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2013 Annual Science Report

Arizona State University Reporting  |  SEP 2012 – AUG 2013

Astrophysical Controls on the Elements of Life, Task 6: Determine Which Elemental or Isotopic Ratios Correlate With Key Elements

Project Summary

Abundances of both common and trace elements can have substantial effects on the habitability of stellar systems. We study the formation and composition of structures in supernova explosions that deliver isotopes that influence habitability to material that will form new stars and planets. We examine ratios of elements that have substantial effects of the mineralogy and interiors of planets. The relative abundances of common elements vary substantially among nearby stars, and we find that the impact of this on a star’s evolution can change the amount of time its planets are habitable by large factors.

4 Institutions
3 Teams
1 Publication
0 Field Sites
Field Sites

Project Progress

This task is largely closed, but does have some connections to work in tasks 2 and 7, that are described below.

Patrick Young, (ASU), Carola Ellinger (University of Texas at Arlington), Chris Fryer, and Gabe Rockefeller (Los Alamos) have produced models of supernovae that follow the process from the onset of the explosion all the way through the interaction of the remnant, with the surrounding interstellar medium. We have detailed how structures are formed in the supernova ejecta at all stages of the explosion and remnant development and have also shown that structures created early in the evolution persist to late times. This means that an individual supernova can cause substantial and highly variable enrichment of particular isotopic species in nearby planet-forming clouds and disks. Liubin Pan, Steve Desch, Frank Timmes, and Evan Scannapieco (ASU) simulated impact of supernova bullets into molecular clouds and show that when cooling of gas is included, dense clumps penetrate and mix efficiently. This addition of material can significantly change the abundances in the molecular cloud. These simulations provide us with a library of cases, which do study co-delivery of isotopes into surrounding material (Refer to Task 2.)

An analysis of ~500 stars by Michael Pagano (from spectra obtained by Paul Butler, Carnegie Institute for Science) plus data from five other groups have provided a robust statistical analysis of elemental abundance ratios in nearby stars. The choice of abundance ratios for analysis has been informed by collaboration with Dan Shim, mineral physicist, and Allen McNamara, geodynamicist. Certain ratios determine the mineral makeup of mantle rocks. Different mineral assemblages have different mechanical properties that affect heat transport and convection in planetary interiors. We find that for O/Fe (important to stellar evolution), Mg/Si, C/O, Ca/Fe, and Al/Fe (important to planetary mineralogy) there is no statistically significant correlation between any of these species. This means that the whole range of potential diversity in important ratios for these elements is likely to be encountered and must be modeled. Additional ratios can be easily derived for other species, as they are identified as important. (Refer to Task 7).