Title Frame
Activity 1:
Jupiter, the
dominant Gas Giant
Module 15:
The Jovian Planets
Summary:
In this Activity, we will investigate:
(a) why Jupiter is an important planet for study,
(b) Jupiter’s vital statistics,
(c) properties,
(d) space missions to Jupiter, and
(e) Comet Shoemaker-Levy 9.
Jupiter is the first of four planets
categorized as Jovian Gas
Giants. Jovian is derived from
the Latin name for Jupiter.
(a) Why is Jupiter an important planet to study?
This image provides some
answers … (Earth added to scale)
Atmosphere properties
Comparisons with Earth
Jupiter’s Satellites
Long term features such as
the Great Red Spot
Jupiter-sized planets have been
found around other stars
Being the Sun’s largest planet, Jupiter might be expected to influence the
trajectories of other planets, comets - and spacecraft!
And more ...
(b) Vital Statistics
Jupiter
Jupiter’s orbit
Approximate values are initially used
Earth
a further 4.2 AU
Sun
150 million km ( = 1 AU - Astronomical Unit )
1 year
~12 years
Different scales for size and distance
Jupiter’s size
Here is our familiar Earth and Jupiter and its
brightest satellites as visible in a small telescope
Jupiter’s size
… and we’ll revisit this feature - larger than 2 Earths
Earth on the same scale as
Jupiter
11.2 Earths in equatorial
diameter
10.5 Earths pole to pole
What might explain this
equatorial bulge?
Jupiter’s mass
The volume of Jupiter would enclose
more than 1000 Earths, yet its mass is
‘only’(!) 318 Earths.
This suggests that it is not
a solid planet.
Jupiter’s Rotation
A non-rotating planet might
be expected to be spherical
Jupiter rotates in just 9 hours
50 minutes at its equator
at a tilt of 3° to its
orbital plane
Its large equatorial bulge from the rapid rotation further
suggests that Jupiter has a non-solid structure. (Along with the
‘low’ mass mentioned in the last frame.)
Yet to unfold: What other factors might contribute to the complex
atmospheric patterns we observe on Jupiter?
Jupiter’s Structure
Let’s dissect Jupiter to see what structure might explain
the factors mentioned in the last two frames . . .
1000 km thick atmosphere
Liquid Hydrogen
Liquid metallic Hydrogen
Rocky Core
Overall, Jupiter appears to be around
71% hydrogen, 24% helium and about
5% heavier elements
Summary to date
Orbit
- over 5 times further from the Sun than Earth
- nearly 12 Earth-years in duration
Size
- over 11 Earths in equatorial diameter
- 10.5 Earths in polar diameter
- 318 Earth masses (but over 1000 Earth volumes)
Rotates - in 9 hours 50 minutes, tilted by 3°
Structure - a small rocky core in liquid Hydrogen with a
relatively thin visible atmosphere
Overall ~71% hydrogen, ~24% helium, ~5% heavier elements
(c) Properties
North
Jupiter’s visible details
Hemispheres: The southern hemisphere (closest to your southern
horizon as you view it) is characterised by the Great Red Spot
Polar
Temperate
Regions
Tropical
Equatorial
Markings are called ...
belts for the darker bands and
zones for the lighter bands
plus light (mainly in S) and dark (N)
ovals and eddies
South
So the Great Red Spot is in the N/S?
belt/zone
southregion?
equatorial
belt ?
and this is the?north tropical zone
Jupiter’s Temperature
The temperature at Jupiter’s cloud tops is around -110°C
Jupiter emits nearly twice the amount of radiation it
receives from sunlight. It thus has its own internal heat
source. This could arise from:
- slow cooling since its original formation
- slow gravitational contraction
- frictional motion of deep internal material
(Unlike Earth) Jupiter has no great variation in
temperature from polar to equatorial regions.
Motions in Jupiter’s atmosphere
Higher west to east winds in Jupiter’s equatorial
region makes this region appear to rotate faster (in
9 hours 50 minutes) than the interior and the rest of
the planet (9 hours 55 minutes).
Winds blowing at different strengths and in
different directions cause the swirling eddies
at the edges of belts and zones.
East
Convection currents, from the variation in
temperature with depth, lead to zones and
belts having different vertical motions.
