Ferrovolcanism: Iron Volcanism on Metallic Asteroids

Abstract

Metallic asteroids, the exposed cores of disrupted planetesimals, are expected to have been exposed while still molten. Some would have cooled from the outside in, crystallizing a surface crust which would then grow inward. Because the growing crust is expected to be more dense than the underlying melt, this melt will tend to migrate toward the surface whenever it is able. Compressional stresses produced in the crust while it cools will be relieved locally by thrust faulting, which will also provide potential conduits for melt to reach the surface. We predict iron volcanism to have occurred on metallic asteroids as they cooled and discuss the implications of this process for both the evolution and the modern appearance of these bodies.

Suprathermal Fe in the Earth's Plasma Environment: Cluster RAPID Observations

“…In addition to the solar wind and ionospheric origin, other potential sources for Fe in space are meteors (Abrahams & Nimmo, 2019) and the lunar surface (Colaprete et al, 2016;Poppe et al, 2016;Tanaka et al, 2009). The fundamental mechanism is the same: Sputtering (i.e., ejection of material) from a surface is caused by bombardment by energetic particles from the solar wind or microsscale dust particles.…”

Morphological Diversity of Impact Craters on Asteroid (16) Psyche: Insight From Numerical Models

“…As a result the morphology of small craters might differ substantially from those of large craters in the presence of small‐scale target heterogeneity. Ferrovolcanism has the potential to cause substantial small‐scale variations in near‐surface strength, density, and surface topography on Psyche (Abrahams & Nimmo, 2019; Johnson et al, 2019). As discussed previously, Johnson et al (2019) showed that repeated ferrovolcanic eruptions can produce a global iron layer on Psyche's surface.…”

“…The dunite layer was modeled as in scenario (a), while the iron core was modeled as either an intact core (scenario b) or a shattered, porous core (scenario c). Impacts into a dunite mantle covered by a thin iron layer. One hypothesis that may explain the observed elevated metal content on Psyche's surface is the presence of a thin iron layer covering the mantle as a result of ferrovolcanism (Abrahams & Nimmo, 2019; Johnson et al, 2019). During the cooling period of proto‐Psyche, compressional stresses produced in the cooling crust were relieved by faults, allowing Fe‐Ni rich material from the core to propagate to the surface in dikes.…”

“…During the cooling period of proto‐Psyche, compressional stresses produced in the cooling crust were relieved by faults, allowing Fe‐Ni rich material from the core to propagate to the surface in dikes. Abrahams and Nimmo (2019) proposed that repeated ferrovolcanic eruptions on a fully metallic asteroid would be able to raise enough molten iron material to the surface to cover a more dense iron shell. Johnson et al (2019) showed that ferrovolcanic eruptions are also possible on iron asteroids covered by a thin mantle; however, an estimate of the amount of molten iron erupted was not given.…”

“…Therefore, here we assumed that the impacts occurred after the iron melt cooled and formed a 50‐m layer covering the mantle. The thickness of the iron layer was chosen based on a plausible estimate of the volume of iron that could be erupted in the absence of a mantle (Abrahams & Nimmo, 2019). The iron layer was modeled as nonporous iron (see scenario b), while the mantle substrate was modeled as in scenario (a). Impacts into dunite‐iron layered targets.…”