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Timeline: Dawn spacecraft glides into orbit of dwarf planet Ceres

After spending nearly eight years floating through deep space, NASA’s Dawn spacecraft finally reached its destination Friday, a dwarf planet in the asteroid belt called Ceres.

NASA confirmed that its spacecraft slid into dwarf planet Ceres’ orbit at 4:39 a.m. today with no complications. “Dawn” will spend the next 16 months in the dwarf planet’s gravitational pull, photographing the largest known object in the asteroid belt.

“Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet,” said Marc Rayman, chief engineer of director of the $473-million mission, in a statement. “Now, after a journey of 3.1 billion miles and 7.5 years, Dawn calls Ceres home.”


Video by Jet Propulsion Laboratory

After making a first stop at asteroid Vesta, another resident of the rocky belt between Mars and Jupiter, Dawn continued onward to Ceres, whose composition remained nebulous to scientists ever since the Hubble Space Telescope captured the earliest images of the dwarf planet.

“[Ceres] is sort of just staying hidden from our eyes, more than I had expected it to be,” Chris Russell, lead investigator of the mission, told the NewsHour in February.

But as Dawn edged closer to Ceres, the dwarf planet’s icy surface came into view. And what scientists saw from a distance was puzzling. A bright spot, then a smaller shiny companion, appeared on Ceres’ surface.

Last month, within 29,000 miles of the dwarf planet, Dawn revealed that Ceres’ bright white spot was actually two located in a large crater. What could the sun be reflecting off the surface of Ceres? Speculations are abound: Is it the crater of an icy volcano? A salt flat? A subsurface ocean? Until more concrete measurements become available, Ceres’ composition will remain an extraterrestrial cliffhanger.

Whatever the case, scientists do think Ceres shows signs of life-sustaining water.

“Ceres is actually the largest water reservoir in the inner solar system other than the Earth,” Jian-Yang Li, of the Planetary Science Institute in Tucson, Arizona, told Space.com.

Li said estimates water makes up nearly 40 percent of Ceres’ volume, although it’s unclear how much of the water is liquid, which is necessary for life.

Ceres, along with Vesta, is a proto-planet that can offer clues to the solar system’s beginning and understanding the formation of its larger counterparts.

Ahead of Dawn’s reappearance from Ceres’ shadow, we put together a timeline of the spacecraft’s 3-billion-mile journey. It is the first mission to reach the orbit of a dwarf planet and also the first to orbit two celestial bodies during a mission.

Dawn mission milestones and accomplishments:

Sept. 27, 2007
Dawn launches.dawnlaunch

February 2009

Dawn uses Mars to slingshot on to Vesta and Ceres, and tests its equipment.

May 2011

The spacecraft returns its first pictures of Vesta.

This image, processed to show the true size of the giant asteroid Vesta, shows Vesta in front of a spectacular background of stars. Image courtesy of NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

This image, processed to show the true size of the giant asteroid Vesta, shows Vesta in front of a spectacular background of stars. Image courtesy of NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

October-December 2011

First science data from Vesta reveals:

  • One of the largest mountains in the solar system.
  • The surface is much rougher than other asteroids, and there’s a greater diversity in the composition of surface
  • Craters in the southern hemisphere that are 1-2 billion years old, and younger than the northern hemisphere
  • Vesta’s “color palette” shows that its composition is more varied than an asteroid, but not quite like Earth or Mars. That means it represents a transitional period in the formation of our solar system.
This full view of the giant asteroid Vesta was taken by NASA’s Dawn spacecraft, as part of a rotation characterization sequence on July 24, 2011, at a distance of 3,200 miles. Image courtesy of NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

This full view of the giant asteroid Vesta was taken by NASA’s Dawn spacecraft, as part of a rotation characterization sequence on July 24, 2011, at a distance of 3,200 miles. Image courtesy of NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

January 2012

Vesta could have ice water beneath the surface.

May 2012

Dawn mission finds that Vesta is more like the Earth’s moon or an early planet than it is an asteroid. It once had a subsurface magma ocean, and about 6 percent of the meteorites on Earth came from Vesta.

This image shows three slices of a class of meteorites that fell to Earth that NASA's Dawn mission has confirmed as originating from the giant asteroid Vesta. The meteorites, known as howardite, eucrite and diogenite meteorites, were viewed through a polarizing microscope, where different minerals appear in different colors. Image courtesy of University of Tennessee

This image shows three slices of a class of meteorites that fell to Earth that NASA’s Dawn mission has confirmed as originating from the giant asteroid Vesta. The meteorites, known as howardite, eucrite and diogenite meteorites, were viewed through a polarizing microscope, where different minerals appear in different colors. Image courtesy of University of Tennessee

August 30, 2012

Dawn leaves Vesta to head on to Ceres, and takes a good-bye shot of Vesta as it leaves.


Video by NASA Jet Propulsion Laboratory

Studying the data from Vesta further suggests that Vesta is a “stunted planet”; a planet that could have been, but was halted early in its development.

It appears to have been bombarded by other asteroids early in its life, but the shapes of its gullies, craters and troughs still leave questions for astronomers. How did they form? Why do they look different from those on the Moon or Mars?

December 2013

Color-coded images of the minerals on Vesta show the proto-planet’s brilliant colors.

This colorful image from NASA's Dawn mission shows material northwest of the crater Sextilia on the giant asteroid Vesta. While a large asteroid impact probably brought the black material, the red material may have been melted by the impact. Image courtesy of NASA/JPL-Caltech/UCLAMPS/DLR/IDA

This colorful image from NASA’s Dawn mission shows material northwest of the crater Sextilia on the giant asteroid Vesta. While a large asteroid impact probably brought the black material, the red material may have been melted by the impact. Image courtesy of NASA/JPL-Caltech/UCLAMPS/DLR/IDA

September 2014

Dawn has mechanical problems and goes into safe mode.

February 2015

Dawn gets closer to Ceres, and sees mysterious bright spots on the surface. The bright spots could be ice volcanoes, salt, surface ice or water, but until Ceres gets closer we won’t know for sure.

This image was taken by NASA's Dawn spacecraft of dwarf planet Ceres on Feb. 19 from a distance of nearly 29,000 miles. It shows that the brightest spot on Ceres has a dimmer companion, which apparently lies in the same basin. Image courtesy of NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

This image was taken by NASA’s Dawn spacecraft of dwarf planet Ceres on Feb. 19 from a distance of nearly 29,000 miles. It shows that the brightest spot on Ceres has a dimmer companion, which apparently lies in the same basin. Image courtesy of NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

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