Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. 24/7 Space News .




IRON AND ICE
Asteroid's Troughs Suggest Stunted Planet
by Staff Writers
Laurel MD (SPX) Sep 28, 2012


An image taken by NASA's Dawn spacecraft on July 24, 2011, shows troughs along the equator of the asteroid Vesta, including Divalia Fossa, which is larger than the Grand Canyon. A new study analyzing these troughs finds that they are probably graben - a dip in the surface with faults on either side that would indicate that Vesta has characteristics much like a planet or large moon. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Enormous troughs that reach across the asteroid Vesta may actually be stretch marks that hint of a complexity beyond most asteroids. Scientists have been trying to determine the origin of these unusual troughs since their discovery just last year.

Now, a new analysis supports the notion that the troughs are faults that formed when a fellow asteroid smacked into Vesta's south pole. The research reinforces the claim that Vesta has a layered interior, a quality normally reserved for larger bodies, such as planets and large moons.

Asteroid surface deformities are typically straightforward cracks formed by crashes with other asteroids. Instead, an extensive system of troughs encircles Vesta, the second most massive asteroid in the solar system, about one-seventh as wide as the Moon. The biggest of those troughs, named Divalia Fossa, surpasses the size of the Grand Canyon by spanning 465 kilometers (289 miles) long, 22 km (13.6 mi) wide and 5 km (3 mi) deep.

The origin of these troughs on Vesta has puzzled scientists. The complexity of their formation can't be explained by simple collisions. New measurements of Vesta's topography, derived from images of Vesta taken by NASA's Dawn spacecraft last year, indicate that a large collision could have created the asteroid's troughs.

But, this would only have been possible if the asteroid is differentiated - meaning that it has a core, mantle and crust - said Debra Buczkowski of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. Because Vesta is differentiated, its layers have different densities, which react differently to the force from the impact and make it possible for the faulted surface to slide, she added.

"By saying it's differentiated, we're basically saying Vesta was a little planet trying to happen."

Her team's research will be published online this Saturday in Geophysical Research Letters, a journal of the American Geophysical Union.

Most asteroids are pretty simple. "They're just like giant rocks in space," said Buczkowski.

But previous research has found signs of igneous rock on Vesta, indicating that rock on Vesta's surface was once molten, a sign of differentiation. If the troughs are made possible by differentiation, then the cracks aren't just troughs, they're graben.

A graben is a dip in the surface that forms when two faults move apart from each other and the ground sinks into the widening gap, such as in Death Valley in California. Scientists have also observed graben on the Moon and planets such as Mars.

The images from the Dawn mission show that Vesta's troughs have many of the qualities of graben, said Buczkowski. For example, the walls of troughs on simpler asteroids such as Eros and Lutetia are shaped like the letter V. But Vesta's troughs have floors that are flat or curved and have distinct walls on either side, like the letter U - a signature of a fault moving apart, instead of simple cracking on the surface.

The scientists' measurements also showed that the bottoms of the troughs on Vesta are relatively flat and slanted toward what's probably a dominant fault, much as they are in Earth-bound graben.

These observations indicate that Vesta is also unusually planet-like for an asteroid in that its mantle is ductile and can stretch under a lot of pressure. "It can become almost silly putty-ish," said Buczkowski. "You pull it and it deforms."

Buczkowski and her colleagues' arguments for differentiation of Vesta are interesting, said planetary scientist Geoff Collins of Wheaton College, in Norton, Mass, who specializes in tectonics, the structure and motion of planetary crusts.

"On many much smaller asteroid bodies, we've seen very narrow troughs that look just like cracks on the surface," said Collins, who was not involved in the new study. "But nothing that looks like a sort of traditional terrestrial graben that you'd find on Mars or the Moon where things have really been pulled apart."

But Collins is not yet fully convinced that Vesta's troughs are graben. An example of rock-solid evidence of graben on Vesta that has yet to be discovered, he said, would be an obvious crater that had been torn in two by a trough.

There are other qualities of Vesta that could be clues to how the troughs formed. For example, unlike the larger asteroid Ceres, Vesta is not classified as a dwarf planet because the large collision at its south pole knocked it out of its spherical shape, said Buczkowski.

It's now more squat, like a walnut. But if Vesta has a mantle and core, that would mean it has qualities often reserved for planets, dwarf planets and moons - regardless of its shape.

