The Science Of Fever Dreams: When We’re Sick, Our Dreams Can Get Extra Weird – What’s That All About?

 

Dreams are usually pretty weird, but there are sometime when they become utterly bonkers. Image credit: Jayesh/ayagizcastrosogarcia/Halyna Lakatosh/vi73777/iStock; modified by IFLScience

D

reams are utterly bonkers at the best of times, yet when we’re feeling a little off-color we can get a glimpse of how deep the rabbit hole really goes. 

Research has shown that fever dreams tend to be more vivid, more emotionally intense, and considerably weirder than regular visits to the dreamscape – so how do we even begin to make sense of the madness? 

"In fever, the brain is not functioning properly, which means that if you are sleeping, then of course, the content [of dreams] is more bizarre."

Professor Michael Schredl

Boggling the mind

Scientific interest in feverish delusions began well before the modern age and has kept psychologists and neuroscientists busy for more than a century. 

Back in 1892, the esteemed Scottish doctor and father of modern pathology, Joseph Coats, contributed an article to the Glasgow Medical Journal in which he recounted an “attack of typhus fever” that he had suffered 26 years previously. 

As his temperature soared, Coats succumbed to “days of delirium”, during which he experienced visions of his sister’s death that were so lifelike that he remained convinced that she had really died even the next day.

What’s particularly striking about all this is that Coats’ fantasies occurred while he was fully awake. Given the absurdity of this conscious malfunction, one can hardly imagine the deceptions the feverish mind is capable of while dreaming.

One scientist who has imagined just that is Professor Michael Schredl, Head of Research at the Sleep Laboratory at the German Central Institute of Mental Health at Heidelberg University. 

“In fever, the brain is not functioning properly, which means that if you are sleeping, then of course, the content [of dreams] is more bizarre,” he tells IFLScience. 

Fever dreams feature a lot more "spatial distortions" than normal dreams.

Image credit: JohnRFirst/shutterstock.com

Having conducted the two largest existing scientific surveys of fever dreams, Schredl discovered that extreme eccentricity is the single biggest attribute separating these ailing apparitions from regular dreams.

In the first of these studies, he and his colleagues found that fever dreams were on average 58 percent more bizarre than control dreams, and that this sense of wackiness was most commonly accounted for by “spatial distortions”. Specific examples of this proportional preposterousness included moving walls, gigantic insects, and “creatures with over-sized arms and legs.”

Seeking to find some sort of explanation for this increase in absurdity, the study authors state that “as waking cognitive processes are affected also by fever, we speculate that the bizarreness and distortions of fever dreams is a result of a brain that doesn’t work properly at high temperatures.” 

We don't know whether they actually had a hot body and this stimulus was directly incorporated into the dream, or whether they simply dreamed about having a hot body.

Professor Michael Schredl

This assertion is backed up by several studies that have indicated that high body temperature – or hyperthermia – significantly interferes with brain connectivity patterns and impairs basic cognition.

For instance, it has been shown that having a core temperature of 38.8°C (101.8°F) compared to that of 37.2°C (98.96°F) can impair memory.  Being exposed to temperatures of 50°C (122°F) for approximately 1 hour messes with signaling in the temporal, frontal, and occipital lobes. This, in turn, could have a negative impact on cognitive functions such as attention, memory, and information processing. 

To date, however, no one has ever tracked the neural activity of feverish participants while dreaming, so it’s impossible to say for sure how the febrile brain produces these maddening visions. 

Acknowledging that such a study would be extremely difficult to conduct, Schredl says that if only we could get a bunch of sleeping sick people into an MRI scanner, we might just get to the bottom of the enigma.

“That would be really great,” he says. “What would be especially interesting would be to see the default mode network – which is for daydreaming and mind wandering, and also possibly for dreaming – and whether this has changed [during a fever dream].”

Turning up the heat

Given the deleterious and potentially even dangerous effects of hyperthermia, it seems slightly odd that our bodies would have evolved to overheat as part of their immune response to infectious pathogens. 

As it happens, scientists still don’t entirely understand the purpose of fevers, although the most widely accepted theory is that raising the internal temperature inhibits the spread and viability of invading microbes. There’s also some evidence to suggest that lymphocytes and other components of the immune system actually work better at slightly higher temperatures.

Heat is a surprisingly common theme of fever dreams, although it is difficult to say if this is a direct result of the fever itself.

