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NASA's Dawn mission is coming to an end after 11 years of global science experience, bringing together breathtaking images and unprecedented achievements in space engineering.
Dawn's mission has been extended several times, exceeding scientists' expectations in his exploration of two planet-like bodies, Ceres and Vesta, which account for 45% of the mass of the main asteroid belt. Now, the spacecraft is about to miss an essential fuel, hydrazine. When that happens, probably between mid-September and mid-October, Dawn will no longer be able to communicate with Earth. It will remain in silent orbit around Ceres for decades.
"While sad to see Dawn's departure from our missionary family, we are extremely proud of her many accomplishments," said Lori Glaze, acting director of the Planetary Science Division at NASA's headquarters in Washington. "This spacecraft not only unlocked scientific secrets on these two small but significant worlds, but it was also the first spacecraft to visit and orbit bodies on two extraterrestrial destinations during its mission. Dawn's scientific and technical achievements will resonate throughout history. "
When Dawn left Cape Canaveral Air Force Base in Florida in September 2007, attached to a Delta II-Heavy rocket, scientists and engineers had an idea of what Ceres and Vesta looked like. Thanks to terrestrial and space telescopes, including NASA's Hubble Space Telescope, the bodies of the asteroid belt between Mars and Jupiter were visible – but even the best images were unclear.
From 2011 to 2012, Dawn swept Vesta, capturing images that surpassed everyone's imaginations – craters, canyons and even mountains. On Ceres in 2015, Dawn showed us a cryovolcano and mysterious bright spots, which scientists later discovered were salt deposits produced by the brackish liquid exposure of the interior of Ceres. Thanks to Dawn's eyes, these luminous points were particularly astonishing, shining like diamonds scattered on the surface of the dwarf planet.
"Dawn's legacy is that he has explored two of the last unexplored worlds of the internal solar system," said Marc Rayman of NASA's Jet Propulsion Laboratory in Pasadena, California, who is Dawn's chief of mission and chief engineer. . "Dawn showed us extraterrestrial worlds that for two centuries were just points of light among the stars. And he produced these richly detailed intimate portraits and revealed exotic and mysterious landscapes different from anything we've ever seen. "
Dawn is the only spacecraft to orbit a body in the asteroid belt. And it's the only spacecraft to orbit two extraterrestrial destinations. These achievements were made possible by ionic propulsion, an extremely efficient propulsion system known to science fiction fans and space enthusiasts. Dawn has pushed the limits of the capabilities and endurance of the system, showing how useful it is for other missions to visit multiple destinations.
Driven by ionic propulsion, Dawn reached Vesta in 2011 and examined it from the surface to the heart for 14 months in orbit. In 2012, engineers maneuvered Dawn out of its orbit and piloted it into the asteroid belt for more than two years before inserting it into orbit around the dwarf planet Ceres, where it collection of data since 2015.
"Vesta and Ceres have each told how and where they were formed, and how they evolved – a fiery magmatic story that led to Vesta and a colder, water-rich story that culminated in the ancient oceanic world of Ceres. . Raymond de JPL, principal investigator of the Dawn mission. "These information treasures will continue to help us understand other bodies of the solar system in the future."
There was so much that scientists did not know about Ceres before Dawn arrived. Raymond was wondering if they could find Ceres covered with a smooth, young surface – a huge ball with a frozen crust. Instead, they found the dwarf planet carrying the chemistry of its former ocean. "What we found was completely mind-blowing. The story of Ceres is only hers, "she said.
Some of the bright, shiny dots turned out to be bright salty deposits, mostly composed of sodium carbonate that made its way to the surface in a melting brine inside or below the crust.
The results reinforce the idea that dwarf planets, not just icy moons like Enceladus and Europa, could have hosted oceans in their history – and could still do so. Analysis from Dawn's data suggests that there may still be some liquid surface below the surface of Ceres and that some areas are relatively recently geologically active, feeding on a deep reservoir.
One of Dawn's biggest revelations about Ceres was in the Ernutet crater area. Organic molecules have been found in abundance. Organic products are part of life, although Dawn's data do not allow to determine whether organic compounds of Ceres have been formed by biological processes.
"It is becoming increasingly obvious that Ernutet's organic material originated in the interior of Ceres, in which case it may have existed for some time in the interior ocean," says Julie Castillo-Rogez, Dawn Project Scientist. and assistant researcher at JPL.
As Ceres presents interesting conditions for scientists studying the chemistry that leads to the development of life, NASA follows strict planetary protection protocols for the removal of the Dawn spacecraft. Unlike Cassini, who deliberately plunged into the atmosphere of Saturn to protect the system from contamination, Dawn will orbit Ceres, which has no atmosphere.
Engineers designed Dawn's final orbit to ensure it will not fail for at least 20 years – and probably decades more.
Rayman, who led the team that flew Dawn throughout the mission and is in its final orbit, likes to think of the end of Dawn as "a celestial monument inert to human creativity and ingenuity."
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