  The loss and gain of volatile elements during planet formation is key for
setting their subsequent climate, geodynamics, and habitability. Two broad
regimes of volatile element transport in and out of planetary building blocks
have been identified: that occurring when the nebula is still present, and that
occurring after it has dissipated. Evidence for volatile element loss in
planetary bodies after the dissipation of the solar nebula is found in the high
Mn to Na abundance ratio of Mars, the Moon, and many of the solar system's
minor bodies. This volatile loss is expected to occur when the bodies are
heated by planetary collisions and short-lived radionuclides, and enter a
global magma ocean stage early in their history. The bulk composition of
exo-planetary bodies can be determined by observing white dwarfs which have
accreted planetary material. The abundances of Na, Mn, and Mg have been
measured for the accreting material in four polluted white dwarf systems.
Whilst the Mn/Na abundances of three white dwarf systems are consistent with
the fractionations expected during nebula condensation, the high Mn/Na
abundance ratio of GD362 means that it is not (>3 sigma). We find that heating
of the planetary system orbiting GD362 during the star's giant branch evolution
is insufficient to produce such a high Mn/Na. We, therefore, propose that
volatile loss occurred in a manner analogous to that of the solar system
bodies, either due to impacts shortly after their formation or from heating by
short-lived radionuclides. We present potential evidence for a magma ocean
stage on the exo-planetary body which currently pollutes the atmosphere of
GD362.
