The Moon’s polar regions may be less hostile to microbes than previously thought. This is the new finding from researchers at NASA and the University of Maryland in the US who say that future crewed missions to the lunar south pole will have to be carefully thought out to limit the unintended transfer of Earth life forms.

High ultraviolet radiation and temperatures make the Moon’s surface a harsh place and not somewhere bacteria and other micro-organisms can easily survive. This is particularly true for the equatorial regions, where all previous crewed missions have been sent. Things might be quite different at the lunar poles, however, since sunlight strikes these high-latitude regions at a low angle because of the Moon’s minimal tilt to the Sun of 1.5°. The result is long permanent shadows where it is cooler. The moonscape is also as rugged here as elsewhere with mountains and hills, which also cast shadows, and deep craters protected from the Sun’s heat and ultraviolet flux. These conditions allow for water ice too.

Because of these unique properties, future crewed missions, such as NASA’s Artemis IV, are scheduled to go to the Moon’s south pole, which has also been identified as a possible future location for a human outpost. The polar regions have already been observed by spacecraft such as ESA’s SMART-1, India’s Chandrayaan, Japan’s Kaguya and NASA’s Lunar Reconnaissance Orbiter. These provided a wealth of information that will be used to prepare future missions.

The problem is that no matter how stringent the sterilization procedures are prior to take-off, the astronauts on these missions will take microbes from Earth with them. Indeed, humans carry millions of microbes on their skin and even more in their bodies.

Landing sites for Artemis IV

To investigate whether microbes could survive in the polar regions, the researchers, led by Prabal Saxena, who works at NASA’s Goddard Space Flight Center, and Stefano Bertone at the University of Maryland, modelled how bacteria and fungi commonly found on human skin would behave in the environment of three candidate landing sites for the upcoming Artemis IV mission. The researchers began by making highly resolved spatial maps of the topography in these regions that included ruggedness, slopes and shadowing effects. They also modelled the UV exposure and temperature in these regions to identify specific locations where micro-organisms could survive for at least 24 h.

They obtained seasonal temperature data on length scales of 240 m from measurements by Lunar Reconnaissance Orbiter’s (LRO) Diviner. As for estimated regional UV (≤320 nm) fluxes, these were gleaned from averaged illumination maps with a pixel scale of 60 m based on topography derived from LRO Lunar Orbiter Laser Altimeter (LOLA) measurements.

“Since the temperatures at the lunar poles are rarely high enough to kill bacteria and low temperatures can preserve microbes on Earth, UV radiation is generally likely to be more dangerous in these regions, says Saxena. “We therefore analysed UV fluxes at finer spatial scales using a technique called ray tracing, and for some regions, included optical effects such as reflection and refraction as sunlight hits the Moon’s surface, leveraging updated LOLA-based topography maps on a scale of 5 m/pixel.”

Understanding how sunlight behaves at the poles is crucial, he adds. “Since the Moon has a very small axial tilt, the Sun appears to hover just above the horizon here, so even small hills and rocks can prevent light from reaching lower-lying ground, creating small, shadowed areas protected from UV rays.”

Up to seven days survival

The simulations revealed that the bacteria and fungi studied could survive in certain niches for up to or potentially beyond seven days. One particular fungus, the Aspergillus, is particularly resistant to UV radiation and could potentially survive in 15 to 30% of the areas assessed, even those that receive some sunlight during the lunar winter. The reconstructions also showed that all five microbes in this study, Bacillus, Deinococcus, Staphylococcus, Aspergillus and Fusarium could possibly survive in certain areas of the De Gerlache Rim’s permanently shaded regions, including when scattered UV light is incorporated into the simulations.

Survival does not mean growth (which requires active metabolism and potential reproduction), however, stresses Saxena. Indeed, surviving microbes are in a dormant, so-called cryptobiotic state and would only grow if the conditions were amenable to life – which is not the case for the Moon as we currently understand it.

“Cells may also be dead,” he tells Physics World, “but even dead cells may persist in the environment as another potential source of contamination.”

