For example, how did icy comets obtain particles that formed at high temperatures, and how did these refractory particles acquire rims with different compositions? Carnegie's theoretical astrophysicist Alan Boss and cosmochemist Conel Alexander* are the first to model the trajectories of such particles in the unstable disk of gas and dust that formed the Solar System.
They found that these refractory particles could have been processed in the hot inner disk, and then traveled out to the frigid outer regions to end up in icy comets. Their meandering trips back and forth could help explain the different compositions of their rims. The research is published in Earth and Planetary Science Letters.
The young Sun is thought to have experienced a series of outbursts caused by the rapid infall of disk gas onto the Sun. The leading mechanism for explaining such outbursts is a phase of disk instability. The researchers modeled the trajectories of several hundred centimeter-sized melilite mineral particles during a phase of disk instability. These particles are similar to calcium-aluminum-rich inclusions (or CAIs), the refractory particles often found in well-preserved meteorites, as well as the comet Wild 2.
Their disk model assumed a marginally gravitationally unstable, fully three-dimensional disk, with a mass of about 5 % of today's Sun and temperatures ranging from a frigid -350 °F (60K) in the outer regions, to a scorching 2240 °F (1500K) near the center. Their calculations allowed the CAIs to orbit in the disk while being subjected to gas drag and the gravity of both the disk and the Sun.
The particles started orbiting in unison, but after about 20 years their trajectories started to diverge significantly. Most struck the inner boundary of the disk at 1 AU (the Earth/Sun distance), while others went to the outer boundary at 10 AU, where they could be swept up by a growing comet. About 10% migrated back and forth in the disk before hitting one or the other boundary.
The researchers then modeled the evaporation and condensation processes that the particles would experience during their migrations and found that such particles were likely to acquire outer rims with varied isotopic compositions recently shown to characterize CAIs.
"CAIs are thought to have formed at the very beginning of the Solar System. Our results show that they must have experienced remarkably complex histories as they were transported chaotically all over the disk," remarked Alexander.
These migrations could explain the different oxygen isotopes that have been found in particles from meteorites. These are varieties of oxygen atoms with different numbers of neutrons, which point to different processing conditions for the particle rims.
Previous work by Boss had shown that oxygen isotope abundances could vary in an unstable disk by the range found in meteorites. Coupled with the new results, these models show that several puzzles may have been solved—an unstable disk can explain both large-scale outward transport of refractory particles, as well as the peculiar rim compositions acquired during their journeys.
"It's nice to solve two problems at once," said Boss. "But there are still many more puzzles about meteorites for us to work on."
* The research also included colleague Morris Podolak at Tel Aviv University and was funded in part by NASA Origins of Solar Systems Program. The calculations were performed on the Carnegie Alpha Cluster supported in part by the NSF.
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.
Structured light and nanomaterials open new ways to tailor light at the nanoscale
23.04.2018 | Academy of Finland
On the shape of the 'petal' for the dissipation curve
23.04.2018 | Lobachevsky University
Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.
Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
23.04.2018 | Physics and Astronomy
23.04.2018 | Physics and Astronomy
23.04.2018 | Trade Fair News