(CNN)NASA's Dawn spacecraft has run out of fuel and dropped out of contact with mission control, the agency said Thursday.
This ends the spacecraft's 11-year mission, which sent it on a 4.3 billion-mile journey to two of the largest objects in our solar system's main asteroid belt. Dawn visited Vesta and Ceres, becoming the first spacecraft to orbit two deep-space destinations.
Dawn missed two communication sessions with NASA's Deep Space Network the past two days, which means it has lost the ability to turn its antennae toward the Earth or its solar panels toward the sun. The end of the mission is not unexpected, as the spacecraft has been low on fuel for some time.
It's the second historic NASA mission this week to run out of fuel and come to an end, as NASA's Kepler Space Telescope did Tuesday.
"Today, we celebrate the end of our Dawn mission -- its incredible technical achievements, the vital science it gave us and the entire team who enabled the spacecraft to make these discoveries," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate in Washington. "The astounding images and data that Dawn collected from Vesta and Ceres are critical to understanding the history and evolution of our solar system."
Vesta and Ceres are considered to be like time capsules from the beginning of our solar system. The experiments Dawn carried out enabled astronomers to look at the different ways Vesta and Ceres formed and evolved, as well as revealing that dwarf planets can also host oceans.
Vesta probably formed in the inner solar system and stayed between Mars and Jupiter, and it evolved just like the other rocky planets there. Its craters provided a road map of impacts on the ancient surface, suggesting that large planets crashed into it. This also suggests that planets were "born big," rather than starting small and growing.
Photos: Dawn: Mission to the beginning of the solar system
Ceres has several craters and linear troughs. In this image taken by NASA's Dawn spacecraft on October 14, 2015, the large crater Lono can be seen near the top right of the photo. The crater below it is called Besua.
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Photos: Dawn: Mission to the beginning of the solar system
You can see part of Ceres' southern hemisphere in this image taken on October 18, 2015. The big crater in the middle of the picture is called Hamori after a Japanese god and protector of tree leaves. The crater is 37 miles (60 kilometers) in diameter. Dawn was 915 miles (1,470 kilometers) above Ceres when the photo was taken.
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Photos: Dawn: Mission to the beginning of the solar system
Ceres has more than 130 bright spots, according to NASA. This false color image shows one of spots -- this one in a crater called Occator. Scientists say the substance appears to be a type of magnesium sulfate called hexahydrite. Scientists use false color to help study differences in surface materials, NASA says.
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Photos: Dawn: Mission to the beginning of the solar system
You get a close-up view of the southern part of Ceres in this image taken on December 10, 2015. You can see craters, troughs and grooves. The spacecraft took these images while it was about 240 miles (385 kilometers) above Ceres, its lowest ever orbit. Dawn will remain at this altitude for the rest of its mission.
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Photos: Dawn: Mission to the beginning of the solar system
This tall, conical mountain on Ceres was photographed from a distance of 915 miles (1,473 kilometers) by NASA's Dawn spacecraft. The mountain, located in the dwarf planet's southern hemisphere, is 4 miles (6.4 kilometers) high. The photo was taken on August 19, 2015.
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Photos: Dawn: Mission to the beginning of the solar system
NASA's Dawn probe captured this image of a 3-mile-tall pyramid-shaped structure rising from a plain on the surface of the dwarf planet Ceres. The discovery has further fueled speculation about just what mysteries Ceres may hold. The image was taken on June 6, 2015.
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Photos: Dawn: Mission to the beginning of the solar system
Dawn gave scientists a big surprise: Ceres has a group of bright spots glowing inside a large crater. The above image is part of a sequence taken by Dawn on May 16, 2015 when the spacecraft was 4,500 miles (7,200 kilometers) away from Ceres. It's the closest view yet of the spots. But what are they? According to the mission's principal investigator, Christopher Russell, scientists have concluded the spots are "due to the reflection of sunlight by highly reflective material on the surface, possibly ice."
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Photos: Dawn: Mission to the beginning of the solar system
Dawn snapped this image of Ceres on March 1, 2015 just before entering orbit on March 6. The image was taken at a distance of about 30,000 miles (about 48,000 kilometers).