The origin of that funny shape is the centerpiece of a different hypothesis about how the troughs formed. Britney Schmidt of the Institute for Geophysics in Austin, Texas, believes the south pole collision knocked Vesta into its current speedy rate of rotation about its axis of about once per 5.35 hours, which may have caused the equator to bulge outward so far and so fast that the rotation caused the troughs, rather than the direct power of the impact.

"It's an enigma why Vesta rotates so quickly," said Schmidt, who was not a part of the current study.

Dawn has already left to explore Ceres, so all the data it will retrieve on Vesta is in hand. Buczkowski said scientists will continue to sort that data out and improve on computer simulations of Vesta's interior. As those analyzes come along, she said she will keep an open mind toward any revelations that come to light, but she doesn't expect her conclusion will change. "I really think that these are graben," she said.

"Large-scale troughs on Vesta: A signature of planetary tectonics" Authors: Buczkowski, D.L., Iyer, K.A., Kahn, E.G., and Barnouin O.S.: JHU-APL, Laurel, Maryland, USA; Wyrick, D.Y.: SWRI, San Antonio, Texas, USA; Scully, J.E.C. and Russell, C.T.: UCLA, Los Angeles, California, USA; Nathues, A., and Le Corre, L.: Max Planck Institute for Solar system Research, Katlenburg-Lindau, Germany; Reddy, V.: Max Planck Institute for Solar system Research, Katlenburg- Lindau, Germany; and University of North Dakota, Grand Forks, North Dakota, USA; Gaskell, R.W., Yingst R.A., Mest S., and Garry, W.B.: PSI, Tucson, Arizona, USA; Roatsch, T., Preusker, F., and Jaumann, R.: DLR, Institute of Planetary Research, Berlin, Germany; Schenk, P.M., LPI, Houston, Texas, USA; Williams, D.A.: Arizona State University, Tempe, Arizona, USA; Raymond, C.A.: JPL, California Institute of Technology, Pasadena, California, USA. After the paper publishes on Saturday, 29 September, it will be accessible here.

.


Related Links
Johns Hopkins University Applied Physics Laboratory
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




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





IRON AND ICE
Dawn: Vesta Got Special Delivery of Hydrated Minerals
Pasadena CA (JPL) Sep 27, 2012
The mechanism that incorporates water into the terrestrial planets is a matter of extensive debate for planetary scientists. Now, observations of the giant asteroid Vesta by NASA's Dawn mission suggest that hydrated materials were delivered to it mainly through a buildup of small particles during an epoch when the solar system was rich in dust. This is a radically different process from th ... read more


IRON AND ICE
China has no timetable for manned moon landing

Senior scientist discusses China's lunar orbiter challenges

NASA sees 'gateway' for space missions

Protection for Moon, Mars astronauts eyed

IRON AND ICE
Mars-like Places on Earth Give Insights into Rover Data

A windshield wiper for Mars dust

Curiosity Finishes Close Inspection of Rock Target

Where is Deimos?

IRON AND ICE
Bryan Campen joins XCOR as Director of Media and Public Relations

B612 Wins Funding Support From Prominent Business Leadersy

Cavenauts return to Earth

Brazil unveils tax incentives to boost tech innovation

IRON AND ICE
China Spacesat gets 18-million-USD gov't support

Tiangong Orbit Change Signals Likely Date for Shenzhou 10

China Focus: Timeline for China's space research revealed

China eyes next lunar landing as US scales back

IRON AND ICE
Space freighter undocking set for Friday

Russia to send all-novice crew to ISS

ATV undocking postponed

Crew Members Prepare for Departure

IRON AND ICE
California Governor Signs the Spaceflight Liability and Immunity Act

Processing is underway with the next Automated Transfer Vehicle to be orbited by Arianespace

Fueling underway with the Galileo satellites for next Soyuz launch from French Guiana

SpaceX, NASA Target Oct. 7 Launch For Resupply Mission To Space Station

IRON AND ICE
Stagnant Interiors Suppress Chances of Life on Super-Earths

Meteors Might Add Methane to Exoplanet Atmospheres

Two 'hot Jupiters' found in star cluster: NASA

Planets Can Form in the Galactic Center

IRON AND ICE
Search for element 113 concluded at last

Kodak dumps inkjet printers, more jobs

Sleek new PlayStation 3 model makes US debut

Pigs' revenge as 'Angry Birds' makers launch new game




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