As researchers who studycancer disparities in young adults, we examine the social and systemic factors that shape who survives a cancer diagnosis. In our recent review of the scientific literature – an analysis that included nearly 470,000 Americans between the ages of 15 and 39 who had been diagnosed with cancer – we found that insurance status is one of the clearest and most consequential factors.
Young people in this age group are often finishing school or starting new jobs, including positions that don’t offer benefits. They’re also aging off a parent’s insurance plan, which happens when you turn 26 under current U.S. law. This instability leaves many young people uninsured or underinsured.
The consequences of no or insufficient health coverage go beyond inconvenience. Adolescents and young adults already tend to see smaller improvements in cancer survival over time compared to children and older adults. This gap has puzzled researchers for years.
Insurance instability appears to make this gap even wider.
Strikingly, patients on Medicaid and uninsured patients often had similar cancer outcomes – and both did worse than those with private insurance. This suggests that simply having some form of coverage isn’t enough if that coverage doesn’t actually open doors to quality care.
What kinds of cancer treatment a patient can access, including clinical trials, is ultimately determined by their insurance. SeventyFour/iStock via Getty Images Plus
One underdiscussed consequence of insurance status is access to clinical trials. These studies are often the pathway to the most advanced treatments available. Yet research has found that the type of insurance a young cancer patient has is a significant predictor of whether they enroll in a clinical trial, with higher enrollment rates for those with private insurance.
For cancers such as early stage Hodgkin lymphoma – a cancer more common in young adults – treatment decisions and access to newer approaches can vary significantly based on where and how a patient receives care, which is often tied to their insurance status.
Clarifying cause and effect
The body of research we analyzed primarily tracked patterns in existing data rather than through controlled experiments. That makes it difficult to say with certainty that insurance status directly causes differences in survival.
However, the pattern we observed was consistent across many studies. Moreover, most studies recorded insurance status only at the time of diagnosis, which misses changes that happen during treatment. Patients may lose or gain coverage in the middle of their care.
Future research that tracks insurance continuously throughout treatment, standardizes how coverage is categorized and examines specific cancer types and age subgroups in greater depth could clarify the picture further.
The good news is that insurance is something society can change. Based on our research, a few key areas stand out.
Expanding coverage could help keep more young cancer patients insured. This might look like policies allowing young adults to stay on a parent’s plan longer, expanding Medicaid and reducing gaps in coverage after diagnosis.
Improving what Medicaid actually covers could make it easier for patients to access top cancer centers. Many doctors and cancer centers limit how many Medicaid patients they see because reimbursement rates are low.
Connecting with financial counselors, patient navigators and care coordinators could help young patients on public insurance or those who lack insurance navigate the system. This support could enable them to get timely access to the right treatments and clinical trials.
Early screening for financial barriers can prompt timely referrals to financial counseling, assistance programs or social work before patients experience treatment delays. Financial support can help patients complete treatment, make their appointments and improve their outcomes.
The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
As a researcher in autism and education and a former secondary school teacher, it took me a while to realise that autistic school staff were rarely included in conversations about inclusion and diversity in schools.
With colleagues, I started the Autistic School Staff Project in 2019, focusing on the experiences, needs and aptitudes of autistic teachers and other education staff.
Our findings show that autistic school staff can experience significant sensory issues in school. These can be from bright, flickering lights, odours from the canteen, and crowding in corridors or during meetings. The greatest impact of all comes from noise: shouting from children and staff during break times, the clang of the school bell and the roar of traffic when windows are open in the summer.
Interestingly, it’s not only a question of volume levels. Whispering from children and humming from technology can also be highly distracting and contribute to feelings of fatigue and overload.
Autistic teachers also told us that the ways neurotypical colleagues communicated and interacted with them could be disorientating and exclusionary. Staff meetings that seemed to lack focus, chit-chats in the school corridor, gossip and school politics could be experienced as confusing and irrelevant.
At the same time, autistic teachers felt their own communication style of being direct and to the point could be misunderstood as rudeness. Similarly, staff social events were often not enjoyed by autistic teachers, even though neurotypical colleagues seemed to really rate them. Changes announced at the last minute by the school leadership team, with instructions that did not seem to make sense, could be highly stressful for autistic teachers. Covering for absent teachers was also found to be very unsettling.
Noisy school environments can cause sensory issues for autistic teachers. Shutterstock
Most tellingly, a number of participants felt they could not be open about being autistic. A key reason for this concerned negative and stigmatising attitudes towards autism that they had to face in school. The teachers also said that autistic children could be poorly treated. Autistic teachers sometimes had to sit through autism training, conducted on the assumption that no-one present was autistic, where the same negative attitudes were evident.
As a result, autistic school staff could be extremely wary about sharing with anyone that they were autistic. They worried that this information would have a negative impact on their careers. Suppressing an autistic identity, known as masking, has been linked with mental health issues.
While some of our participants had been able to disclose being autistic in school, and had even had a good experience of this, others said that it had made life even harder. This was because attitudes would change towards them in a negative way, or they might not even be believed.
Passion and support
Fortunately, a number of positives also came out of our study. Monotropism – a key autistic trait that denotes a tendency to have very intense interests – can mean that autistic teachers develop strong subject expertise and teach with passion. Even the job itself links with monotropic tendencies, as autistic teachers told us that they loved their work and were highly motivated by it. In addition, autistic teachers felt that they were very thorough and organised.
Above all, autistic teachers felt they were making a significant contribution to supporting inclusion in school. They were sensitive to the needs of neurodivergent children and others at risk of marginalisation, and were willing to try alternative approaches with children who were struggling. One teacher said:
I never gave up on a child because I think probably too many people gave up on me. I could see myself in a lot of the children.
In addition, some of those who had been open about being autistic were valued by colleagues because of their insights in relation to neurodiversity. Autistic teachers also felt that they could be a role model for autistic children and their parents.
Autistic teachers are a valuable part of the school workforce and are already making an important contribution to inclusion. However, it’s important to remove the barriers they can face across their careers.
This includes providing more flexibility and support for autistic student teachers. Making recruitment practices inclusive and accessible – such as by providing questions in advance, and offering in-person and remote options for interviews – would also benefit autistic teachers, as would developing neurodiversity-inclusive school communities.
Participants were clear that autism training should be run by autistic people, and that withdrawing to a quiet space should not be misinterpreted by colleagues as being anti-social. Addressing the sensory impacts of schools would benefit both children and staff. Providing staff with agency in decision-making can be empowering. We also need to reconsider the conventional role of the teacher, and question if the current format of standard duties, such as parents’ evenings and covering for absent colleagues, should be re-evaluated through a neurodiversity-inclusive lens.
Rebecca Wood has received funding from the ESRC and the John and Lorna Wing Foundation.
The country has certainly suffered many tactical losses. But its missiles and drones have been strategically successful.
Iran so far has launched at least 5,400 such projectiles. Surprisingly, less than a tenth of them have targeted Israel, its traditional rival.
Missiles over Israel
Israel faced about 450 Iranian missile attacks during the war’s first four weeks. The rate of fire fell rapidly after the first weekend but has never halted.
Some missiles carry several hundred kilograms of explosives, enough to destroy an entire building. The rest instead dispense dozens of cluster bombs over wide areas. Those are less powerful but still lethal.
But interceptorssometimes miss. And their supply is limited. Consequently, at least nine large warheads and 150 cluster bombs have hit populated areas.
These numbers imply that almost all Iranian missiles are accurate enough to need interception. By contrast, during Israel’s earlier conflicts with Gaza in 2008, 2011 and 2014, less than a third of incoming rockets were so accurate.
