What it is
Carbon, hydrogen and nitrogen (atmophile elements) were thought to have accreted late during planetary formation, yet cosmochemical and astrophysical evidence suggests they were already present while small bodies such as Vesta were forming. That is a puzzle, because high-temperature magmatic events on small bodies should have outgassed these ultravolatile elements, their gravity being too weak to retain them. In experiments on magma ocean-like mixtures, the authors found that gas bubbles attach strongly to metal droplets, forming bubble-metal compounds that resist segregation.
Why it matters
The compounds would have given small bodies a way to keep their atmophile elements: under low gravity, compounds a millimeter to a centimeter across would have been able to sink, trapping those elements in the interior. Early flotation of such compounds would have enhanced the mantle's endowment of siderophile (iron-loving) elements, eliminating the need for late accretion. The mechanism links core formation to the early entrapment of atmophile elements and provides a framework for reconciling volatile delivery across planetary bodies with models of planetary accretion.
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Filed underAstro and Planetary Science, Planetary Science and Exploration, High-pressure geophysics and materials