The work could apply beyond the Moon, he says. Indeed, a number of different airless bodies such as Mercury, Ceres, some asteroids and comets and exoplanets that may have similar properties could also have potential survivable niches for microbial life. Understanding how these niches may exist, how life may be transferred to them and how human exploration may leave its mark will all serve as a key testbed for future potential human exploration of Mars, which likely has far more habitable environments.

“We need to understand what was there before us, because when we search for signs of life beyond our planet on these bodies, we will want to make sure it’s not stuff we brought,” says Saxena.

The research is described in Science Advances.

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The UK’s Science and Technology Facilities Council (STFC) recently announced funding cuts to a range of physics and astronomy projects as it seeks to reduce costs. One of the most high-profile casualties is e-MERLIN, a network of seven radio telescopes spread across the UK, including the iconic Lovell Telescope at Jodrell Bank.

To discover what the cuts could mean for UK science and the livelihoods of those affected, podcast host Andrew Glester caught up with two astronomers at Jodrell Bank: Simon Garrington, e-MERLIN director, and David Williams-Baldwin, an e-MERLIN research support scientist.

They discuss why the cuts have caused such alarm among scientists, how the UK astronomy community is mobilizing in opposition, and why the consequences could extend far beyond Jodrell Bank.

e-MERLIN combines signals from its telescopes to produce sharp radio images of the Universe – with a resolution comparable to that of the Hubble Space Telescope. As things stand, funding for the telescope array will run out in March 2028, putting the future of the network and scientific operations at Jodrell Bank in doubt.

It’s an uncertain time for an observatory that was granted UNESCO World Heritage status in July 2019 for its historical contributions and its technical and scientific ingenuity since the 1940s.

An STFC spokesperson emphasises that Jodrell Bank is “not closing” and “will continue to play an important role in UK science”. This includes the Square Kilometre Array Observatory that has its headquarters at Jodrell Bank as well as other radio astronomy research projects in the UK and elsewhere.

“We recognise the strength of feeling about Jodrell Bank and the e-MERLIN network, and the contribution they have made to UK science. The achievements of the scientists, engineers and staff who have supported e-MERLIN over many years are widely respected across the research community,” they add. “We are focusing on the next generation of radio astronomy to ensure UK researchers continue to be at the forefront of the field. Rising cost pressures mean that we have had to make difficult choices about STFC funding to make sure we are able to fund world class research sustainably into the future.”

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A radiation shielding vest tested during the uncrewed Artemis I flight in 2022 has been shown to significantly reduce the radiation dose that future astronauts or deep-space tourists might receive.

The data for this analysis were obtained via seating two human-tissue-equivalent female torso phantoms in the Orion crew capsule. While the “Zohar” phantom wore the new AstroRad vest, its travel companion “Helga” did not. Numerous radiation dosimeters placed in and on the phantoms allowed the received radiation dose to be compared.

“Exposure to radiation in space is unavoidable, and a single major solar particle event (SPE) can deliver more than one-third of NASA’s 600 millisievert career effective-dose limit. A three-year round trip to Mars would equal or exceed the career limit, which corresponds to a 3% mortality risk from radiation-induced cancer. So we developed the AstroRad vest to significantly reduce this hazard,” explains immunologist Oren Milstein, CEO of StemRad Radiation Protection, which began developing the vest with Lockheed Martin in 2015.

The shielding thickness varies throughout the garment according to the radiation sensitivity of the underlying organs, with breasts, colon, lungs, ovaries, stomach and red bone marrow having concentrated shielding in the test vest. Milstein was inspired to develop this targeted architecture based on the experiences of his PhD supervisor, who treated the first responders to the 1986 Chernobyl nuclear power plant disaster.

With damage to bone marrow the accepted cause of death for all those emergency workers who lost their lives within months of the accident, “that heritage instilled in me a desire to protect people from radiation by selective shielding of the bone marrow,” Milstein explains, adding that the female focus of this experiment is because women have a higher predicted risk of radiation-induced cancer than men.

