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A small 3D printed grid of pillars, artificially coloured green to represent the presence of bacteria

Credit: Gabriella Bocchetti

The month’s best science images

Using a 3D printer, researchers have built minuscule tower blocks for bacteria, creating a system that can generate electricity from sunlight and water. The tiny pillars — coloured green in this electron-microscopy image — are just 600 micrometres high and have a branching, densely packed structure that provides surfaces for the bacteria to grow on. They are made of metal oxide nanoparticles, so that they can act as electrodes harvesting waste electrons that the bacteria generate during photosynthesis. “The electrodes have excellent light-handling properties, like a high-rise apartment with lots of windows,” says bioinorganic chemist and co-author Jenny Zhang. They “allow for a balance between lots of surface area and lots of light — like a glass skyscraper”. The technique proved more efficient than other methods of producing bioenergy from photosynthesis.

See more great science images, selected by Nature’s photo team.

Nature | Leisurely scroll

Reference: Nature paper

Tree cooling goes beyond carbon

Tropical forests have a crucial role in cooling Earth’s surface by extracting carbon dioxide from the air. But only two-thirds of their cooling power comes from their ability to suck in CO2 and store it. The other one-third comes from their ability to create clouds, humidify the air and release cooling chemicals. When scientists analysed these ‘biophysical’ effects alongside carbon storage, they found that the world’s tropical forests collectively cool the surface of the planet by around 1 °C.

Nature | 5 min read

Reference: Frontiers in Forests and Global Change paper

Robotic boat to map Tongan volcano

An uncrewed boat will soon begin surveying the underwater volcano Hunga Tonga–Hunga Ha’apai in the Pacific Ocean to understand exactly what happened when it erupted in January. The explosion sent a giant plume of ash into the upper atmosphere and triggered a tsunami that damaged buildings on nearby Tonga. A 12-metre-long robotic boat, Maxlimer, will map the shape of the volcano’s submerged opening over several weeks. A crewed ship from New Zealand, the RV Tangaroa, will help to investigate, but for safety reasons will spend limited time over the volcano’s opening.

BBC | 5 min read

Read more: Why the Tongan eruption will go down in the history of volcanology (Nature | 8 min read)

Research highlights: 1-minute reads (Nature paywall)

Ancient ‘harbour’ was a ritual pool

The Phoenicians were master seafarers who ruled the Mediterranean between 1200 bc and 300 bc. The Phoenician island city of Motya includes a large water basin that was long thought to be an artificial harbour. A pedestal discovered in the basin has a carved foot that matches up with a statue found nearby of Ba'al, the Phoenician god of tempests, supporting the idea that the water body is a sacred pool dedicated to the god.

Cold treatment for cells points to diabetes cure

Transplanting beta islets — which produce insulin — into people with diabetes can restore the ability to regulate blood-sugar levels, curing the disease. But beta islets are difficult to preserve for more than a few days, limiting the use of this experimental therapy. Now, a protocol for freezing the cells allows them to be safely stored for months.

Astronomy’s carbon footprint is sky-high

The first rough estimate of astronomy’s total impact on Earth’s climate suggests that, between them, space missions and ground-based observatories emit greenhouse gases equivalent to more than one million tonnes of carbon dioxide each year. Large observatories, such as the Hubble Space Telescope and the Very Large Telescope in Chile, topped the list as the most carbon intensive.

Some amino acids make mice eat less and explore more

The response to ‘non-essential’ amino acids, which can be made in the body, might help animals to seek out more important nutrients.

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Features & opinion

Population shifts reshape nations

“Japan is ageing so rapidly that if current trends continue, the nation could eventually disappear altogether”, writes Jennifer Sciubba in her data-packed book 8 Billion and Counting. The twenty-first century “is less a story about exponential population growth than it is a story about differential growth — marked by a stark divide between the world’s richest and poorest countries”, she writes.

Nature | 6 min read

Video: soft robot made of magnetic slime

A controllable blob made of polymer mixed with particles of neodymium magnet could crawl around your body to engulf harmful objects, such as button batteries, that were accidentally swallowed. The prototype “magnetic turd” can also grasp and reconnect cut wires and squeeze through narrow 1.5-millimetre channels. “It’s very much like mixing water with [corn] starch at home,” says engineer and co-author Li Zhang. “When you touch it very quickly, it behaves like a solid. When you touch it gently and slowly, it behaves like a liquid.”

The Guardian | 3 min read

Reference: Advanced Functional Materials paper

Where I work

Laura Aiudi, marine biologist on a trawler off Cesenatico's coast, testing the turtle excluder modified net.

Laura Aiudi is a field researcher at the University of Pisa, Italy.Credit: Elisabetta Zavoli for Nature

Marine biologist Laura Aiudi is working on a net that saves the lives of endangered species — but still protects the livelihood of fishermen. She holds a net designed to allow turtles to escape: it has a hole at the top they can swim out of. The net is dubbed TED — short for ‘turtle excluder device’. “I love this work,” says Aiudi. “I’m from a fishing family … I’m used to the smell of fish.” (Nature | 3 min read)

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