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Running out of gas, NASA's Dawn mission is about to end after 11 successful years in space. Dawn's mission was unique in NASA's list of explorers. Although slightly less known than the Curiosity rover on Mars or a spacecraft like New Horizons, which flew over Pluto, some said that Dawn was the first truly interplanetary mission, as it put into orbit two planetary bodies: l '; asteroid Vesta and the dwarf planet Ceres. This is unusual in other ways – unlike most NASA missions, Dawn is not an acronym. Instead, it bears the name of the goal of the mission – to return to the dawn of the solar system.
To do this, the spacecraft has orbited on both Vesta and Ceres, two bodies extremely different from each other, but both can answer questions regarding the early days of the solar system. Vesta is the second largest object in the main asteroid belt and it is thought that the majority of meteorites found on Earth come from Vesta. Ceres is unique in that it is the largest body of the asteroid belt, after all, it is large enough to be classified as a dwarf planet. Ceres is thought to have formed much further in the solar system and has spent millions of years migrating inward, making it a perfect combination of outdoor solar system and internal solar system.
Bodies like this one have not been modified by weather conditions or geological processes like Earth, with its storms and volcanoes. In some respects, Vesta and Ceres are time capsules of the early days of the solar system. Any opportunity to study them can tell us a lot about the type of materials that existed billions of years ago as well as the types of processes that gave us the solar system we know today. Dr. Carol Raymond, principal researcher at Dawns, says that Vesta and Ceres "represent two different chapters in the history of the solar system. Vesta is a good example of the internal solar system – it is a dry rocky body while Ceres forms with much more water.
Overall, this mission, with a relatively modest budget of $ 500 million, far exceeded its expectations. Each part of the spacecraft always works perfectly, but the hydrazine fuel used to keep the spacecraft facing the Earth is dangerously low. If Dawn can no longer direct her antenna towards us, NASA engineers can no longer communicate with her, making further observation unnecessary.
NASA believes the mission will end between mid-September and mid-October. Once they can no longer connect to the spacecraft, we will know that the mission is complete. The spacecraft will remain in orbit around Ceres for 20 years or more, but eventually it will have an impact on Ceres. Because the planet had a lot of water and ice and could still be geologically active, planetary protection required that the spacecraft not reach the surface so as not to contaminate future research. The planetary protection guidelines indicate that they must keep the spacecraft away from the planetary body for at least 20 years in order to give NASA time to launch a new mission. There is a chance that we can go back to Ceres with new astrobiological glasses to see if life exists there, or if it was the case before. And while the end of each mission is bittersweet, the Dawn team is thoughtful and grateful for all that Dawn has delivered. "The trip was long and impressive," says Raymond. Dawn's mission director, Marc Rayman, agrees. "I am sad to see his end and I could not be happier with the success he had."
Let's take a look at some of the highlights of the Dawn mission:
Spatialship
The Dawn spacecraft is often referred to as a tie hunter; think that Star Wars meets real space exploration. The main thruster of the Dawn spacecraft consists of an element called xenon and is used in an ion engine to accelerate in space. Ionic propulsion is ten times more efficient than other types of propulsion used on Earth, even if it takes time to get in gear. While it takes Dawn four days to go from 0 to 60 miles an hour, after 11 years of travel, it has reached a speed of 25,000 miles an hour. The force of these xenon-laden particles that are expelled from the engine is so small that it pushes the spaceship with about the same force as a piece of paper placed on your hand. But that's all you really need in the space where gravity does not exist. Keep this engine running in the long run and it's one of the most effective ways to navigate in space. Dawn has proven just how successful this type of propulsion can be and the blue glow of xenon is likely to appear in future missions.
Overall picture of Vesta:
This is Vesta, located nearly 300 miles inland and composed of the primordial building blocks of our solar system. Until Dawn approached this great asteroid, it was only a fuzzy rocky body imagined by the Hubble Space Telescope. Throughout its orbit around Vesta, Dawn discovered that this asteroid looked more like a baby planet, giving scientists insights into what proto-planets look like. "Vesta is a time capsule from the earliest days of solar system formation," says Raymond. After collecting data directly from orbit, the team can now track the evolution of Vesta through modeling and what they have found is that Vesta is probably formed within 1.5 million years of our solar system. This means that the first pebbles that existed around our star helped create the asteroid. As for the space rocks, they are not much older than Vesta.
Dark spots on Vesta:
After some initial explorations, Dawn spotted strange features on the surface that were unexpected. "One of the things that really surprised us," says Raymond, "is that there was a dark matter stain hydrated on Vesta. "It was thought that Vesta was drier than the moon because of its gravity. Because of this, the moon can hold more ice, but we found that piece of hydrated material at the equator that was enriched in hydrogen.
The team found that even though it was not very humid in this dark area of Vesta, the minerals themselves were hydrated, which they did not expect to find. Also called hydroxyls, hydrated minerals contain water in their crystalline structure. Hydrated minerals have also been found on Mars. Although it's not water, it's proof of a story about water.
"This is neither water nor ice, but it was a big surprise and a great discovery," says Raymond.
Overall picture of Ceres:
Ceres was once classified as an asteroid, but now joins the largest ranks of the smaller bodies of our solar system, next to Pluto, Eris and other dwarf planets. Ceres is about 600 miles away (a little less than the distance between New York and Detroit). Although it may seem small enough, compared to other planets, for something that resides in the asteroid belt, it's huge. After leaving Vesta, Dawn orbited Ceres and captured this image of the icy world. The team was not sure about the history of Ceres, but it became much more fascinating and complex than expected. After some initial reconnaissance, they discovered that Ceres probably had an ocean below the surface and could even remain geologically active. Strange bright dots began to appear scattered in size around the planet and, after further examination, turned out to be hydrated salts.
Inner Crater Crater:
When Dawn spotted these bright spots on Ceres, scientists wondered what could cause such a difference in contrast with the surface. Upon closer examination, they realized that it was salty ice mounds pushed upward to the surface of the dwarf planet. We know that Ceres probably was formed in the outdoor solar system, where it was cool enough for the water to freeze, instead of burning under the hot sun. For millions of years, Ceres has migrated inland, but like many bodies of the outer solar system, it has retained a lot of water.
Ahuna Mons
Ceres has a huge mountain 13,000 feet in height and is called Ahuna Mons. This striking landmark is proof that the dwarf planet was recently geologically active – and this could still be the case. The white streaks on the sides are in sodium carbonate. This material is not common in the solar system. It is found here on Earth, in the plumes of Enceladus and Ceres. What could these three have in common? We know that life exists here, and researchers think there is a chance it exists on Enceladus. Could it exist on Ceres? There is only one way to know it. Dawn is about to run out of gas, so another future mission will have to continue its exploration mission.
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