Category: 7. Science

We usually think of satellites as small objects orbiting planets or stars. But in the broader universe, galaxies themselves can have satellites—smaller galaxies bound by gravity that orbit a larger host, carrying with them stars, gas, dust, and dark matter.

Most of what we know about satellite galaxies comes from studying the Milky Way and other similarly large galaxies. But a new study led by Dartmouth astronomers broadens that understanding by exploring the satellites of dwarf galaxies—systems less than a tenth the size of the Milky Way.

The multi-institutional survey triples the number of dwarf galaxies surveyed for satellites, the researchers report in The Astrophysical Journal . The study identifies 355 candidate satellite galaxies, including 264 that were previously undocumented. The researchers suggest that 134 of these candidates are highly likely to be satellite galaxies.

“Studying these systems can help us piece together conditions in the early universe,” says author Burçin Mutlu-Pakdil , an assistant professor of physics and astronomy at Dartmouth.

“This project fills a critical gap, offering fresh insights into the process of how galaxies form and its connection to dark matter,” Mutlu-Pakdil says. “Our goal is to build a statistical sample of the smallest galaxies in the universe, as they are the most dominated by dark matter and serve as clean laboratories for understanding its nature.”

By analyzing the satellite galaxies orbiting host galaxies of various sizes and environments, the researchers aim to uncover how external conditions influence satellite formation. For instance, studies of large, Milky Way-sized galaxies suggest that larger galaxies tend to host a greater number of satellite galaxies.

“With this survey, we’ll be able to test whether those predictions hold true with much smaller host galaxies,” says Laura Hunter, a postdoctoral fellow in Mutlu-Pakdil’s research group and corresponding author of the study.

“Astronomy is a field where you can’t run experiments,” Hunter says. “All you can do is observe and make as many measurements as you can, and then put that data into a simulation and see whether it reproduces your observations. If it doesn’t, that tells us that there’s something wrong with our assumptions or our model of the universe.”

To search for dwarf satellites, the team analyzed publicly available imaging data from the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys. In addition to Hunter and Mutlu-Pakdil, co-authors of the study include Dartmouth graduate student Emmanuel Durodola and Rowan Goebel-Bain ’25.

The researchers selected 36 host galaxies to investigate. The hosts varied in size and in proximity to other galaxies, both of which are factors that could impact satellite formation. The team used an algorithm to remove “noise” from the images, such as bright sources of light from other stars or galaxies, and to identify objects that could be satellite galaxies. They then visually inspected each candidate satellite to rule out those that were due to image defects or faint light halos around bright stars or galaxies.

This survey is the first step towards understanding how dwarf satellites differ from the satellite galaxies of larger hosts. The team is currently conducting a follow-up campaign to confirm that the candidate satellites are indeed satellite galaxies, and to characterize properties such as their size, distribution, how much gas and debris they contain, and their rates of star formation.

“Getting the answers will require a lot of resources and telescope time, but the impact will be incredible for understanding the nature of dark matter and galaxy formation at the smallest scale,” Mutlu-Pakdil says. “Each one of them holds a little clue about the physics of how galaxies form.”

As giant planet HIP 67522 b orbits its host star, it triggers its own doom. The planet orbits HIP 67522, a young star slightly larger than the Sun, in just 7 Earth days. At just 17 million years old, the star is far more active than our Sun, regularly flaring and releasing massive amounts of energy and stellar material.

By using observations from three exoplanet telescopes, scientists have found that these flares don’t occur at random times and locations like on our Sun. Instead, they are concentrated at a particular time in the planet’s orbit, which suggests that the planet itself could be triggering the flares. What’s more, the flares are also pointed at the planet, bombarding it with nearly 6 times more radiation than it would experience if the flares occurred at random.

“We want to understand the space weather of these systems in order to understand how planets evolve over time, how much high-energy radiation they get, how much wind they’re exposed to, what consequences that has on the evolution of their atmospheres, and, down the line, habitability,” said Ekaterina Ilin, lead researcher on the discovery and an astronomer at the Netherlands Institute for Radio Astronomy (ASTRON) in Dwingeloo.

