Evidence for a Dynamo in the Main Group Pallasite Parent Body

• Published in: Science (American Association for the Advancement of Science) Vol. 338; no. 6109; pp. 939 - 942
• Main Authors: Tarduno, John A., Cottrell, Rory D., Nimmo, Francis, Hopkins, Julianna, Voronov, Julia, Erickson, Austen, Blackman, Eric, Scott, Edward R.D., McKinley, Robert
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 16.11.2012; The American Association for the Advancement of Science
• Subjects: Asteroids; Boundaries; Cooling; Core mantle boundary; Cosmochemistry. Extraterrestrial geology; Crystals; Demagnetization; Earth sciences; Earth, ocean, space; Exact sciences and technology; Liquids; Magnetic fields; Magnetization; Meteorites; Meteorites. Tectites. Impactites; Meteors & meteorites; Olivine; Parents; Planets; Protoplanets; Rotating generators; meteorites; magnetic field; magnetic minerals; petrogenesis; magnetic intensity; parent bodies; pallasites; metals; olivine; demagnetization; provenance; silicates; remanent magnetization; stony irons; nesosilicates; nickel; asteroids; saturation magnetization; coercivity; dynamos; planetesimals; mineral inclusions; magnetic properties; magnetic hysteresis; paleomagnetism; iron; injection; thermal models
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1223932

Understanding the origin of pallasites, stony-iron meteorites made mainly of olivine crystals and FeNi metal, has been a vexing problem since their discovery. Here, we show that pallasite olivines host minute magnetic inclusions that have favorable magnetic recording properties. Our paleointensity measurements indicate strong paleomagnetic fields, suggesting dynamo action in the pallasite parent body. We use these data and thermal modeling to suggest that some pallasites formed when liquid FeNi from the core of an impactor was injected as dikes into the shallow mantle of a ~200-kilometer-radius protoplanet. The protoplanet remained intact for at least several tens of millions of years after the olivine-metal mixing event.