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Using pollen to make paper, sponges and more

At first glance, Nam-Joon Cho’s lab at Singapore’s Nanyang Technological University looks like a typical research facility — scientists toiling away, crowded workbenches, a hum of machinery in the background. But the orange-yellow stains on the lab coats slung on hooks hint at a less-usual subject matter under study.

The powdery stain is pollen: microscopic grains containing male reproductive cells that trees, weeds and grasses release seasonally. But Cho isn’t studying irksome effects like hay fever, or what pollen means for the plants that make it. Instead, the material scientist has spent a decade pioneering and refining techniques to remodel pollen’s rigid outer shell — made of a polymer so tough it’s sometimes called “the diamond of the plant world” — transforming the grains to a jam-like consistency, Knowable Magazine reports.

This microgel, Cho believes, could be a versatile building block for many eco-friendly materials, including paper, film and sponges.

A lot of people think of pollen, when it’s not fertilizing plants or feeding insects, as useless dust, but it has valuable applications if you know how to work with it, says Cho, who coauthored an overview of pollen’s prospective applications in the 2024 “Annual Review of Chemical and Biomolecular Engineering.” He’s not the only scientist to think so. Noemi Csaba, a nanotechnology and drug delivery researcher at the University of Santiago de Compostela in Spain, wants to develop hollowed-out pollen shells into protective vehicles to deliver drugs to the eyes, lungs and stomach.

Researchers studying pollen’s usefulness to people are a rare breed, Csaba says. “I find it a bit surprising,” she says. “Pollen is a very, very interesting biomaterial.”

Softening the shell

To begin working with pollen, scientists can remove the sticky coating around the grains in a process called defatting. Stripping away these lipids and allergenic proteins is the first step in creating the empty capsules for drug delivery that Csaba seeks. Beyond that, however, pollen’s seemingly impenetrable shell — made up of the biopolymer sporopollenin — had long stumped researchers and limited its use.

A breakthrough came in 2020, when Cho and his team reported that incubating pollen in an alkaline solution of potassium hydroxide at 80 degrees Celsius (176 degrees Fahrenheit) could significantly alter the surface chemistry of pollen grains, allowing them to readily absorb and retain water.

The resulting pollen is as pliable as Play-Doh, says Shahrudin Ibrahim, a research fellow in Cho’s lab who helped to develop the technique. Before the treatment, pollen grains are more like marbles: hard, inert and largely unreactive. After, the particles are so soft they stick together easily, allowing more complex structures to form. This opens up numerous applications, Ibrahim says, proudly holding up a vial of the yellow-brown slush in the lab.

When cast onto a flat mold and dried out, the microgel assembles into a paper or film, depending on the final thickness, that is strong yet flexible. It is also sensitive to external stimuli, including changes in pH and humidity. Exposure to the alkaline solution causes pollen’s constituent polymers to become more hydrophilic, or water-loving, so depending on the conditions, the gel will swell or shrink due to the absorption or expulsion of water, explains Ibrahim.

This winning combination of properties, the Singaporean researchers believe, makes pollen-based film a prospect for many future applications: smart actuators that allow devices to detect and respond to changes in their surroundings, wearable health trackers to monitor heart signals, and more. And because pollen is naturally UV-protective, there’s the possibility it could substitute for certain photonically active substrates in perovskite solar cells and other optoelectronic devices.

Cho’s lab has also demonstrated that paper made from pollen can be printed on. It may be a sustainable alternative to traditional paper for writing, printing and packaging, according to Cho, who has patented the microgel’s production process. Producing traditional paper destroys trees and is resource-intensive, requiring up to 13 liters of water for every page made. Pollen is naturally released in bulk from seed-producing plants, and deriving paper from it requires only a few simple steps. Ink can be removed with a simple alkaline solution wash — a process that lets the paper be reused.

Additionally, freeze-dried pollen microgel forms porous sponges. These could be made into such things as scaffolds for tissue engineering, or used to stem bleeding or to absorb oil spills.

Cho’s team usually works with sunflower and camellia pollen that they purchase inexpensively as a bee pollen mixture, mainly from China. But they say their alkaline hydrolysis method would work well with a broad swath of plant species. Pollen is abundant, Cho adds — a single floret of the common sunflower, for instance, produces 25,000 to 67,000 grains every summer. Moreover, it’s easy to collect from bees in commercial hives.