Astronauts currently shield from SPEs in “storm shelters” consisting of barricades of supplies, or by moving into areas containing more hardware against the walls. AstroRad provides a similar level of protection to the most robust shelter configuration while also “allowing the astronaut wearing it to move around the cabin and continue mission-critical tasks,” radiation physicist Jordan Houri, lead scientist for space exploration at StemRad, tells Physics World.

To maintain flexibility, the vest is constructed from thousands of hexagonal tessellated rods of high-density polyethylene (HDPE) sandwiched between two layers of elastic fabric. The shielding components can also slide past one another and stretch. HDPE was chosen for its high proportion of hydrogen – which is extremely effective at shielding against charged particle space radiation.

While Artemis I did not encounter a solar storm, Orion traversed the inner Van Allen belt, whose protons cover a similar energy range to those in SPEs. This enabled the team to construct a Monte Carlo model of the experiment for testing different radiation environments.

“We created digital twins of Helga and Zohar, the AstroRad vest, radiation detectors and spacecraft shielding,” explains Houri. “Using this model, we generated hundreds of billions of virtual protons and electrons representing the radiation environment of the inner Van Allen belt, before comparing the predicted detector responses directly with the measurements recorded during Artemis I.”

With close agreement found, the researchers then simulated measured SPEs from August 1972 and October 1989. As detailed in their recent Science Advances paper, this revealed that wearing AstroRad would reduce effective dose by around 60% in an August 1972-type scenario, and by almost 40% for a 1989-type SPE – sparing astronauts the dose equivalent from up to 193 and 131 days of deep space travel, respectively.

Combining these results with those from previous experiments, which tested the vests’ ergonomics on the International Space Station, is allowing the researchers to improve comfort and ease of motion, and reduce mass. They are also exploring whether lighter, empty vests could be filled with recycled polyethylene after launch.

Alongside the health benefits, reducing radiation exposure makes economic sense as it extends astronauts’ careers, concludes Milstein, who hopes that the AstroRad vests can help “make lunar habitation and Mars travel truly sustainable and not just a dream”.

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NASA’s Transiting Exoplanet Survey Satellite (TESS) mission has notched up its first discovery of an exoplanet via a method known as microlensing. The planet is a “super Jupiter” known as Gaia23bra b, and TESS observed it when the planet and its host star acted as a gravitational lens, magnifying the light from a second, more distant background star.

Astronomers have several ways of finding planets beyond our solar system. The most successful of these by far – and the one that TESS was designed for – is the transit method, which is responsible for roughly 75% of all exoplanet detections to date. This approach relies on observing the periodic dimming of a star’s light as a planet passes between the star and an observer here on Earth.

The transit method does have limitations, however. The main limitation is that we can see transits for only a small number of planets, namely those with orbital planes that are almost exactly edge-on to Earth. An alternative approach known as photometric microlensing is somewhat more flexible in this respect, as it relies on the star-planet system magnifying the light from a background star, which is known as the source. This magnification occurs because the gravitational pull of the planet-star system warps space, bending and magnifying the source’s light (as Albert Einstein predicted as part of his general theory of relativity) like a lens and producing characteristic spikes in its brightness.

A second bite at the exoplanetary cherry

Astronomers initially identified a planet in the Gaia23bra system using observations made in 2023 by the European Space Agency’s now-retired Gaia space telescope. However, while Gaia picked up the unexpected brightening of a background star, it did not identify this event as coming from a binary-star system, and it could not pick out the planet itself because its observations were too sparse, explains Mallory Harris, an astronomer at the University of New Mexico, US who led the TESS study.

In the new work, Harris and colleagues scoured TESS data from the same period. Because TESS’ observations were much denser – it observed the region every 200 seconds for nearly 60 days – they were able to identify extra features in the brightness of the light curve that indicated the presence of a planet in the system. Subsequent analyses revealed that this planet is about 1.63 times the size of Jupiter, and it orbits its host – an orange dwarf star 20% smaller than our Sun – at a distance similar to that of Jupiter from our Sun.

