Transcript Io - University of Ottawa

A Jovian Satellite: The Tormented
Fireball of our Solar System!
By: Kimberly Miller
Historical Findings
• The satellite Io was discovered on January 7th,
1610 by Astronomer and Scientist Galileo
Galilei using a homemade telescope.
• Appearing as three stars linearly transecting
Jupiter, intrigue captivated the astronomer the
following night, as these stars seemed to shift in
the wrong direction.
• This allowed for the discovery of a forth star (later
known as Ganymede) and the notion that, after a
week of observation, these were indeed planetary
bodies that remained in the orbiting realm of
Jupiter.
• This discovery was historical in providing
evidence that sustained the Copernican system
theories and how the Earth is not the center of the
Universe.
• Io was numerically labeled: I, according to the
Medicean planet system (Europa II, Ganymede III,
and Callisto IV).
Born: February 15th, 1564
Died: January 8th, 1642
• Simon Marius is also given credit for discovering the satellites
within the same time frame and was in fact the provider of the
names we are familiar with presently (Io, Callisto, Europa, and
Ganymede).
• Io was named, based on a suggestion from Johannes Kepler, after the
maiden daughter of the River (according to Roman mythology),
having been clandestinely courted by the Roman God, Jupiter.
Data Table: Io
Mass (kg)
Mass (Earth = 1)
Equatorial radius (km)
Equatorial radius (Earth = 1)
Mean density (gm/cm^3)
Mean distance from Jupiter (km)
Rotational period (days)
Orbital period (days)
Mean orbital velocity (km/sec)
Orbital eccentricity
Orbital inclination (degrees)
Escape velocity (km/sec)
Visual geometric albedo
Mean surface temperature
Magnitude (Vo)
8.94e+22
1.4960e-02
1,815
2.8457e-01
3.55
421,600
1.769138
1.769138
17.34
0.004
0.040
2.56
0.61
-143°C
5.02
Satellite Images
• Io is the innermost Galilean satellite of Jupiter, and much like its
siblings, is characterized by an extremely unique feature.
• During the Voyager encounters of the 1970s, initial pictures displayed
an unusually young surface, the only body in the solar system with no
substantial impact craters.
• As images were taken for navigation purposes, immense eruptive
plumes were recorded inadvertently. Subsequent observations
confirmed that Io is horded by volcanic activity.
• In October 1989, the artificial satellite Galileo was launched into orbit,
its mission to recuperate a more detailed analysis of the Jovian system
only viewed in flybys of the Voyager mission.
• Galileo reached within 900 km of Io's surface preceding the orbit
insertion in 1995, however it did not revisit until October 11th 1999, as
scientists thought the task too risky.
Jupiter’s hold on Io is due to:
• The reason Galileo has spent less time observing Io is due to the danger to the
spacecraft; Io lies deep in Jupiter's intense radiation belts.
• When the Galileo satellite recorded its images, it observed that as Io passed
through Jupiter's shadow, it was outlined by a thin ring of glowing gas, illuminated
by the impact of electrons from Jupiter's magnetosphere.
• As Jupiter rotates with its magnetosphere, it brushes by Io collecting with it about
1,000 kilograms (1 ton) of material per second.
• The ionized gases from Io's volcanic eruptions create a torus of plasma, resembling
a doughnut shaped cloud around Jupiter, that is emanated by ultraviolet.
• The heavy ions in the torus migrate outward creating a pressure that inflates the
Jovian magnetosphere, doubling its relative size.
• The more energetic sulphur and oxygen ions that fall along the magnetic field, and
into the planet's atmosphere, are few that manage to result in auroras.
• Io acts as an electrical generator as it moves through the Jovian magnetic field,
developing 400,000 volts across its diameter and generating an electric current of 3
million amperes that flows along the magnetic field into Jupiter's ionosphere.
• This hypothesis explains the active volcanism on Io as a result of Jupiter’s
magnetic field, in turn amounting to the largest known electric circuit in the solar
system.
THE MAGNETIC FIELDS OF GALILEAN SATELLITES
Io: Internal and Composition Speculation
• Io is relatively the size of the Earth’s moon.
• Io’s violent volcanic activity has raised scientists curiosity, as recorded
