Terrifying tarantula fangs and more — October’s best science images

Hammer time. A study of bonnethead (Sphyrna tiburo) embryos at different developmental stages shows that hammerhead sharks start to grow their iconic head shape about halfway through gestation. In this small species of hammerhead shark, the cartilage that forms the hammer takes about two months to develop. It first appears near the nose and then expands sideways.

Forest highway. Photographer Fernando Constantino Martínez Belmar won the photojournalism category of the Natural History Museum in London’s Wildlife Photographer of the Year competition with this shot of a rainforest in Paamul, Mexico. The trees in the region had been cleared to make way for a large cross-country railway. To reach a location where he could launch the drone used to capture this image, he had to travel through an underground cave system for four kilometres. “This photo captures the sheer magnitude and violence of deforestation,” says competition judge Celina Chien. “Towering trees are made to look like spilled matchsticks. It instils almost a sense of panic — this laceration across the Earth that seems to go on forever into our future.”

Heat map. This video captures the heat emitted by a train at night as it moves through Chicago, Illinois. The footage was captured by a thermal imaging satellite, HOTSAT-1, which carries the highest-resolution commercial infrared sensor in orbit. HOTSAT-1 was built by London-based climate-technology company SatVu and can trace hot and cold features as small as 3.5 metres wide. Its creators say the spacecraft has many potential applications, such as helping urban planners to pinpoint buildings in need of better insulation. It could also be used to identify ‘heat islands’, areas that are hotspots for absorbing and releasing heat.

Ring of fire. Astronomy writer Jeff Kanipe captured this stunning image of the annular solar eclipse in Rio Rancho, New Mexico, on 14 October. He used a solar filter and a 600-millimetre lens to take the picture. The ‘ring of fire’ effect happens when the Moon is at its farthest point from Earth when it passes in front of the Sun.

Silent warning. This video shows chemical signals passing along the leaves of an Arabidopsis thaliana plant as it senses the airborne volatile organic compounds (Z)-3-hexenal and (E)-2-hexenal, which are released by damaged plants.

The signals are carried by calcium ions. Researchers have developed a way to visualize the warning process by labelling calcium with a fluorescent protein. The plants’ ability to detect their neighbours’ warning messages allows them to activate defences against herbivores.

Fluorescent fur. Researchers have shown that a broad range of mammals glows under ultraviolet light. By analysing 146 specimens, including frozen and chemically preserved bats, platypuses, wombats and bandicoots, the researchers found that skin, claws and white or light-coloured fur are often fluorescent. They also discovered that creatures glowed white or yellow more often than they did blue, pink or orange. Because nocturnal animals displayed more-intense fluorescence than did mammals that are active during the day, the team speculated that visual signals might have a larger role in communication among nocturnal mammals than previously thought. But the fluorescence could also just be a side effect of having unpigmented fur or skin.

Searching for stardust. This colourful cloud of dust and stars was imaged by NASA’s James Webb Space Telescope. The shot shows a star-forming region in the Small Magellanic Cloud, a galaxy close to the Milky Way that contains low amounts of heavy elements, such as silicon and oxygen. These elements are required for the formation of cosmic dust, so researchers did not expect to find this much cosmic dust in the region. Yet the blue swirls in this image reveal an abundance of dusty silicates and sooty chemicals known as polycyclic aromatic hydrocarbons. The more-diffuse red smears show dust that has been heated by stars. And the bright spots and filaments in the picture are regions filled with protostars — collections of gas and dust that are collapsing in on themselves to form stars.

Smashing Ceres. This cloud of dust was produced by shooting at organic compounds, similar to those found on the dwarf planet Ceres, at high velocities using NASA’s Ames Vertical Gun Range at Moffett Federal Airfield in California. Ceres — which is the largest object in the asteroid belt between Mars and Jupiter — hosts plenty of water ice and complex organic molecules that contain carbon and hydrogen. This suggests that the dwarf planet could have once harboured the key ingredients for life, but whether the organic molecules originated on Ceres or were delivered there by comets is unclear. Researchers have now helped to shed light on this mystery by testing how well such organic compounds can withstand high-velocity impacts. Using data from NASA’s Dawn space probe, the team also mapped the areas of Ceres with the highest abundance of these chemicals. Together, the findings suggest that the molecules probably formed on Ceres in the presence of water.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory