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  • Writer's pictureSven Piper

Dawn Mission

Updated: 7 days ago

NASA’s Dawn Mission was a mission to examine the asteroids Ceres and Vesta.

In fact, the mission was canceled in March 2006, but a short time later, NASA management decided to reinstate the Dawn mission due to support from many scientists around the world.

"We revisited a number of technical and financial challenges and the work being done to address them," said NASA Associate Administrator Rex Geveden, who chaired the review panel. "Our review determined the project team had made substantive progress on many of this mission's technical issues, and, in the end, we were confident the mission would succeed."

The Dawn spacecraft used ion propulsion to gain the additional velocity needed to reach Vesta after leaving the Delta rocket. It also utilized ion propulsion to spiral to lower altitudes on Vesta, depart Vesta and cruise to Ceres, and enter a low altitude orbit at Ceres.

Dawn's goal was to characterize the conditions and processes of the solar system's earliest epoch by investigating in detail two of the largest protoplanets remaining intact since their formation. It measured their mass, shape, volume, and spin rate using imagery, laser altimetry, and gravity data. Dawn recorded the protoplanets' elemental and mineral composition to determine their thermal history and evolution and provided context for meteorites. Furthermore, Dawn imaged the surfaces of Ceres and Vesta to determine their bombardment and tectonic history, used gravity and spin state to estimate the size of any metallic core, and employed infrared and gamma-ray spectrometry to search for water-bearing minerals.

Mission Overview:

  • Internal structure, density, and homogeneity of two complementary protoplanets, 1 Ceres and 4 Vesta, one wet and one dry.

  • Determine shape, size, composition, and mass.

  • Surface morphology, cratering.

  • Determine thermal history and size of core.

  • Understand the role of water in controlling asteroid evolution.

  • Test the current paradigm of Vesta as the howardite, eucrite, and diogenite (HED) parent body and determine which, if any, meteorites come from Ceres.

  • Provide a geologic context for HEDs.

The Targets

Asteroid Ceres
Asteroid Ceres

  • Ceres, the largest asteroid and the first to be discovered, is named after the Roman goddess of agriculture. It was discovered by Giuseppe Piazzi of the Palermo Observatory on January 1, 1801.

  • Vesta, the brightest asteroid, is named for the ancient Roman goddess of the hearth and is the only asteroid ever visible with the naked eye. Found on March 29, 1807, by Heinrich Olbers, it is the second most massive and the third largest asteroid, revolving around the Sun in 3.6 terrestrial years and has an average diameter of about 520 km (320 miles). Its surface composition is basaltic.

Science Payload:

  • Framing Camera: German Aerospace Center, DLR, Institute of Space Sensor Technology and Planetary Exploration, Berlin.

  • Mapping Spectrometer: The Institute for Astrophysics in Space (IAFS), Rome.

  • Gamma Ray and Neutron Spectrometer: Los Alamos National Laboratory, Los Alamos, NM.

Mission Results:

  • Dawn's cameras showed several long sets of grooves called fossae, one of which, Divalia Fossa, stretches more than halfway around the asteroid’s equator, as well as several large impact craters, three of which, Marcia, Calpurnia, and Minucia, form a snowmanlike arrangement.

  • Dawn observed two very bright spots, Vinalia Faculae and Cerealia Facula, in Occator crater. The bright spots were highly reflective salts left behind when briny water from an underground reservoir percolated upward and evaporated.

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