Image credit: Lukas Gojda/shutterstock.com

Despite the gaps in our comprehension, one thing we do know is that fever is an incredibly ancient, shared feature among life forms across the planet, with the typical hyperthermic response to infection having first evolved around 600 million years ago. 

When a trait has been around for that long and inherited by so many different species, you can be pretty sure it does more good than harm and carries a significant survival advantage.

Funnily enough, temperature also pops up as a common theme in fever dreams. In the second of Schredl’s studies, heat-related topics featured in 10 percent of fever dreams compared to just 2.22 percent of control dreams. 

And if you are very ill, I think most people don't expect to experience positive emotions, but more the negative emotions. That’s why fever dreams are also more negatively toned, because it's a stressful situation.

Professor Michael Schredl

To give an idea of how the subject manifests in the infected slumberer’s mind, one study participant described a nightmare in which “the air is so hot that breathing hurts [...]. I see a red glow in the corner of my eyes and I turn around to see an enormous lava ball coming down the mountain heading toward the city and me.”

“I am running faster and faster, the air grows hotter and hotter, the lava ball is changing directions in pursuing me and does not affect the houses,” continues the account. “It seems the lava ball has the task of getting me.”

It’s thus very tempting to conclude that the experience of having a high temperature triggers these heat-related dreams, although Schredl and his colleagues are keen to stress that there are currently no studies testing whether real-world heat stimuli are superimposed into sleepers’ dreams in the same way that sounds and other environmental elements are. 

“We don't know whether they actually had a hot body and this stimulus was directly incorporated into the dream, or whether they simply dreamed about having a hot body,” says Schredl.

The continuity hypothesis

It goes without saying that dreams are still something of a mystery to us, but most scientists do at least subscribe to the so-called continuity hypothesis, which states that dreams tend to reflect our waking-life experiences, emotions, and thoughts – albeit sometimes in strange and abstract ways. 

“For instance, if you have stress, then your dreams are more stressful, even if you don't dream about the actual stressor,” explains Schredl.

“And if you are very ill, I think most people don't expect to experience positive emotions, but more the negative emotions. That’s why fever dreams are also more negatively toned, because it's a stressful situation,” he adds. 

Sure enough, almost 95 percent of fever dreams reported by Schredl’s initial study participants were accompanied by negative emotions. A high proportion even included the dreamer being threatened by everything from dogs, stones, and insects to terrorists and “big spheres”.

Fever dreams typically include fewer characters, a possible reflection of the mental state's isolation.

Image credit: Dmytro Lytvak 3D/shutterstock.com

Sticking with the continuity hypothesis, it suddenly becomes less surprising to learn that themes related to health and illness tend to occur more frequently in fever dreams than regular dreams. 

Fever-tinged visions also typically include fewer characters and interactions than your typical dream, which may reflect the experience of social isolation that most people impose on themselves when ill.

What’s less clear, however, is whether the continuity hypothesis can account for the fact that fever dreams tend to be so much more emotionally intense than everyday dreams. 

Even more intriguingly, Schredl’s research revealed that around 40 percent of fever dreams are lucid dreams, in which the dreamer is fully aware that they are dreaming. 

Unable to explain the remarkable lucidity of these diseased hallucinations, the study authors cautiously hold their tongues, allowing themselves only to remark that “this supports the notion that fever has an effect on the cognitive processes during sleep.”

In some ways, then, our understanding of fever dreams hasn’t progressed all that much since Dr Coats described them as “imperfection[s] in the completeness of sleep.” Fortunately for him (and his sister), these unsettling apparitions can’t do us any harm, no matter how real they might seem.

Why Too Much Cannabis Can Flip an Anxiety Switch in the Brain

 

A newly identified neural pathway may help explain why cannabinoids can amplify fear under stressful conditions. Credit: Shutterstock

For the first time, researchers have identified brain cells that help drive anxiety in mice exposed to cannabinoids.

Confronted with a scent derived from fox urine, mice given a synthetic cannabinoid froze more often and spent less time investigating the odor than mice given a placebo. The drug belongs to the same class of substances as THC, the main psychoactive ingredient in cannabis. Following the animals’ reactions gave Northwestern University researchers a way to investigate how cannabinoids can heighten anxiety when the surroundings turn threatening.

The researchers traced the response to a small group of brain cells called somatostatin neurons in the central amygdala, a region that processes fear and stress. Their study, published October 2 in Nature Communications, identified these cells as contributors to the anxious behavior, opening a path to understanding how the drug and a stressful encounter work together.

Cannabinoids weaken the brain’s anxiety brake

To connect the animals’ behavior with activity inside their brains, the team tested several doses of the synthetic cannabinoid while tracking how long the mice stayed near the predator odor and whether they froze or fled. A small microscope implanted in the animals’ brains recorded neural activity during those encounters, allowing the researchers to watch the cells as the mice responded.

Study authors Drs. Sachin Patel (left) and Farhana Yasmin looking at brain recordings from central amygdala neurons. Credit: Gr8y Productions

Experiments on brain tissue let the scientists examine how the drug altered communication between neurons. Somatostatin cells normally receive signals that restrain their activity, effectively putting a brake on them. Senior author Dr. Sachin Patel, chair of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine, explained what happened when that restraint weakened: “Higher doses of cannabinoids and environmental stress worked together to synergistically release the ‘brake’ on the central amygdala, which in turn drove excessive anxiety.”

Genetically silencing the somatostatin neurons reduced the drug-treated mice’s avoidance of the predator scent, providing evidence that these cells helped drive the response. “The results of this study could explain why a good trip can turn bad pretty quickly if people consume too much cannabis or the situation they are in turns stressful or scary,” Patel said.

Study senior author Dr. Sachin Patel and colleagues in his lab at Northwestern University Feinberg School of Medicine in Chicago. Credit: Gr8y Productions

A possible anxiety target beyond cannabis

Cannabis use in the United States has increased in recent years, along with emergency department visits related to its adverse effects. Earlier research has also linked cannabis use with a greater long-term risk of anxiety, while anxiety and mood disorders have been rising globally.

“Understanding how cannabis affects brain function to generate its psychoactive effects could ultimately reveal new ways to counteract negative consequences should they arise in some people,” Patel said. The current experiments used a synthetic cannabinoid in mice, leaving researchers to establish whether the same cellular mechanism explains anxiety in people who use cannabis.

Study authors Drs. Sachin Patel and Saptarnab Naskar examine a heat map showing where the mice moved when exploring the threatening odor. Credit: Gr8y Productions

“Suppressing the activity of somatostatin neurons in the central amygdala could represent a final pathway for reducing anxiety symptoms, not just in the context of cannabis side effects,” Patel explained. Quieting those cells made mice less avoidant of the fox-derived scent. Whether that change in their response to a predator’s odor can point toward relief for human anxiety remains to be tested.

Reference: “Cannabinoid modulation of central amygdala population dynamics during threat investigation” by Farhana Yasmin, Saptarnab Naskar, Danyal Zaidi, Isaac Kandil, Michelle Kwon, Luis E. Rosas-Vidal and Sachin Patel, 2 October 2026, Nature Communications.
DOI: 10.1038/s41467-026-77957-4

Supported by the National Institutes of Health (grants MH100785 and K08 MH126166) and the Brain & Behavior Research Foundation’s Young Investigator Awards.

https://scitechdaily.com/why-too-much-cannabis-can-flip-an-anxiety-switch-in-the-brain/

Defense News: Wearable counter‑drone tech enters frontline service across US, Ukraine and IDF units

Wearable counter‑drone tech enters frontline service across US, Ukraine and IDF units

The wearable counter‑drone kit, deployed by Ukrainian troops and IDF forces and integrated into US Army exercises under EUCOM as top US commander warns troops will be ‘hunted’ by autonomous systems

By Anna Aharonheim, Jerusalem Post, October 6, 2026

https://www.jpost.com/defense-and-tech/article-910744

Skylock's Wearable Kit counter-drone solution (photo credit: Autonomous Guard)

Autonomous Guard’s Wearable Kit counter-drone system has been used by Ukrainian troops and undergone operational testing with the US Army in Europe and maneuvering forces in Gaza by the IDF, Defense & Tech by The Jerusalem Post.

The system is a compact RF detection and jamming device that can detect hostile drones up to two kilometers away, providing early warning for units on the move. Its jamming capability extends to three kilometers, enabling forces to disrupt drone operations before the aircraft reaches visual range. It provides directional alerts, allowing troops to take cover or reposition before a drone identifies their location.

When interception is required, SkyLock’s RF guns, which are handheld jamming devices that do not require precise aiming, can be used to neutralize incoming drones. The company says this combination of early warning and rapid response is designed to reduce exposure during reconnaissance and targeting cycles.

