Imagine a planet with more than thirty
moons. One of them is larger than Mercury and is enveloped
in a nitrogen-filled atmosphere more massive than our
own. The planet itself has 95 times the mass of Earth,
yet its density is so low it could float in champagne!
That would be a truly spectacular cocktail, for this
planet is Saturn, the true Lord of the Rings.
A joint US-European space mission called
Cassini-Huygens will reach Saturn this summer after a
seven-year voyage. The mission consists of an orbiter
(Cassini) carrying a probe (Huygens), which will descend
into the atmosphere of the giant satellite Titan. "Landfall" with
this miniature solar system will occur on June 11, when
the spacecraft passes Saturn's most distant satellite,
Phoebe, a strange, dark body that moves backward in its
orbit around Saturn. On July 1, the spacecraft will cross
the planet's ring plane, and a powerful rocket engine
will slow it down, sending it into orbit around Saturn.
After deploying Huygens on Christmas Day, Cassini will
spend the next four years examining Saturn, its magnificent
rings, its complex magnetic field and trapped radiation
belts, and many of its fascinating satellites. Huygens
will enter Titan's atmosphere on January 14, 2005, and
then make a 2.5-hour descent to the surface, where it
will continue to transmit data if it survives the landing.
Titan is certainly the most intriguing satellite in
the solar system, a moon that enables a kind of cosmic
time travel. Titan's environment resembles in some respects
the conditions on the early Earth before life began.
We often think of life developing on Earth in the primordial
soup of warm little tide pools. On Titan we will be looking
for primordial ice cream, the results of spontaneous
organic chemistry still taking place in the atmosphere
today, held in deep freeze on the satellite's surface.
And that surface may well be extraordinary! Lakes, rivers,
rainstorms, and waterfalls of liquid natural gas may
sculpt a crater-pocked landscape of frigid ice coated
with deposits of organic aerosols. Titan is a flammable
world, but its temperature is so low that there is no
source of oxygen that would allow it to burn.
IfA astronomer Tobias Owen was one of the originators
of the Cassini-Huygens mission and the chair of the
U.S. Study Team that began work with the Europeans
to develop this mission in 1984. He is presently an
interdisciplinary scientist and a member of three of
the experiment teams that will be analyzing the rich
harvest of data to be returned by the spacecraft. These
results will be brought to the IfA for study by our
graduate students and for presentation to our classes
and to the community.
For more information, see http://saturn.jpl.nasa.gov/index.cfm and http://www.rssd.esa.int/Huygens/Mission/Overview.html
Who were Cassini and Huygens?
Giovanni Domenico Cassini (1625-1712)
was an Italian-born French astronomer who discovered
four of Saturn's satellites and the division in Saturn's
rings that is now named for him. He also measured the
rotation periods of Mars and Jupiter, participated in
measuring the distance to Mars by triangu-lation, and
improved the estimate of the solar system's dimensions.
Christiaan Huygens (1629-95)
was the Dutch astronomer who discovered Titan in 1655.
While others had observed Saturn's rings, he was the
first to correctly interpret what they saw.
Join the great adventure
of exploring the Saturn system by checking the Imaging
Team Web site, http://ciclops.lpl.arizona.edu/, as Cassini-Huygens
reveals new worlds.