Meanwhile, more than 90 per cent of Iran’s missiles and drones have targeted Arab countries in the Persian Gulf.
Number of Iranian missiles and drones arriving daily over Israel and the UAE, February 28 to March 27. Published news reports, CC BY
Drones across the Persian Gulf
Saudi Arabia, Jordan, Iraq, Kuwait, Bahrain, Qatar, Oman and the United Arab Emirates (UAE) collectively reported around 4,900 Iranian attacks during the first four weeks. Only one fifth were missiles: the rest were drones.
These countries have stated they are neutral in the war. However, they do have defence agreements with the U.S., and some host American military facilities.
These countries defend themselves using weapons like the U.S.-made Patriot and Israeli-made SPYDER interceptors. Drone experts from Ukraine now advise the defenders too.
For example, the UAE reported attacks by 1,835 drones, 378 ballistic missiles and 15 cruise missiles. As of March 10, it claimed to have intercepted 94 per cent of the drones and 99 per cent of the missiles.
The deadliness of these attacks has varied.
Continuing lethality
In Israel, Iranian missiles have killed 20 people, implying roughly 4.1 deaths per hundred missiles arriving.
That’s less than the 5.1 the country saw during its 2025 war with Iran. But it’s four to 40 times higher than the rates it suffered from rockets in earlier Gaza and Lebanon conflicts.
There were about 0.6 deaths per hundred Iranian attacks in Kuwait, Bahrain and the UAE combined. That’s much lower than Israel’s rate, presumably because those countries were attacked by drones and short-range missiles carrying smaller warheads.
Interestingly, although the quantity of Iranian attacks fell after the first week, their lethality did not. Death rates per projectile in Arab countries showed little change week-to-week. In Israel, the rates were highest in Week 3.
In fact, Iranian missiles keep hitting precise targets, like U.S. military aircraft parked beside runways.
So, U.S. and Israeli warplanes have bombed thousands of targets, killed thousands of civilians, and slowed Iran’s missile fire. But they haven’t stopped it.
That’s not surprising. Airstrikes alone didn’t stop rocket fire during Israel’s previous conflicts in Gaza and Lebanon. Ground invasions were needed for that.
Trump recently, and inadvertently, admitted this weakness. While discussing Iran’s closure of the Strait of Hormuz, he said “it would be great if we could do something, but theyhave to open it.”
This strategic failure despite tactical success is reminiscent of the Vietnam War. U.S. units had overwhelming firepower as they killed enemy soldiers. But body countsby themselves indicated little about strategic progress.
Trump talks about being the greatest U.S. president in history. So, perhaps his Iran war will make him the new leader on that policy failure list.
Michael J. Armstrong does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
The Artemis II astronauts, (L-R) Reid Wiseman, Victor Glover, Christina Koch and Jeremy Hansen, pose with the Space Launch System rocket.Nasa / John Kraus
Every mission to deep space is fraught with danger. A hardware failure during launch, an equipment malfunction far from Earth, or a small space rock hitting the vehicle are all scenarios astronauts will train for.
As humans set off for the Moon for the first time in more than 50 years, one persistent threat they face is from solar radiation.
Intense bursts of radiation from the Sun, known as solar particle events, can endanger the lives of space travellers, particularly those venturing beyond low Earth orbit (LEO). During these events, high speed, charged particles stream out from the Sun and into space.
Exposure to these particles could lead to radiation sickness or, in the worst cases, prove fatal. On space stations and other crewed vehicles travelling in LEO, astronauts are afforded a high degree of protection by the magnetic bubble surrounding Earth (the magnetosphere).
But in interplanetary space, where Artemis II is headed, humans are much more exposed to outpourings of solar radiation.
The Sun’s magnetic activity fluctuates on a cycle lasting roughly 11 years. During this cycle, sunspots (areas of reduced temperature caused by intense magnetic fields) can cause eruptions known as flares, as well as solar particle events. These rise and fall in frequency with the solar cycle.
Solar activity (represented here by sunspot numbers) fluctuates on an 11-year cycle. Noaa
The current solar cycle reached its maximum, when the Sun is generally at its most active, in 2024 and is now in a slowly declining phase leading to the minimum, when the Sun is quietest. The current cycle should reach the minimum in 2031.
Not all solar cycles are the same and the current one has been rather undistinguished in terms of activity, as was the previous cycle that reached maximum in 2014. Recently, however, the Sun woke from its slumber.
On November 11 2025, a large solar particle event increased ground level radiation by about 145% for two hours, as measured by the University of Surrey’s neutron monitor at the Met Office station at Lerwick, Shetland.
The Earth’s magnetosphere acts as a shield, protecting the planet from solar particles. Esa
This was also detected by University of Surrey SAIRA (Smart Atmospheric Ionising Radiation) monitors installed on two transatlantic flights and on rapid response meteorological balloon flights at Lerwick, Cambourne and near Utrecht in the Netherlands.
Work is in hand to unscramble this complex event to determine the radiation increases worldwide using the University of Surrey computer model MAIRE (Model for Atmospheric Ionising Radiation Effects). This calculates radiation levels at aviation altitudes for normal atmospheric conditions, as well as for enhanced radiation events caused by increased solar activity.
Three immediate research papers are in production to describe the radiation monitors and their calibration, to summarise the flight data and to compare the data with available models.
A close call
The solar particle event on November 11 2025 serves to tell us that, whatever the probabilities might be, the Sun can always take us by surprise.
To underline the importance of such events for deep space missions, let’s rewind the clock to 1972. At the time, the Sun was in a similar declining phase in its 11-year cycle as we are today. Then, between August 2 and August 11 1972, the Sun unleashed one of the largest solar particle events of the space age.
A massive solar particle event occurred between the Apollo 16 (pictured) and Apollo 17 missions in 1972. Nasa / Charles M. Duke Jr
This gigantic release of charged particles from the Sun occurred in between the Apollo 16 (April 1972) and Apollo 17 (December 1972) missions to the Moon.
This event was much bigger than the one in November 2025 – by a factor of 40. If it had taken place while astronauts were in space, the radiation dose could have caused severe illness or even have been fatal.
The Apollo crews had a lucky escape. But the solar particle event made an impact on on Earth. The ensuing geomagnetic storm is thought to have caused 4,000 US-laid mines to spontaneously detonate in Hanoi harbour during the Vietnam war, causing confusion and alarm on both sides.
Travelling to the Moon means astronauts are no longer protected by the Earth’s magnetic bubble, or magnetosphere. Nasa
There are ways to prepare for similar events in future. The most dangerous aspect of this radiation is its high energy component, which can penetrate shielding on spacecraft. The Surrey Space Centre Space Environment & Protection team are currently working on a detector, called the High Energy Proton instrument, that definitively measures this high energy component of solar particle radiation.
It does this through the light flashes emitted when the particles transit a transparent medium at velocities exceeding the speed of light. Astronauts often report seeing such flashes of light, even with their eyes closed, that can be caused by solar particles or high-energy cosmic rays passing through the retina or optic nerve.
The University of Surrey radiation detectors could now fly on a lunar orbiting mission towards the end of the decade. On this mission, they will characterise the danger to lunar bases as well as to the Earth. Nasa is planning to spend US$20 billion (£15 billion) on a base at the south pole of the Moon. A separate outpost is planned by China and Russia.
Radiation warning systems can give astronauts the time they need to retreat to storm shelters within a base or spacecraft where increased and specially designed shielding is used.