SkyLock’s Sky Spotter Pro, a wearable system used at higher command levels such as battalion forward command posts, allows operators to preload friendly drone data during mission planning, reducing false alarms and improving identification accuracy. This helps troops distinguish between hostile and friendly platforms.

The Wearable kit seen on troops in Ukraine, helps warfighters detect hostile drones (credit: Courtesy)

Sky Spotter Pro can detect drones at ranges of up to five kilometers, or three kilometers in complex terrain. It can also identify the drone operator's location, enabling units to direct fire and close the operational loop more quickly. Additionally, SkyLock provides a wearable module that identifies friendly drones to prevent accidental interception.

Wearable counter‑UAS systems have seen widespread use in the Russia‑Ukraine conflict, where both sides rely heavily on small drones for reconnaissance and targeting. According to Autonomous Guard, interest in wearable systems is increasing among militaries, police forces, border units, and prison services.

The system has been sold to hundreds of US Army operations in the US European Command (EUCOM) and other combatant commands worldwide, including Ukraine’s Armed Forces. In July, EUCOM tested the system during a large-scale exercise in Germany. The Defense Post reported that participants included the 2nd Cavalry Regiment, a 4,800-person agile unit stationed at the Rose Barracks in Vilseck that specializes in a full spectrum of operations in support of EUCOM and the NATO alliance.

As AI‑enabled drones are becoming more resilient to jamming, defense officials say wearable counter‑UAS systems are likely to play a growing role in infantry protection by providing mobile coverage in environments where aerial threats are persistent, adaptive, and increasingly autonomous.

Russian drone flies in the sky over the city after a Russian drone strike, amid Russia's attack on Ukraine, in Kyiv, Ukraine November 2, 2024. (credit: REUTERS/GLEB GARANICH)

‘Hunted by autonomous systems’

In a keynote address at the Air, Space and Cyber Conference in Maryland in September, chairman of the Joint Chiefs of Staff Gen. Dan Caine said US forces should assume they will be “hunted by autonomous systems, jammed across the spectrum, and tracked in real time,” citing lessons from the Russia‑Ukraine war. 

According to a report in DefenseScoop, Caine said FPV drones equipped with AI‑enabled computer vision can now continue toward targets even when GPS signals or control links are disrupted.  

“We have to transition the joint force to be prepared to fight and win our future wars by generating and delivering lethality at scale with an agile, optimized, high-low mix of combat capabilities to give the young members of the 2.8 million-member all-volunteer joint force the tools that they need before they need them,” Caine said.

Referring to the Russia-Ukraine war, Caine said that the life expectancy of a new Russian recruit on the frontline in certain areas was as little as 20-30 minutes.

“Think about that. This is what happens when low-cost precision [weaponry] is fielded fast, adapted quickly, and scaled across the battlefield. The price of lethal exchange is decreasing day over day,” he said.

“In the future fight, advantage will go to the side that can see first, who can understand first, decide first, and act first, and along the way be a learning organization,” Caine said, adding that “AI is here now and it’s already changing the way militaries see, sense, decide and act.”

Wearable solution

Note that Skylock is an Israeli defense technology company based in the town of Kfar Saba in Israel 

THIS PAGE WAS POSTED BY SPUTNIK ONE OF THE SPUTNIKS ORBIT BLOGhttps://disqus.com/HOME/FORUM/THESPUTNIKSORBIT-BLOGSPOT-COM

Radio galaxy from 12.5 billion years ago may be most powerful ever found

VLASS image of TXS 2354+015. The red cross marks the position of the optical source. Credit: arXiv (2026). DOI: 10.48550/arxiv.2609.28632

Astronomers have confirmed a powerful radio galaxy from nearly 12.5 billion years ago. The source, TXS 2354+015, was originally identified as a high-redshift candidate from its characteristic drop in optical light, and follow-up spectroscopy placed it at a redshift of 4.946. Their paper was posted to the arXiv preprint server

Radio-loud AGNs

When material falls onto a galaxy's central supermassive black hole, the resulting accretion activity can power an active galactic nucleus (AGN) and launch powerful relativistic jets of plasma, producing large amounts of radio waves. Such a galaxy is called a radio-loud active galactic nucleus (RLAGN). The energy that the jets carry can influence star formation in the galaxy and heat its surrounding gas.

This "AGN feedback" is incorporated in simulations to correctly predict the number of galaxies in the universe. Such powerful galaxies in the early universe—called high-z RLAGNs—tend to mark the locations of the most massive, earliest-forming galaxies and galaxy clusters.

