A rare a beautiful peek into the minor-planet 4 Vesta. The story of how it got here is extraordinary, and I’m not talking about the trip that meteor hunter Michael Farmer had to take to Morocco to negotiate with the desert nomads.
4 Vesta accounts for 9% of the mass of the asteroid belt — big enough to provide enough gravity for a differentiated crust, mantle and core, like Earth and Mars, but unlike smaller moons and asteroids. The rocks from Vesta date back to the formation of the Solar System, 4.566 billion years ago (older than Earth itself and very close to the oldest thing you can touch). Vesta is the brightest asteroid in the night sky, occasionally visible from Earth with the naked eye.
Normally, the material deep beneath the surface of a planet stays there, and not even on Earth have we drilled deep enough to sample what is down there.
But Vesta had a colossal collision of planet-busting proportions. It left behind a mountainous crater twice as tall as Mt. Everest and 90% the diameter of Vesta itself. We know this from visual and spectroscopic analysis by the Hubble telescope and, more recently, the by the DAWN spacecraft that orbited Vesta for a year.
About 1 billion years ago, 1% of Vesta’s mass was violently ejected by a high-speed impactor, including several layers of crust (breccias, basalt and igneous rock) and perhaps as deep as the mantle. “Vesta likely came close to shattering,” said DAWN principal investigator Carol Raymond, noting that the blow left concentric sets of fracture lines around Vesta’s equator.
Some of the ejected rock was large enough to become “V-type asteroids” of their own right, and a few of those ended up in an unstable region of the asteroid belt in an orbital resonance with Jupiter, the big boy circling farther out. Every 100 million years, some of the asteroids in that region get ejected out, and a handful of those have been found to have randomly ended up in near-Earth orbits. Those V-type asteroids are subsequently struck by other impactors in multiple events over a subsequent time period of 6-73 million years, dislodging smaller rocks in random directions, a few of which hit Earth. A few of those are large enough to survive the burn of reentry but not so large as to burst into fragments from the impact of hitting the atmosphere at speeds exceeding Mach 32.
Where do they land? Two-thirds of all meteorites are lost in the ocean (due to the surface area ratios of ocean to land). And almost all of the stony landfalls will remain undiscovered because they do not stand out as special rocks from a distance if not witnessed as a fall. So these incredible cosmic voyagers are generally undiscovered except for witnessed falls, or lying on the ice sheets of Antarctica (where it is illegal to export meteors) and some states in Northwest Africa (where it is legal-ish) where the nomads know that if they find a rock in the desert, it’s a meteorite, and if it’s stony (less dense than the common meteorites of iron), then it might be rare and valuable (but that takes subsequent testing).
There are three broad classes of meteorites from 4 Vesta — the HED of Howardite, Eucrite and Diogenite — based on how deep the ejecta came from. This is the 5.6 kg main mass of NWA 8563, a rare monomict eucrite of cooled lava from various depths. I partnered with Michael Farmer to buy it from the nomads in Morocco. It’s somewhat like wildcatting for oil or minerals; you commit to buy it before you know what kind of stony meteorite it will turn out to be (Mars, Moon, or from places unknown). We had it sliced and analyzed and were delighted to learn of its origin. We were also delighted at how beautiful it looks inside, with a mysterious green and clearly differentiated clasts. Farmer said it is unlike anything he has seen before, and he has been a full-time meteorite hunter and trader for many decades. It is a melt breccia with mixed clasts of both shallow and deep material from Vesta’s crust.
From the DAWN mission, we now know that Vesta is the only intact, layered planetary building block surviving from the very earliest days of the solar system, forming within the first 10 million years, long before Earth.
Another view
Another perspective on the H.E.D.’s
4 Vesta, imaged up close by the DAWN spacecraft which orbited for a year:
“This mosaic synthesizes some of the best views the spacecraft had of the giant asteroid Vesta. Dawn studied Vesta from July 2011 to September 2012. The towering mountain at the south pole – more than twice the height of Mount Everest – is visible at the [left side] of the image. The set of three craters known as the "snowman" can be seen at the top right.” — 
“One of the goals of the Dawn mission was to test the hypothesis that three specific classes of meteorites were related to Vesta. The elemental data (from Dawn’s GRaND neutron spectrometer instrument) and the spectral data (from its Visual and Infrared spectrometer, VIR) have confirmed the HED connection. In particular, most of Vesta’s surface looks like howardites, which are the type that’s a mixture of the other two. That isn’t surprising; the impact that created Vesta’s south polar basin (actually two overlapping impacts) happened a very long time ago, and more recent impacts have dug into the surface and mixed material around. And gravity data have also confirmed the fact that Vesta is denser toward its center, which is consistent with the differentiation story.” — from 
"The locals had seen a cobra 🐍 in the brush and were trying to chase it out. It never appears again and we all lazed the inferno day away under those palms. Heat stroke would happen in minutes if exposed from 10 am-5 pm. One man died out hunting the meteorite fall the day after I left." — Farmer (and a story about him in 
Pre-DAWN, the Hubble spectroscopic analysis of 4 Vesta was a good match for the Eucrite meteorites on Earth:
“For nearly 40 years HED meteorites have been linked to asteroid 4 Vesta because of the very close match in IR and visible spectra between the meteorites and the asteroid. This spectral link was strengthened with the discovery of a dynamic physical link between 4 Vesta and a family of asteroids that can be connected to Earth’s orbit via resonances, such as the 3:1 mean motion resonance with Jupiter and the v6 secular resonance between Jupiter and Saturn. This connection was dramatically strengthened by Hubble Space telescope images that revealed a large 400 km crater in the south pole of 4 Vesta. This enormous crater has been suggested to be the source of the many HEDs that have made their way to Earth.” — 
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