La mission qui devait percer le mystère de l'Humanité

The video discusses humanity's enduring quest to understand its origins and the universe, focusing on the Rosetta mission to a comet. For centuries, people have sought answers to "Where do we come from?" through myths, religion, and scientific exploration. The narrative begins with the discovery of ancient tablets, representing early human inquiries, and transitions to modern scientific endeavors. In the 1980s, two decades after the first space probes, scientists turned their attention to comets, believing they could offer insights into the solar system's formation and the origin of life. While Darwin's theory suggested life originated in Earth's primitive oceans, a century later, a biology student recreated early Earth conditions in a lab, producing amino acids—the "building blocks of life"—from water and atmospheric gases, reinforcing the idea of a common origin for all life. Concurrently, understanding of the universe progressed with the Big Bang theory and galaxy studies. The first cometary exploration involved five probes, including the Soviet Vega and European Giotto, targeting Halley's Comet in 1986. Comets were seen as "archives" of the early solar system, preserved in a "deep freeze" for 4.5 billion years since the sun and planets formed. The mission revealed that Halley's Comet was surprisingly dark, darker than charcoal, and its blackness was due to organic matter—carbon, hydrogen, and nitrogen molecules. This discovery was a scientific shock, as it suggested that the building blocks of life might not have originated solely on Earth but could have come from space, a theory previously considered fringe. The success of Vega and Giotto underscored the need for a more ambitious mission to directly analyze a comet's nucleus. The goal was to determine if comets contained the same organic molecules essential for life on Earth, which would imply an extraterrestrial origin for these ingredients. This led to the proposal of the Rosetta mission, the European Space Agency's (ESA) most expensive undertaking at the time. Initially, Rosetta was a joint project with NASA, as the Americans possessed the necessary expertise in deep space navigation and powerful launchers like Ariane 5, which could carry the heavy probe. A key challenge was the comet's elliptical orbit, which meant it would spend long periods in the frigid outer solar system, far from the sun, where solar power would be insufficient. NASA's mini-nuclear reactors were crucial for powering instruments in such extreme cold, a technology not mastered by Europeans. However, in the early 1990s, the US withdrew from the project, citing excessive costs. This left the European team with a formidable challenge: how to proceed without American technology and the ability to return samples to Earth. The solution was innovative: instead of bringing samples back, they would send a sophisticated laboratory to the comet itself. This mission was named Rosetta, after the Rosetta Stone, which unlocked the secrets of ancient Egypt, symbolizing the mission's goal to decipher the origins of life. The lander module was named Philae, after the obelisk that aided Champollion in translating hieroglyphs. Designing Philae was incredibly complex, given the limited resources. It had a total power budget of only 10 watts, half that of a small refrigerator bulb, to power 40 kg of electronics and 10 scientific instruments, including a panoramic infrared camera, X-ray spectrometer, radar sounder, magnetometer, and a drill capable of penetrating 30 cm into concrete, despite operating on minimal power. A crucial instrument, Cosac, included a mass spectrometer and a chromatograph to determine the chirality (handedness) of molecules. The discovery of left-handed amino acids, like those used by life on Earth, would strongly support an extraterrestrial origin for life's building blocks and explain a long-standing biological enigma. With the Americans gone, ESA had to overcome several hurdles. Ariane 5, then under development, became the new launch vehicle. For power, Rosetta relied on massive solar panels and a risky hibernation strategy. Beyond Jupiter's orbit, where solar energy was too weak for communication, Rosetta would be shut down almost entirely for three years, with only heating resistors active to prevent fuel from freezing. An automatic wake-up was programmed for when it approached the comet. This "absolute silence" period was a source of immense anxiety for the mission team. The launch, initially scheduled for January 2003, was delayed due to an Ariane 5 failure, necessitating a change of target comet to 67P/Churyumov–Gerasimenko (nicknamed "Chury"). Rosetta finally launched on March 2, 2004. Its journey involved a complex series of gravitational assists, using Earth and Mars to accelerate and slingshot it towards Chury. After several flybys and a final acceleration, Rosetta embarked on its deep space journey. In July 2011, seven years after launch, Rosetta entered hibernation as it moved too far from the sun to generate sufficient