Dawn mission reaches Ceres

The NASA Dawn satellite has arrived at Ceres, the largest body in the asteroid belt, and is the first mission to orbit a dwarf planet.  On Friday 6 March, the Dawn satellite was captured by the gravity of Ceres and successfully went into orbit.

Ceres: as seen by the Dawn spacecraft on 1 March 2015 as a distance of 48,000 km from the dwarf planet. (Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

The Dawn spacecraft was launched in September 2007, and after receiving a gravity assist from March in February 2009, it arrived at the asteroid Vesta on 16 July 2011.  Dawn orbited and mapped the surface of Vesta for just over a year, sending back over 30,000 images of the giant asteroid. It continued on its journey for another 3.5 years,  finally arriving at the dwarf planet Ceres in February 2015. Now in orbit, Dawn will spend its first 15 days completing an orbit of Ceres. It will then slowly spiral closer towards the surface and begin mapping the dwarf planet. The mission is currently scheduled to end in mid-2016.

The trajectory of the Dawn spacecraft over the lifetime of its 8 year mission. (Credit: NASA/JPL/Marc Rayman)

Dawn has arrived at ‘dark side’ of Ceres, approached the night side of the dwarf planet that faces away from the Sun. Our next daytime view of Ceres will be in mid-April.  Images taken on the approach to Ceres in mid-February have already present some very interesting surprises: two extremely bright spots were imaged in a 92 km-wide crater, possible due to liquid or highly reflective material on the surface. The central spot is twice as bright as its smaller companion and is unresolved in the images, which means it is less than 4 km in size. We’ll have to wait for higher resolution images before we can determine the nature of these intriguing bright spots!

Dawn’s image of Ceres on 19 February 2015 at a distance of nearly46,000 km, showing two bright spots in a 92-km crater. (Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

Both the asteroid Vesta (with a diameter of just over 520 km) and the dwarf planet Ceres (almost twice as large with a diameter of 950 km) are both thought to be surviving protoplanets left over from the formation of the Solar System.  The three main scientific drivers of the Dawn mission are:  (1) to capture the earliest moments in the origin of the solar system enabling us to understand the conditions under which these objects formed; (2) to determine the nature of the building blocks from which the terrestrial planets formed; and (3) to contrast the formation and evolution of two small planets that followed very different evolutionary paths so that we understand what controls that evolution.


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[Sarah Maddison]

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