Abstract
The high vapor pressure of volatile metal halides and chalcogenides
(e.g., of Cu, Zn, Sn, Pb, As, Sb, Bi) at typical Venus surface temperatures,
coupled with the altitude-dependent temperature gradient of approximately
8.5 K km-1, is calculated to transport volatile metal vapors to the
highlands of Venus, where condensation and accumulation will occur.
The predicted geochemistry of volatile metals on Venus is supported
by observations of Cu, Zn, Sn, Pb, As, Sb, and Bi minerals around
terrestrial volcanic vents, spectroscopic observations of CuCl in
volcanic gases at Kilauea and Nyiragongo, and large enrichments of
these and other volatile elements in terrestrial volcanic aerosols.
A one-dimensional finite difference vapor transport model shows the
diffusive migration of a thickness of 0.01 to > 10 mum/yr of moderately
to highly volatile phases (e.g., metal halides and chalcogenides)
from the hot lowlands (740 K) to the cold highlands (660 K) on Venus.
The diffusive transport of volatile phases on Venus may explain the
observed low emissivity of the Venusian highlands, hazes at 6-km
altitude observed by two Pioneer Venus entry probes, and the Pioneer
Venus entry probe anomalies at 12.5 km.
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