New research from a team including Carnegie's Doug Rumble and Liping Qin focuses on one particularly old type of meteorite called diogenites. These samples were examined using an array of techniques, including precise analysis of certain elements for important clues to some of the Solar System's earliest chemical processing. Their work is published online July 22 by Nature Geoscience.
At some point after terrestrial planets or large bodies accreted from surrounding Solar System material, they differentiate into a metallic core, asilicate mantle, and a crust. This involved a great deal of heating. The sources of this heat are the decay of short-lived radioisotopes, the energy conversion that occurs when dense metals are physically separated from lighter silicate, and the impact of large objects. Studies indicate that the Earth's and Moon's mantles may have formed more than 4.4 billion years ago, and Mars's more than 4.5 billion years ago.
Theoretically, when a planet or large body differentiates enough to form a core, certain elements including osmium, iridium, ruthenium, platinum, palladium, and rhenium—known as highly siderophile elements—are segregated into the core. But studies show that mantles of the Earth, Moon and Mars contain more of these elements than they should. Scientists have several theories about why this is the case and the research team—which included lead author James Day of Scripps Institution of Oceanography and Richard Walker of the University of Maryland—set out to explore these theories by looking at diogenite meteorites.
Diogenites are a kind of meteorite that may have come from the asteroid Vesta, or a similar body. They represent some of the Solar System's oldest existing examples of heat-related chemical processing. What's more, Vesta or their other parent bodies were large enough to have undergone a similar degree of differentiation to Earth, thus forming a kind of scale model of a terrestrial planet.
The team examined seven diogenites from Antarctica and two that landed in the African desert. They were able to confirm that these samples came from no fewer than two parent bodies and that the crystallization of their minerals occurred about 4.6 billion years ago, only 2 million years after condensation of the oldest solids in the Solar System.
Examination of the samples determined that the highly siderophile elements present in the diogenite meteorites were present during formation of the rocks, which could only occur if late addition or 'accretion' of these elements after core formation had taken place. This timing of late accretion is earlier than previously thought, and much earlier than similar processes are thought to have occurred on Earth, Mars, or the Moon.
Remarkably, these results demonstrate that accretion, core formation, primary differentiation, and late accretion were all accomplished in just over 2 to 3 million years on some parent bodies. In the case of Earth, there followed crust formation, the development of an atmosphere, and plate tectonics, among other geologic processes, so the evidence for this early period is no longer preserved.
"This new understanding of diogenites gives us a better picture of the earliest days of our Solar System and will help us understand the Earth's birth and infancy," Rumble said. "Clearly we can now see that early events in planetary formation set the stage very quickly for protracted subsequent histories."
This work was supported by NASA.
The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
Doug Rumble | EurekAlert!
Hundreds of bubble streams link biology, seismology off Washington's coast
22.03.2019 | University of Washington
Atmospheric scientists reveal the effect of sea-ice loss on Arctic warming
11.03.2019 | Institute of Atmospheric Physics, Chinese Academy of Sciences
DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.
The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...
Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.
The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...
Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.
Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.
A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...
Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.
"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...
11.03.2019 | Event News
01.03.2019 | Event News
28.02.2019 | Event News
25.03.2019 | Trade Fair News
25.03.2019 | Life Sciences
25.03.2019 | Information Technology