Cruise Over Ceres

A prominent mountain with bright streaks on its steep slopes is especially fascinating to scientists. The peak’s shape has been likened to a cone or a pyramid. It appears to be about 4 miles (6 kilometers) high, with respect to the surface around it, according to the latest estimates. This means the mountain has about the same elevation as Mount McKinley in Denali National Park, Alaska, the highest point in North America.

Source: NASA

This artist’s concept shows NASA’s Dawn spacecraft arriving at the dwarf planet Ceres, the most massive body in the asteroid belt. Dawn is the first mission to visit a dwarf planet – a round body that orbits the sun but, unlike a planet, does not clear its orbital path of other objects.

Ceres Bright Spots Seen Closer Than Ever

NASA’s Dawn mission captured a sequence of images, taken for navigation purposes, of dwarf planet Ceres on May 16, 2015. The image showcases the group of the brightest spots on Ceres, which continue to mystify scientists. It was taken from a distance of 4,500 miles (7,200 kilometers) and has a resolution of 2,250 feet (700 meters) per pixel. 

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn Spacecraft Inside View

This illustration shows an inside view of the Dawn spacecraft. Source: NASA

Dawn, part of NASA’s Discovery Program of competitively selected missions, was launched in 2007 to orbit the large asteroid Vesta and the dwarf planet Ceres. The two bodies have very different properties from each other. By observing them both with the same set of instruments, Dawn will probe the early solar system and specify the properties of each body.

Dawn’s voyage milestones

Illustration of the relative locations (but not sizes) of Earth, the sun, Dawn and Ceres on April 12, 2015. (Earth and the sun are at that location every April 12.) The distance from Earth to Dawn is the same as the distance from the sun to Dawn. The images are superimposed on the trajectory for the entire mission, showing the positions of Earth, Mars, Vesta, and Ceres at milestones during Dawn’s voyage.

Dawn’s four mapping orbits

Each orbit is designed to provide a better view than the one before, and Dawn will map the orb thoroughly while at each altitude. The names for the orbits – rotation characterization 3 (RC3); survey; high altitude mapping orbit (HAMO); and low altitude mapping orbit (LAMO) – are based on ancient ideas, and the origins are (or should be) lost in the mists of time. Readers should avoid trying to infer anything at all meaningful in the designations. After some careful consideration, your correspondent chose to use the same names the Dawn team uses rather than create more helpful descriptors for the purposes of these blogs. That ensures consistency with other Dawn project communications. After all, what is important is not what the different orbits are called but rather what amazing new discoveries each one enables.

Dawn’s Blue Glow

Source: NASA

This artist’s concept shows NASA’s Dawn spacecraft arriving at the dwarf planet Ceres (lower right). Dawn travels through space using a technology called ion propulsion, in which ions are accelerated out of an engine, giving the spacecraft thrust. The xenon ions glow with blue light.

Dawn RC3 Image 10

This image of Ceres is part of a sequence taken by NASA’s Dawn spacecraft on May 4, 2015, from a distance of 8,400 miles (13,600 kilometers).

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn RC3 Image 9

This image of Ceres is part of a sequence taken by NASA’s Dawn spacecraft on May 4, 2015, from a distance of 8,400 miles (13,600 kilometers).

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA 

The bright spots on Ceres

This image is part of a sequence of images taken by NASA’s Dawn spacecraft on May 4, 2015, from a distance of 8,400 miles (13,600 kilometers), in its RC3 mapping orbit. The image resolution is 0.8 mile (1.3 kilometers) per pixel. 

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

In this closest-yet view, the brightest spots within a crater in the northern hemisphere are revealed to be composed of many smaller spots. However, their exact nature remains unknown.

Ceres from a distance of 13,600 km

This image of Ceres is part of a sequence taken by NASA’s Dawn spacecraft on May 4, 2015, from a distance of 8,400 miles (13,600 kilometers). 

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn mission at Vesta and Ceres

nasa.gov

The asteroid Vesta and the recently categorized dwarf planet Ceres have been selected because, while both speak to conditions and processes early in the formation of the solar system, they developed into two different kinds of bodies. Vesta is a dry, differentiated object with a surface that shows signs of resurfacing. It resembles the rocky bodies of the inner solar system, including Earth. Ceres, by contrast, has a primitive surface containing water-bearing minerals, and may possess a weak atmosphere. It appears to have many similarities to the large icy moons of the outer solar system.

By studying both these two distinct bodies with the same complement of instruments on the same spacecraft, the Dawn mission hopes to compare the different evolutionary path each took as well as create a picture of the early solar system overall. Data returned from the Dawn spacecraft could provide opportunities for significant breakthroughs in our knowledge of how the solar system formed.

Vesta, more than an asteroid. Indeed, almost a planet

Even though it doesn’t quite qualify as a ‘proper’ planet, the second most massive asteroid in the Solar System, Vesta – which has a diameter of approximately 530 kilometres – exhibits numerous planetary characteristics. This is just one of the many significant results of NASA’s Dawn mission, published in the journal Science on 11 May 2012. The Dawn spacecraft has been orbiting Vesta since 16 July 2011.

