The Dawn Legacy of NASA, End of Mission

Dawn's mission has been extended several times by exploring Ceres and Vesta, which, combined, 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 September and October, Dawn will lose her ability to communicate with Earth. It will remain in silent orbit around Ceres for decades.

"While it will be 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 Washington headquarters. "Not only did this spacecraft unlock scientific secrets about these two small but significant worlds, but it was also the first to visit and orbit bodies at two extraterrestrial sites during its mission.

Dawn took off from Cape Canaveral Air Base in September 2007, attached to a Delta II-Heavy rocket. From 2011 to 2012, the spacecraft swept Vesta, capturing images of craters, canyons and even mountains of this planet-like world.

Then, in 2015, Dawn's cameras spotted a cryovolcano and mysterious bright spots on Ceres, which scientists later discovered were salt deposits produced by the exposure of brackish liquid from the sea. interior of Ceres.

"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, mission director and chief engineer. from Dawn. "Dawn showed us extraterrestrial worlds that for two centuries were just points of light among the stars, and she produced these richly detailed intimate portraits and revealed exotic and mysterious landscapes different from what we have never seen. "

Engineering practices

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 aimed at visiting 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.

The mission was aimed at Ceres and Vesta as they function as time capsules, intact survivors of the first part of our history.

"Vesta and Ceres each told how and where they were formed and how they evolved – a fiery magmatic story that led to rocky Vesta and a colder, water-rich history that resulted in the ancient world Oceanic 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."

Ceres spectacular

On the surface of Ceres, scientists have discovered the chemistry of an ancient ocean. "What we found was completely breathtaking – the story of Ceres is just divided all over its surface," said Raymond.

Some of the bright spots turned out to be bright, salty deposits, consisting mainly 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 below the surface of Ceres and that some areas were relatively recently geologically active, feeding in 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 matter is one of the building blocks of life, although Dawn's data do not determine whether Ceres organic matter was formed from biological processes.

"It is becoming increasingly evident that Erbyet 's organic material originated from within Ceres, in which case it would have existed for some time in the early days of the ocean," said Julie Castillo – Rogez , Dawn Project Scientist and JPL Assistant Researcher.

Vibrant Vesta

At Vesta, Dawn mapped the craters of this planet-like world and revealed that its northern hemisphere had suffered larger impacts than expected, suggesting that there were more large objects in the belt. asteroids that scientists thought.

In 1996, the Hubble Space Telescope retransmitted images of a mountain in the center of a huge Vesta basin now called Rheasilvia. Dawn's mapping showed that she was twice the height of the mount. Everest, and he revealed canyons that rival the size of the Grand Canyon.

Dawn also confirmed that Vesta was the source of a widespread family of meteorites.

Towards the end

Dawn continued to collect high-resolution images, gamma-ray spectra and neutron spectra, infrared spectra, and gravimetric data at Ceres. Nearly once a day, it will fly over Ceres about 35 kilometers from its surface, about three times the altitude of a jet plane, collecting valuable data up to what it is. It spends the last hydrazine that powers the thrusters.

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 remain in orbit around Ceres, which has no atmosphere.

Engineers have designed Dawn's final orbit to ensure that 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 reached its final orbit, likes to think of the end of Dawn as "a celestial monument inert to human creativity and ingenuity."

Explore more:
Mission at dawn: new orbit, new opportunities

More information:
More information on the legacy of Dawn's mission is here: dawn.jpl.nasa.gov/mission/toolkit/