power. The spacecraft was spun to stabilize it and conserve energy, with minimal power allocated to thermal control to prevent fuel freezing. After 31 months of silence, on January 20, 2014, Rosetta successfully reawakened, sending its first signal back to Earth, 800 million kilometers away. The next challenge was locating Chury. Despite precise knowledge of Rosetta's position, the comet's exact location was uncertain by thousands to millions of kilometers. Rosetta's cameras eventually spotted the comet as a faint moving point against the fixed star background. As Rosetta approached, the first images revealed Chury's unusual, "duck-like" shape, which posed a significant challenge for Philae's landing. The initial plan required a flat, football-field-sized landing site, which the comet clearly lacked. After months of observation, engineers identified 10 potential landing sites. Following intense debate among scientists and operational teams, the Agilkia site was chosen. On November 12, 2014, Philae was released from Rosetta at an altitude of 22 km, beginning a seven-hour freefall. Due to Chury's irregular gravity and rotation, Philae's trajectory was highly complex. The lander was equipped with three systems to secure it to the surface: a cold gas thruster to push it down, screws in its legs for hard ground, and two harpoons for soft or sandy surfaces. During the descent, Philae's onboard computer encountered an issue, requiring a risky reboot. The thruster, crucial for pinning Philae to the surface, failed. Philae touched down but, without the thruster, it bounced. It bounced twice, traveling several kilometers before coming to rest. The team initially celebrated the landing, but quickly realized something was wrong when images showed Philae's footprints but no lander. Communication was lost as Philae moved out of Rosetta's line of sight. The next morning, after frantic work to program new commands, Rosetta re-established contact. Philae was alive but precariously wedged in the shadow of a cliff, rendering its solar panels mostly useless. Its batteries would provide a maximum of 60 hours of scientific operations. Despite the challenging position, Philae managed to conduct many experiments. While the drill could not reach the surface, cometary dust that entered the lander during the bounce was analyzed by the Cosac instrument, revealing 16 simple organic compounds. However, no complex sugars, amino acids, or their chirality could be definitively identified. Philae's batteries eventually ran out, and it went silent. Rosetta continued to orbit Chury, hoping Philae would reawaken as the comet approached the sun. In June 2015, Philae unexpectedly sent a signal, confirming it was still functional. It had been waking up intermittently since April, whenever sufficient solar energy was available, but Rosetta's increased distance due to cometary outgassing had prevented sustained communication. As Chury neared the sun, it became more active, with jets of gas and dust erupting from its interior. Rosetta, equipped with two mass spectrometers (Crosina and Rosina), was able to analyze this escaping primordial matter. Crosina detected a "festival" of organic molecules, including hydrogen cyanide, formaldehyde, and ammonia—molecules that can react to form amino acids. Rosina, focusing on gases, made an astonishing discovery: oxygen. The presence of highly reactive oxygen, preserved for 4.5 billion years, suggested it was trapped in ice before the solar system even formed, pushing the origin of life's ingredients back to the interstellar cloud. Rosina also found ethane, propane, benzene, and, most importantly, glycine—the simplest amino acid, confirming Miller's lab findings in space. Rosetta's findings revolutionized the understanding of origins. Comets, once thought to be mostly ice with some grains, were revealed to be primarily organic matter with some ice. This changed perspectives on the early solar system and the potential for comets to deliver vital ingredients to primordial Earth. Organic matter constitutes about half of a comet's solid nucleus. The mission demonstrated that life's emergence required not just energy and water, but complex organic matter and elements like phosphorus, supplied by these ancient celestial bodies. However, the question of chirality remained unanswered, as mass spectrometers could only weigh molecules, not determine their handedness. As Rosetta's mission neared its end, it was decided to gently de-orbit and land it on the comet in September 2016. In its final days, Rosetta took high-resolution images of the suspected landing site of Philae, and just before impact, a team member spotted Philae in one of the last images. Rosetta made a controlled descent, impacting the comet and ending its historic mission. The data collected by Rosetta and Philae continue to be studied, promising further discoveries. The mission, driven by humanity's fundamental question of "Where do we come from?", has not only provided answers but also opened up many new questions, revealing the vast and complex puzzle of our cosmic origins.