Magnetic Interactions

Space weather is common in our solar system. At Earth’s relatively safe distance from the Sun, space weather manifests as aurorae and enhanced solar wind that, nonetheless, can wreak havoc on navigation and communication systems.

But in exoplanet systems, space weather can be far more deadly. Stars have strong magnetic fields, which are even stronger and more turbulent when stars are young. A star’s magnetic field lines stretch out from its surface, carrying superheated plasma along with them. Field lines regularly twist and tangle and coil until they eventually snap back into place, releasing stored energy and stellar material in a flare or coronal mass ejection (CME).

Astronomers have observed exoplanets orbiting so close to their stars that their atmospheres or even rocky surfaces are being blasted away by intense stellar radiation, winds, and flares. But for decades, astronomers have theorized that the connection between stars and close-in planets can go both ways.

According to the theory, some planets orbit so close to their star that they are inside the star’s magnetic boundary, the so-called sub-Alfvénic zone. Such a so-called short-period planet could gather up magnetic energy like a windup toy as it orbits and release it in waves along the star’s magnetic field lines. When the energetic waves reach the star’s surface, they could trigger a flare back toward the planet.

The idea was born after the discovery of the first exoplanet—51 Pegasi b—in 1995 showed astronomers that planets could orbit extremely close to their host stars (51 Pegasi b has a 4.23-day orbit). Ilin said that although the theory has existed since the early 2000s, it has taken a while to find even one exoplanet that might fit the bill because most planets discovered thus far orbit much older stars with few flares and weak magnetic fields.

Too Close for Comfort

Ilin and her colleagues combed through thousands of confirmed and candidate exoplanets detected by the now-retired Kepler Space Telescope and the extant Transiting Exoplanet Survey Satellite (TESS). They looked for young, flaring stars with close-in giant planets—a very broad search with hundreds of results—and narrowed their search down by looking for planets that might orbit within the sub-Alfvénic zone and for stars with strange flare timings.

“It was really a shot in the dark,” Ilin said.

After a long, tedious search, the team homed in on HIP 67522 and its two planets: planet HIP 67522 b, with its 7-day orbit, and a second giant planet with a 14-day orbit. The star’s flares were clustered together, but only barely within the margin of significance.

“The expectation was that it would have one of the strongest magnetic interactions based on how close the star is to the [inner] planet, how big the star is, how big the planet is, how young it is, [and] how strong a magnetic field we expect,” Ilin said. Despite the marginal significance, she thought, “Oh, actually, it might be worth a second look.”

The researchers observed the star with the European Space Agency’s Characterising Exoplanets Satellite (CHEOPS) for 5 years. They characterized 15 stellar flares during that period, a typical number for this size and age of star, but found that the flares clustered together when the innermost planet passed between the star and the telescope’s vantage point at Earth.

“When the planet is close to transit, the flaring goes up by a factor of 5 or 6, and that should not happen,” Ilin explained. “Statistically, almost impossible.”

“It is fascinating to see clustered flaring following the planet as it orbits its star,” said Evgenya Shkolnik, an astrophysicist at Arizona State University in Tempe who was not involved with this research. Some of Shkolnik’s past work investigated enhanced stellar activity in Sun-like stars with hot Jupiters, but those stars were much older and did not flare as much as HIP 67522. “It makes sense that more flares could be triggered through the same type of magnetic star-planet interactions we observed,” she said.

Like other short-period giant planets, HIP 67522 b likely would have been losing its atmosphere to stellar radiation no matter what because of how closely its orbits—indeed, the planet is about the size of Jupiter but just 5% its mass. But because the flares are synced with HIP 67522 b’s orbital period, Ilin’s team calculated that HIP 67522 b is experiencing roughly 6 times the stellar radiation that it would if the flares were randomly distributed, and the corresponding CMEs are pointed directly at it.

The team’s simple estimates show that because of this increased radiation, the planet is losing its atmosphere about twice as fast as it would otherwise.

“It makes its life even worse by whipping up this interaction…and firing all these CMEs directly into the planet’s face,” Ilin said. These results were published in Nature.

