Our best science images of 2020

Beneath its sharp spines, the purple sea urchin, Paracentrotus lividus, conceals a treasure: its bright orange gonads, the only edible part of this echinoderm. Affected by pollution, the degradation of its habitat and overfishing, the species has in the past few years been in sharp decline off the coasts of the French island of Corsica.

In this tiny ghost town, the skyscrapers are the result of a microelectronics experiment and were created by plasma etching of a sample of silicon. In this case, the silicon wafer lacked the desired uniformity: the presence of a contaminant in the material led to a manufacturing defect, causing these grooves that resemble the storeys of a building.

The ever-changing iridescence on the surface of this soap bubble tells us about the tiny variations in the film’s thickness. The brighter the colours, the thinner the bubble. When the colour verges on bright yellow, as seen here at the top, the bubble will soon burst. The tiny coloured patches, which are thinner and therefore lighter than the surrounding film, move up as a result of gravity, while the liquid flows inexorably down to the base. This phenomenon makes the bubble thinner over time.

On an ice floe in the Svalbard archipelago, this female Arctic walrus drifts along with the current. In that region, where temperatures are rising twice as quickly as in the rest of the world, melting ice is threatening these mammals’ habitat. Scientists are monitoring the seabed in order to study the changes that are disrupting Arctic ecosystems.

On the left is a rare, natural variation of a moss with a branched stem, rather like a two-pronged fork. Since modern mosses have retained some of the characteristics of the earliest land plants, such variations are a valuable resource to shed light on how plant architecture diversified in the course of evolution.

When a drop of liquid water is placed on an icy surface, the freezing front travels upwards, forming a sharp point at the top. In this case, the difference between two drops of water – one pure (left) and the other containing a surfactant (right) – is striking. It shows that a single icy water droplet can be sensitive to the presence of impurities.

A little-known world that comes in an astonishing variety of shapes and sizes, marine plankton lie at the base of the entire oceanic food chain. This image provides a tiny glimpse, just a few millimetres across, of the amazing diversity of planktonic life in the bay of Banyuls-sur-Mer, on the French Mediterranean coast.

This giant plankton, which measures 2.6 mm across and lives in the cold waters of the Pacific, goes by the name of Coelodendrum furcatissimum, and belongs to the group Phaeodaria (Rhizaria). It lives at a depth of 450 metres, and is very fond of marine snow, the continuous shower of organic detritus that falls into the abyss. Traces of this can be seen on its skeleton, in the form of multiple brown particles.

In a coral reef off the Gambier archipelago, in French Polynesia, researchers collected a specimen of Leptoseris hawaiiensis at a depth of some 172 metres. This discovery shows that some surface corals migrate towards the sea floor, where they can find refuge and thrive.

Jewels of the microscopic world, diatoms are brown, single-celled microalgae found in every aquatic environment. The specimen shown here is a centric diatom, but there are several thousand other species of all shapes and sizes, which can be identified by their frustule, a transparent, rigid cell wall made of silica. These photosynthesis champions produce around a quarter of the Earth’s oxygen.

When making microprocessors, one of the basic steps consists in depositing a layer of photosensitive resin on the surface of a wafer of semiconducting material, in this case gallium arsenide. The material is etched through this layer of resin. On this coin-sized component, resin residues appear to have mysteriously burgeoned, revealing delicate patterns that bring to mind the shape of sakuras, the ornamental cherry trees of Japan.

Whether spherical, cylindrical, or conical, protists come in a multitude of different shapes, and their distinctive features are revealed only under the microscope. The tremendous variety of these small nucleus-containing unicellular organisms reflects the multiple paths that the evolution of eukaryotes has taken. Some lines of protists, like those shown in the image, have developed an exoskeleton, made of silica (glass), strontium, calcium carbonate or cellulose, which protects their single cell.

A chocolate mousse, sea spume and (as shown here) soap lather all conceal the same scientific enigma: how do foams interact with the surfaces they touch? By altering the roughness of a glass slide with tiny glass beads a few tens of micrometres in size (shown in violet), researchers discovered that the size of the bubbles isn’t all that matters and that in order for a foam to stick rather than slip, the length of the tiny channels between the bubbles (in black in the image) must be smaller than the size of the surface asperities (i.e. the glass beads).

When a space launcher takes off, the blast is so loud that the sound waves produced can damage the structure of the rocket and the material it is carrying. In this image obtained using numerical simulations, scientists have succeeded in faithfully reproducing the mechanisms at work during this deafening acoustic wave. The image shows, in orange, the jets of hot gas expelled when the engines are ignited.

During extreme weather events such as storms and floods, huge amounts of sand are carried in suspension over long distances. Close inspection of this idealised numerical simulation reveals the chaotic motion of sand grains, showing how the suspended particles leave traces of turbulence as they pass through the fluid.

On the Coriolis rotating platform, researchers model on a small scale the effect of Earth’s rotation on the movement of winds, tides and ocean currents. This image shows an experiment attempting to reproduce the Kuroshio (meaning “black current” in Japanese), a warm marine current in the Pacific Ocean that flows around the islands of Japan. The small eddies are not due to a natural ocean phenomenon but rather to the unpredictable remnants of turbulence that formed right at the end of the experiment!