A HISTORY BETWEEN EARTH'S MOON AND VESTA

VestaThis full view of the giant asteroid Vesta was taken by NASA's Dawn spacecraft, as part of a rotation characterization sequence on July 24, 2011, at a distance of 3,200 miles (5,200 kilometers). A rotation characterization sequence helps the scientists and engineers by giving an initial overview of the character of the surface as Vesta rotated underneath the spacecraft. This view of Vesta shows impact craters of various sizes and troughs parallel to the equator. The resolution of this image is about 500 meters per pixel. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/I

 

FROM: NASA

NASA and international researchers have discovered that Earth's moon has more in common than previously thought with large asteroids roaming our solar system.

Scientists from NASA's Lunar Science Institute (NLSI), Moffett Field, Calif., discovered that the same population of high-speed projectiles that impacted our lunar neighbor four billion years ago, also hit the asteroid Vesta and perhaps other large asteroids.

The research unveils an unexpected link between Vesta and the moon, and provides new means for studying the early bombardment history of terrestrial planets. The findings are published in the March issue of Nature Geoscience.

"It’s always intriguing when interdisciplinary research changes the way we understand the history of our solar system," said Yvonne Pendleton, NLSI director. "Although the moon is located far from Vesta, which is in the main asteroid belt between the orbits of Mars and Jupiter, they seem to share some of the same bombardment history."

The findings support the theory that the repositioning of gas giant planets like Jupiter and Saturn from their original orbits to their current location destabilized portions of the asteroid belt and triggered a solar system-wide bombardment of asteroids billions of years ago called the lunar cataclysm.

The research provides new constraints on the start and duration of the lunar cataclysm, and demonstrates that the cataclysm was an event that affected not only the inner solar system planets, but the asteroid belt as well.

The moon rocks brought back by Apollo astronauts have long been used to study the bombardment history of the moon. Now the ages derived from meteorite samples have been used to study the collisional history of main belt asteroids. In particular, howardite and eucrite meteorites, which are common species found on Earth, have been used to study asteroid Vesta, their parent body. With the aid of computer simulations, researchers determined that meteorites from Vesta recorded high-speed impacts which are now long gone.

Researchers have linked these two datasets, and found that the same population of projectiles responsible for making craters and basins on the moon were also hitting Vesta at very high velocities, enough to leave behind a number of telltale impact-related ages.

The team’s interpretation of the howardites and eucrites was augmented by recent close-in observations of Vesta's surface by NASA’s Dawn spacecraft. In addition, the team used the latest dynamical models of early main belt evolution to discover the likely source of these high velocity impactors. The team determined that the population of projectiles that hit Vesta had orbits that also enabled some objects to strike the moon at high speeds.

"It appears that the asteroidal meteorites show signs of the asteroid belt losing a lot of mass four billion years ago, with the escaped mass beating up on both the surviving main belt asteroids and the moon at high speeds" says lead author Simone Marchi, who has a joint appointment between two of NASA’s Lunar Science Institutes, one at the Southwest Research Institute (SwRI) in Boulder, Colorado, and another at the Lunar and Planetary Institute in Houston, Texas. "Our research not only supports the current theory, but it takes it to the next level of understanding."

The NLSI is headquartered at NASA Ames Research Center, Moffett Field, Calif. The Dawn mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate, Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala.

VESTA: PROTOPLANET SIZED ASTEROID

FROM: NASA
Vesta Sizes Up

This composite image shows the comparative sizes of nine asteroids. Up until now, Lutetia, with a diameter of 81 miles (130 kilometers), was the largest asteroid visited by a spacecraft, which occurred during a flyby. Vesta dwarfs all other small bodies in this image.


Asteroid Vesta also is considered a protoplanet because it's a large body that almost became a planet and has a diameter of approximately 330 miles (530 kilometers). Image Credit: NASA/JPL-Caltech/JAXA/ESA

WHAT IS AN ASTEROID REALLY LIKE ONCE YOU GET TO KNOW THEM

FROM: NASA

WASHINGTON -- Findings from NASA's Dawn spacecraft reveal new details 
about the giant asteroid Vesta, including its varied surface 
composition, sharp temperature changes and clues to its internal 
structure. The findings were presented today at the European 
Geosciences Union meeting in Vienna, Austria and will help scientists 
better understand the early solar system and processes that dominated 
its formation. 

