Figure 1.
Detection of the three
outbursts. Panels a-c
are observations at the
W.M. Keck Observatory;
the image in panel d
was captured at Gemini
N. Figure adapted from
de Pater et al., 2014,
and de Kleer et al., 2014.
During this time, volcanic activity was both
widespread and vigorous on all the terrestrial planets and many smaller bodies; ancient
volcanic features on their surfaces preserve
records of this activity. As the Solar System
aged and cooled, active volcanism died out
on most of these bodies, while on planets
such as Earth, where it still takes place today,
the activity has vastly diminished in intensity.
An exception to this trend is Jupiter’s moon
Io, which hosts hundreds of active volcanoes over a surface area smaller than the
continent of Asia. The most energetic eruptions on Io dwarf anything we see on Earth
today — in temperature, power, and spatial
extent. Io’s blasts can produce sulfurous
plumes that reach hundreds of miles above
the moon’s surface.
The moon’s extreme volcanism is powered
by tidal heating: Io is locked in an orbital resonance with the neighboring moons Europa
and Ganymede, meaning that it encounters
these moons at the same position in each orbit. This leads to a coherent gravitational pull
that forces Io into an eccentric path around
January 2015
Jupiter. The changing distance from Jupiter
over the course of each orbit — a mere 1.77
days — causes the moon’s surface to bulge
by varying amounts, which generates the intense internal friction that heats Io’s interior
and powers its volcanic activity.
Although Io is the only of Jupiter’s moons to
display active surface volcanism, the gravitational interaction that heats its interior also
acts on Europa and Ganymede, keeping their
interiors warm enough to host subsurface
oceans of liquid water. Though the heating
processes in these moons are hidden from
view by their icy surfaces, the insight we
gain into heat dissipation in Io’s interior is directly applicable to Europa and Ganymede,
and can help us understand the formation
and history of their hidden oceans.
Observing Volcanoes
from a Volcano
On the night of August 15, 2013, Imke de
Pater (University of California Berkeley), a
member of our team, used the W.M. Keck
2014 Year in Review
GeminiFocus
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