NASA DAWN Mission: Near-True Colour Image of Vesta impact craters

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

Three impact craters of different sizes, which some have said are arranged in the shape of a snowman, make up one of the most striking features on Vesta, as seen in this view from NASA's Dawn mission.

In this view the three "snowballs" are upside down, so that the shadows make the features easily recognizable.

North is to the lower right in the image, which has a resolution of 230 feet (70 meters) per pixel.

The image is composed of many individual photographs taken between October and December 2011 by Dawn's framing camera.

The NASA Dawn space probe is equipped with two identical European designed cameras, Framing Camera 1 (FC1) and Framing Camera 2 (FC2). 

Should one of the cameras fail during the mission, the other can replace it. 

The mission itself would not be endangered.

Credit: Max Planck Institute

They were obtained during the high-altitude mapping orbit, at about 420 miles (680 kilometers) above Vesta's surface.

The largest of the three craters, Marcia, has a diameter of about 40 miles (60 kilometers). The central crater, which is about 30 miles (50 kilometers) in diameter, is named Calpurnia, and the lower crater, named Minucia, has a diameter of about 14 miles (22 kilometers).

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, scientists combined images acquired by the framing camera in two near-infrared channels (0.917 microns and 0.749 microns) and an ultraviolet channel (0.438 microns).

The true colours of the surface of Vesta differ somewhat from what is displayed here, but this mode of reproduction allows subtle changes in material properties across the craters and material ejected from impacts to be detected.

In both Marcia and Calpurnia, landslides can be seen; also, dark material has been exposed below the rim of Marcia.

The Dawn mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington.

UCLA is responsible for overall Dawn mission science. The framing camera project is funded by the Max Planck Society, DLR and NASA/JPL.

More information about the Dawn Mission is online at: .

ESA SMART-1 Lunar Image: Messy peaks of Zucchius

Credit: ESA /SMART-1 /AMIE camera team/ Space Exploration Institute

Even to the naked eye, our Moon looks heavily cratered.

The snippet of carved and pitted lunar surface shown in this image lies within a 66 km-wide crater known as Zucchius.

From our perspective, Zucchius is located on the edge of the southwest limb of the Moon.

AMIE camera

The crater's uneven and messy appearance is a result of how it formed. Lunar craters like Zucchius were created when rocky bodies, such as, meteors and asteroids, collided with the Moon at speeds of tens of kilometres per second, smashing holes into its surface.

More forceful impacts caused material to spring back upwards, a bit like a water droplet hitting a body of water.

This process formed a peak in the centre of the impact crater, as shown here by the cluster of bobbly mounds.

Zucchius's central peak and other features are quite well preserved. They are thought to have formed in the last 1.2 billion years, a time dubbed the 'Copernican period'.

This is very recent compared to the Moon's age of 4.4 billion years.

Earth was also cratered in this way, were it not for our planet's different conditions it would look a lot like the Moon.

Plate tectonics, the atmosphere and the presence of liquid water have all contributed to changing the shape and appearance of Earth's surface over time, eroding, covering and smoothing away surface blemishes.

This image was taken with the Advanced Moon Imaging Experiment on board ESA's SMART-1 on 14 January 2006, as the spacecraft skimmed just 753 km above the Moon's surface.

Zucchius was named after the 17th-century Italian astronomer Niccolò Zucchi, who was involved in some of the first designs for the reflecting telescope, and who made early observations of Jupiter's belts and spots on Mars.

Where have all the impact craters gone?

Ouarkziz Impact Crater. Credit: NASA

Impact craters reveal one of the most spectacular geologic process known to man.

During the past 3.5 billion years, it is estimated that more than 80 bodies, larger than the dinosaur-killing asteroid that struck the Yucatan Peninsula 66 million years ago, have bombarded Earth.

However, tectonic processes, weathering, and burial quickly obscure or destroy craters.

For example, if Earth weren't so dynamic, its surface would be heavily cratered like the Moon or Mercury.

Work by B.C. Johnson and T.J. Bowling of Purdue University, predicts that only about four of the craters produced by these impacts could persist until today, and geologists have already found three such craters (larger than 170 km in diameter).

Their study, published online for Geology on 22 May 2014, indicates that craters on Earth cannot be used to understand Earth's bombardment history.

Johnson and Bowling write, however, that layers of molten rock blasted out early in the impact process may act as better records of impacts, even after the active Earth has destroyed the source craters.

The authors suggest that searches for these impact ejecta layers will be more fruitful for determining how many times Earth was hit by big asteroids than searches for large craters.

More information: B.C. Johnson and T.J. Bowling. Where have all the craters gone? "Earth's bombardment history and the expected terrestrial cratering record." Geology, G35754.1, first published on May 22, 2014, DOI: 10.1130/G35754.1