Engineers use storage lockers as a radiation shelter inside a mockup of Orion. Nasa
If astronauts travelling in Orion – the spacecraft used on Artemis II – receive advance word of a solar storm, they are instructed to get into storage lockers in the floor of the spacecraft. This places the crew next to Orion’s heat shield, making this area one of the most protected parts of the vehicle.
Warning systems can also help on Earth. During periods of high solar radiation, controllers could instruct aircraft to fly at lower altitudes and latitudes – and in extreme cases remain grounded.
Computing revolution
One big difference between the Apollo and Artemis missions is in the rapid development of microelectronics since the 1960s and 70s. This has led to trillion-fold increases in computer memory density and thousand-fold improvements in speed.
The Apollo computers were pioneering, but struggled to cope with the workload as Neil Armstrong and Edwin “Buzz” Aldrin descended to the lunar surface during the Apollo 11 mission in 1969. However, there is a downside to this as the technology packed into modern spacecraft is vulnerable to radiation.
The charge depositions from individual particles often exceed the amount required to change the state of the computer memory bits. In some cases it could destroy the device. It is now arguable whether the greater hazard from solar particle events is to astronaut health or to the flight electronics aboard spacecraft.
In 1972, the Apollo astronauts were very lucky. In this new age of exploration, when so many nations have designs on travel to deep space, we can’t afford to leave astronaut safety to the whims of fortune.
Clive Dyer does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
Literature expresses complex and nuanced ideas – the powerful feelings that define us as human beings and the detailed observations that illuminate all aspects of our lives. It does so with words put together with consummate skill.
So, surely silence is a nothingness, an affront to the communication of both rational argument and strong emotion – literature’s opposite, even its anathema?
Well, no. In my new book Silence: A Literary History, I’ve set out to show that, over 1,200 years, English literature has spoken to us – and spoken to us eloquently – through silences as well as through words. Without silences, both formal and thematic, we wouldn’t have the exquisite hush of medieval lullabies, the suspenseful secrets of the realist novel, or the jagged fragmentation of modernist poetry.
We would lose implicitness, a good deal of ambiguity, much precision, a powerful mode of protest and a variety of moods. Iago would explain exactly why he wanted to destroy Othello in Shakespeare’s play. The dog would bark in the night time in The Hound of the Baskervilles, by Arthur Conan Doyle. And D.H. Lawrence’s sex scenes would come with a running commentary.
The start of silence
If silence has a starting point in English literary history, it’s a man at sea. The 9th-century poem The Wanderer, composed in the Old English language of the Anglo-Saxons, communicates the sheer strangeness of silence via an alien grey seascape in which the protagonist is utterly alone.
This silence is composed not of complete noiselessness – the hail beats on the waves and a seabird occasionally mews – but of an intense and total absence of human voices.
A reading of The Wanderer.
The poem conveys the difficulty of this silence – its wretched, aching loneliness and its perpetual reminder of lost happiness. But it also portrays silence as a duty, the mark of a seasoned warrior forged by Graeco-Roman stoicism, the Germanic hero ethos and Christian asceticism.
And it confronts readers, here at the very beginnings of English literature, with a silent inner voice: the necessary basis of an interior life.
Scroll on 1,200 years. En route, we will take in the tongue-tied silences of Renaissance love poetry, the green silences of 18th-century pastoral scenes and the dumbfounded wonder of the romantic sublime.
We will pause, awestruck, at Tennyson’s great epic of speechless grief, In Memoriam. We will relish the social silences of the Victorian novel, from the hilariously awkward to the emotionally profound.
The fascism-bordering silences of Modernism will make us shiver, before we ponder 20th-century experiments with visual, acoustic and dramatic silences. And we will arrive at the genre-defying, multimedia poetry collection that is Jay Bernard’s Surge (2019).
Voices that we cannot hear
In 2016, Bernard took up a residency at the George Padmore Institute in London, an archive dedicated to radical Black history in Britain. The New Cross fire, which in 1981 had killed 13 young Black people, was playing on their mind. And then on June 14 2017, as Bernard puts it: “Grenfell happened”.
Bernard was sickened by the similarities: “The lack of closure, the lack of responsibility and the lack of accountability” at the centre of both conflagrations.
Surge’s response takes its title from a remark by the Black activist Darcus Howe, one of the organisers of the Black People’s Day of Action in 1981: “When you surge and you don’t deal with the question, barbarism expresses itself.”
Jay Bernard talks about their work.
Speaking over the barbarism, Surge registers a gamut of other silences as it winds between the New Cross and Grenfell fires, and historic and ongoing injustices to Black people.
There is the “muffling” of the New Cross fire by the police, and the details that were literally “tippex’d out” of the file. The silence of the media cannot dispel the weighty silences of the ghostly dead. Then there are the silences that surround transness: hiddenness, rejection and defiance of conventional categories.
With this last issue, we can scroll back up the centuries again. The 13th-century romance Silence, written in Old French by a Cornishman, Heldris de Cornualle, relates the legend of a girl-child being brought up as a boy called Silence because women are forbidden to inherit their parents’ estates. This causes a furious argument between the characters of Nature and Nurture, which anticipates our own age’s differences over transness by eight centuries.
“They have insulted me,” complains Nature, “by acting as if the work of Nurture / were superior to mine!”
But Reason, on behalf of Nurture, urges Silence to resist Nature’s blandishments, or “you will never train for knighthood afterwards. / You will lose your horse and chariot.”
Nature is the winner in the story, but the poem is able to accommodate Silence as both male and female – effortlessly embracing apparent contradictions in such lines as “he was a girl”.
Woman Reading in the Reeds, Saint-Jacut-de-la-mer by Édouard Vuillard (1909). The Fitzwilliam Museum
I believe noticing silences in literature makes us better readers. We come to recognise that some things are better left unsaid – indeed, that some things can’t be said. As a result, our antennae become attuned to literature’s stock-in-trade: the indirect and the inexplicit.
Importantly, we become aware of who hasn’t spoken. All this means we gain a better understanding of what communication is, and how we interact with other people. As our reading acquires a new, slower tempo and a new rhythm, our interpretations change.
What can silences speak to us about? Some of the profoundest aspects of our existence: our understanding of what makes a self; our sense of sacredness; our most powerful and intimate feelings; our place in the natural world; our capacity for wonder. All we have to do is notice.
The excerpt from Silence: A Thirteenth-Century French Romance was translated by Sarah Roche-Mahdi. This article features references to books that have been included for editorial reasons, and may contain links to bookshop.org. If you click on one of the links and go on to buy something from bookshop.org The Conversation UK may earn a commission.
Kate McLoughlin was awarded a Major Research Fellowship by the Leverhulme Trust to write Silence: A Literary History.
The only thing harder than losing weight is keeping it off. Many people who lose weight find themselves stuck in the cycle of “yo-yo dieting” – losing weight and gaining it all (and sometimes more) back again.
This recent paper, published in BMC Medicine, presents the findings of two separate weight loss trials that were conducted five years apart.
The first trial (trial 1) looked at 278 participants who were overweight or obese. Participants were randomised to follow either a low-fat or low-carb Mediterranean diet – either with or without exercise. All participants lost a comparable amount of weight at the end of the 18-month trial. But those who incorporated exercise achieved the biggest decrease in visceral fat (a dangerous type of fat that is stored around the organs).
The second trial (trial 2) was conducted five years later. Similar to trial 1, the 294 participants followed a Mediterrean-style diet for 18 months. But this time, one group ate a diet very high in polyphenol-rich foods (naturally-occurring plant compounds which have been linked to health benefits such as lower risk of chronic disease). The second group ate a normal Mediterranean diet, while the third group followed normal healthy diet guidelines.
While both Mediterrnanean diet groups lost weight and saw improvements in their overall health, the polyphenol group lost more visceral fat.
A unique aspect of trial 2 was that it included around 80 participants from trial 1. Some of these participants weighed more than they did at the start of the first trial. Such weight recidivism is common following weight loss. This is due to various biological and physiological functions that reduce metabolism and increase hunger, causing people to regain weight and store fat.
The authors compared the people who rejoined the research project against their health and weight status at the start of trial 1. They assessed body weight and other aspects of health – including body fat and blood sugar levels. Despite the re-joiners weighing around the same (if not more) than they did at the start of trial 1, they had lower levels of abdominal fat and visceral fat five years later.
Their metabolic health was also better than it was at the start of the first trial, based their blood lipid (fat) levels, cardiovascular health and blood sugar control.
On the surface, this appears to be good news – suggesting participants retained some of the health benefits of the weight they lost the first time around, despite regaining the weight.
Yet, the results suggest that the very adaptations which helped the re-joiners stay healthy despite regaining weight could potentially have repercussions later. To understand why this is the case requires a grasp of how the body responds to a calorie deficit.
Weight loss and body fat
Our fat stores (known as adipose tissue) serve as our main energy (calorie) buffer when there’s no food to provide that fuel. These stores are sacrificed to cover the energy shortfall, causing fat cells to shrink. Visceral fat is the first to go, followed by the more beneficial fat cell stores.
But when people stop dieting, the body puts priority on regaining lost fat. Indeed, our body replenishes fat stores far more quickly than it does muscle or protein stores. More importantly, in response to this shrinkage, the body compensates by making more fat cells. It does this to help the body better cope the next time there’s a fuel crisis.
So dieting literally makes you fatter in the long run. But thankfully, this will most likely be healthier subcutaneous fat (in the hips, thighs, buttocks and torso) instead of around the organs as harmful visceral fat.
So even though you’ll be carrying excess weight, you’ll experience fewer of the metabolic issues caused by unwanted visceral fat – such as insulin resistance and high cholesterol, which elevate your risk of cardiovascular disease and diabetes.
But with the higher capacity to store fat comes the risk of overshooting your original weight. This may also have implications for yo-yo dieting.
The weight loss cycle
In the paper, the re-joiners who took part in trial 2 did manage to lose weight again. But, on average, they lost slightly less than the trial’s first-timers. That said, when all of the participants from trial 2 were followed up five years later, the re-joiners from trial 1 had regained less, too. They had also retained more of the health benefits of losing weight.
Taking stock of the whole weight-loss journey, it appears that those who regained weight and then joined trial 2 are at a comparable place at the end of ten years to those who just did trial 1.
But there are a few caveats to the trial’s findings.
First, the paper only examined body fat. It didn’t provide any information on lean tissue (such as muscle). This is important, as when we lose weight we lose both fat and muscle. Given muscle’s importance for a healthy metabolism, a lack of muscle could result in even greater weight gain.
It’s also not clear whether regaining weight changes the nature of muscle tissue. There are two key types of muscle fibre. Type 1 is smaller and more efficient at burning fat. Type 2 is larger, faster and more powerful – important for explosive exercise.
Overall, the paper shows us that weight loss is still beneficial for your health – even if it requires a few attempts to get to your goal weight. But to avoid potentially gaining more weight the second time around, it’s key to establish good diet and lifestyle changes that are sustainable long-term.
Adam Collins is affiliated with Form Nutrition Ltd as consultant Head of Nutrition
Source: The Conversation – UK – By Robyn Klingler-Vidra, Vice Dean, Global Engagement | Associate Professor in Political Economy and Entrepreneurship, King’s College London
One firm, Taiwan Semiconductor Manufacturing Company (TSMC), produces more than 90% of the world’s most advanced semiconductor chips. These chips are essential for smartphones, artificial intelligence, high-performance computing and cutting-edge military systems.
Taiwan’s dominance of advanced chips acts as a chokepoint for the global economy. Days or weeks without their manufacturing would affect the supply and price of numerous products around the world. This is comparable to how the current disruption to shipping in the Persian Gulf due to the Iran war is affecting oil-dependent markets globally.
Taiwanese semiconductor manufacturing supremacy has transformed the island nation into what I have described in my research as a “niche superpower”. It wields outsized global influence by commanding a strategically indispensable industry.
Taiwan did not stumble into this position. In the 1970s, Taiwanese technocrats recognised that the nation could not immediately compete at the world’s electronics frontier. One of them was Kwoh-Ting Li, then minister of economic affairs, who is often referred to as the “father of Taiwan’s economic miracle”.
At that time, Taiwan lacked the financial capital and technological skills to compete with industry leaders such as Japan and the US. So rather than trying to dominate the entire semiconductor industry from design through to production, Taiwanese policymakers focused on building capabilities in precision manufacturing. This is the most operationally demanding part of the semiconductor value chain.
Established in 1973 by the Taiwanese government, the Industrial Technology Research Institute carefully acquired semiconductor process technology through licensing agreements with the now defunct US firm Radio Corporation of America (RCA). It then trained a generation of Taiwanese engineers.
The pivotal moment came in 1987, when Morris Chang established TSMC. Chang, a US-trained engineer who had spent decades at American semiconductor multinational Texas Instruments, devised what is now known as the “pure-play foundry” model.
Rather than designing and manufacturing its own branded chips, this meant that TSMC would manufacture chips for other firms. This strategic choice was transformative because it reassured American and European semiconductor companies that TSMC would not compete with them. It allowed major tech firms such as Qualcomm and later Nvidia to outsource chip production to Taiwan without fear of intellectual property leakage or strategic rivalry.
The Taiwanese semiconductor industry grew within the Hsinchu Science Park, a major industrial cluster south of the Taiwanese capital of Taipei. By the early 1990s, Hsinchu Park hosted more than 140 chip manufacturing firms and employed around 30,000 workers. The strength of the cluster attracted legions of Taiwanese engineers back from the US, helping Taiwan become the global leader in the production of advanced semiconductors.
The ‘silicon shield’
Taiwan’s semiconductor dominance has played an overt role in protecting the island from its existential threat – a Chinese invasion. This phenomenon was explicitly named in 2021 in an article published in Foreign Affairs magazine, where the former Taiwanese president, Tsai Ing-wen, argued that Taiwan’s semiconductor industry acts as a “silicon shield”.
The dependence of the global economy on Taiwanese-made advanced chips, she argued, means the disruption caused by a Chinese invasion would trigger catastrophic global economic consequences. Taiwan’s allies would thus be compelled to come to its defence.
In recent years, Taiwan’s silicon shield has come under threat. Following the start of US export restrictions on advanced chipmaking equipment to China in 2020, Beijing has accelerated its efforts to build indigenous capacity in chip manufacturing. It has significantly increased investment in its semiconductor industry.
Semiconductors were the underperformer in the Made in China 2025 strategy, through which Chinese leadership aimed to transform their nation into a high-tech manufacturing superpower. China fell short of its goals for the localisation of semiconductor production and global market share, missing targets by the 2025 deadline.
However, Chinese chip manufacturers like HiSilicon and Semiconductor Manufacturing International Corporation have been gaining momentum. A proposal by 13 Chinese chip industry executives in March outlined aims to increase self-sufficiency to 80% by 2030. China’s semiconductor self-sufficiency is currently around 33%.
At the same time, Washington is pushing to bring semiconductor manufacturing back onshore. Biden-era initiatives such as the Chips and Science Act offered incentives for TSMC’s sprawling manufacturing facility in Arizona, which opened in 2022 as part of US efforts to boost domestic chip production.
