Les concentrations en dioxyde de soufre dans les zones polluées de l’Inde ont diminué d’environ 40 % entre avril 2019 et avril 2020. Grâce aux données fournies par le satellite Sentinel-5P du programme Copernicus de l’Union européenne, des scientifiques ont élaboré de nouvelles cartes qui montrent la chute des concentrations à travers le pays en ces temps de COVID-19.

Des tests qui font appel à plusieurs technologies spatiales sont en cours pour permettre aux personnels de santé, aux volontaires de la protection civile et aux membres des services d’urgence de continuer à venir en aide à d’autres personnes.

Alors que la crise immédiate causée par la pandémie de coronavirus s’estompe en Europe, des stratégies de tests à grande échelle sont nécessaires pour permettre la reprise économique, vitale.

Strange times meet strange clouds. Noctilucent or ‘night shining’ clouds (NLC) are captured over Knowlton Church in Dorset, UK, by astrophotographer Ollie Taylor in the early hours of 22 June.

A summer phenomenon, these rare clouds are visible when the Sun is below the viewer’s horizon, shining light on these tenuous wisps. First mentioned in 1885, just two years after the Krakatoa volcanic eruption, one of the most destructive on record, they were once considered a rare meteorological phenomenon. The clouds have been sited more frequently over the past few years, linked by many to increased greenhouse gas emissions.

Thanks to a dedicated network of NLC trackers, including live space weather updates, Czech-based NLC webcam observations and a Facebook group, Ollie got a great night’s worth of photography.

“It was an excellent night of shooting, arriving at location in the evening already greeted by noctilucent clouds better than I had previously seen in the south of England,” says Ollie. 

Taken between 2 and 2:50am, the clouds lend a ghostly glow to the 12^th century church in the middle of a Neolithic henge monument. “The electric blue complemented the misty landscape and eerie structure,” Ollie says of this picture-perfect moment.

But what exactly is a noctilucent cloud?

NLCs form in the mesosphere, the upper and more complex part of Earth’s atmosphere. While the lower atmosphere warms during this period, atmospheric circulation pushes air upwards, where it expands and cools. This means the mesosphere is cold enough for water vapour to freeze into clouds of ice crystals that form on meteoric dust and other particles found at the so called edge of space.

The rarefied atmosphere at these altitudes is electrically charged and some of these charges are transferred to the ice crystals, creating a so-called dusty plasma in the region.  

Considered the fourth state of matter, plasma – or electrically charged gas – is ubiquitous in the universe. In order to study dusty plasmas, scientists have taken plasma research to low Earth orbit, where weightlessness allows particles to be suspended and more easily studied.

The Plasma Kristall-4 experiment, a joint European-Russian endeavour since 2006, has just run its 10^th campaign on the International Space Station. The recipe is simple: apply electrical current to create a plasma-filled tube and coax dust particles to behave like atoms and form three-dimensional crystal structures. By adjusting the voltage across the experiment chamber, scientists can tailor their interactions and observe each particle as if in slow motion. Using PK-4, researchers across the world can follow how matter melts, how waves spread in fluids and how flows change at the atomic level. 

A team of scientists has already made use of the technical knowhow gained from developing the ISS experiment, to build plasma devices that disinfect wounds at room temperature. This revolution in healthcare has many practical applications, from food hygiene to treatment of skin diseases, water purification and even neutralising bad odours.

As for these noctilucent clouds, they are visible from Earth and also in space. ESA astronauts Luca Parmitano and Tim Peake also took pictures of the clouds during their missions on board the International Space Station.

The arrival of NASA astronauts Bob Behnken and Doug Hurley in the first crewed SpaceX Dragon on 31 May brought the Space Station crew to five and heralded the start of a new month of science 400 km above our heads. 

This panorama of the International Space Station is a wider view of what ESA astronaut Luca Parmitano was capturing on camera during the first of a series of historic spacewalks that took place in November 2019.

Author, journalist and researcher Lee Brandon-Cremer created this photo by stitching together three images taken by Luca as he made his way to the worksite during the first Extravehicular Activity or EVA to service the Alpha Magnetic Spectrometer (AMS), the Station’s dark matter detector.

"For every spacewalk there are thousands of images taken. Sometimes a few images jump out at me,” he explains. “One day I realised I could stitch these images together to expand the scene and show what the astronaut sees in a broader sense.”

To create this view, Lee first went looking for images with common points. This proved tricky: of the 1000 or so images he scanned, he found three that could be worked into two expanded photos of the Space Station. 

He then joined and lightly edited the images to create a smooth photograph, a technique referred to as “stitching”.

In the final image you can see the white panel radiators that keep the Space Station cool. The spacecraft on the left is a Soyuz. On the right is the Kibo module, with Japanese flag visible. The Space Station is flying to the right in this picture.

Nowadays we are spoiled for space imagery. From satellites circling the Earth and spacecraft taking selfies to astronaut snaps from the International Space Station, there is no shortage of photographs at which to marvel – and they are easy to access.

Aside from the critical role these images play in aiding scientific studies of Earth, the Solar System and outer space, they are important tools for science communication and public engagement.

One advantage of space imagery made public is how it engages citizen scientists and students all over the world. Take two projects as examples:

Cities at Night asks residents to identify major cities at night as seen by astronauts from the Space Station to help map out and combat light pollution. The Climate Detectives school project tasks students with investigating a local climate problem and proposing a solution by studying Earth observation satellite imagery.

For others like Lee, the images are a source of inspiration and creativity.

“It’s truly thrilling for me to recreate these broader views and it makes me wonder how many more unique views like this one captured by Luca are hiding in space agency archives,” Lee adds.

Download the high resolution image in the link above.