Après les 2 éclipses mémorables du mois de mars 2025, un nouveau cycle d'observations astronomiques s'ouvre. Un essaim d'étoiles filantes, les Lyrides, fera notamment son retour. Voici tous les phénomènes à observer à l'œil nu en avril 2025.

C'est la découverte de ce mois de mars… sur Mars : Une roche, pleine de sphérules, unique et encore inconnue, a été découverte par le rover Perseverance. Qu'est-ce que cela implique ?

A new study warns that toxic Martian dust contains fine particles and harmful substances like silica and metals that pose serious health risks to astronauts, making missions to Mars more dangerous than previously thought. The Guardian reports: During Apollo missions to the moon, astronauts suffered from exposure to lunar dust. It clung to spacesuits and seeped into the lunar landers, causing coughing, runny eyes and irritated throats. Studies showed that chronic health effects would result from prolonged exposure. Martian dust isn't as sharp and abrasive as lunar dust, but it does have the same tendency to stick to everything, and the fine particles (about 4% the width of a human hair) can penetrate deep into lungs and enter the bloodstream. Toxic substances in the dust include silica, gypsum and various metals. "A mission to Mars does not have the luxury of rapid return to Earth for treatment," the researchers write in the journal GeoHealth. And the 40-minute communication delay will limit the usefulness of remote medical support from Earth. Instead, the researchers stress that limiting exposure to dust is essential, requiring air filters, self-cleaning space suits and electrostatic repulsion devices, for example.

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La nouvelle suscite l'agitation depuis le 24 mars 2025 : des scientifiques du CNRS ont découvert les plus longues molécules organiques jamais identifiées sur Mars. Pourraient-elles être le reflet d'une forme de vie sur la planète rouge ? Explications.

NASA's Curiosity rover has detected the largest organic molecules ever found on Mars -- decane, undecane, and dodecane -- suggesting that complex prebiotic chemistry may have occurred in the planet's ancient lakebeds. The findings have been published in the Proceedings of the National Academy of Sciences. From a press release: Scientists probed an existing rock sample inside Curiosity's Sample Analysis at Mars (SAM) mini-lab and found the molecules decane, undecane, and dodecane. These compounds, which are made up of 10, 11, and 12 carbons, respectively, are thought to be the fragments of fatty acids that were preserved in the sample. Fatty acids are among the organic molecules that on Earth are chemical building blocks of life. Living things produce fatty acids to help form cell membranes and perform various other functions. But fatty acids also can be made without life, through chemical reactions triggered by various geological processes, including the interaction of water with minerals in hydrothermal vents. While there's no way to confirm the source of the molecules identified, finding them at all is exciting for Curiosity's science team for a couple of reasons. Curiosity scientists had previously discovered small, simple organic molecules on Mars, but finding these larger compounds provides the first evidence that organic chemistry advanced toward the kind of complexity required for an origin of life on Mars. The new study also increases the chances that large organic molecules that can be made only in the presence of life, known as "biosignatures," could be preserved on Mars, allaying concerns that such compounds get destroyed after tens of millions of years of exposure to intense radiation and oxidation.

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"SpaceX founder Elon Musk has said his Starship rocket will head to Mars by the end of next year," writes the BBC, "as the company investigates several recent explosions in flight tests." Human landings could begin as early as 2029 if initial missions go well, though "2031 was more likely", he added in a post on his social media platform X... The billionaire said in 2020 that he remained confident that his company would land humans on Mars six years later. In 2024, he said he would launch the first Starships to Mars in 2026, with plans to send crewed flights in four years. Musk has said that the coming Mars mission would carry the Tesla humanoid robot "Optimus", which was shown to the public last year.

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A new study published in the Journal of Geophysical Research Planets reveals that atmospheric gravity waves play a crucial role in driving latitudinal air currents on Mars, particularly at high altitudes. Phys.Org reports: The study applied methods developed to explore Earth's atmosphere to quantitatively estimate the influence of gravity waves on Mars' planetary circulation. [...] "On Earth, large-scale atmospheric waves caused by the planet's rotation, known as Rossby waves, are the primary influence on the way air circulates in the stratosphere, or the lower part of the middle atmosphere. But our study shows that on Mars, gravity waves (GWs) have a dominant effect at the mid and high latitudes of the middle atmosphere," said Professor Kaoru Sato from the Department of Earth and Planetary Science. "Rossby waves are large-scale atmospheric waves, or resolved waves, whereas GWs are unresolved waves, meaning they are too fine to be directly measured or modeled and must be estimated by more indirect means." Not to be confused with gravitational waves from massive stellar bodies, GWs are an atmospheric phenomenon when a packet of air rises and falls due to variations in buoyancy. That oscillating motion is what gives rise to GWs. Due to the small-scale nature of them and the limitations of observational data, researchers have previously found it challenging to quantify their significance in the Martian atmosphere. So Sato and her team turned to the Ensemble Mars Atmosphere Reanalysis System (EMARS) dataset, produced by a range of space-based observations over many years, to analyze seasonal variations up there. "We found something interesting, that GWs facilitate the rapid vertical transfer of angular momentum, significantly influencing the meridional, or north-south, in the middle atmosphere circulations on Mars," said graduate student Anzu Asumi. "It's interesting because it more closely resembles the behavior seen in Earth's mesosphere rather than in our stratosphere. This suggests existing Martian atmospheric circulation models may need to be refined to better incorporate these wave effects, potentially improving future climate and weather simulations."