These incentives for TSMC included up to US$6.6 billion (£5 billion) in direct investment and significant tax credits. TSMC committed an initial US$65 billion to the plan, with the Trump administration announcing in March 2025 that the company would boost its US investment by a further US$100 billion.
Elon Musk also recently announced plans for advanced chip facilities in Texas for his two companies, Tesla and SpaceX. In light of Musk’s concerns that companies like TSMC are not producing the volume of chips his companies need, the so-called “Terafab” venture aims to consolidate every stage of the semiconductor production process under one roof and is expected to cost in the range of US$25 billion. Other companies investing in chip fabrication in the US include Micron, Texas Instruments and Intel.
Despite US and Chinese efforts, replicating Taiwan’s manufacturing ecosystem is difficult. It requires not only capital and equipment, but also knowledge that has been accumulated over decades as well as dense supplier networks and an unparalleled engineering workforce.
TSMC has struggled to hire talent in Arizona, and has resorted to flying thousands of workers in from Taiwan in a bid to improve the skills of locals. And while TSMC is now producing semiconductors at the cutting edge of 2-nanometre scale, the Chinese self-sufficiency goals aim to have “entirely domestically produced equipment” for the less sophisticated 7-nanometre and 14-nanometre generations of chips.
The difference between 2nm and 7nm chips is significant – a 45% increase in performance while using 75% less power. The narrower chips are used for advanced processes such as cutting-edge AI, while the wider ones are used in a broader range of electronics, like smartphones, desktop processors and automobiles.
Taiwan’s semiconductor story is ultimately one of strategic foresight. By choosing manufacturing over design, embedding itself within US-led technological networks and cultivating world-class process expertise, Taiwan transformed structural vulnerability into structural power.
Through its semiconductor dominance, Taiwan stands out as the quintessential niche superpower. But history shows that superpower status, including in niches, is never permanent. The technological frontier moves, rivals learn and allies hedge.
For Taiwan, remaining indispensable to the global economy will require not only staying ahead technologically. It will also require carefully orchestrating the political, financial and human capital foundations that made its silicon shield possible in the first place.
Robyn Klingler-Vidra received a research grant from the Chiang Ching-kuo Foundation between 2019 and 2023. The grant funded research on the educational and professional background of north-east Asia’s innovation policy leaders across the post-war period. The study was published in World Development in April 2025 and is available here: https://www.sciencedirect.com/science/article/pii/S0305750X25000646.
Des pépins de raisin retrouvés sur des sites archéologiques peuvent sembler anodins. Pourtant, l’analyse de leur ADN donne accès à l’histoire plurimillénaire de la vigne cultivée.
Nous avons séquencé le génome de pépins vieux de plusieurs millénaires, révélant une histoire déjà entrevue par l’archéologie : celle de l’introduction de la viticulture en France, des échanges de cépages à l’échelle européenne et de pratiques agricoles anciennes qui ont laissé des traces jusqu’à aujourd’hui.
Nos résultats, publiés tout récemment dans Nature communications, montrent notamment que certains cépages emblématiques, comme le pinot noir variété phare de Bourgogne, étaient déjà présents au Moyen Âge.
Comment avons-nous analysé l’ADN de pépins de raisin vieux de 4 000 ans ?
L’histoire de la vigne s’est longtemps appuyée sur l’étude morphologique des pépins. Cette puissante approche a permis de distinguer de grandes tendances, notamment sur le caractère sauvage ou domestique des pépins, et retracer les débuts de la viticulture.
Cependant, certaines questions restaient difficiles à trancher : origine géographique des cépages, relations de parenté, ou encore les modes de multiplication (croisement ou reproduction clonale) et circulation des plants. L’ADN ancien pouvant être préservé au cœur même des pépins apporte ici une aide particulièrement décisive, comme témoin des relations entre les vignes du passé et celles d’aujourd’hui.
Nous avons ainsi analysé 49 pépins provenant de différents sites archéologiques, majoritairement français, et couvrant près de 4 000 ans, de l’âge du Bronze à la fin du Moyen Âge. Ces pépins gorgés d’eau ont été préservés dans des contextes spécifiques, humides, ayant contribué à une bonne préservation de leur ADN.
Pépins anciens (à gauche) et pépins modernes (à droite). S. Ivorra, CNRS, Fourni par l’auteur
L’ADN a été extrait dans le laboratoire spécialisé en ADN ancien du Centre d’anthropobiologie et de génomique de Toulouse, conçu pour isoler et manipuler les molécules aussi rares que dégradées qui ont traversé les époques dans les restes archéologiques. Cet ADN ancien a pu être décrypté grâce à des technologies de séquençage de pointe jusqu’à en lire la totalité de l’information génétique, soit ici un texte génétique d’environ 500 millions de lettres.
Ces données permettent d’établir les relations génétiques entre individus, d’identifier les origines des cépages et de retrouver les techniques de propagations passées : soit par croisement, mélangeant des variétés d’origine ou de qualités distinctes ; soit par reproduction clonale (par bouturage, marcottage ou greffe) pour maintenir à l’identique dans le temps une variété qui leur était particulièrement précieuse.
Notre découverte prouve l’ancienneté de la viticulture
Les premières vignes cultivées apparaissent en France aux alentours de -600 avant notre ère, avec le développement des échanges méditerranéens, notamment du vin. Elles coexistent avec des vignes sauvages locales, et des croisements entre ces deux types contribuent à la diversité des cépages.
Les analyses génétiques confirment également l’existence de circulations à longue distance dès cette période. Des influences venues d’Ibérie, des Balkans ou du Proche-Orient témoignent des échanges des plants et de savoir-faire à l’échelle de la Méditerranée et, plus généralement, de l’Europe.
Autre point important : la multiplication clonale apparaît comme une pratique ancienne et commune, déjà en place dès l’âge du Fer. Elle a permis de maintenir certaines variétés d’intérêt sur de longues périodes et de les diffuser sur de longues distances.
C’est dans ce cadre que nous avons identifié un pépin médiéval considéré comme étant génétiquement identique au pinot noir actuel, illustrant la continuité de certains cépages sur plusieurs siècles.
Quelles perspectives pour ces recherches ?
L’apport de l’ADN ancien ne se limite pas à confirmer des scénarios existants : il ouvre aussi de nouvelles pistes.
En combinant données anciennes et modernes, il devient possible d’aller plus loin dans la caractérisation des vignes du passé. Des approchesrécentes permettraient par exemple d’inférer certaines caractéristiques des raisins anciens, comme la couleur des baies ou certains traits liés au goût.
Ces méthodes pourraient aussi permettre de mieux comprendre les adaptations des cépages aux environnements du passé, ou encore les choix opérés par les sociétés anciennes dans leurs pratiques agricoles.
À terme, ces recherches contribuent à mieux documenter la diversité génétique de la vigne et son évolution, un enjeu important dans le contexte actuel de changements climatiques.
Tout savoir en trois minutes sur des résultats récents de recherches, commentés et contextualisés par les chercheuses et les chercheurs qui les ont menées, c’est le principe de nos « Research Briefs ». Un format à retrouver ici.
Rémi Noraz a reçu des financements de l’ANR MICA (ANR-22-CE27-0026).
L’humain s’est placé au-dessus de toutes les autres espèces animales. Comment changer notre relation avec elles pour sortir d’une logique de domination et aller vers des formes de coexistence et de coopération ?
Chaque année, des milliards d’animaux sont élevés, transportés et abattus pour répondre aux besoins alimentaires, scientifiques ou industriels des sociétés humaines. Cette utilisation intensive du vivant pose une double question. Elle est d’abord éthique, car elle implique la souffrance et la mise à mort d’êtres vivants sensibles. Elle est aussi environnementale et sanitaire : la déforestation pour l’élevage intensif, la pollution conséquente et la proximité accrue entre espèces favorisent les déséquilibres écologiques et l’émergence de maladies.
Le concept de One Health (une seule santé) et la crise du Covid-19 rappellent que la santé humaine dépend étroitement de celle des animaux et des écosystèmes. Ces crises ne sont pas indépendantes. Elles révèlent un même rapport au vivant, fondé sur l’exploitation et la mise à distance physique et émotionnelle. Comprendre ce rapport est une condition nécessaire pour le transformer.
Une domination héritée : spécisme et colonisation
Les recherches en éthologie ont profondément renouvelé notre regard sur les animaux. De nombreuses espèces manifestent des émotions, des capacités d’apprentissage, des formes de coopération et des relations sociales complexes. Chez certains primates, mais aussi chez des éléphants, des corvidés ou des cétacés, on observe des comportements qui suggèrent des formes de conscience, d’empathie, de culture et de deuil.
À gauche : femelle macaque japonais gardant son bébé mort et probablement en deuil. À droite : comportement culturel de rodéo chez les macaques japonais. Cédric Sueur, Alexandre Bonnefoy, Fourni par l’auteur
Pourquoi, malgré ces connaissances, continuons-nous à exploiter les animaux à grande échelle ? Une partie de la réponse tient à notre héritage culturel. Les sociétés occidentales modernes se sont construites sur une séparation entre l’humain et le reste du vivant, associée à une hiérarchisation qui place l’homme au sommet.
Le concept de « spécisme », inventé par Richard Ryder en 1970, désigne cette discrimination fondée sur l’espèce. Il conduit à considérer que les intérêts des humains priment systématiquement sur ceux des autres êtres qui souffrent tout autant. Dans sa structure, ce mécanisme n’est pas sans analogie avec le racisme ou le sexisme : il repose sur une différence érigée en critère de domination.
Décoloniser notre rapport aux animaux, de Cédric Sueur, éditions Odile Jacob, 2026. Fourni par l’auteur
Le spécisme décrit cependant avant tout une attitude morale, un biais cognitif et éthique dans la manière dont nous évaluons les intérêts des différentes espèces. La notion de « colonisation animale », que je développe dans Décoloniser notre rapport aux animaux (Odile Jacob, 2026), cherche à aller plus loin en désignant les structures concrètes qui organisent et perpétuent cette domination.
Là où le spécisme interroge les représentations, la colonisation animale pointe les dispositifs institutionnels, économiques et culturels qui les rendent opératoires : les animaux sont appropriés, contrôlés, transformés en ressources économiques et symboliques. Le droit les protège partiellement en tant qu’êtres vivants sensibles, tout en les maintenant dans le régime des biens. L’économie en fait des marchandises et tend à invisibiliser les violences qui leur sont infligées. Ces dimensions se renforcent mutuellement et stabilisent un système de domination qui dépasse la seule question des représentations pour s’incarner dans des pratiques, des lois et des rapports de pouvoir.
D’autres ontologies du vivant
Cette manière de penser n’est pourtant pas universelle. De nombreuses sociétés non occidentales, comme les Achuar d’Amazonie, les aborigènes d’Australie ou les Japonais, envisagent les relations entre humains et non-humains autrement. Plutôt que de séparer radicalement les êtres, elles insistent sur les continuités, les interdépendances et les relations.
Les travaux de l’anthropologie, en particulier de Philippe Descola (les Lances du crépuscule, 1993) ou de Bruno Latour (Enquête sur les modes d’existence, 2012), ont ainsi montré l’existence de différentes « ontologies », c’est-à-dire des manières de définir et de se représenter ce qui existe et comment les êtres sont liés. Ces sociétés ou ethnies sont, par exemple, animistes et attribuent aux animaux une intériorité – autrement dit une vie intérieure faite d’intentions, d’émotions, de perceptions et de subjectivité propre, comparable à celle que nous reconnaissons aux humains – ou les considèrent comme des partenaires inscrits dans des réseaux de relations.
À Kuma Tsamé Totsi (Togo), des roussettes frugivores, protégées comme êtres tabous par le village, échappent à la chasse et forment d’importantes colonies, jouant un rôle clé dans la régénération forestière. Cédric Sueur, Fourni par l’auteur
Sans idéaliser ces perspectives, elles offrent des ressources pour sortir d’une vision strictement utilitariste du vivant. Elles invitent à penser une coexistence fondée non sur la domination, mais sur la réciprocité et l’attention aux interdépendances.
Transformer nos pratiques quotidiennes
Décoloniser notre rapport aux animaux suppose d’abord de transformer nos pratiques les plus ordinaires. L’alimentation constitue un levier central : réduire la consommation de produits animaux permet de limiter à la fois la souffrance animale et l’impact environnemental.
Au-delà, il s’agit de repenser la manière dont nous partageons les espaces. L’urbanisation a longtemps exclu les autres espèces. Une approche « zooinclusive » développée par la chercheuse Émilie Dardenne propose au contraire d’intégrer leurs besoins dans la conception des villes : favoriser la présence d’oiseaux, d’insectes ou de petits mammifères, aménager des continuités écologiques ou encore adapter les bâtiments pour accueillir d’autres formes de vie.
Cette approche trouve déjà des traductions concrètes. Certaines villes européennes, comme Vienne, Bruxelles ou Londres, ont ainsi intégré des nichoirs et des gîtes à chauves-souris dans les façades de bâtiments rénovés. D’autres ont aménagé des passages fauniques sous les axes routiers pour permettre les déplacements des mammifères sauvages, ou encore maintenu des toitures végétalisées favorisant la biodiversité des pollinisateurs. À Singapour, la politique des « corridors verts » cherche explicitement à reconnecter des fragments d’habitats naturels au sein du tissu urbain. En France, la trame verte et bleue, inscrite dans la législation depuis le Grenelle de l’environnement, constitue une tentative institutionnelle d’intégrer ces continuités écologiques à l’échelle du territoire.
Ces transformations ne relèvent pas seulement de choix individuels, mais aussi de décisions collectives en matière d’aménagement et de politiques publiques.
Repenser la conservation de la faune sauvage
La protection des animaux sauvages s’inscrit souvent dans une logique de gestion : il s’agit de réguler, contrôler, parfois éliminer certaines populations jugées problématiques. Les carnivores sont particulièrement visés. En France, le loup cristallise les tensions entre éleveurs et défenseurs de la nature depuis son retour naturel dans les Alpes dans les années 1990. En Afrique, le lion fait l’objet de conflits similaires : lorsqu’il s’attaque au bétail des communautés rurales, il est perçu comme une menace directe pour la survie économique des familles, ce qui conduit à des empoisonnements ou des abattages, parfois tolérés voire encouragés par les autorités locales.
Les grands herbivores ne sont pas épargnés : en Afrique australe et orientale, les éléphants, dont les populations se sont reconstituées dans certaines zones protégées, provoquent des destructions massives de cultures, écrasent des habitations, tuent des êtres humains. Ces conflits humains-éléphants poussent des communautés à réclamer des abattages, voire à tolérer le braconnage comme seule réponse à une menace perçue comme existentielle. Le braconnage lui-même, souvent présenté uniquement sous l’angle criminel, s’alimente parfois de cette exaspération locale, même s’il est également structuré par des réseaux internationaux aux enjeux économiques considérables. Cette approche gestionnaire prolonge, sous d’autres formes, une relation de domination du vivant, ce que l’historien Guillaume Blanc nomme un nouveau colonialisme vert : des décisions prises depuis l’extérieur, au nom de la nature, sans tenir compte des réalités vécues par les populations locales.