“This discovery is extremely exciting,” said Antoine Strugarek, an astrophysicist at the French Alternative Energies and Atomic Energy Commission in Paris who was not involved with the research. “Such magnetic interactions are clearly the prime candidate to explain the observed phenomenon, and no other theories are really convincing to explain these observations, to the best of my knowledge.”

Expanding the Search

Strugarek explained that the magnetic interaction observed in the HIP 76522 system has a few analogs in our own solar system. The Sun experiences “sympathetic flares,” he said, in which a solar flare in one spot can trigger another one nearby—they account for about 5% of solar flares. And in the Jupiter system, the Galilean moons Io, Ganymede, and Europa propagate waves along their orbits that trigger polar aurorae on Jupiter.

For HIP 76522, “the theory is that the perturbation originates from the exoplanet. This is definitively a possibility, and extremely exciting for future research,” Strugarek said. He added that he would like to see future work constrain the geometry of HIP 76522’s magnetic field to better understand the star-planet connection.

He also wants to go back into the archives to look for more exoplanets like this. “Now that we have one tentative system, we need to scrutinize all the compact star-planet systems with large flares for such occurrences,” Strugarek said. “This should be ubiquitous for very compact systems.

Shkolnik added, “I would love to see dedicated observing programs at both higher- and lower-energy wavelengths, namely, in the far-ultraviolet, submillimeter, and radio wavelengths.” The far ultraviolet is more sensitive to flares, and finding more flares might confirm the theory that the planet is triggering them.

Thus far, HIP 76522 b is the only planet discovered to be magnetically influencing its star. Ilin said that when her team started looking into HIP 76522 b, it was the youngest short-period planet in their catalogs. TESS has since observed several more, and Ilin’s team is ready to investigate them.

The researchers also hope to flip the script on star-planet interactions. Instead of starting with an exoplanet and looking for clustered stellar flares, they want to first look for flare patterns and then find the planet causing them. The untested technique could detect exoplanets around stars that other detection methods struggle with: young, active stars.

“It is a bit of a statistically tough cookie,” she said, “but it will be quite exciting if we can make that happen.”

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

Citation: Cartier, K. M. S. (2025), Exoplanet triggers stellar flares and hastens its demise, Eos, 106, https://doi.org/10.1029/2025EO250284. Published on 5 August 2025.

Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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Marybeth Collins

Between 2003 and 2021, Earth saw a net gain in photosynthesis primarily driven by land plants, while marine phytoplankton productivity declined, according to a new study published August 1 in Nature Climate Change. The findings suggest that terrestrial ecosystems are becoming increasingly critical to global carbon uptake—but this shift may mask deeper vulnerabilities in the planet’s climate system.

Net primary production (NPP)—the amount of carbon plants and algae store after respiration—is a key indicator of ecosystem health and carbon cycle stability. Duke University researchers analyzed 19 years of satellite-based data across land and ocean, revealing an annual global increase of 0.1 billion metric tons of captured carbon, largely due to high-latitude forest growth and longer growing seasons.

“Net primary production determines ecosystem health, provides food and fibers for humans, mitigates anthropogenic carbon emissions, and helps to stabilize Earth’s climate,” said Yulong Zhang, lead author and research scientist at Duke’s Nicholas School of the Environment.

Rising Land Gains, Sinking Marine Losses

The study shows:

• Terrestrial NPP increased by 0.2 billion metric tons of carbon per year, especially in boreal and temperate zones like Canada, Siberia, and parts of Europe.
• Marine NPP declined by 0.1 billion metric tons of carbon per year, most notably in tropical Pacific and Indian Ocean regions, due to reduced nutrient mixing from ocean stratification.

These trends were tracked using multiple satellite datasets that measured chlorophyll activity, surface greenness, sea surface temperatures, and precipitation variability.

El Niño’s Outsized Influence

While land productivity has generally trended upward, ocean productivity proved more volatile. The decline in marine photosynthesis has been closely tied to El Niño and La Niña events, which shift trade winds and water column mixing patterns. These shifts are increasingly frequent and severe under global warming.