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Hidden layers of rock below the surface of Mars "strongly suggest" the presence of an ancient ocean, according to an international team of scientists including researchers at Penn State. From the university's announcement: The new research offers the clearest evidence yet that the planet once contained a significant body of water and a more habitable environment for life, according to Benjamin Cardenas, assistant professor of geology at Penn State and co-author on the study. "We're finding places on Mars that used to look like ancient beaches and ancient river deltas," Cardenas said. "We found evidence for wind, waves, no shortage of sand — a proper, vacation-style beach." The Zhurong rover landed on Mars in 2021 in an area known as Utopia Planitia and sent back data on the geology of its surroundings in search of signs of ancient water or ice. Unlike other rovers, it came equipped with rover-penetrating radar, which allowed it to explore the planet's subsurface, using both low and high-frequency radar to penetrate the Martian soil and identify buried rock formations. By studying the underground sedimentary deposits, scientists are able to piece together a more complete picture of the red planet's history, Cardenas explained. When the team reviewed radar data, it revealed a similar layered structure to beaches on Earth: formations called "foreshore deposits" that slope downwards towards oceans and form when sediments are carried by tides and waves into a large body of water. "This stood out to us immediately because it suggests there were waves, which means there was a dynamic interface of air and water," Cardenas said. "When we look back at where the earliest life on Earth developed, it was in the interaction between oceans and land, so this is painting a picture of ancient habitable environments, capable of harboring conditions friendly toward microbial life." When the team compared the Martian data with radar images of coastal deposits on Earth, they found striking similarities, Cardenas said. The dip angles observed on Mars fell right within the range of those seen in coastal sedimentary deposits on Earth... The study also provided new information on the evolution of the Martian environment, suggesting that a life-friendly warm and wet period spanned potentially tens of millions of years. Mars "was evolving," Cardenas says in the announcement. "Rivers were flowing, sediment was moving, and land was being built and eroded. "This type of sedimentary geology can tell us what the landscape looked like, how they evolved, and, importantly, help us identify where we would want to look for past life." CNN notes that the research was published Monday in the journal Proceedings of the National Academy of Sciences.

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Mars 2025 s'annonce rempli de phénomènes astronomiques superbes. Ce mois-ci, une éclipse de Lune et une éclipse de Soleil seront visibles en France métropolitaine. Mais, ce n'est pas tout : voici toutes les dates à noter.

Chinese scientists are developing a lightweight Mars drone capable of both rolling on the ground and flying using contra-rotating coaxial rotors. Space.com reports: The air-ground dual-purpose unmanned aerial vehicle (UAV) weighs only 10.6 ounces (300 grams), equivalent to the weight of an apple. The development team is at the School of Astronautics (SoA) of the Harbin Institute of Technology. Seen as showing promising potential in future Mars science work, the UAV can take off at any time, traverse obstacles, and boasts superb endurance, reports state-owned China Central Television (CCTV). "On the ground, it mainly rolls by shifting its center of gravity," said Zhu Yimin, a Ph.D candidate at SoA. "In the air, it relies on a pair of contra-rotating coaxial rotors, controlled by a steering engine to adjust the forward direction, to control torque and force, ultimately achieving stable flight," Zhu told CCTV. The UAV work entails multiple models of air-ground dual-mode robots with different configurations, CCTV reports. These robots move by rolling close to the ground, which reduces energy consumption, and can achieve a flight endurance time of more than six times that of traditional drones of the same size. According to Zhang Lixian, a professor within the SoA, the hope is that the aerial vehicle can show off its long endurance and observational abilities on Mars. "Our second goal is for such machines to be suitable for construction in many underground spaces and for exploring unknown underground spaces. We also need robotic means for inspection and environmental detection. We have now materialized all these functions," said Zhang. A video of the drone can be found here.

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Le soir du vendredi 28 février 2025, un « alignement » de 7 planètes (Mars, Jupiter, Uranus, Vénus, Neptune, Mercure et Saturne) est annoncé. Pourtant, cela ne reflète pas réellement la position des planètes dans le système solaire. Que peut-on voir ?

La planète rouge est la plus explorée du système solaire. Mars est à la fois un monde froid, désertique et dynamique. Taille, couleur, distance, particularités... : voici tout de ce qu'il faut savoir au sujet de notre voisine.

Des relevés fournis par le rover Zhurong, envoyé sur Mars, confirment l'existence d'un vaste océan au nord de la planète rouge, qui aurait été accompagné d'un rivage similaire aux plages terrestres. À quelques détails près.

Ce n'est pas pour rien que Mars est décrite comme la planète rouge. Et comprendre les matériaux martiens, c'est retracer l'histoire de notre voisine. Ainsi, les recherches sur sa couleur permettent d'avancer un peu plus sur la question d'une possible vie passée sur Mars.

Comprendre les matériaux martiens, c'est retracer l'histoire de la planète rouge. Ainsi, ces recherches sur sa couleur permettent d'avancer un peu plus sur la question d'une possible vie passée sur Mars.

Un « alignement » de 7 planètes (Mars, Jupiter, Uranus, Vénus, Neptune, Mercure et Saturne) est annoncé le soir du vendredi 28 février 2025. L'expression ne reflète pas la position réelle des planètes dans le système solaire. Que verra-t-on exactement ?

Le ciel hivernal continuera de fasciner les amateurs d'astronomie en février 2025. Ce mois-ci, plusieurs conjonctions sont visibles à l'œil nu. Vénus atteint également sa magnitude maximale. Voici comment regarder ces phénomènes facilement.