Complementary techniques

The transit technique is particularly sensitive to planets that orbit close to their star because these planets are the most likely to transit and block out most of their host stars’ light as they pass in front of them. In contrast, Harris explains that microlensing is most sensitive to planets orbiting at Earth-like distances or further from their stars, making it better for studying planetary systems more like our own solar system. “With microlensing, we can find smaller planets with greater orbital distances, including worlds in the habitable zone of their star and even farther away,” she says.

The transit technique and microlensing are therefore complementary because each reveals a category of planet that the other may not be able to detect, adds team member Diana Dragomir. The only problem, Harris notes, is that microlensing observations are limited-time opportunities. “Microlensing events happen once and they’re gone – they don’t repeat,” Harris says. “I like to joke that we’ll probably find the first Earth analogue with microlensing and then wave at it as it goes by because we’ll never see it again.”

That said, Harris says that Gaia23bra will be an important observing target for the Nancy Grace Roman Space Telescope. “Microlensing is currently the only method capable of detecting Earth‑mass planets at Earth‑like orbital distances,” she explains. “We already knew that this technique could find planets, because it has done so in the past using ground-based observatories.

“What we demonstrated in this work is that high-cadence observations (even with low spatial precision) and high-precision long-baseline observations can work together to find a microlensing planet. And that it is possible to specifically do this by pairing TESS observations with those from another instrument.”

This synergy between long-time-scale surveys and high cadence observations could be therefore applied towards future searches for potentially habitable worlds, she tells Physics World. Although Gaia was retired last January, making it unlikely that astronomers will find many additional events via a Gaia–TESS combination, Harris adds that there could nevertheless be other microlensing planets in the past eight years of archived TESS observations. “I’m excited to see whether there are other events like this already hiding in the TESS data and whether future surveys can work together with TESS to find more microlensing planets in different parts of the galaxy,” she says.

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A collaboration of researchers in North America has reported their findings from the first diagnostic X-ray imaging performed in space. X-ray images recorded during an orbital spaceflight exhibited similar overall quality to those taken preflight on Earth, demonstrating the feasibility of adding radiography as a diagnostic tool for crew health.

With humans venturing further into space and spending more time in this harsh environment, the risk of adverse medical events increases. Accurate and timely diagnosis and treatment is a must-have. Currently, the only reliable medical imaging modality available to astronauts in spaceflight is ultrasonography – which is operator dependent, requires substantial training and relies on limited acoustic windows.

X-ray imaging, on the other hand, benefits from low operator dependence, rapid acquisition and typically higher spatial resolution than ultrasound. Digital radiography could also offer superior diagnostic capabilities for many medical conditions of concern during spaceflight, including dental disease, musculoskeletal trauma, inhalational injury, collapsed lung and arthritis.

Traditional X-ray scanning systems are bulky, produce a lot of radiation and are sensitive to motion – making them less than ideal for sending into space. But a new generation of portable X-ray scanners shows potential to survive the spaceflight and be operated by crew members with minimal training.

“It’s been a dream for aerospace medicine to have more than one imaging modality for diagnosing illnesses and injuries in space,” says lead researcher Sheyna Gifford, an assistant professor of aerospace medicine at the Mayo Clinic in Rochester, MN, in a press statement.

Scanning in space

In a study led by co-author David Lerner, the researchers first demonstrated the feasibility of X-ray imaging in simulated microgravity in 2022. During a parabolic flight, they used a commercial off-the-shelf digital radiography system to successfully capture radiographs of a human subject and a phantom during lunar gravity (1/6g), Martian gravity (1/3g) and microgravity.

In this latest project, reported in in Radiology, Gifford and her team investigated the performance of a similar portable digital radiography system aboard the Dragon spacecraft, during the Fram2 spaceflight mission, a 3.5-day polar orbital flight launched on 31 March 2025 on a SpaceX Falcon 9 rocket. The imaging system comprised a commercial off-the-shelf, FDA-cleared, portable, digital X-ray generator (Impact Wireless; MinXray) along with an FDA-cleared flat-panel detector.

