Glossary
VOLATILES - Elements or substances which
condense (and vaporize) at relatively low
temperatures, such as nitrogen, methane and
water. Those which condense at high temperatures, like corundum (Al2O3) at 1758K or 1485°C,
are refractory.
CRYOVOLCANISM - ‘Cool’ volcanic activity,
where ‘cold slurries’ of volatiles such as water,
ammonia or methane, erupt and flow across a
surface, in the same way that molten rock erupts
and flows as lava in warmer environments.
SOLID-STATE CONVECTION - Convection taking
place in a solid, without the need for melting.
For Pluto this would be within viscous, frozen
volatiles.
TECTONIC - Related to the process of deformation within the crust of a planetary body and
associated structural effects, such as faulting.
INSOLATION - Solar radiation reaching a
planetary surface.
SUBLIMATION - Transition of a substance directly
from a solid to a gas without passing through the
intermediate liquid phase. This occurs with volatiles at Pluto’s surface as its atmospheric pressure
is too currently low for them to exist as liquids.
PLASMA - State of matter, created by adding
energy (e.g. solar) to a gas and driving electrons
from atoms, leaving electrically-charged
particles or ions.
MAGNETOSPHERE - Region of space surrounding
an astronomical object in which charged
particles are controlled by that object’s
magnetic field.
(GEOMETRIC) ALBEDO - The fraction of the solar
radiation falling on a body which is reflected by
that body. Pluto’s average albedo varies regionally from 0.49 to 0.66 – darker areas reflect only
49% of incident light, whereas the brighter areas
reflect 66%. For comparison, Earth’s average
albedo is about 0.37 (37%) and our Moon’s
about 0.12 (12%).
ASTRONOMICAL UNIT (AU) - Mean distance
between the Earth and the Sun, equal to 149.6
million km.
PERIHELION - Closest point to the Sun of any solar
system body in orbit around it.
APHELION - The opposite, being the furthest point
in its orbit from the Sun.
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