However, the central black hole and surrounding regions of most powerful early-universe RLAGNs are hidden by a bubble of dusty gas, with only the radio jet able to escape and be seen directly. In particular, a 2024 study suggests as many as 90% of these sources at redshifts greater than 3.5 might be hidden in the ultraviolet and optical bands. Because they are obscured, they are difficult to find and confirm spectroscopically.

Optical cutouts in the five Subaru HSC SSP survey bands. The white circle marks the position of the candidate HzRG. Right plot: AB magnitudes in the five HSC-SSP bands. Credit: arXiv (2026). DOI: 10.48550/arxiv.2609.28632

Missing radio galaxies

The dominant approach to hunting radio sources, which identifies unusually steep spectra, appears to miss a large portion of the true population. To work around this, astronomers instead combined deep optical imaging with radio catalogs, searching for galaxies whose light showed the telltale "dropout" signature of extreme distance. This is known as the Lyman-break technique: Intervening clouds of neutral hydrogen absorb ultraviolet light, causing the galaxy's observed optical spectrum to drop off abruptly at these high redshifts.

In this work, the team led by Barbara Balmaverde of the INAF Astrophysical Observatory of Turin combined deep optical imaging from Subaru's Hyper Suprime-Cam Subaru Strategic Program survey with radio catalogs such as TGSS at 150 MHz and VLASS at 3 GHz to find radio sources whose optical counterparts show the characteristic "dropout" feature within the redshift range of 4.5 to 5.3, when the universe was 1.1 billion to 1.3 billion years old.

In their search, they found an interesting candidate, TXS 2354+015, whose optical spectrum showed a prominent Lyman-alpha emission line. They verified the redshift using a second, fainter emission line. Based on the emission line position, the team confirmed the redshift at 4.946, when the universe was less than 1.2 billion years old. This makes it the second-most-distant radio galaxy ever found.

They also checked whether this was a chance alignment. The precise positional match between optical and radio data, the extremely rare radio brightness and the expected ratio between the radio and optical emission all supported the conclusion that this is a genuine radio source with an optical counterpart.

The most powerful of all

When researchers calculated its intrinsic radio power, TXS 2354+015 turned out to be more powerful than any other known high-redshift radio galaxy in the existing literature. Its estimated radio power at 500 MHz exceeds the previous record-holder from a 2008 census. "TXS 2354+015, thus, appears to be the most powerful radio galaxy known to date," the team writes in the paper.

Researchers also estimated a possible host galaxy mass of around 2 trillion solar masses. This number makes it one of the brightest galaxies known. "This estimate is clearly plagued by several large uncertainties, in particular by the age of the stellar population," the team notes.

Researchers found that TXS 2354+015 does not meet the usual ultra-steep-spectrum selection criteria. Its discovery through the optical dropout method supports the idea that the standard radio selection technique is incomplete, likely missing a meaningful fraction of the true obscured radio galaxy population in the early universe.

https://phys.org/news/2026-10-radio-galaxy-billion-years-powerful.html

An Alien Civilization Lived on Mars. But a Nuclear Disaster Wiped It Out, a Controversial Theory Claims.

 https://www.popularmechanics.com/science/a73939479/mars-aliens-nuclear-theory/

So why haven’t we seen evidence of it?

• John Brandenburg—a plasma physicist at an aerospace development company—argues that there was an alien civilization on Mars.
• He cites data from NASA’s Curiosity rover, claiming that xenon levels on the Red Planet indicate a nuclear disaster wiped the population out.
• Brandenburg’s theory poses striking questions in the broader search for extra terrestrial life; namely: How would we know if another civilization already came and went?

The aliens were next door, and somebody killed them. That’s the story plasma physicist John Brandenburg, PhD, tells about Mars. His theory suggests that a civilization built monuments on our neighboring planet before nuclear explosions wiped it out. He also argues that humanity must investigate—because we could face the same danger. 

In his 2014 Journal of Cosmology paper, Brandenburg presents Martian chemistry and supposed ruins as evidence of a planetary massacre. Both the journal’s editorial standards and Brandenburg’s theory itself have drawn criticism from other scientists. But the decisive question is whether his proposed explanation fits the measurements he provides. Dismissing the alleged attack leaves another question worth asking. If a civilization had flourished somewhere in our solar system and disappeared billions of years before we started looking, what would remain? Could we send a rover across its former home without ever knowing what had been there?