Prior to the mission, three crew members received 4 hr of training on the portable X-ray system and acquired preflight X-ray images of the hand, forearm, abdomen, pelvis, chest and a quality control phantom. They then recorded the same anatomic and phantom images whilst in space, and also imaged a smartwatch to investigate the potential for non-destructive testing.

During anatomic imaging, the devices were handheld by the crew members, while the phantom and smartwatch were secured to the detector for imaging. The crew reported that they found it easy to use the X-ray system and follow the imaging protocols.

Back on Earth

To assess the quality of the seven X-ray images acquired by the crew, three independent radiologists evaluated and compared the preflight and in-flight anatomic radiographs, finding no differences in overall image quality, contrast resolution or spatial resolution. For central-body radiographs (chest, abdomen and pelvis), image positioning was worse in-flight than preflight. Despite this, all X-rays achieved good or near-excellent diagnostic quality (rated on a  5-point Likert scale).

Phantom radiographs recorded in space exhibited good spatial and contrast resolution, imaging low-contrast targets down to the smallest 2-mm target and easily visualizing high-contrast meshes ranging from 20 to 60 lines per inch, with 80 lines per inch remaining visible. The smartwatch radiograph clearly showed the watch’s internal components at the submillimetre scale.

The research team found that the X-ray generator had sustained minor re-entry damage, but its internal components and X-ray output were not affected. Similarly, the detector passed visual inspection and quality control tests. The researchers also recorded a set of postflight X-rays (on non-crewmembers) following the same in-flight protocols. These showed no qualitative differences from the preflight or in-flight radiographs.

“By acquiring the first human and equipment X-rays in space, our study demonstrates the feasibility of in-orbit radiography and expanded diagnostic capabilities for crew health and hardware evaluation,” says Gifford. “Acquiring diagnostically useful X-rays in space is something that anyone can do. Three very talented nonmedical people with four hours of training in one of the harshest environments did it right and did it well.”

Gifford points out that a spaceflight-ready radiography system could also prove indispensable for mission-critical non-medical tasks. “For sustained human presence in space, X-rays are critical not just for crew members but also for other mission components like electronics and spacesuits. The only way to look inside these objects without taking them apart is to X-ray them,” she explains.

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A compact optical technology that has already proved its worth in Earth-bound applications could be on its way to space after researchers at the University of California San Diego, US showed that it can map the Sun’s magnetic field just as well as traditional instruments. By making polarization gratings from specially engineered metasurfaces rather than a complex assembly of optics, the researchers say that future solar-observing missions could benefit from reduced complexity and cost as well as size.

“Our work makes use of recent advancements in nanoscale optical technologies to help improve the hardware for making astronomical observations of the Sun,” says study leader Noah Rubin of UC San Diego’s Jacobs School of Engineering. “We believe this is one of the first times that metasurface optics – which have been a subject of intense interest in both academic research and industry for about a decade – have been used to improve scientific instrumentation of any kind outside of a lab/academic proof-of-concept.”

Polarized light and solar magnetic fields

Although light emitted by the Sun is generally unpolarized – that is, the light waves do not vibrate along a particular axis – strong magnetic fields that develop near sunspots can polarize this light via the quantum mechanical Zeeman effect. These magnetic fields are closely associated with space weather events such as solar storms that can damage electronic infrastructure both on Earth and in orbit. Studying the Sun’s magnetic activity by monitoring areas of polarized light is thus an important step towards detecting or predicting such storms in time to take protective action.

Usually, measuring the polarization state of light means analysing different polarization directions using a device such as a waveplate that mechanically rotates between exposures. Rubin compares this process to taking several photographs through polarized sunglasses held at different angles, then combining them to obtain a fuller picture of what’s going on.

While this technique works, and instruments that use it have already been sent into space, the image analysis process is very time-consuming. It also requires an external power source, and the need to mechanically rotate the waveplate introduces extra complexity and cost, says Rubin.

