Subscribe free to our newsletters via your
. 24/7 Space News .




IRON AND ICE
Dawn Views Dark Side of Vesta
by Staff Writers
Pasadena CA (JPL) Jul 29, 2011


NASA's Dawn spacecraft obtained this image with its framing camera on July 23, 2011. It was taken from a distance of about 3,200 miles (5,200 kilometers) away from the giant asteroid Vesta. Image Credit: NASA et al

Dawn took this image over Vesta's northern hemisphere after the spacecraft completed its first passage over the dark side of the giant asteroid. It is northern hemisphere winter on Vesta now, so its north pole is in deep shadow.

The Dawn science team is working to determine the significance of the distinct features in this image, which include large grooves or ridges extending for great distances around Vesta.

This image was taken by Dawn's framing camera on July 23, from a distance of 3,200 miles (5,200 kilometers).

earlier related report
When is an Asteroid Not an Asteroid?
On March 29, 1807, German astronomer Heinrich Wilhelm Olbers spotted Vesta as a pinprick of light in the sky. Two hundred and four years later, as NASA's Dawn spacecraft prepares to begin orbiting this intriguing world, scientists now know how special this world is, even if there has been some debate on how to classify it.

Vesta is most commonly called an asteroid because it lies in the orbiting rubble patch known as the main asteroid belt between Mars and Jupiter. But the vast majority of objects in the main belt are lightweights, 100-kilometers-wide (about 60-miles wide) or smaller, compared with Vesta, which is about 530 kilometers (330 miles) across on average. In fact, numerous bits of Vesta ejected by collisions with other objects have been identified in the main belt.

"I don't think Vesta should be called an asteroid," said Tom McCord, a Dawn co-investigator based at the Bear Fight Institute, Winthrop, Wash. "Not only is Vesta so much larger, but it's an evolved object, unlike most things we call asteroids."

The layered structure of Vesta (core, mantle and crust) is the key trait that makes Vesta more like planets such as Earth, Venus and Mars than the other asteroids, McCord said. Like the planets, Vesta had sufficient radioactive material inside when it coalesced, releasing heat that melted rock and enabled lighter layers to float to the outside. Scientists call this process differentiation.

McCord and colleagues were the first to discover that Vesta was likely differentiated when special detectors on their telescopes in 1972 picked up the signature of basalt. That meant that the body had to have melted at one time.

Officially, Vesta is a "minor planet" - a body that orbits the sun but is not a proper planet or comet. But there are more than 540,000 minor planets in our solar system, so the label doesn't give Vesta much distinction. Dwarf planets - which include Dawn's second destination, Ceres - are another category, but Vesta doesn't qualify as one of those. For one thing, Vesta isn't quite large enough.

Dawn scientists prefer to think of Vesta as a protoplanet because it is a dense, layered body that orbits the sun and began in the same fashion as Mercury, Venus, Earth and Mars, but somehow never fully developed. In the swinging early history of the solar system, objects became planets by merging with other Vesta-sized objects. But Vesta never found a partner during the big dance, and the critical time passed. It may have had to do with the nearby presence of Jupiter, the neighborhood's gravitational superpower, disturbing the orbits of objects and hogging the dance partners.

Other space rocks have collided with Vesta and knocked off bits of it. Those became debris in the asteroid belt known as Vestoids, and even hundreds of meteorites that have ended up on Earth. But Vesta never collided with something of sufficient size to disrupt it, and it remained intact. As a result, Vesta is a time capsule from that earlier era.

"This gritty little protoplanet has survived bombardment in the asteroid belt for over 4.5 billion years, making its surface possibly the oldest planetary surface in the solar system," said Christopher Russell, Dawn's principal investigator, based at UCLA. "Studying Vesta will enable us to write a much better history of the solar system's turbulent youth."

Dawn's scientists and engineers have designed a master plan to investigate these special features of Vesta. When Dawn arrives at Vesta in July, the south pole will be in full sunlight, giving scientists a clear view of a huge crater at the south pole. That crater may reveal the layer cake of materials inside Vesta that will tell us how the body evolved after formation. The orbit design allows Dawn to map new terrain as the seasons progress over its 12-month visit. The spacecraft will make many measurements, including high-resolution data on surface composition, topography and texture. The spacecraft will also measure the tug of Vesta's gravity to learn more about its internal structure.

"Dawn's ion thrusters are gently carrying us toward Vesta, and the spacecraft is getting ready for its big year of exploration," said Marc Rayman, Dawn's chief engineer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We have designed our mission to get the most out of this opportunity to reveal the exciting secrets of this uncharted, exotic world."

.


Related Links
Dawn at NASA
Dawn at JPL
Asteroid and Comet Mission News, Science and Technology






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








IRON AND ICE
'Trojan' asteroid shares Earth's orbit
Paris (AFP) July 28, 2011
Earth is not alone in its orbit around the Sun - a small 'Trojan' asteroid sits in front of our planet and leads it, according to British science revue Nature, which published the discovery Thursday. This diminutive asteroid has a diameter of just 300 metres but is called a Trojan because of its particular position in a stable spot either in front of a planet or behind it. Because the astero ... read more


IRON AND ICE
Unique volcanic complex discovered on Lunar far side

Moon Express Announces Dr. Alan Stern as Chief Scientist

Northrop Grumman Honored by IEEE for Development of Lunar Module

Two NASA Probes Tackle New Mission: Studying The Moon

IRON AND ICE
NASA's Next Mars Rover to Land at Gale Crater

Opportunity Closing In On Spirit Point At Endeavour Crater

MAVEN Mission Completes Major Milestone

NASA says Mars mountain will read like 'a great novel'

IRON AND ICE
SwRI suborbital astronaut payload specialists move to flight planning phase, release mission patch

Graybiel Lab poised for next chapter of space exploration

Space Program Mavens Comment on the Future of Space Exploration

This Time It's Both Rocket Science AND Surgery

IRON AND ICE
Why Tiangong is not a Station Hub

China to launch experimental satellite in coming days

Spotlight Time for Tiangong

China launches new data relay satellite

IRON AND ICE
Voyage to Vaccine Discovery Continues with Space Station Salmonella Study

New uses for Space Station

ISS to be sunk after 2020: Russian space agency

Certification for ISS onboard astronaut

IRON AND ICE
Russia sends observation satellite into space

NASA inks agreement with maker of Atlas V rocket

Russia launches 2 foreign satellites into orbit

ILS Proton Successfully Launches the SES-3 Satellite for SES

IRON AND ICE
Exoplanet Aurora Makes For An Out-of-this-World Sight

Distant planet aurorae modeled

Exoplanet Aurora: An Out-of-this-World Sight

Ten new distant planets detected

IRON AND ICE
Vietnam Selecting Belgium For Second EO Satellite

1 tiny electron could be key to future drugs that repair sunburn

Apple, Samsung overtake Nokia in smartphone market

Turksat turns to GMV for control of its satellites




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement