Volatile processing on planetesimals: The story from iron meteorites

Dr. Marc Hirschmann, University of Minnesota, presented, "Volatile processing on planetesimals: The story from iron meteorites."

About the talk:
The major volatiles necessary for life and habitability – hydrogen, carbon, nitrogen – are plentiful in protoplanetary disks, and so understanding the delivery of these materials to habitable terrestrial planets amounts to accounting for the processes of loss that yield planets with “the right amount” of life-essential materials. Our understanding of what constitutes “the right amount” is unfortunately limited, but the natural starting point is to begin with the inventory on Earth, and in particular in the Bulk Silicate Earth. In the first part of this talk, I’ll present some of the constraints on major volatile abundances in the bulk silicate Earth, with an emphasis on volatile element ratios that place constraints on the accretion and early differentiation processes. In the second part, I’ll examine volatile loss during differentiation of planetesimals.

The processes leading to formation of terrestrial planets can shed volatiles during the stages of nebular processing, planetesimal differentiation, and planetary accretion, but the planetesimal stage has been less-examined than the others. I will focus on iron meteorites. The evidence provided by iron meteorites has previously received little attention, but reconstruction of their parent body carbon contents indicates that planetesimal differentiation is an open system process that leads to significant volatile loss. Further, the patterns of volatile loss given by the carbon/sulfur ratios of meteorite parent bodies require that the loss process occurred from the silicate portion of the planetesimal. If terrestrial planets originate from oligarchic growth, rather than directly from undifferentiated pebbles, then devolatilization during small-body differentiation is a key process in shaping the volatile inventory of terrestrial planets.

Видео Volatile processing on planetesimals: The story from iron meteorites канала Carnegie Earth & Planets Laboratory