“In space-based applications, a satellite itself can be moving while this component reorients, causing a highly undesirable blurring effect,” he explains. “As a result, designers of these systems often invest considerable resources into mechanical remediation and engineering to correct the motion of the telescope on the satellite, and this frequently ends up being substantially more expensive than the telescope optics themselves.”

A metasurface solution

In the new study, which is detailed in Science Advances, Rubin and colleagues solved this problem by creating a polarization-sensitive metasurface that splits light into its different polarization components. A camera-like system containing this metasurface polarization grating can then form multiple images of a scene in parallel. Rubin explains that each image in this scene is analysed with respect to a different polarization state, meaning that the system can measure the polarization of light simultaneously and passively in a single camera frame.

Rubin notes that this technique of condensing an instrument that would ordinarily involve a complex assembly of optics into a single, flat surface has previously made its way into applications as diverse as facial recognition in mobile phones and the preparation of complex photon states in quantum optics experiments. “In this work, we show that these advantages translate to polarization imaging in astronomy,” he tells Physics World.

Comparable results

Working with industrial partners at BAE Systems Space & Mission Systems in Colorado, US (formerly known as Ball Aerospace, which Rubin describes as “well-known for its involvement in the development of the James Webb Space Telescope, Hubble and countless other NASA missions”), the team designed a specialized telescope built around such a metasurface polarization grating. They also deployed their instrument on the Dunn Solar Telescope in New Mexico, US, and showed that they could quantitatively map the magnetic fields in sunspots by capturing simultaneous polarization images of these spots.

The researchers report that their results were comparable to those obtained by the state-of-the-art NASA Solar Dynamics Observatory mission in-orbit, highlighting what Rubin calls “the significant advantages that these metasurface components can offer when designed in conjunction with more traditional optical systems”. The UC San Diego team is now exploring ways of integrating its technology into future NASA solar-observing space missions.

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A galaxy that formed around a billion years after the Big Bang is in its death throes thanks to a powerful galactic wind that is blasting its gas into space, say astronomers at Australia’s Swinburne University of Technology. The discovery, which is based on data from the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, could help explain why some of the universe’s earliest massive galaxies ceased to form new stars.

One of the JWST’s most surprising discoveries is that when the universe was between one and two billion years old, it already contained large numbers of massive galaxies. Astronomers think these galaxies may have acquired most of their mass in intense bursts of star formation. But at some point, that process stopped: in technical terms, the galaxies became quiescent.

“These galaxies seemed to have formed all their stars very quickly and then they suddenly died, all within the first two billion years of the universe being formed,” says Rebecca Davies, who led the new research.

The CRISTAL-02 galaxy

One possible explanation for the onset of quiescence is that when galaxies collide with each other, the resulting winds “blow away” the hydrogen fuel required for new stars to form. To investigate this hypothesis, Davies and colleagues focused on a galaxy called CRISTAL-02, which was one of 20 galaxies in the recent ALMA-CRISTAL survey of early star-forming galaxies.

“When we looked at the data, it stood out because it was the only one that showed strong evidence for a galaxy wind,” Davies explains. “We saw this as an excellent opportunity to study how winds impacted the evolution of galaxies in the early universe.”

The light from CRISTAL-02 travelled for approximately 12.7 billion years to reach us, meaning that we see it as it was one billion years after the Big Bang. Because the universe has been expanding since then, the galaxy’s spectra appear highly red-shifted. This meant the Swinburne astronomers needed the JWST’s infrared-sensing capabilities to analyse a spectral feature known as the hydrogen-alpha (Hα) line that is normally red. They also used ALMA to analyse CRISTAL-02’s C II line, which comes from ionized carbon and has a (non-redshifted) wavelength of 158 mm. Both emission lines can yield important information about the properties of early galaxies.

Living fast and dying young

From the ALMA-CRISTAL survey’s measurements of Hα luminosity, astronomers knew that CRISTAL-02 forms stars at a rate of around 260 M_☉ per year. This is about three times the average value for “main-sequence” star-forming galaxies at similar mass and redshifts.