Au Malawi, un éléphant traverse une réserve gérée par une ONG controversée, symbole des tensions entre conservation, accaparement des terres et droits des populations locales face aux modèles imposés étrangers. Cédric Sueur, Fourni par l’auteur
Décoloniser la conservation consiste à reconnaître davantage l’autonomie des animaux, leur « souveraineté sauvage », comme la définissent les philosophes Donaldson et Kymlicka, et à respecter leurs habitats. Cela implique de passer d’une logique de contrôle à une logique de coexistence, en cherchant des formes de médiation entre les intérêts humains et non humains. Des initiatives de terrain, comme le projet Cibel dans la forêt du bassin du Congo, montrent qu’il est possible de concilier activités humaines et présence de la faune sauvage, à condition d’accepter la complexité de ces relations.
Décoloniser les sciences
La science elle-même n’échappe pas à ces enjeux. Les animaux y sont souvent considérés comme des objets d’étude ou des modèles expérimentaux. Intégrer leur « agentivité animale », c’est-à-dire leur capacité à agir et à influencer les situations, conduit à repenser les protocoles de recherche vers une coopération humain – non humain plutôt que vers des sacrifices animaux.
En primatologie, par exemple, certaines approches cherchent à limiter les contraintes imposées aux animaux et à mieux prendre en compte leurs comportements spontanés. Lancée par l’éthologue Tetsuro Matsuzawa, cette approche d’observation participante est une collaboration humanimale. Plus largement, le développement de méthodes alternatives permet de réduire le recours à l’expérimentation animale. Décoloniser les sciences ne signifie pas renoncer à la recherche, mais en interroger les présupposés et les finalités des utilisations animales.
Expérience comportementale de terrain à Shodoshima, au Japon, où un chercheur collabore avec un macaque dans une tâche cognitive, sans enfermement, contrainte ni stress pour l’animal. Cédric Sueur, Fourni par l’auteur
L’expérimentation animale constitue un point de tension majeur. Si certains travaux sont justifiés par des enjeux de santé, d’autres apparaissent plus discutables au regard des souffrances infligées. Des outils comme le « cube de Bateson » proposent d’évaluer les recherches en fonction de leurs bénéfices attendus, de leur probabilité de réussite et des dommages causés aux animaux. Mais dans la pratique, la réflexion éthique reste souvent limitée. Décoloniser l’expérimentation suppose de renforcer ces exigences, de développer des alternatives et de questionner la légitimité même de certaines recherches.
Vers une coexistence
Décoloniser notre rapport aux animaux, c’est finalement transformer en profondeur notre manière d’habiter le monde. Il ne s’agit pas de supprimer toute relation avec eux, mais de sortir d’une logique de domination pour aller vers des formes de coexistence et de coopération, ce qui est nommé le « capital animal ». Les animaux ne sont plus de simples matériaux pour manger ou se vêtir, mais sont des aides sociales, des passeurs culturels (ils nous transmettent des informations sur notre environnement) et des managers écosystémiques (ils nous aident à gérer nos écosystèmes).
Ce changement est à la fois éthique, écologique et politique. Il implique de reconnaître que les humains ne sont pas extérieurs au vivant, mais en font partie. Dans un contexte de crises multiples, repenser nos relations avec les autres espèces apparaît non comme un luxe, mais comme une nécessité pour la survie de tous dont l’humanité.
Cédric Sueur est l’auteur de l’ouvrage « Décoloniser notre rapport aux animaux » publié aux Editions Odile Jacob dont l’article fait mention.
Source: The Conversation – France in French (2) – By Agnès Cousin, Astronome adjoint, Responsable scientifique de SuperCam, IRAP, Centre national d’études spatiales (CNES); Université de Toulouse
Le 10 mai 2025, 1 500 jours martiens après s’être posé sur le cratère Jezero, Perseverance se prend en photo. On peut voir la poussière qui s’est accumulée sur le rover durant tout ce temps.Nasa/JPL-Caltech/MSSS
Depuis cinq ans, le rover Perseverance nous en apprend plus sur la géologie de Mars, et ainsi sur les anciennes conditions de la Planète rouge. Aurait-elle pu abriter la vie par le passé ? Les études se succèdent, la dernière en date venant de sortir en mars 2026. On dresse le bilan des découvertes permises par SuperCam, l’un des instruments principaux du rover.
Le 18 février 2026, nous avons fêté les cinq ans de l’atterrissage du rover Perseverance sur Mars, dans le cratère de Jezero. À la suite du succès du précédent rover Curiosity, qui explore toujours la Planète rouge depuis son atterrissage en août 2012, la Nasa a lancé la mission « Mars 2020 ». Après plus de six mois de voyage, Perseverance se pose sur Mars avec en son bord de nombreux instruments, dont le nôtre, appelé SuperCam. C’est le début d’une nouvelle ère d’exploration martienne : la recherche de potentielles traces de vie ancienne et la collecte d’échantillons qui devraient un jour revenir sur Terre !
Bien sûr, nous nous intéressons aussi à la géologie et au climat de Mars. Le cratère Jezero n’a pas été sélectionné par hasard comme site d’atterrissage : les observations orbitales y montrent un ancien delta de rivière très bien préservé, ainsi que des signatures de carbonates, des minéraux qui se forment lorsque des roches interagissent avec de l’eau et du CO₂. Ce sont donc de précieux témoins des conditions qui régnaient lors de leur apparition sur Mars. Ces observations orbitales démontrent donc que l’eau a joué un rôle important dans l’histoire de ce site.
Le delta qu’explore Perseverance, vue aérienne. Nasa/JPL/Université d’Arizona
Sur Terre, les environnements des lacs et des deltas sont aussi les meilleurs pour piéger et préserver des molécules organiques, qui se retrouvent mélangées aux sédiments très fins transportés par la rivière, puis enfouies dans le delta où ils se déposent. Le site de Jezero fournit donc l’enregistrement d’un environnement passé propice à la conservation de molécules organiques et est, de ce fait, un bon endroit pour chercher des conditions favorables à l’émergence de la vie.
Durant les trois premiers mois de la mission, chacun des instruments et des sous-systèmes du rover ont pu se mettre en marche et commencer à fournir de précieuses informations. En particulier, cette période est marquée par le premier vol historique du drone Ingenuity, le 19 avril 2021. Ce démonstrateur technologique a prouvé la faisabilité de vols motorisés dans l’atmosphère ténue de Mars, ouvrant alors une nouvelle dimension de l’exploration martienne.
Explorer le fond d’un ancien lac martien
Parmi les sept instruments embarqués par Perseverance, on trouve SuperCam, qui constitue la « tête » du rover. Il a été développé en collaboration entre la France et les États-Unis. Cet instrument combine plusieurs spectromètres, des appareils capables d’analyser la composition chimique et minéralogique de la surface de Mars. En plus des spectromètres, SuperCam embarque une caméra, afin de documenter le contexte géologique des lieux où sont réalisées les analyses, et un microphone, qui permet d’étudier l’atmosphère de Mars. En France, nous sommes 13 instituts impliqués dans cette aventure martienne.