 Brandenburg—who did not respond to requests for an interview—argues that we’ve already found evidence of nuclear explosions in Mars’s atmosphere, focusing particularly on the Red Planet’s xenon measurements. Xenon comes in several forms, called isotopes, each with different numbers of neutrons in their atoms. Timothy Swindle, PhD—a professor emeritus and director emeritus at the University of Arizona’s Lunar and Planetary Laboratory—explains that radioactive decay and reactions caused by radiation can add to that mix. If an explosion produced the xenon on Mars, scientists would expect to find those isotopes in certain proportions. 

Some of the evidence Brandenburg referenced comes from pieces of Mars that landed here on Earth. NASA’s Curiosity, a car-sized rover that landed on Mars in August 2012, gave scientists a way to check these meteorite findings against the atmosphere of our celestial neighbor itself.

“My battery is low and it’s getting dark.” In 2019, those final words shook the internet when NASA announced that Curiosity’s predecessor—Opportunity—shut down after more than a decade of exploring Mars. But was the rover’s last transmission as poetic as this heart-wrenching line seems to be? Sadly, no. The quote is taken out of context; in actuality, it’s a Tweet from a science journalist who was summarizing accounts of Opportunity’s last moments. What really occurred was a cocktail of unfortunate circumstances. Data from Opportunity told the team that it was low on battery, and a blinding sandstorm was incoming. Scientists instructed Opportunity to hunker down through the storm and conserve energy. After the weather cleared, they were unable to make contact with the rover again. But perhaps the internet’s favorite probe—the one that “lived” for years in isolation so that it could send information back to Earth—deserves the cinematic ending we imagine for it.

The “spacecraft measurements by Curiosity match those in one class of Martian meteorites quite closely,” Swindle says, apart from small differences in isotopes Brandenburg doesn’t discuss. Older rocks, on the other hand, tell a somewhat different story. Allan Hills 84001, a Martian meteorite found in Antarctica in 1984, contains a slightly different xenon mix, Swindle says, “suggesting that the atmosphere may have changed over billions of years.” And when asked if the xenon measurements support Brandenburg’s explosion claim, Swindle disagrees. “In a word, no,” he says.

Brandenburg focuses on the unusually high proportion of xenon-129 in Mars’s atmosphere. A nuclear explosion could produce it, but its presence alone hardly clinches the case. Swindle says the problem becomes clearer when you look at how Brandenburg tries to recreate the full Martian xenon pattern. In the 2014 paper, Brandenburg starts with the isotope mix found in Earth’s atmosphere, then calculates what would happen if xenon measured after nuclear tests were added to it. He adds just enough of the nuclear-test xenon to bring xenon-129 up to the level measured on Mars. That isotope is bound to match because Brandenburg used it to set the proportions.

Several other isotopes also appear to line up. But Swindle points out that fission, the splitting of atomic nuclei that causes a nuclear explosion, doesn’t produce four of them. Their agreement says only that Mars’s starting xenon looks similar to Earth’s, not that an explosion occurred. The meaningful test is whether the mixture also matches the other isotopes that fission does produce. It doesn’t. The fit gets progressively worse among the heavier isotopes. At xenon-136, Swindle says Brandenburg’s plotted mixture contains 50 percent more than the amount measured on Mars. “Normally, if you can’t match it to within a few percent, it’s not a good match at all,” he says.

Swindle also identifies an internal contradiction. Brandenburg invokes a shift toward lighter fission products to explain xenon-129. Swindle says that shift should produce progressively less xenon as you move from isotope 131 to 132, 134, and 136. But Brandenburg’s calculated mixture already predicts too much of those heavier isotopes compared to the amounts measured in Mars’s atmosphere, and the gap gets larger with each one. “The mismatch is in the opposite direction,” Swindle says.

There’s another possible source of xenon-129. Radioactive iodine-129 decays into it naturally, although that explanation brings its own timing problem. Half of the iodine-129 decays every 15 million years, so most of it would have disappeared early in Mars’s history. The difficult part, Swindle says, is coming up with a timeline in which Mars released so much decay-produced xenon-129 after the planet had already lost most of its atmosphere.

Here, it’s important to distinguish between Brandenburg’s 2014 and 2023 papers. In the more recent work, he uses different xenon comparisons. The paper was published by Scientific Research Publishing—an organization included on librarian Jeffrey Beall’s archived list of potentially predatory resources. Swindle’s criticism addresses the comparisons in the 2014 paper, not the newer analysis.