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Photos: Dawn: Mission to the beginning of the solar system
"Ceres has really surprised us," said Carol Raymond, Dawn's deputy principal investigator. "The first images have produced some really puzzling features." One of the puzzles: two bright white spots that showed up in photographs taken by Dawn on February 19.
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Photos: Dawn: Mission to the beginning of the solar system
Another puzzling feature on Ceres is a pancake-shaped basin seen in the lower right side of this image. The image was taken on February 19 from a distance of nearly 29,000 miles (47,000 kilometers). The basin is nearly 186 miles (300 kilometers) across.
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Photos: Dawn: Mission to the beginning of the solar system
This mosaic is made up of images taken by Dawn on February 19 from a distance of nearly 29,000 miles (47,000 kilometers).
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Photos: Dawn: Mission to the beginning of the solar system
These two views of Ceres were taken on February 12, when Dawn was about 52,000 miles (84,000 kilometers) from Ceres. The images were taken about 10 hours apart.
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Photos: Dawn: Mission to the beginning of the solar system
Dawn took this picture on approach to Ceres on January 25. It was about 147,000 miles (237,000 kilometers) from the dwarf planet.
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Photos: Dawn: Mission to the beginning of the solar system
On its way to Ceres, Dawn spent more than 300 days taking photos of the protoplanet Vesta. These three images show Vesta coming into view as the spacecraft approached in July 2011.
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Photos: Dawn: Mission to the beginning of the solar system
As the spacecraft prepared to leave Vesta behind, scientists created this mosaic of the best views taken during Dawn's stay.
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Photos: Dawn: Mission to the beginning of the solar system
This is Vesta's Numisia crater. It's about 19 miles (31 kilometers) in diameter.
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Photos: Dawn: Mission to the beginning of the solar system
This image compares an image of Vesta taken by Dawn as it moved in on the protoplanet with one taken by the Hubble Space Telescope. Before the Dawn mission, the Hubble image was the best available.
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Photos: Dawn: Mission to the beginning of the solar system
Workers check on the spacecraft, at left, as they prepare to mate it with the upper stage booster rocket on the right.
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Photos: Dawn: Mission to the beginning of the solar system
Workers at Cape Canaveral prepare Dawn for launch by removing its transportation canister. Dawn was then mated with a Delta II rocket.
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Photos: Dawn: Mission to the beginning of the solar system
A worker checks the xenon feed system on Dawn.
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Photos: Dawn: Mission to the beginning of the solar system
Dawn's mission started at 7:34 a.m. ET on September 27, 2007, at Cape Canaveral, Florida. Dawn was launched into space on a Delta II rocket.
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Ceres formed farther from the sun and migrated to the same area of the inner solar system. On the surface, Dawn found ammonia, which requires the cold temperatures of the outer solar system to form.
Vesta didn't have as much water as Ceres, so it melted its own interior to form a metallic core and rocky crust, while Ceres has a rocky clay-like mantle and an outer ice-water-rich shell. This is why the scientists studying Dawn's data believe that Ceres once hosted an ocean, and there could even be liquid beneath the surface.
Dawn also detected an abundance of organic molecules in one of Ceres' craters, which might have come from the planet's ocean. On Earth, these same organic molecules are associated with life.
Bright features on the dark surface of Ceres and a giant, lone volcano suggest that the dwarf planet's surface has been geologically active recently.
"The fact that my car's license plate frame proclaims 'My other vehicle is in the main asteroid belt' shows how much pride I take in Dawn," said Mission Director and Chief Engineer Marc Rayman at NASA's Jet Propulsion Laboratory. "The demands we put on Dawn were tremendous, but it met the challenge every time. It's hard to say goodbye to this amazing spaceship, but it's time."
Dawn will remain in orbit around Ceres for at least the next 20 years, although the engineers putting it into this orbit are confident that it could last 50 years. They don't want it to collide with Ceres because there is a chance that it could disrupt some intriguing chemistry on the dwarf planet -- chemistry that could lead to the development of life.
"In many ways, Dawn's legacy is just beginning," Principal Investigator Carol Raymond at JPL said. "Dawn's data sets will be deeply mined by scientists working on how planets grow and differentiate, and when and where life could have formed in our solar system. Ceres and Vesta are important to the study of distant planetary systems too, as they provide a glimpse of the conditions that may exist around young stars."