The latest observations, however, suggest that it won’t maintain this pace for long. Davies and colleagues identified a huge plume of C II emissions that extends as far as 7 kiloparsecs (kpc) to the north-east of CRISTAL-02, making it almost as long as the galaxy itself. This is a telltale sign that gas is being driven out of the galaxy. The fact that the gas in this plume is blue-shifted by 100 km s^-1 lends further support to this explanation.

If this rapid blowout continues, Davies says that CRISTAL-02 will cease to exist in less than 50 million years. But the team’s findings may have implications beyond the fate of this single galaxy. “Our results could help to explain how some of the earliest massive quiescent galaxies in the universe behave,” she tells Physics World. “When the JWST started observing distant galaxies in 2022, it found far more evolved galaxies in the early universe than models predicted. These galaxies seemed to have formed all their stars very quickly and then suddenly died, all within the first two billion years of the universe. The galaxy we discovered seems to be following this path.”

Learning about the early universe

Davies explains that because the early universe was much more compact than it is now, collisions between galaxies were common. During such collisions, gas funnels towards the galactic centres, triggering strong bursts of star formation but also producing strong winds that eventually drive the gas away. “If many early galaxies collide and experience rapid growth, then it may not be surprising at all that we see so many dead galaxies in the early universe,” she says.

The researchers stress that the present work, which is detailed in the Monthly Notices of the Royal Astronomical Society, is based on a case study of just one galaxy. They now need to observe other early, massive galaxies caught during periods of intense growth to determine whether they, too, experience powerful winds that could rapidly expel their gas and stop them from forming stars.

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Black carbon particles released by rocket launches remain in the upper atmosphere for much longer than sooty particles produced by sources on the ground. This finding, which comes from a study led by researchers at University College London (UCL), UK, suggests that the soot created in deploying “megaconstellations” containing hundreds or thousands of satellites could have poorly understood and potentially serious consequences for the Earth’s climate.

“Rocket launches are a unique source of pollution, injecting harmful chemicals directly into the upper layers of the atmosphere and contaminating Earth’s last remaining relatively pristine environment,” says the study’s lead author, UCL atmospheric chemist Connor Barker.

The number of rockets being launched into space has increased dramatically since 2019, and the trend shows few signs of stopping. This year has already seen more launches than the whole of 2020, and space industry experts believe the eventual total could surpass 2025’s figure of 329. The increase has primarily been driven by the Falcon 9 rockets launched by the US firm SpaceX, though China also logged a record 92 launch attempts in 2025.

“An unregulated geoengineering experiment”

In the new work, Barker and colleagues analysed data from rocket launches and satellite re-entries from 2020 to 2022. Their results, which they detail in Earth’s Future, show that the soot particles lingering in the upper atmosphere are 540 times more effective at altering climate than ground-based soot emissions from sources such as cars and power plants.

“Space industry pollution is like an unregulated geoengineering experiment,” says Barker. Soot particles from burning kerosene in rocket fuel absorb sunlight, he explains, which prevents it from reaching the Earth’s surface. The result is a small cooling effect, which might sound like a good thing in the context of rising global temperatures. However, Barker stresses that this cooling is minimal compared to the global warming caused by other human-generated emissions, while the particles themselves could have “many other serious unintended consequences”.

Predictions likely to underestimate future impact

As well as quantifying recent space industry emissions, the researchers make predictions about future ones. According to their calculations, by 2029 the space industry will be releasing about 870 tonnes of soot into the atmosphere each year. By way of comparison, Baker notes that according to the latest UK government figures, the annual emissions of the country’s entire passenger car fleet amounted to just 728 tonnes.

The team based its predictions on projections of data from 2020-2022, which is considered the beginning of the megaconstellation satellite era. Because of this, Barker cautions that they are likely to be underestimates, making the problem even more urgent. “It is critical that we understand the environmental impacts of satellite megaconstellations now while their impact is small, before any unforeseen consequences are difficult to reverse or repair,” he tells Physics World.