“The ocean’s primary production responds much more strongly to El Niño and La Niña than land ecosystems,” said Shineng Hu, co-author and assistant professor at Duke. “A series of La Niña events helped reverse marine declines briefly after 2015, but the long-term trend remains downward.”

Why It Matters

According to the Global Carbon Project and IPCC AR6 reports, oceans currently absorb about 25% of anthropogenic CO₂ emissions. A continued decline in marine primary productivity would weaken this vital sink, increase atmospheric CO₂ concentrations, and destabilize tropical food chains.

At the same time, while expanding forests help offset emissions, their future is also uncertain. Deforestation, wildfires, pest outbreaks, and drought-induced diebacks threaten the durability of terrestrial carbon sinks. In 2023 alone, the Amazon rainforest lost nearly 5,000 km² of canopy—its highest rate in five years.

Moreover, a 2024 study in Science Advances warned that boreal forest gains might slow as Arctic warming accelerates permafrost thaw and soil carbon loss.

Integrated Monitoring Urged

Zhang and his co-authors stress that monitoring Earth’s productivity requires a joined-up approach, covering both land and ocean ecosystems.

“Whether the decline in ocean primary production will continue—and how long and to what extent increases on land can make up for those losses—remains a key unanswered question,” Zhang said.

Looking Ahead

This new Earth system imbalance—forest productivity up, ocean productivity down—should influence how nations model carbon budgets and design climate policies. It reinforces the need for:

• Strong forest preservation and reforestation
• Reductions in nutrient runoff that further degrade ocean ecosystems
• Improved long-term satellite monitoring (like NASA’s upcoming PACE mission)

The ICL imaged by Englert and his colleagues revealed a special type of galactic merger happening in Abell 3667. Normally, Englert says, mergers that involve the largest galaxy in a cluster, called the brightest cluster galaxy or BCG, occur gradually as it steals stars from many smaller galaxies that surround it. But this new research shows something different happening in this case. Abell 3667 is actually made of two galaxy clusters, each with its own BCG, that are now merging together. The ICL bridge discovered by the researchers suggests that the larger BCG is stealing stars from the smaller one — an event known as a rapid or aggressive merger. As the two BCGs merge, so too do the smaller galaxies that surround them, making Abell 3667 the product of two merging clusters. Data from X-ray and radio frequency observations had suggested a rapid merger in Abell 3667, but this is the first optical evidence to back it up. 

The appearance of intracluster light in these new images offers a tantalizing preview of what’s to come when the Vera C. Rubin Observatory becomes fully operational later this year or early next. Using a telescope twice the size of Blanco and the largest camera ever built, the Rubin telescope will perform a 10-year scan deep into the entire southern sky, a project called the Legacy Survey of Space and Time.

“Rubin is going to be able to image ICL in much the same way as we did here, but it’s going to do it for every single local galaxy cluster in the southern sky,” Englert said. “What we did is just a small sliver of what Rubin is going to be able to do. It’s really going to blow the study of the ICL wide open.”

That will be a scientific bonanza for astronomers and astrophysicists. In addition to revealing the history of galaxy clusters, the ICL holds clues to some of the most fundamental mysteries of the universe, particularly dark matter — the mysterious, invisible stuff thought to account for most of the universe’s mass.

“ICL is quite important for cosmology,” Dell’Antonio said. “The distribution of this light should mirror the distribution of dark matter, so it provides an indirect way to ‘see’ the dark matter.”

Seeing the unseeable — that’s a powerful telescope. 

The Victor M. Blanco Telescope and the Vera C. Rubin Observatory are operated by NOIRLab, the U.S. national center for ground-based, nighttime optical astronomy operated by the National Science Foundation. The research was funded by NSF (AST-2108287), the U.S. Department of Energy (DE-SC-0010010) and the NASA Rhode Island Space Grant Consortium.

Japanese researchers say they have discovered the mechanism by which exposure to PM2.5 air pollution causes airway dysfunction, and how the resulting damage might be reversed.