average surface temperatures were around -143°C, a result of this satellite’s
far distance from the sun, questioning the interior’s continuous molten state.
• Even though eruptions occur on Io at magnificently high temperatures, once
the volcanic gases are emitted, they instantly freeze and condense.
• Even though Io exhibits an iron core, it
is still only a minor amount of the
overall content.
• The interior characteristics of the moon
are inferred from gravity field and
magnetic field measurements by the
Galileo spacecraft.
• Io has a metallic (iron, nickel) core
(shown in gray) drawn to the correct
relative size. The core is surrounded by
a rock shell (shown in brown). Io's rock
or silicate shell extends to the surface.
(© Copyright Calvin J. Hamilton)
•
•
•
•
•
•
Molten Io
Io is recognized as the most
volcanically active body in the solar
system, spewing ~100 times more lava
than the Earth.
This tormented satellite is governed
by the magnetic forces of attraction
from Jupiter and other surrounding
satellites nearby.
Io's orbit around Jupiter is elliptical,
where the distance between them
changes during a complete orbit.
When Io is close to Jupiter, the
latter’s gravity attempts to distort Io
into an egg shape. The further away
from Jupiter Io reaches, the more it
relaxes into a spherical shape.
In addition, the other large Galilean satellites exert on Io their
gravitational influences, pulling it in other directions still, like a giant
tug-of-war.
Io’s surficial rising and falling surface is relative to the same forces
(gravity) that cause the rise and fall of tides of Earth's oceans. This
process is called tidal flexing.
This flexing creates bulges as big as 100 meters, producing a great
frictional tension, where heat is generated and releases a significant
amount of energy in violent volcanic eruptions.
Map projections: Io’s hot spots
Unimaginable Heat
•
•
•
•
•
•
•
•
Determination of Io’s heat capacity is based on how brightly the volcanoes glow at
variable visible and near-infrared wavelengths, also a necessary measurement of lava
composition.
Plumes from the volcanoes extend to more than 300 km(190 miles) above the surface,
with material being ejected at speeds up to a km(0.6 miles) per second.
Typical Earth volcanoes eject basaltic lavas--iron, magnesium and calcium silicates rich
in the minerals olivine and pyroxene.
Basaltic melts typically have temperatures ranging from 1,300 to 1,450 in Kelvin (1,050
to 1,200 degrees Celsius). Contrary-wise, telescopic observations of Io several years ago
suggested temperatures of 1,500 to 1,800 in Kelvin.
This hypothesis eliminated substances with low melting points, such as liquid sulfur,
which until then had been assumed as a dominant volcanic fluid on Io.
Galileo's measurements proved otherwise again, as Io’s lavas were reaching
temperatures of 1,700 to 2,000 Kelvin, where magma this hot has not been common on
Earth for more than three billion years.
“This discovery of high-temperature silicate volcanism provides us with an extremely
important clue to understanding the geophysical processes within Io” quote McEwen.
Io provides scientists with the possible key into the Earth's geologic youth, when its
interior temperatures were higher and the composition of the upper mantle differed
from present days.
Io: in retrospect
• The camera and spectrometer of Galileo together have
discovered a total of 41 hot spots on Io, where a total of
60 are assumed.
• Voyager 1 was able to observe nine colossal eruptions on
its flyby, later verified by Voyager 2, where those visible
were still violently active.
• Here are names of the most active volcanoes on Io:
Prometheus, Zamama, Masubi, Pillan Patera, Reiden
Patera, Marduk, Pele, Ra Patera, Loki Patera, and
Babbar Patera.
Cited Works:
 http://www.solarviews.com/r/jup/io2.gif
 http://www.jpl.nasa.gov/galileo/news23.html

http://www.solarviews.com/eng/galdisc.htm

http://www.jpl.nasa.gov/galileo/ganymede/discovery.html

http://www.solarviews.com/eng/io.htm

http://www.sciam.com/2000/0200issue/0200johnson.html

http://www.sciam.com/2000/0200issue/0200johnsonbox2.html
 http://www.jpl.nasa.gov/galileo/io/vgrio.html
 http://www.solarviews.com/eng/iomap.htm
 http://www.solarviews.com/cap/jup/io4.htm
 http://www.jpl.nasa.gov/galileo/news23.html