L’instrument SuperCam (ici lors de sa fabrication) a été construit par un consortium franco-américain mené en France par l’Institut de recherche en astrophysique et planétologie et le Cnes, et aux États-Unis par le LANL et le JPL. À ce jour, il a effectué plus de 650 000 tirs laser pour analyser plus de 1 300 roches, pris de nombreux spectres de lumière infrarouge, des photos et enregistré les sons de Mars. Bruno Dubois/OMP, Fourni par l’auteur
Très rapidement après l’atterrissage, SuperCam a acquis un panorama d’une butte, nommée Kodiak, qui nous a permis de confirmer la nature du delta dans Jezero, à savoir qu’il est formé de sédiments charriés par une rivière se jetant dans un lac. Un tel système permet de reconstruire l’histoire passée de l’eau dans cette région. Ces observations nous ont montré que le niveau du lac fluctuait, mais qu’il s’agissait d’un lac fermé la plupart du temps, c’est-à-dire sans cours d’eau qui en ressort, contrairement à ce que les observations orbitales avaient suggéré auparavant.
Quinze mois plus tard, Perseverance est arrivé au pied du delta dont l’exploration a confirmé ces premières observations et a permis de mieux comprendre l’évolution du lac au cours du temps. Plus récemment, sur la bordure du cratère, SuperCam a découvert du quartz pour la première fois de manière certaine sur Mars ! Le quartz n’est pas rare lorsqu’il est observé dans une roche magmatique, du granite par exemple. Mais dans le cas de cette observation, le contexte est très différent, sans relation avec du volcanisme. Cette roche est probablement liée à un impact de météorite qui aurait facilité la circulation et la remontée d’eau chaude en fracturant la roche, créant un système hydrothermal et des conditions propices à la formation de quartz.
Entre la première photographie de Kodiak et l’arrivée au delta, la première campagne scientifique a débuté en juin 2021 en explorant deux types d’environnements géologiques du fond du cratère. Perseverance a d’abord trouvé des roches volcaniques. Pour se repérer sur Mars, les géologues donnent des noms informels aux zones étudiées. Ainsi la première formation de roches volcaniques a été appelée « Màaz ». Il s’agit d’une succession de coulées de lave à la surface. La seconde (appelée « Seítah ») correspond à un cumulât d’olivines, des roches constituées de gros grains obtenus en cristallisant un minéral, l’olivine, en profondeur sous la surface. Ces roches ont été très peu altérées par l’eau.
Les modèles suggèrent que ces deux environnements géologiques ne proviennent pas de la même source magmatique, mais de deux volcans différents ou de deux chambres magmatiques différentes sous un même volcan. Des échantillons de ces roches, s’ils reviennent sur Terre, nous permettront de dater ces terrains et de mieux comprendre leur mise en place par rapport à la formation du lac présent sur le site.
Mars, anciennement habitable, voire habitée ?
C’est en bordure de cet ancien lac que Perseverance a détecté, en 2024, les carbonates dont nous parlions plus haut, en grande quantité, confirmant les détections orbitales. Il est important de déterminer leur abondance in situ, car ces sédiments ont pu piéger le carbone de l’atmosphère, qui devait être plus épaisse dans le passé. L’analyse minutieuse de ces roches nous a permis de comprendre leur processus de formation : il s’agirait de roches magmatiques ayant longuement interagi avec l’eau du lac et du système hydrothermal, enrichie par le CO2 dissout dans l’eau.
La prise en compte de ce processus dans le cycle du carbone martien donne une nouvelle perspective au devenir du carbone et de l’habitabilité passée de cette planète. En effet, la communauté recherchait jusque-là des carbonates similaires aux calcaires des anciens fonds océaniques terrestres. Or, comme nous l’avons vu, les observations de Perseverance montrent qu’un autre processus de formation des carbonates a eu lieu sur Mars. Il faut donc le prendre en compte pour étudier le cycle du carbone martien et son influence sur les conditions climatiques passées, lesquelles déterminent combien de temps l’eau a pu rester liquide à la surface de Mars, qui en est dépourvue aujourd’hui. La présence d’eau étant nécessaire pour rendre la planète habitable, c’est ce qui rend cette découverte importante.
C’est d’ailleurs dans le même secteur, dans la vallée de l’ancienne rivière se déversant dans le lac, que Perseverance a détecté des traces potentielles de biosignatures. La présence simultanée de matière organique et de phosphate et sulfure de fer rappelle des réactions chimiques qui, sur Terre, sont parfois utilisées par les microorganismes dans des processus biologiques. Seule l’analyse sur Terre de ces échantillons pourra trancher sur l’origine de ces composés et répondre à la question de l’habitabilité passée de Mars.
Une étude récente, menée grâce au radar à bord du rover, a pu mettre en évidence la présence d’un environnement fluvial enfoui sous le delta actuel, démontrant que de l’eau circulait déjà il y a plus de 3,7 milliards d’années. Ces observations sont particulièrement importantes pour l’habitabilité passée de la planète et les recherches de biosignatures anciennes.
Écouter l’atmosphère sur une autre planète
Perseverance, depuis cinq ans, a aussi scruté l’atmosphère martienne. SuperCam et un autre instrument, MastCam-Z ont observé une aurore diffuse, comme une aurore boréale, mais qui ne se limite pas aux pôles, pour la première fois depuis la surface martienne. Mais c’est le microphone de SuperCam qui s’est nous a permis de sonder l’atmosphère de la planète, en dressant pour la première fois le paysage sonore martien. Ces écoutes permettent de déduire des propriétés importantes de l’atmosphère comme la vitesse du son qui varie selon la nature de l’atmosphère. Les bruits enregistrés sont aussi sensibles à la turbulence atmosphérique, ce qui permet d’étudier ces petits flux d’air proche de la surface.
Toujours grâce au microphone, nous avons récemment pu mettre en évidence des décharges électriques, de sortes de petits éclairs qui apparaissent dans des tourbillons qui soulèvent la poussière dans l’atmosphère. Cette détection permet d’apporter de nouvelles informations, car la dynamique des poussières dans l’atmosphère influe sur sa température et donc sur le climat. Ces petits éclairs pourraient aussi jouer un rôle insoupçonné dans la chimie atmosphérique et à la surface, par exemple en interagissant avec les composants chlorés pour former de nouvelles molécules, ou en cassant certaines molécules déjà existantes.
Après 43 km parcourus, et près de 1 500 roches martiennes analysées par SuperCam, Perseverance est désormais sorti du cratère de Jezero et explore sa bordure. Cette région expose des terrains vieux de plus de 3,8 milliards d’années, c’est-à-dire antérieurs à l’impact qui a formé le cratère, voire même à la formation du grand bassin régional Isidis dans lequel il se trouve. Ces roches sont les plus anciennes jamais étudiées in situ par un rover martien et offrent donc une fenêtre unique sur les premiers millions d’années de l’histoire de Mars. Les analyses en cours devraient révéler les conditions environnementales qui régnaient sur la planète rouge à cette époque reculée. Jezero tient bien ses promesses en termes de richesses des terrains, et de nombreuses découvertes nous attendent encore !
Agnès Cousin a reçu des financements du CNES, pour le projet Mars2020/SuperCam. Son laboratoire de recherche (IRAP) a aussi pour tutelle l’université de Toulouse et le CNES.
Olivier Gasnault a reçu des financements du CNES pour le projet Mars2020/SuperCam ; il est salarié du CNRS. Son laboratoire de recherche (IRAP) a aussi pour tutelle l’université de Toulouse.
Magali Bouyssou et Valérie Mousset ne travaillent pas, ne conseillent pas, ne possèdent pas de parts, ne reçoivent pas de fonds d’une organisation qui pourrait tirer profit de cet article, et n’ont déclaré aucune autre affiliation que leur poste universitaire.