Three impact craters of different sizes, arranged in the shape of a snowman, make up one of the most striking features on Vesta. In this view the three 'snowballs' are upside down, so that the shadows make the features easily recognisable. North is to the lower right in the image, which has a resolution of 70 metres per pixel. The image is composed of many individual photographs taken during the high-altitude mapping orbit, at about 680 kilometres above Vesta's surface. The largest of the three craters, Marcia, has a diameter of 60 kilometres. The central crater, which is about 50 kilometres in diameter, is named Calpurnia, and the lower crater, named Minucia, has a diameter of about 22 kilometres. Marcia and Calpurnia are possibly the result of an impact by doublet asteroids, whereas Minucia was formed by a later impact. To derive the colour information, images acquired by the German camera system on the Dawn spacecraft in two near-infrared channels (917 nanometres and 749 nanometres) and an ultraviolet channel (438 nanometres) were combined to create what is referred to as a pseudo-true colour image. The true colours of the surface of Vesta appear somewhat different, but the subtle changes in material properties across the craters and impact ejecta can be detected. In both Marcia and Calpurnia, landslides can be seen; also, dark material has been exposed below the rim of Marcia. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

You're beautiful, Vesta

When UCLA's Christopher T. Russell looks at the images of the protoplanet Vesta produced by NASA's Dawn mission, he talks about beauty as much as he talks about science.

South polar impacts on Vesta. The map indicates that the Vesta surface is not uniform, with a sharp contrast between the northern and southern regions. These data suggest that the region around the Rheasilvia basin is richer in diogenites than the equatorial regions. The north-south variation in minerals indicates that the deep crust exposed in the southern Rheasilvia region is dominated by pyroxene-rich, diogenitic material while the equatorial region seems to retain the most ancient eucrite-rich mineralogy. In this image, blue shows a richer concentration of diogenite minerals and yellow shows a richer concentration of eucrite minerals. The visible and infrared mapping spectrometer collected the data used to create this mosaic image in August 2011, from an average altitude of about 1,700 miles or (2,700 kilometers). Credit: NASA/JPL-Caltech/UCLA/INAF/MPS/DLR/IDA

Vesta in Perspective

The giant asteroid Vesta is shown here as the smallest body among other similar bodies in the solar system: Mars, Mercury, Earth's moon and the dwarf planet Ceres. With Dawn's findings, Vesta is the only intact layered planetary building block with an iron core known to be remaining since the early days of the solar system. This makes it more like terrestrial planets and Earth's moon than other asteroids.

Credit: NASA/JPL-Caltech/UCLA

Source: 

• NASA/JPL, May 10, 2012

The violent past of Vesta

A team of researchers led by a NASA Lunar Science Institute (NLSI) member based at Southwest Research Institute has discovered evidence that the giant impact crater Rheasilvia on Asteroid Vesta was created in a collision that occurred only about 1 billion years ago, much more recently than previously thought. This result is based on the analysis of high-resolution images obtained with the Dawn spacecraft, which entered orbit around Vesta in July 2011.

This movie uses data from NASA’s Dawn spacecraft to simulate the view from the spacecraft flying over the surface of the giant asteroid Vesta. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The topography of Vesta

The gravitational pull on Dawn is the cumulative effect of all the matter in Vesta. Gravity diminishes with distance, and the spacecraft is subjected to a changing force as the inhomogeneous protoplanet rotates and the ship revolves around it. When Dawn is closer to locations with greater density, it experiences a stronger tug and when it is near regions with less powerful gravity, the attraction is weaker. By carefully mapping the exquisitely small variations in the probe's orbital motion, navigators can calculate how the mass is distributed within Vesta. This has already enabled the discovery of a dense iron core, one of the reasons scientists believe it has a complex geological history more akin to planets than to typical asteroids.

The Vesta cartographic coordinate system used in the Gazetteer of Planetary Nomenclature and on this map has not been approved by the IAU Working Group on Cartographic Coordinates and Rotational Elements. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Eucrites from Vesta

The HED (howardite, eucrite and diogenite) meteorites are a large group of meteorites believed to originate from Vesta, a hypothesis that is consistent with current Dawn observations. The eucrites are crystallized lavas that have the composition of basalt, the most common lava type on the Earth. The QUE 97053 (left) and EET 90020 (right) eucrites, pictured here, were recovered in Antarctica.

Credit: Hap McSween (University of Tennessee), and Andrew Beck and Tim McCoy (Smithsonian Institution)

Howardites from Vesta

The HED (howardite, eucrite and diogenite) meteorites are a large group of meteorites believed to originate from Vesta, a hypothesis that is consistent with current Dawn observations. Howardites are regolith breccia rocks, meaning that they formed through the grinding and fusion of rock and dust that occurs during meteor impacts on the surface of Vesta. 

Credit: Hap McSween (University of Tennessee), and Andrew Beck and Tim McCoy (Smithsonian Institution)

Diogenites from Vesta

The diogenites originated deep within the crust of Vesta and resemble rocks, both in texture and composition, which we find in the lower crust of the Earth. The QUE 99050 (left) and GRA 98108 (right) diogenites, pictured here, were recovered in Antarctica. These images are of thin slices of the meteorites as viewed through a polarizing microscope. 

Credit: Hap McSween (University of Tennessee), and Andrew Beck and Tim McCoy (Smithsonian Institution)