Dawn spacecraft leaves asteroid Vesta and the dwarf planet Ceres flies

The Dawn spacecraft is on its method to become the first spacecraft that orbited two remote celestial bodies of the solar system and studied. Dawn is on 5 September after over one year orbit around Vesta and leave this in 2.5 years to fly to the dwarf planet Ceres. Even these celestial bodies should examine Dawn at close range. The probe is expected in February 2015 in Ceres. Dawn launched on 27 September 2007. The end of the mission is scheduled for July 2015.

Giant impact basins on the South Pole. Deep furrows around the equator. Dark material in the craters, which brings the planetary scientists into puzzles. And a mountain that is more than twice as high as Mount Everest. The asteroid Vesta by the Dawn spacecraft orbited since July 2011 with a German camera system on board has brought the scientists astounded. "The expectations were more than fulfilled the mission," says planetary scientist Ralf Jaumann of the German Aerospace Center (DLR). Now we have to say goodbye: The probe swings early September from orbit and fly on to the dwarf planet Ceres. Meanwhile, icy, covered by dark carbon crust could an ocean of water, the scientists expect.

The first image of asteroid Vesta was taken from 975,000 kilometers - Vesta was then seen only as a small dot. In the first half of 2012, planetary scientists Vesta have observed from a height of up to only 175 kilometers and won initial findings: "We know for example that Vesta is known as a differentiated body, just like a planet in three layers - core, mantle and crust - is built, "explains DLR planetary researchers. In addition, the spectral signatures of the asteroids have confirmed that a specific, rare variety of the earth discovered meteorites originated from Vesta.

Vestas characteristics, the scientists can wonder: on two separate occasions were the heavenly bodies in the distant past by a powerful impact shaken at its south pole, so that two huge, overlapping basins originated at this point. Around the equator has a system formed by the impacts of furrows. That two times in the course of time, large collisions in the same place took place is very unusual. But has this amazing fact for the scientists and their research implications: to be able to look instead to an intact crust that planetary scientists see on a real shambles. "The strikes have destroyed the original crust and with these ruins also covers parts of the crust intact," says Jaumann. "We see in the eject are just one or two billion years old - and that's for damn young planetary geologists." What a shambles and debris ejections were almost over the entire asteroid distributed. "This shambles we have now put together like a puzzle."

Puzzle for planetary scientists

The more than 28,000 images, which recorded the German camera on board during the recent mission of Vesta show, also in dark material and the numerous craters. Whence comes this dark material? And what processes were running in the past from the asteroid Vesta? "This observation, it still retains many mysteries on" emphasizes Jaumann. Also, the large amount of hydrogen protons, the researchers at the Dawn team found on Vesta raises questions. A part of them could out of the solar wind come - ". Vesta but there is significantly more hydrogen protons, as we expected," also for the different, sometimes very unusual crater forms the planetary geologists have no final statement. "We are slowly gaining an understanding."

The Rheasilvia-impact basin at the south pole of Vesta: The perspective, shown in false color topography of the south pole of Vesta shown in shades of blue parts of the 500-kilometer Rheasilvia-impact basin, and in the center of the structure, a more than 20 km high mountain range in green, yellow and red tones - the highest mountain in the solar system . The global surface topographic model of Vesta was derived from DLR scientists from thousands of individual images by stereo photogrammetric.

Can be explained through the story of asteroid Vesta are still generations of researchers working with the previously obtained data, estimates Jaumann. "So far we have only scratched the surface." In one year, circled in the Dawn to Vesta, scientists have measured the whole surface of the asteroid and mapped. Although Vesta is smaller than a planet, the speed with which the geologists, physicists and photogrammetric DLR has carried out the survey task, a record in itself. Now, the findings on the topography of results, for example by gravitational and spectral measurements are considered together. "There are still many questions that we have not answered yet."

Landslides in the crater Marcia is a 58 km diameter crater near the equator of Vesta. The topography of the crater is a bit unusual, and does not have the typical bowl shape, such as a moon crater. The reason for this probably lies in mass movements in the interior of the crater. From the right edge of the crater is material slid into the interior of the crater, and has thereby created a flatter slope. The image shows details up to a size of 70 meters.

Next target: Ceres

With the flight to Ceres, the largest asteroid discovered so far that has only recently been received by the International Astronomical Union, the status of a dwarf planet, a new chapter of the Dawn mission. The first time a spacecraft will leave orbit of a body, then to fly to another celestial body and observe from its orbit.

In February 2015, Dawn arrive at their new target, 415 million kilometers from the sun. Here Ceres is an object as it hardly contradictory to Vesta could be: Instead of a solid rock crust like Vesta Ceres will have on his inner rock core an outer layer of ice. In this layer of water could also be included. Possibly could the dwarf planet have a very thin atmosphere? "Circled, yet never a spacecraft is in orbit around such a body," says planetary scientist Jaumann.

At the beginning of the orbit of Ceres will run 5900 km above the surface? It is reduced by five months of 1300 km altitude. Is possible to achieve an even closer orbit around five months later, about 700 kilometers above Ceres, if the primary mission is extended.

The mission of "Dawn"

The mission of "Dawn" is the Jet Propulsion Laboratory (JPL) led by the American space agency NASA. JPL is a division of the California Institute of Technology in Pasadena. The University of California at Los Angeles is responsible for the scientific mission.

The original 1240 kg heavy spacecraft has a wingspan of its solar cells of almost 20 meters - they could in the sun distance of the earth produce 10 KW electric power. At the distance of Ceres only 1 KW will be available.

For interplanetary flight Dawn uses an ion engine. This increase, although the flight times considerably, but much weight can be saved for conventional fuel: while rocket engines for a short time can produce large thrust ion engines produce light only a slight acceleration - however, over months or even years. For the same task, the ion engine requires significantly longer needed for this purpose, however, only one-tenth to one twentieth as much fuel.

The camera system on board the spacecraft was headed by the Max Planck Institute for Solar System Research in Katlenburg-Lindau in collaboration with the Institute of Planetary Research of the German Aerospace Center (DLR) in Berlin and the Institute of Computer and Communication Networks Brunswick designed and built.