A large portion of natural and human-made air pollutants fall under the PM2.5 category, which relates to airborne particles below 2.5µm diameter. It includes dust, vehicle exhaust and wildfire smoke. When inhaled, it is believed to cause severe airway damage and respiratory diseases. To understand how exactly air pollution particles affect the respiratory system, the researchers ran a series of experiments on mice. They exposed the mice to environmental pollutants and then examined their respiratory tracts for changes in structure and function.

“Our results were quite informative. We found that PM2.5 air pollutants negatively affect mucociliary clearance, a major protective mechanism in the respiratory tract,” said lead author, Noriko Shinjyo of the University of Osaka, which led the research. “Mucociliary clearance basically involves trapping pollutants in a sticky mucus and then sweeping the pollutants out the airway with hair-like projections called cilia.”

The researchers’ findings seemed to confirm that the pollutants caused oxidative injury in the airways, which facilitates the formation of lipid peroxide-derived aldehydes. This substance is a reactive aldehyde that damages the protective cells in the airway, including airway cilia. As damaged airway cells and cilia can no longer move debris and pollutants out of the airways, the risk of infection is increased.

The team also attempted to ascertain how to restore normal cellular function and reverse damage. For this, the researchers investigated how one gene from the ALDH family, known to protect the body against harmful aldehydes, may counter the effect of airway pollutants.

“Aldehyde dehydrogenase (ALDH1A1) is an enzyme that plays an important role in protection against aldehydes. We used experimental mice that lacked ALDH1A1 to investigate the impact of air pollutants without the gene,” said Yasutaka Okabe, senior author. “As expected, the mice had impaired cilia formation and function and high levels of aldehydes.”

The research team also appeared to find that the absence of ALDH1A1 left the cells at a higher risk of serious respiratory infection when exposed to air pollutants. The importance of ALDH1A1 was further emphasized when it was also found that drug-enhanced ALDH1A1 levels improved the mice’s mucociliary function in response to pollutants.

These findings appear to reveal how PM2.5 pollutants disrupt the lungs’ self-cleaning system. The work also offers a potential therapeutic target: the enzyme ALDH1A1.

The results were published in The Journal of Clinical Investigation.

A vast blob of hot rock moving slowly beneath the Appalachian Mountains in the northeastern US is now thought to be the result of a divorce between Greenland and Canada some 80 million years ago.

A study by an international team of researchers challenges the existing consensus in both geographical and chronological terms. It was previously thought the breaking up of the North American and African continents was responsible, some 180 million years ago.

To test their assertion, the researchers used a combination of existing data and computer modeling to link the hot blob to a geological formation in the Labrador Sea in the North Atlantic dated to around 85-80 million years ago.

Related: Mysterious Blobs Deep Inside Earth May Fuel Deadly Volcanic Eruptions

“This thermal upwelling has long been a puzzling feature of North American geology,” says earth scientist Thomas Gernon, from the University of Southampton in the UK.

“It lies beneath part of the continent that’s been tectonically quiet for 180 million years, so the idea it was just a leftover from when the landmass broke apart never quite stacked up.”

Technically known as the Northern Appalachian Anomaly (NAA), the 350-kilometer- (217-mile-) wide blob of hot rock hasn’t been in any particular hurry to get to its present location, moving at a rate of around 20 kilometers every million years. At that rate, the blob should pass New York in around 10 to 15 million years or so.

However, the research team suggests this anomaly is one of the main reasons the Appalachians are still in place. The heat helps the continental crust remain buoyant, contributing to the mountains being uplifted further over the years.

The new study builds on previous work from some of the same researchers. Known as the ‘mantle wave’ theory, it posits blobs of hot rock rise in a lava-lamp style when continents break apart, triggering a variety of geological phenomena such as volcanic eruptions and formation of mountains.

“Our earlier research shows that these drips of rock can form in series, like domino stones when they fall one after the other, and sequentially migrate over time,” says geophysicist Sascha Brune, from the GFZ Helmholtz Centre for Geosciences in Germany.

“The feature we see beneath New England is very likely one of these drips, which originated far from where it now sits.”

Further analysis and tracking of the hot rock will help to confirm its origins. Meanwhile, the same theories and techniques can be used to identify other geological features like this.