Pollen-based products have some way to go before reaching the market, Ibrahim adds; the key right now is to predict challenges and devise sustainable solutions. With other biomaterials researchers are working on, such as chitosan and cellulose, a crustacean or a tree must be destroyed. Compared with that, pollen is considerably less resource-intensive: “We’re not destroying the plant,” he says. “We’re not even destroying the flowers.”

This story was produced by Knowable Magazine and reviewed and distributed by Stacker.

The Rosalind Franklin mission’s chance of finding evidence of past life on Mars has been boosted by two studies that show that the rover won’t have to travel far to find materials potentially laden with organic molecules. Instead, natural processes could bring those materials to the rover, as revealed in two separate presentations at the EPSC–DPS2025 Joint Meeting in Helsinki this week.

Rosalind Franklin is a European Space Agency (ESA) mission currently scheduled to blast off to Mars in 2028. The rover will land in Oxia Planum, which is a large plain rich in clay minerals that formed in water billions of years ago.

The first study presented at EPSC–DPS2025, by Dr Aleksandra Sokołowska of Brown University in the USA and Imperial College London, describes how the identification of 258 rockfalls in the region of the landing site provides the opportunity for the rover to explore previously inaccessible material.

The second study, presented by Ananya Srivastava of the University of Western Ontario in Canada, reveals how organic-rich clays in Oxia Planum may have originated from elsewhere on Mars and been deposited through a series of floods over 3.5 billion years ago.

Will Rosalind Franklin See the Rolling Stones?

Identifying the rockfalls at Oxia Planum requires the highest resolution imagery from the HiRISE camera on NASA’s Mars Reconnaissance Orbiter, which can resolve objects as small as one metre. Many of the boulders brought to the ground by rockfalls are smaller than 2.5 metres and the largest is up to eight metres across. What really gives them away are their tracks, which can be metres deep and run for 500 metres.

Sokołowska and her colleagues identified the rockfalls at 48 sites thanks to a semi-automatic process, with deep-learning algorithms spotting candidate rockfalls that were then followed-up by a human being for verification. Most rockfalls were found on the steep slopes of craters, mounds and cliffs.

“We have reasons to believe that fresh rockfalls could be very common,” said Sokołowska. “More rockfalls are likely waiting to be found, as our manual follow-ups on small areas revealed many more than our semi-automatic search over the whole Oxia Planum region.”

The chance of Rosalind Franklin finding itself in the path of an onrushing rockfall is slim. Instead, the rover will be able to use them to its advantage.

Image from the HiRISE camera on NASA’s Mars Reconnaissance Orbiter showing rockfalls and their trails in the Oxia Planum region. Image credit: Aleksandra Sokołowska (Imperial College)/NASA/HiRISE/University of Arizona. larger image

“The discovery of rockfalls in Oxia Planum opens up the exciting possibility for the rover to increase the diversity of its samples with material that would otherwise be inaccessible,” said Sokołowska.

Fragments of rock that had been embedded on slopes of mounds, crater walls and other steep cliff-faces before falling would have been partly shielded from the radiation that drenches Mars from space. This, in theory, will improve the chances of organic molecules surviving intact in them. The dirt displaced from metres below the surface by the tracks gouged out by the rockfalls could also provide a new source of accessible samples for the rover to examine.

Sokołowska’s work shows that impact craters play an important role in creating the conditions for the rockfalls, in terms of fracturing the ground and distributing loose material on slopes. She further explains that “Other factors that contributed to the development of rockfalls could include thermal stresses or early fluvial erosion, but a tectonic origin seems unlikely.

The impacts themselves do not necessarily trigger the rockfalls, however. “In terms of triggers, we found no link with recent marsquakes or new impact craters,” said Sokołowska.

Martian clays reveal episodic flooding on ancient Mars

Image from the HiRISE camera on NASA’s Mars Reconnaissance Orbiter showing rockfalls and their trails in the Oxia Planum region. Image credit: Aleksandra Sokołowska (Imperial College)/NASA/HiRISE/University of Arizona. larger image

Clays are a prime target for Rosalind Franklin because they can preserve organic molecules, many of which are precursors to the building blocks of life. The clay-bearing geological units in Oxia Planum have compositionally different lower and upper sections (presented in false-colour infrared maps as orange and blue, respectively). It was previously suggested that these represent a single extensive clay unit, with an orange unit at the base overlain by a blue one, consistent with an in-situ formation of the clays.

