging Strategy Presenters: Christina Deaver, Utah Valley University; Marie Taylor, Utah Valley University; Meghan Weinpress-Galipeau, South Carolina Aquarium; Madeline Fry, Utah Valley University; Hannah Bouchillon, South Carolina Aquarium; Patricia A. Fair, Medical University of South Carolina; Jessica A. Cusick, Utah Valley University Latebreaking Poster Presentation
5:00 PM – 6:30 PM MT	Beaver Fever: Giardia duodenalis in North American Beavers (Castor canadensis) Located in Utah Presenters: Elena B. Green, Utah State University; Sara B. Weinstein, Utah State University Latebreaking Poster Presentation

 

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Learn more about the upcoming ESA Annual Meeting, July 26–31, on the meeting website.

ESA invites press and institutional public information officers to attend for free. To register, please contact ESA Public Affairs Manager Mayda Nathan directly at mayda@esa.org.

The Ecological Society of America, founded in 1915, is the world’s largest community of professional ecologists and a trusted source of ecological knowledge, committed to advancing the understanding of life on Earth. The 8,000 member Society publishes six journals and a membership bulletin and broadly shares ecological information through policy, media outreach, and education initiatives. The Society’s Annual Meeting attracts 4,000 attendees and features the most recent advances in ecological science. Visit the ESA website at https://www.esa.org.

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