For 50 years, it has generally been thought
that belts are regions of falling gas and
zones are regions of rising gas. Recent
Cassini data now suggests it is the other
way around. For more details, see:
http://saturn.jpl.nasa.gov/news/press-releases-03/20030306-pr-a.cfm
Belts are regions of rising gas, higher pressure
Zones are regions of falling gas, lower pressure
The convection process is shown in
animations in the next slide . . .
zones
Convective currents
The belt and zone
pattern is driven by
convective currents
due to the
temperature gradient
from Jupiter’s interior.
belts
increasing
temperature
Composition of atmosphere
Spectroscopic fingerprinting of Jupiter’s upper
atmosphere indicates three main layers of clouds:
Frozen ammonia crystals
Ammonium hydrosulphide crystals
Frozen water crystals
Normally the crystals in all three layers are white.
Apparently temperature differences at different depths,
(plus molecules including elements such as sulphur and
phosphorus, which can assume many colours under
different conditions of temperature and ultraviolet sunlight),
produce the many colours seen in Jupiter’s atmosphere.
Frozen ammonia crystals
Ammonium hydrosulphide crystals
Frozen water crystals
Colours at different depths are indicated above:
brown - deepest, warmest; and red - highest, coolest.
The turbulent circulation in Jupiter’s atmosphere reveals
the colours at different depths - producing the zones,
belts, ovals and eddies.
The Great Red Spot
Earth to scale
The most famous example of Jupiter’s
markings is the Great Red Spot, which
has persisted for over 300 years.
It is an anti-cyclonic storm rotating
between opposed winds in ~6 days.
Its cooler, higher altitude clouds appear
redder than surrounding regions.
With 600+ km/hr winds, a turbulent region indeed . . .
(d) Space Missions to Jupiter
Much of our information about our own planet is from our
first hand experience of it.
Our knowledge about Jupiter comes from:
- photographs - from Earth (ground and orbit) and from spacecraft
- spectroscopic information from reflected sunlight
- theory - e.g. size, mass and rotation leads to conclusion about
internal structure
- two additional first hand sources of information:
 the Galileo spacecraft probe into Jupiter’s atmosphere
 the 1994 entry of Comet Shoemaker Levy 9 into
Jupiter’s atmosphere
The Pioneer 10 & 11, Voyager 1 & 2, Galileo and
Cassini spacecraft missions are summarised in the
next frames . . .
The Pioneer space probes
Pioneer 10, launched May 1972, passed Jupiter at a
distance of 130,000 km in December 1973. It
photographed Jupiter and the Great Red Spot, satellites
Europa, Ganymede and Callisto, and measured the
extent of Jupiter’s radiation belts.
Pioneer 11, launched April 1973, passed 43,000 km
below Jupiter’s south pole in December 1974, moving
on to photograph the Saturnian system from September
1979.
Both crafts are heading out of the Solar System in
opposite directions. Pioneer 10 was over 12 billion km
from Earth in February 2004 (compared with Pluto’s
mean distance from Sun of 5.85 billion km).
The Voyager spacecrafts
Voyager 1, launched September 1977, reached Jupiter
in March 1979, closely photographing satellites Callisto,
Ganymede, Europa and Io, before approaching 280,000
km from Jupiter. It went on to photograph Saturn
(November 1980) before heading out of the Solar
System.
Voyager 2, launched August 1977, reached Jupiter in
July 1979, passing close to satellites Callisto,
Ganymede and Europa before its 714,000 km approach
to Jupiter. Most of the photos in this Unit are from
Voyager 2. It went on to photograph Saturn (August
1981), Uranus (January 1986) and Neptune (August
1989), before heading out of the Solar System.
The Voyager flight paths
Note the use of gravity assists (most notably at Saturn) to deflect and assist
craft on to the next target. Gravity assists are evident in the Galileo
spacecraft flight path, 2 frames on . . .
Pioneer and Voyager ‘exit from Solar System’
The Galileo Spacecraft
Features:
Launch inwards toward Venus
Gravity assists at Venus and
Earth(2)
Close-up images of two
asteroids
Asteroid Ida
and its orbiting
1km sized
companion
Dactyl
Arrived 1995
Images of Comet SL-9 impact
out of sight from Earth (see
later frame)
Descent of probe from Galileo
(see next frame)
Probe descent from Galileo
A probe separated from the Galileo spacecraft and
descended to its destruction through Jupiter’s atmosphere.
In the next diagram, heights and pressures are given
relative to a level where the pressure is the same as an
Earth surface pressure of 1000 millibars (1 bar):
The Galileo Mission
The separation and descent of the
Probe and insertion of the Galileo
spacecraft into orbit around Jupiter.
Findings:
• Anticipated atmospheric conditions
(temperature, pressure etc) were
confirmed
• The general cloud layer model was
confirmed although the lower water clouds
were absent (or free on the day!)
• The Hydrogen/Helium proportions were confirmed
• Heavier elements, including C,N,S, were detected.