Srivastava and her team studied clay units exposed in crater walls and found that, throughout Oxia Planum, there are multiple layers of alternating orange and blue sections. Furthermore, by comparing compositional data from NASA’s Mars Reconnaissance Orbiter (MRO) and ESA’s Mars Express missions with high-resolution imagery from MRO and ESA’s Trace Gas Orbiter, Srivastava’s team found a pattern. Craters at lower elevations tend to have thicker orange and blue layers than those at higher elevations, and overall the average thickness of these layers increases downslope of ancient highlands to the north-west of Oxia Planum.

An image of a crater in Oxia Planum, presented in false colour from the HiRISE camera on the Mars Reconnaissance Orbiter. The blue and oranges sections show multiple layers of clay units deposited in Oxia Planum and revealed at the crater wall. Image credit: Ananya Srivastava (University of Western Ontario) /NASA/HiRISE/University of Arizona. Larger image

“These results, particularly the variation in the layer thickness, imply that the clays may have originated elsewhere before being transported and deposited in the Oxia basin,” said Srivastava.

The clays were likely brought to Oxia Planum by rivers running from the highlands, the dried-out valley networks of which are still visible. The multiple layers indicate that there may have been cyclical or transient bursts of water that spilled into Oxia Planum about 3.5 billion years ago, before Mars completely lost its liquid water. The repeated clay-bearing layers may therefore be a signature of Mars’s ancient climate and geological conditions, offering clues as to how Mars evolved early in its history.

“The clays could record a far wider range of ancient Martian climatic conditions than previously believed if they came in multiple pulses from various source regions,” said Srivastava. “This diversity of environments improves the prospect that organic molecules were preserved under favourable conditions, strengthening the chances of uncovering the most thrilling discovery – clues for life beyond Earth.”

Further information

Aleksandra Sokołowska, Ingrid Daubar, Ariyana Bonab, Ian Haut, Valentin Bickel, Peter Fawdon, Peter Grindrod, and Susan Conway, https://doi.org/10.5194/epsc-dps2025-1727

Paper: Sokołowska, A. J., Daubar, I. J., Bonab, A., et al, ‘Fresh Rockfalls Near the Landing Site of ExoMars Rosalind Franklin Rover: Drivers, Trafficability and Implications’, npj Space Exploration, 1, 5 (2025) https://doi.org/10.1038/s44453-025-00008-7

This work was funded by the NASA MDAP grant #80NSSC22K1086.

Ananya Srivastava, Livio Tornabene, Gordon Osinski, Christy Caudill, Vidhya Ganesh Rangarajan, Peter Fawdon, Joe McNeil, Peter Grindrod, Ernst Hauber, Joel Davis, and Maurizio Pajola, https://doi.org/10.5194/epsc-dps2025-1001

Astrobiology,

The International Space Station has been in orbit around the Earth, at least in some form, since November of 1998 — but not without help. In the vacuum of space, an object in orbit can generally be counted on to remain zipping around more or less forever, but the Station is low enough to experience a bit of atmospheric drag. It isn’t much, but it saps enough velocity from the Station that without regular “reboosts” to speed it back up , the orbiting complex would eventually come crashing down.

Naturally, the United States and Russia were aware of this when they set out to assemble the Station. That’s why early core modules such as Zarya and Zvezda came equipped with thrusters that could be used to not only rotate the complex about all axes, but accelerate it to counteract the impact of drag. Eventually the thrusters on Zarya were disabled, and its propellant tanks were plumbed into Zvezda’s fuel system to provide additional capacity.

Visiting spacecraft attached to the Russian side of the ISS can transfer propellant into these combined tanks, and they’ve been topped off regularly over the years. In fact, the NASA paper A Review of In-Space Propellant Transfer Capabilities and Challenges for Missions Involving Propellant Resupply, notes this as one of the most significant examples of practical propellant transfer between orbital vehicles, with more than 40,000 kgs of propellants pumped into the ISS as of 2019.

But while the thrusters on Zvezda are still available for use, it turns out there’s an easier way to accelerate the Station; visiting spacecraft can literally push the orbital complex with their own maneuvering thrusters. Of course this is somewhat easier said than done, and not all vehicles have been able to accomplish the feat, but over the decades several craft have taken on the burden of lifting the ISS into a higher orbit.

Earlier this month, a specially modified SpaceX Cargo Dragon became the newest addition to the list of spacecraft that can perform a reboost. The craft will boost the Station several times over the rest of the year, which will provide valuable data for when it comes time to reverse the process and de-orbit the ISS in the future.