Brandenburg also sees another clue supporting his explosion theory in the ratio of argon-40 to argon-26 on Mars, which is higher than it is on Earth. He argues that Mars must have received an unusual dose of argon-40. However, Swindle says that considering the actual amounts of these isotopes paints a different picture. Per gram of planet, Mars’s atmosphere has only about 2 percent as much argon-36 as Earth’s, and it also has less argon-40. In other words, the ratio is high because Mars has so little argon-36, not because it has an unexplained surplus of argon-40. All things considered, Swindle would not say an ancient explosion was impossible. He calls the isotopic evidence “very, very weak.”

Outside scientists have other ideas about what may have happened to Mars’s xenon. In their 2024 Science Advances study, “Impact sculpting of the early martian atmosphere,” Oliver Shorttle and his colleagues used laser-driven shocks and computer models to study the effects of objects colliding with early Mars. They found that repeated collisions during the solar system’s first 200 to 300 million years of existence could’ve knocked xenon out of the planet’s atmosphere. The lighter xenon isotopes escaped more easily than the heavier ones, changing the balance of what remained. That could explain much of the pattern scientists measure today, although the study doesn’t explain the extra xenon-129 at the center of Brandenburg’s argument.

What we do know is that Mars once had rivers and lakes, and researchers have found ways to explain how they dried out—without nuclear devastation. Measurements from NASA’s MAVEN spacecraft show how solar wind and radiation stripped away atmospheric gas on Mars. Some of the water went into the rocks and may still be there, bound up in minerals in the planet’s red crust. This put the estimated amount of water at 30 to 99 percent of the planet’s original conditions, according to a 2021 study published in Science. Having water makes Mars a place worth searching for life, but it doesn’t tell us if anything lived there.

Any microbes living on Mars might’ve had somewhere to go as the surface dried out, perhaps underground, where conditions could have allowed them to survive. But Brandenburg is asking us to imagine inhabitants who built things, which is a much bigger leap. “We see zero evidence of ancient technological species in the Solar System,” says Jason Wright, PhD, a Pennsylvania State University astronomy and astrophysics professor and director of the school’s Extraterrestrial Intelligence Center.

Wright points to Gavin Schmidt and Adam Frank’s 2018 Silurian Hypothesis paper, which asks how an earlier industrial civilization might register in Earth’s geological record. (Though it doesn’t make an argument that one existed.) Wright says we might have only a few million years before the evidence becomes too hard to recognize as something a civilization left behind. The paper also considers chemical signatures that might outlast recognizable artifacts.

On Mars, Wright imagines a rover discovering an unmistakably technological device buried in sand. However, erosion complicates its survival. “Many artifacts that we, or our ancestors, considered to be durable may not persist for million-year timescales,” says Jacob Haqq-Misra, PhD, an astrobiologist and senior research investigator at Blue Marble Space, a nonprofit research institute based in Seattle.

Haqq-Misra suggests machine learning could help search high-resolution Martian imagery for anomalies. Recognition would require investigation with experts in natural planetary processes. “We should investigate all anomalies, but we should not assume all anomalies are evidence of aliens,” he says. A strange feature could eventually reveal an ordinary explanation or something scientifically new. The investigation has value even when the anomaly turns out to have a natural cause.

Brandenburg’s 2014 paper turns his alleged catastrophe into a warning about hostile civilizations. He proposes human exploration to help humanity avoid a similar fate. But Wright rejects the premise that cosmic silence necessarily requires an explanation: “The Fermi paradox isn’t really a problem that demands an answer.” Interstellar travel is difficult, and we have done limited searching.

Likewise, the Great Filter—a proposed obstacle to life’s advancement—need not exist. Wright cautions that nuclear war would not necessarily eliminate all human life, much less establish a universal fate. “We regularly project our own existential fears onto hypothetical aliens,” he says.

Haqq-Misra offers a possibility without a massacre: “Another civilization could have even visited the solar system long ago, with few if any traces left behind.” Civilizations might miss one another in space and time.

Understanding what alien traces could look like is worthwhile. However, before we treat Mars as a warning, the isotope mix predicted by Brandenburg’s proposed explosion needs to match what we actually found there. As is the case with all of our search for extraterrestrial life thus far, the question still remains: Are we—and have we always been—truly alone in the cosmos?

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