In fact, the researchers think they might have already spotted a ‘mirror’ to the NAA, under north-central Greenland and also originating from the Labrador Sea.

“The idea that rifting of continents can cause drips and cells of circulating hot rock at depth that spread thousands of kilometers inland makes us rethink what we know about the edges of continents both today and in Earth’s deep past,” says Derek Keir, a geophysicist from the University of Southampton.

The research has been published in Geology.

In the middle of Chile’s Atacama desert, there’s lots of activity as construction on the Extremely Large Telescope (ELT) is still underway, with cranes helping to move pieces in place.

What is it?

The ELT is the European Southern Observatory’s (ESO) $1.4 billion project to create the next-generation observatory.

There’s a massive planet out there, far beyond our solar system, that’s speeding around its star so fast it completes an entire orbit in just 16 hours. It’s 870 light-years away and on a one-way path toward destruction.

Researchers from Macquarie University have tracked the slow-motion fall of this planet – TOI-2109b – and confirmed that it’s spiraling closer to its star.

A planet death spiral begins

TOI-2109b is what astronomers call an “ultra-hot Jupiter.” It’s nearly five times the mass of Jupiter and almost twice its size. But what really sets it apart is how close it orbits its star – even closer than Mercury orbits our Sun.

“Just to put it into context – Mercury’s mass is almost 6,000 times smaller than Jupiter’s, but it still takes 88 days to orbit our Sun,” said Dr. Jaime Alvarado-Montes, a Macquarie research fellow who led the study.

“For a huge gas giant such as TOI-2109b to fully orbit in 16 hours – it tells us that this is a planet located super close to its star.”

It’s the fastest orbit of any hot Jupiter ever found. And that speed is part of what’s sealing its fate.

Closing in on its star

Using 14 years of data from NASA’s TESS mission, ESA’s CHEOPS satellite, and ground-based telescopes, the team found that the planet’s orbit is shrinking and unstable.

By running the numbers through different models and comparing with direct observations, the team concluded that TOI-2109b’s orbital period is decreasing.

In the next three years alone, it could shorten by at least 10 seconds. That doesn’t sound like much – but in the world of orbital mechanics, it’s huge.

“This planet and its interesting situation could help us figure out some mysterious astronomical phenomena that so far we really don’t have much evidence to explain,” said Dr. Alvarado-Montes. “It could tell us the story of many other solar systems.”

Planets don’t live forever

Planets don’t live forever. But the way they die isn’t always clear – and it rarely looks the same twice. Some may be ejected from their solar systems entirely, flung into deep space after chaotic interactions with other planets.

Others might slowly spiral into their stars, especially if they orbit too close. And some get torn apart by gravity, stripped by radiation, or collide with other objects. Most of what we know about planetary death comes from simulations and theories.

Actual observations are rare, because the timescales are usually huge – far longer than a human lifetime. That’s what makes TOI-2109b so important. It offers a chance to catch a planet in the act of dying, rather than piecing together what happened long after it’s gone.

Ripped, swallowed, or stripped

Scientists see three possible endings for TOI-2109b. One, the star’s crushing gravity could pull it apart. Two, the star might swallow it whole as it spirals inward. Or three, it could have its outer gas layers stripped away by intense radiation, leaving behind a dense, rocky core.

That third outcome is especially interesting. If TOI-2109b ends up as a bare core, it could help explain the origins of some rocky planets found in other systems.

These stripped-down worlds might be the fossil remains of gas giants that got too close to their stars. The idea changes how we think about planetary life cycles.

A warning from deep space

TOI-2109b may be 870 light-years away, but what happens to it could reshape how we think about other worlds – including our own.

If gas giants can be torn apart or stripped down by their stars, it might explain why we find small, rocky planets in places where they shouldn’t exist. Maybe they’re just the hardened cores of giants that got too close.

Each orbit brings new clues. And the closer TOI-2109b drifts to its star, the more clearly we’ll see how violent – and unpredictable – planetary evolution can be.