This diagram shows Galileo’s 11 orbits
amongst the satellites of Jupiter.
Many detailed photographs and
information on the structure of natural
satellites were obtained by Galileo
(covered later in the Unit Satellites &
Rings of the Jovian Planets)
The Galileo mission ended on 21 September 2003. Galileo’s
propellant was almost depleted and the spacecraft was put in
a collision course with Jupiter to avoid an impact with the
satellite Europa (which is thought to be one of the best
candidates for hosting life).
The Cassini Orbiter
En route to Saturn, the Cassini
orbiter did a Jupiter flyby in
December 2000 as part of its
“VVEJGA trajectory” (VenusVenus-Earth-Jupiter Gravity
Assist). Simultaneous
observations were made with
Galileo, Cassini and HST to
return to highest ever
resolution images of the
Jupiter.
True colour Cassini mosaic made from 27 images with
a 60km resolution. Taken on 29 December 2000 during
closest approach (at a distance of ~10 million km).
(e) Comet Shoemaker-Levy 9
Carolyn and Eugene Shoemaker
and David Levy discovered a
comet in 1993 which appeared as
a ‘string of pearls’.
Its orbit was calculated to be about Jupiter, not about
the Sun. Jupiter had captured the comet on its entry
to the inner Solar System and Jupiter’s tidal forces
had broken the comet into a number of fragments.
Furthermore, calculations showed that on its next
orbit it would impact with Jupiter in July 1994.
A year after its
discovery the
Hubble Space
Telescope showed
the many
fragments of
Comet SL9, which
were named ‘A’ to
‘W’
Months ahead of the impact,
the mathematics leading to this
artist’s portrayal of the impact
site - just out of view from
Earth - proved accurate to
within minutes
Comet SL-9 Impact sites
As Jupiter rotated (left to right in each of the
above images) impact sites progressively
came into view a few minutes after the
impact behind lower-left of Jupiter
This sequence (from bottom to top) show an impact followed by the
changing appearance of its scattered material in Jupiter’s turbulent
atmosphere (together with a previous impact site rotating into view)
[Hubble Space Telescope images from Earth-orbit]
Comet SL9 Impacts - other images
A small sample from the hundreds of images obtained . . .
An infrared image from
the MSSSO 2.3m
telescope showing the
actual K fragment
fireball and the stillwarm remains of three
other sites
Though launched before SL-9’s discovery,
the Galileo spacecraft was uniquely placed
for a direct view of the impact site, as this
sequence shows
Hubble Space
Telescope ultraviolet
image showing the
debris in the southern
hemisphere (and Io in
the north), labelled by
fragment letters.
Outcomes from Comet SL-9
It provided further evidence of Jupiter’s role in affecting
trajectories of Solar System bodies.
It provided a great example of the power of mathematical
orbit calculation in predicting the precise times of the
fragment impacts.
Most telescopes (professional and amateur; orbiting Earth
and en-route to Jupiter) gave some time to observing
impacts in many wavelengths - e.g. UV, visible, IR etc. and their imaging ability was successfully tested and used.
SL-9’s direct impacts provided further information on the
nature of Jupiter’s atmosphere - wind speeds and
directions, density etc.
Spectroscopic examination of the impact debris had the
potential for information about the composition of Jupiter’s
atmosphere - what produces its many colours, for example.
Sulphur was detected but work continues to separate what
might have been from Jupiter and what from the comet
fragments!
A final contemplation
This image superimposes, to the same
scale, one of the Comet SL-9 impact sites
with our own planet.
Two Hollywood movies have (since SL-9)
used the theme of a potential comet or
asteroid impact with Earth.
Whether an Earth-approaching object
could be destroyed or diverted is a
question for discussion.
To at least maintain observations and
information on potential Near Earth
Objects would seem both wise and, like
SL-9, good fields for scientific observation
and research.
In the next Activity we will look at the other Jovian
gas giant planets - Saturn, Uranus and Neptune.
Image Credits
NASA: http://www.nasa.gov
Indexed status of all NASA spacecraft
http://www.hq.nasa.gov/office/oss/missions/index.htm
Hubble Space Telescope images indexed by subject
http://oposite.stsci.edu/pubinfo/subject.html
Cassini image of Jupiter
http://photojournal.jpl.nasa.gov/catalog/PIA04866
Comet Shoemaker-Levy 9 Collision with Jupiter
http://www.jpl.nasa.gov/sl9/sl9.html
View of Australia
http://nssdc.gsfc.nasa.gov/image/planetary/earth/gal_australia.jpg
Now return to the Module 15 home page, and
read more about Jupiter in the Textbook
Readings.
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