Reboosting the Russian Way

By far the easiest way for a visiting spacecraft to reboost the ISS is to dock with the rear of the Zvezda module. This not only places the docked spacecraft at what would be considered the “rear” of the Station given its normal flight orientation, but puts the craft as close as possible to the Station’s own thrusters. This makes it relatively easy to compute the necessary parameters for the thruster burn.

Historically, reboosts from this position have been performed by the Russian Progress spacecraft. Introduced in 1978, Progress is essentially an uncrewed version of the Soyuz spacecraft, and like most of Russia’s space hardware, has received various upgrades and changes over the decades. Progress vehicles are designed specifically for serving long-duration space stations, and were used to bring food, water, propellants, and cargo to the Salyut and Mir stations long before the ISS was even on the drawing board.

Reboosts could also be performed by the Automated Transfer Vehicle (ATV). Built by the European Space Agency (ESA), the ATV was essentially the European counterpart to Progress, and flew similar resupply missions. The ATV had considerably greater cargo capacity, with the ability to bring approximately 7,500 kg of materials to the ISS compared to 2,400 kg for Progress.

Only five ATVs were flown, from 2008 to 2014. There were several proposals to build more ATVs, including modified versions that could potentially even carry crew. None of these versions ever materialized, although it should be noted that  the design of the Orion spacecraft’s Service Module is based on the ATV.

American Muscle

Reboosting the ISS from the American side of the Station is possible, but involves a bit more work. For one thing, the entire Station needs to flip over, as the complex’s normal orientation would have the American docking ports facing fowards. Of course, there’s really no such thing as up or down in space, so this maneuver doesn’t impact the astronauts’ work. There are however various experiments and devices aboard the Station that are designed to point down towards Earth, so this reorientation can still be disruptive.

Depending on the spacecraft, simply flipping the Station over might not be sufficient. In the case of the Space Shuttle, which of the American vehicles performed the most reboost maneuvers by far, the entire complex had to be rotated into just the right position so that the thrusters on the spaceplane would be properly aligned with the Stations’ center of mass.

As described in the “AUTO REBOOST” section of the STS-129 Orbit Operations Checklist, the Shuttle’s computer would actually be given control of the maneuvering systems of the ISS so the entire linked structure can be rotated into the correct position. A diagram in the Checklist even shows the approximate angle the vehicle’s should be at for the Shuttle’s maneuvering thrusters to line up properly.

With the retirement of the Space Shuttle in 2011, maintaining the Station’s orbit became the sole domain of the Russians until 2018, when the Cygnus became the first commercial spacecraft to perform a reboost. The cargo spacecraft had a swiveling engine which helped get the direction of thrust aligned, but the Station did still need to rotate to get into the proper position.

After performing a second reboost in 2022, the Cygnus spacecraft was retired. It’s replacement, the upgraded Cygnus XL — is currently scheduled to launch its first mission to the ISS no earlier than September 14th.

Preparing for the Final Push

That brings us to the present day, and the Cargo Dragon. SpaceX had never designed the spacecraft to perform a reboost, and indeed, it would at first seem uniquely unsuited for the task as its “Draco” maneuvering thrusters are actually located on the front and sides of the capsule. When docked, the primary thrusters used for raising and lowering the Dragon’s own orbit are essentially pressed up against the structure of the ISS, and obviously can’t be activated.

To make reboosting with the Dragon possible, SpaceX added additional propellant tanks and a pair of rear-firing Draco thrusters within the spacecraft’s un-pressurized “trunk” module. This hollow structure is usually empty, but occasionally will hold large or bulky cargo that can’t fit inside the spacecraft itself. It’s also occasionally been used to deliver components destined to be mounted to the outside of the ISS, such as the for the outside of the ISS, such as the International Docking Adapter (IDA) and the roll-out solar panels.

While the ability to have the Dragon raise the orbit of the International Space Station obviously has value to NASA, the implications of this experiment go a bit farther.

SpaceX has already been awarded the contract to develop and operate the “Deorbit Vehicle” which will ultimately be used to slow down the ISS and put it on a targeted reentry trajectory sometime after 2030. Now that the company has demonstrated the ability to add additional thrusters and propellant to a standard Dragon spacecraft via a module installed in the trunk, it’s likely that the Deorbit Vehicle will take a similar form.

So while the development of this new capability is exciting from an operational standpoint, especially given deteriorating relations with Russia, it’s also a reminder that the orbiting laboratory is entering its final days.