The team isn’t done watching. In fact, the next few years could be the most revealing yet. They’ll keep tracking the orbit for signs that one of the planet’s three possible fates is beginning. It’s not often astronomers get to witness a planet mid-collapse.

TOI-2109b is giving us a rare look at a planet in real-time crisis – and it’s changing what we thought we knew about the life and death of worlds.

Image credit: NASA/CXC/M. Weiss

The full study was published in the journal The Astrophysical Journal.

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Astronauts exploring the Moon will need all the help they can get, and scientists have spent lots of time and plenty of money coming up with different systems to do so. Two of the critical needs of any long-term lunar mission are food and oxygen, both of which are expensive to ship to the Moon from Earth. So, a research team from the Technical University of Munich spent some of their time analyzing the effectiveness of using local lunar resources to build a photobioreactor (PBR), the results of which were recently published in a paper in Acta Astronautica.

The concept around PBRs is simple enough – enclose some sort of biological system, like algae, give it the raw material it needs to live, such as carbon dioxide and water, and harvest the resulting “waste” products, like oxygen and the algae itself. Nature has a way of optimizing its processes, so depending on the design of the PBR, and especially on the choice of algae, they can be extremely effective at creating those useful outputs with very little waste.

However, they’re not so great at doing so on the lunar surface, which is why they would need to be enclosed in a system protected from the lunar environment, which includes direct sunlight since the radiation that goes along with it would kill the living organisms inside the reactor. Harvesting the materials needed to build that protective system is the focal point of the paper.

Fraser discusses how living off the land in space would work.

It considered two different types of PBR – a “tubular” air lift and a “flat panel” airlift (FPA). The FPA variety was more efficient, but required more maintenance than its tubular counterpart. Building either variety would result in a cost savings of at least a few million dollars per system, assuming a $100,000/kg launch cost to the Moon. For the tubular system, it could be even more, with some estimates ranging up to $50M in savings by building it out of local resources.

Resources for most of the structural materials are already abundant on the Moon, and there has already been plenty of work on making the metals out of lunar regolith that would be required to build its base structure. However, the algae inside the PBR require light, and that has to either come from internal lighting, which is extremely power intensive and requires advanced components like LEDs, or can come from the Sun, which would require clear glass in at least part of the exterior housing. So far, no one has successfully created clear glass out of lunar resources, though that is an area of ongoing research.

LEDs are an example of another necessary component that is much harder to produce locally – electronics, and, to go along with that, plastics, such as sealing o-rings or the baseboards for printed circuit board assemblies. Research into how to make plastic on the Moon is also ongoing, but still a long way off from utilization in a mission. However, the algae itself in the PBRs could be used as a biological feedstock for the plastic, though that would still require at least a beginning seed from Earth to get the process going.

Phosphorous is another critical element of life that needs to be somehow collected on the Moon in order for a long-term biological presence there, as Fraser discusses with Harry Brodsky, a PhD student at UC Boulder.

Unfortunately, carbon, one of the primary ingredients in plastics, is relatively rare on the Moon, as are elements critical for the long-term survivability of the algae, such as nitrogen and chlorine. To ensure none of those precious materials are wasted, the authors suggest recycling astronaut waste water, which will also contain at least some of those elements, as a way to “close the loop”.

However, there are plenty of challenges to overcome if PBRs are to be integrated as a mission-critical component of any long-term lunar mission. The authors themselves suggest a hybrid approach that utilizes more traditional in-situ resource utilization (ISRU) methods, like Molten Regolith Electrolysis, for oxygen production, while utilizing PBRs for their combination of food production alongside oxygen production.

Both technologies are useful, and will eventually find their place in a lunar colony. Until that time, though, research will continue on the best way to get the most out of the lunar resources we can access, and we’ll undoubtedly see some improved designs of PBRs, lunar-derived glass, and even algae harvesting methods by then.

Learn More:

L. Salman et al – In-situ manufacturing of photobioreactors on the Moon using local resources

UT – Astronauts Could Rely on Algae as the Perfect Life Support Partner

UT – Instead of Building Structures on Mars, we Could Grow Them With the Help of Bacteria

UT – Bacteria Could Make Rocket Fuel on Mars

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