Asteroid Vesta more like Earth than realized, study shows

Jan 21, 2013 by Amina Khan
Asteroid Vesta. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

The cold, dead asteroid Vesta might have had a very active inner life early in the solar system's history, according to an unusual analysis of a Saharan meteorite.

Vesta might have had a magma ocean underneath its rocky exterior, allowing bits of mineral to rise and fall between softer and harder layers of material, according to a study published online Sunday by the journal Nature Geoscience. If confirmed, that would make it more like Earth and the solar system's other than scientists had realized.

The report provides a fresh look at the , supplementing data sent back from Vesta by NASA's Dawn spacecraft.

"People think asteroids are big, gray, cold, almost potato-shaped lumps of rock that sometimes crash into the Earth and threaten us," said study leader Beverley Tkalcec, a planetary geologist at Goethe University in Frankfurt, Germany. Instead, she said, "it has a dynamic interior similar to what might have been at the beginning of the Earth."

Hot or not, Vesta is one big potato, about the size of Arizona. It was big enough to have experienced melting inside, causing the heavier material to sink to the center and the lighter stuff to rise to the crust.

Vesta and the dwarf planet Ceres - the next target for the - represent planetary embryos that never fully formed. And since their rocks haven't been chewed up by ongoing tectonic processes, as Earth's have, they can be nearly as old as the solar system, which came into being more than 4.5 billion years ago.

The new study, by a trio of European scientists, is based on an examination of a called NWA 5480 that is thought to have been carved out of Vesta's mantle by an impact with another asteroid. The meteorite, called a diogenite, was found in northwest Africa, and it is part of a family of that are linked to the asteroid by their chemical and .

Unlike other studies, which focus on what a meteorite is made of, Tkalcec's team concentrated on how the stuff inside this meteorite was arranged. If Vesta had been active beneath the surface, the mineral structure of this sample would show some clues, they thought.

The researchers used a technique called electron backscatter diffraction, which involves bouncing electrons off a crystal to reveal the shape of its structure. They focused on a mineral in the meteorite called olivine. Instead of looking like the crystals had piled up regularly on top of one another, they found that the crystal lattice looked deformed. Something unexpected had happened to these rocks.

So the researchers compared the meteorite's internal structure with those of rocks on Earth. They found one type with a remarkably similar pattern: igneous rocks formed by forces in Earth's mantle. This meteorite, they realized, was probably formed in a similar way - its strange structure the result of solid material sinking into the softer layers below, leaving the original rock deformed.

The researchers plugged what they learned about this meteorite into a computer model of Vesta. It showed that, under the conditions that created the meteorite, Vesta could have been filled with a .

The inside of the young asteroid may have looked something like a lava lamp, Tkalcec said.

"When you have dense solid material over partially molten material, then it's unstable," said Harry McSween, a planetary geoscientist at the University of Tennessee in Knoxville and co-investigator for the Dawn mission. "The top's trying to become the bottom and the bottom's trying to become the top."

If true, the finding could mean that Vesta experienced some of the same internal churning as Earth - for a short time, anyway.

It pushes theories about Vesta's formation "a lot further forward," said McSween, who wasn't involved in the study. "It's a really interesting paper," he said - one that may inspire scientists to look deeper into meteorites' mineral structure for clues about the parent asteroid's history.

Explore further: France raises heat on decision for next Ariane rocket

More information: Paper: DOI: 10.1038/ngeo1710

add to favorites email to friend print save as pdf

Related Stories

Space mountain produces terrestrial meteorites

Jan 02, 2012

When NASA's Dawn spacecraft entered orbit around giant asteroid Vesta in July, scientists fully expected the probe to reveal some surprising sights. But no one expected a 13-mile high mountain, two and a half ...

When is an asteroid not an asteroid?

Mar 30, 2011

(PhysOrg.com) -- 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 ...

The interior of asteroid Vesta

Jan 06, 2011

(PhysOrg.com) -- Researchers from the University of North Dakota and from the Max Planck Institute for Solar System Research in Germany have discovered a new kind of asteroid using NASA’s Infrared Telescope ...

Recommended for you

Halfway through Blue Dot mission

26 minutes ago

Halfway through his six-month Blue Dot mission, ESA astronaut Alexander Gerst is sharing the International Space Station with only two colleagues: Maxim Suraev and Reid Wiseman.

Miranda: An icy moon deformed by tidal heating

15 hours ago

Miranda, a small, icy moon of Uranus, is one of the most visually striking and enigmatic bodies in the solar system. Despite its relatively small size, Miranda appears to have experienced an episode of intense ...