Spacecraft images, taken 420 miles (680 kilometers) and 130 miles (210 
kilometers) above the surface of the asteroid, show a variety of 
surface mineral and rock patterns. Coded false-color images help 
scientists better understand Vesta's composition and enable them to 
identify material that was once molten below the asteroid's surface. 

Researchers also see breccias, which are rocks fused during impacts 
from space debris. Many of the materials seen by Dawn are composed of 
iron- and magnesium-rich minerals, which often are found in Earth's 
volcanic rocks. Images also reveal smooth pond-like deposits, which 
might have formed as fine dust created during impacts settled into 
low regions. 

"Dawn now enables us to study the variety of rock mixtures making up 
Vesta's surface in great detail," said Harald Hiesinger, a Dawn 
participating scientist at Münster University in Germany. "The images 
suggest an amazing variety of processes that paint Vesta's surface." 

At the Tarpeia crater near the south pole of the asteroid, Dawn 
revealed bands of minerals that appear as brilliant layers on the 
crater's steep slopes. The exposed layering allows scientists to see 
farther back into the geological history of the giant asteroid. 

The layers closer to the surface bear evidence of contamination from 
space rocks bombarding Vesta's surface. Layers below preserve more of 
their original characteristics. Frequent landslides on the slopes of 
the craters also have revealed other hidden mineral patterns. 

"These results from Dawn suggest Vesta's 'skin' is constantly 
renewing," said Maria Cristina De Sanctis, lead of the visible and 
infrared mapping spectrometer team based at Italy's National 
Institute for Astrophysics in Rome. 

Dawn has given scientists a near 3-D view into Vesta's internal 
structure. By making ultrasensitive measurements of the asteroid's 
gravitational tug on the spacecraft, Dawn can detect unusual 
densities within its outer layers. Data now show an anomalous area 
near Vesta's south pole, suggesting denser material from a lower 
layer of Vesta has been exposed by the impact that created a feature 
called the Rheasilvia basin. The lighter, younger layers coating 
other parts of Vesta's surface have been blasted away in the basin. 

Dawn obtained the highest-resolution surface temperature maps of any 
asteroid visited by a spacecraft. Data reveal temperatures can vary 
from as warm as -10 degrees Fahrenheit (-23 degrees Celsius) in the 
sunniest spots to as cold as -150 degrees Fahrenheit (-100 degrees 
Celsius) in the shadows. This is the lowest temperature measurable by 
Dawn. These findings show the surface responds quickly to 
illumination with no mitigating effect of an atmosphere. 

"After more than nine months at Vesta, Dawn's suite of instruments has 
enabled us to peel back the layers of mystery that have surrounded 
this giant asteroid since humankind first saw it as just a bright 
spot in the night sky," said Carol Raymond, Dawn deputy principal 
investigator at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, 
Calif. "We are closing in on the giant asteroid's secrets." 

Launched in 2007, Dawn began its exploration of the approximately 
330-mile- (530-kilometer-) wide asteroid in mid-2011. The 
spacecraft's next assignment will be to study the dwarf planet Ceres 
in 2015. These two icons of the asteroid belt have been witness to 
much of our solar system's history. 

Dawn's mission is managed by JPL for NASA's Science Mission 
Directorate in Washington. Dawn is a project of the directorate's 
Discovery Program, managed by NASA's Marshall Space Flight Center in 
Huntsville, Ala. UCLA is responsible for overall Dawn mission 
science. Orbital Sciences Corp. in Dulles, Va., designed and built 
the spacecraft. The German Aerospace Center, the Max Planck Institute 
for Solar System Research, the Italian Space Agency and the Italian 
National Astrophysical Institute are international partners on the 
mission team.