Monday, November 19, 2012

NASA's Dawn Mission -- Post 2

Today I will post some more pictures from NASA's dawn mission. The Dawn spacecraft approached the asteroid Vesta in July 2011. The image below was taken from a distance of about 26,000 miles (41,000 kilometers) away from Vesta. This asteroid is considered a protoplanet because it is a large body that almost became a planet. Each pixel in the image corresponds to roughly 2.4 miles (3.8 kilometers).

NASA's Dawn spacecraft obtained this image with its framing camera on July 18, 2011. It was taken from a distance of about 6,500 miles (10,500 kilometers) away from the protoplanet Vesta. The smallest detail visible is about 1.2 miles (2.0 km).

The image was taken on July 24, 2011, from a distance of about 3,200 miles (5,200 kilometers).

This image of Vesta's equator was put together from two clear filter images, taken on July 24, 2011 by the framing camera instrument aboard NASA's Dawn spacecraft. The  image shows hills, troughs, ridges and steep craters. The framing camera has a resolution of about 524 yards (480 meters) per pixel.

Enormous troughs that wrap around the giant asteroid Vesta may actually be dropped blocks of terrain bounded by fault lines, suggesting a geologic complexity beyond that of most asteroids. Since the discovery of the troughs last year in data from NASA's Dawn spacecraft, scientists have been working to determine the story behind these unusual features. The research reinforces the claim that Vesta has a core, mantle and crust, a structure normally reserved for larger bodies, such as planets and large moons.

The biggest of those troughs, named Divalia Fossa, surpasses the size of the Grand Canyon. It spans 289 miles (465 kilometers) in length, 13.6 miles (22 kilometers) in width and 3 miles (5 kilometers) in depth.

Thee composite images below show three views of the comparatively fresh crater named Vibidia on the giant asteroid Vesta. A black-and-white image that highlights topography, a colorized image that highlights composition and a combination of the black-and-white and colorized images to show the relationship between topography and composition are included here.

The impact that created Vibidia occurred at the edge of a cratered highland in the equatorial region and extends to a basin known as Veneneia. It appears to be located in a gentle depression, presumably an older crater. Scientists think a relatively small object caused the crater, which features many boulders inside and rays of dark material. As on the moon, bright rays can be the result of compositional differences in material thrown out by the impact compared to the surrounding terrain. Or bright rays can indicate differences in maturity -- that is, the amount of time the surface has been exposed to subsequent bombardment by micrometeoroids and cosmic rays. Vibidia exhibits a particularly colorful blanket of ejected material, demonstrating that the surface and the layer just beneath are made up of many different kinds of materials. These patterns reflect a complex interplay of ancient volcanic and impact processes that shaped Vesta's crust. The impact that created Vibidia also appears to have caused an area with a width five times the diameter of the crater to collapse.

The framing camera has seven color filters that allow it to image Vesta in a number of different wavelengths of light. Being able to image in many wavelengths enhances features and colors that would otherwise be indistinguishable to the human eye. In this colorized image, scientists assigned different color channels to specific ratios of wavelengths of radiation. In this scheme, green shows the relative strength of a particular mineralogical characteristic -- the absorption of iron. Brighter green signifies a higher relative strength of this band, which indicates chemistry involving pyroxene. On the other hand, reddish colors indicate either a different mineralogy or a stronger weathered surface.

These images are composite images made from those taken during Dawn's high-altitude mapping orbit (420 miles or 680 kilometers above the surface) on Oct 27, 2011. They cover an area that is about 40 by 40 miles (60 by 60 kilometers). This area is near the edge of the Rheasilvia basin in Vesta's southern hemisphere. Data reveal temperatures can vary from as warm as minus 10 degrees Fahrenheit (minus 23 degrees Celsius) in the sunniest spots to as cold as minus 150 degrees Fahrenheit (minus 100 degrees Celsius) in the shadows.

Here is a NASA video compiled to celebrate the success of the first half of the Dawn mission. Enjoy your flight around Vesta.


Image credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

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