User comments : 10

Adjust slider to filter visible comments by rank

Display comments: newest first

cantdrive85
1 / 5 (12) Jan 21, 2013
I guess that comets Wild 2 and Tempel 1 must have had molten cores as well, being that olivine was found on them as well as a number of other celestial bodies.
Then again, electrical discharge produces the heat and pressure needed to create such minerals, as well as many other characteristics of rocky bodies such as cratering, rilles, cometary comas, cometary x-rays, etc....
Parsec
5 / 5 (4) Jan 21, 2013
I guess that comets Wild 2 and Tempel 1 must have had molten cores as well, being that olivine was found on them as well as a number of other celestial bodies.
Then again, electrical discharge produces the heat and pressure needed to create such minerals, as well as many other characteristics of rocky bodies such as cratering, rilles, cometary comas, cometary x-rays, etc....

Read the article again. You would need to demonstrate your assertion about electrical discharge being the source of the mineral displacement and unexpected spatial pattern, as well as explain why the calculations on magma heating are incorrect.
baudrunner
1 / 5 (4) Jan 21, 2013
A probe placed in an orbit around an asteroid with 25/1000th the gravity of Earth? That sounds pretty far-fetched.
antialias_physorg
5 / 5 (5) Jan 21, 2013
A probe placed in an orbit around an asteroid with 25/1000th the gravity of Earth? That sounds pretty far-fetched.

Why is that far fetched? An orbit around Vesta is either very low or very slow. Either of which is very good for taking images.
Orbital specs here:
http://en.wikiped...ta_orbit

Basically: As long as a body has any gravity you can put a probe in orbit.
RealScience
5 / 5 (4) Jan 21, 2013
A probe placed in an orbit around an asteroid with 25/1000th the gravity of Earth? That sounds pretty far-fetched.


It isn't even difficult, as long as you can control your thrust.
Vesta has a surface escape velocity of 0.36 km/s, so call it ~0.3 km/s from the height of a low orbit. A circular orbit would then have a velocity of √2 times that, or ~0.2 km/s = 720 km/h. At ~600 km an orbit's circumference would be just under 2000 km, so an orbit would take a bit less than 3 hours.

Such orbits even happen naturally - several asteroids have been found to have other asteroids as 'moons'.
yyz
5 / 5 (2) Jan 21, 2013
"A probe placed in an orbit around an asteroid with 25/1000th the gravity of Earth? That sounds pretty far-fetched."

We've already orbited and landed a probe on an asteroid much smaller than Vesta: http://en.wikiped...hoemaker
Jonseer
3.7 / 5 (3) Jan 21, 2013
A probe placed in an orbit around an asteroid with 25/1000th the gravity of Earth? That sounds pretty far-fetched.


What are you measuring?

NASA says the gravity on Vesta is a couple of magnitudes higher than that, even if it is just a fraction of Earth's.

Since you think it amazing, you must be assuming it's gravity based on the fraction of mass that Vesta is of the Earth, and that's not how gravity works.
Torbjorn_Larsson_OM
5 / 5 (2) Jan 22, 2013
Planet formation theory survives testing again. (I.e. originally hydrostatic rounded bodies have been plastic.)

"electrical discharge produces the heat and pressure needed to create such minerals".

Ha ha haaa (snort)!

It is fact that lightning discharges can produce minerals, but fulgurites are amorphous glasses and diminutive compared to mantle or crust mineral bodies. [ http://en.wikiped...ulgurite ]

Similarly any crustal deformations from disharges such as craters or rille analogs are meter scale at most. Comas and cosmic ("cometary"?) x-rays are known to to be produced by discharges.

The asteroid belt has no known discharges, but maintains charge balance as overall the EM field has to do.

Above all, "such minerals" are known to be exclusive mantle products and for good reasons of its vs the mantle's physics.

If you find otherwise, do the science and pass peer review publication and then come back to actual science blogs.
Torbjorn_Larsson_OM
5 / 5 (1) Jan 22, 2013
Oops, meant olivine is "crustal" product. (Common, derives from melts.)

@baudrunner: The best detailing of Dawn's operations is IMHO Dawn chief engineer and mission director Mark Rayman's "Dawn Journal" [ http://www.planet...-rayman/ ]:

"After more than 950 days of ion thrusting, with an effective change in velocity of more than 6.6 kilometers per second (15,600 mph), Dawn's orbit is so much like Vesta's that their paths around the Sun are quite similar. Less than a month ago, they were coming together at 240 meters per second (540 mph). Today, the relative speed has declined to only 110 meters per second (250 mph). By July 16, Dawn will be traveling no faster toward Vesta than you can drive in a car. The probe will be close enough and slow enough that the protoplanet's gravity will tenderly take the approaching explorer in its grasp.
Torbjorn_Larsson_OM
5 / 5 (1) Jan 22, 2013
[cont] The next log will be posted shortly after Dawn is in a high, loose orbit around Vesta, still spiraling down toward survey orbit, where it will begin making detailed studies of its home for the subsequent year." ["Dawn Journal", June 2011.]