While scientists have made great progress in the last few years, Baker says that are still large uncertainties in our emission estimates for the industry and our understanding of how they affect the atmosphere. “We hope that this work spurs further research to measure space industry emissions and highlights the need to regulate the geoengineering impacts of the space industry,” he says.

Team leader Eloise Marais, a professor of atmospheric chemistry and air quality at UCL, echoes this sentiment. “So far, there has been limited effort to effectively regulate this type of pollution,” she says.

The researchers are now working on an emissions tracker to visualize these emissions across the entire space age. “We are also using satellite imagery to remotely detect and quantify rocket launch emissions,” Barker reveals.

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Thanks to new “transit” observations of the hot Jupiter exoplanet WASP-94A b using the James Webb Space Telescope (JWST), researchers at Johns Hopkins University in the US have discovered a striking weather pattern on this distant world. Their work could help provide a clearer picture of the atmospheres on exoplanets, which has been very limited until now.

When an exoplanet passes in front of (or transits) its host star, some of the light from that star passes through the planet’s atmosphere. By detecting this light using telescopes, either ground-based or in space, astronomers are able to obtain the exoplanet’s atmospheric light spectrum.

A team led by Sagnick Mukherjee and David Sing has now analysed data on WASP-94A b from the space-based JWST and have found that the mornings on this exoplanet are extremely cloudy – with water absorption features in the spectrum – while its evenings are very clear. Clouds likely form on the planet’s colder, permanent nightside where temperatures are low enough for minerals to condense. Winds then carry those clouds towards the morning limb (the leading edge of the atmosphere), explains Mukherjee.

“As these cloud particles are dragged farther toward the hotter dayside, the clouds evaporate or sink deeper, leaving the evening side much clearer,” he says. “This is a clear discovery of a planet-wide cloud cycle in action on a distant exoplanet.”

Part of a broader survey

The researchers, who detail their findings in Science, decided to study WASP-94A b as part of a broader survey of exoplanet atmospheres with the JWST called the “Grand Tour Program”. The goal of this project, says Mukherjee, is to better understand the composition of these exoplanets and the physical processes at play in their atmospheres.

One of the main difficulties encountered during such observations is how small the signals that we are trying to look at are, he explains. However, in this case, the asymmetry between the morning and evening side of the planet was rather dramatic, which made it possible to separately probe the two.

Until now, researchers only had access to a single averaged spectrum of WASP-94A b – and indeed most other exoplanets studied over the last decade –from observations made by the Hubble telescope, for example. The chemical composition of the exoplanet’s atmosphere was therefore highly biased, says Mukherjee, and it was thought that the levels of oxygen and carbon there were hundreds of times higher than on the Sun. “This finding baffled us because this result could not be explained by planet formation theories. The new data show that WASP-94A b only contains only about five times as much oxygen and carbon.”

“Being able to resolve the cloudy morning and clear evening separately therefore gives us a much cleaner view of what the atmosphere is actually made of,” Mukherjee tells Physics World. “And this is not just relevant to hot-Jupiters like WASP-94A b, but might be extended to all exoplanet atmospheres that we are trying to understand using the transit method.”

“One of the most exciting aspects”

For Mukherjee, this is one of the most exciting aspects of the JWST era. “We are taking a step beyond simply detecting the atmospheres of distant planets and are now beginning to map their weather, chemistry, and three-dimensional structure in extraordinary detail.”

Indeed, using WASP-94A b as a benchmark, the Johns Hopkins team has already studied eight other hot gas giants and discovered the same distinctive cloud cycle on two other worlds: WASP-39 b and WASP-17 b. “Inspired by these observations, our collaboration, co-led by David Sing, myself and our colleague Guangwei Fu, is about to receive more than 180 hours of new JWST data to understand weather on diverse exoplanets and measure how their weather and cloud-coverage vary with planet temperature and gravity,” reveals Mukherjee.

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