June 30, 2004 | David F. Coppedge

Cassini to Rewrite Textbooks on Saturn

Hundreds of scientists and engineers are waiting with eager anticipation for SOI: Saturn Orbit Insertion, as the schoolbus-sized Cassini spacecraft races for its closest approach to the ringed planet tonight.  Just before closest approach, Cassini will fire its main engine for 96 minutes to slow down the spacecraft and allow Saturn to capture it in orbit (see guide to SOI and diagram on the Cassini website).
    Right after the burn, for about 75 minutes, Cassini will be flying high over the rings at close range.  The instruments will gather as many measurements and pictures as it can, because it will never again be this close to the rings or to Saturn.  Scientists do not predict that the high-resolution cameras will be able to resolve individual ring particles from this range – the best resolution will be about 50 meters per pixel, and most particles are much smaller than 10 – but it may detect wakes, waves and streams that will provide clues to the dynamic evolution of ring particles over time.  There should be good sample images of all three main rings, C, B, and A, as well as the narrow F ring.  After downloading its data during the night, Cassini will point to Titan for its first of 45 encounters.
    Saturn has already provided Cassini’s instruments with a puzzle: the rotation rate appears to be slowing down.  According to Cassini’s radio and plasma wave detectors, Saturn is rotating about 1% slower than when Voyager made measurements in 1981.  (This is determined by timing radio pulses in the planet’s magnetic field, which is presumed to originate from deep within the fluid planet’s interior.)  Jupiter’s rotation rate has been rock solid for 50 years of measurements, so why Saturn should show this change is without explanation at this time.  The principal investigator for the radio and plasma wave instrument suspects it has something to do with the fact that Saturn’s polar and magnetic field axes are almost perfectly aligned, to within 0.2 degree – a characteristic unique to Saturn.  All other planets with magnetic fields show an offset of 10 degrees or more.  It is that offset that generates the magnetic dynamo, according to favored models; these models, however, cannot account for a field on an axisymmetric body.  How Saturn can have a magnetic field with a negligible offset is a major puzzle Cassini scientists hope to solve.
Update  Stupendous success!  The orbit insertion burn occurred flawlessly.  Cassini followed its trajectory exactly as predicted, and then turned to capture the data and images.  Relieved scientists and engineers expressed their enthusiasm at the performance of the spacecraft.  Now the four-year adventure begins.  Some of the first science results will be posted in the July issue as soon as available.

We hope to be able to bring you findings and analyses that the media will miss or misinterpret.  For instance, the media will always interpret phenomena in terms of the Sacred Parameter A, the “age of the solar system” (4.5 billion years), a figure invariably assumed without question, even when apparently young phenomena are being observed.
    Of special interest will be the rings, not only because of their beauty, but because of their apparent youth.  Most ring scientists believe that the rings had to form relatively recently.  Even if 100 million years were allowed, that would only be 1/50 of the Sacred Parameter.  To hold onto A, they have to invoke ad hoc theories of a comet wandering into the Roche Limit of Saturn and disrupting.  Even so, the forces of plasma drag, sputtering, micrometeorite bombardment, light pressure and collisions would dissipate the rings in short order.  Will embedded moons be found to feed new material into the rings?  Stay tuned.
    Also, we will provide balance to the claims about Titan having “prebiotic chemistry” that might be like the “building blocks of life” or like the “early earth in deep freeze.”  One scientist was even heard suggesting that Titan’s atmosphere may be a natural laboratory for the Miller Experiment (see 05/02/2003 headline).  Such statements assume evolution in spite of the evidence.  Also, it will be interesting to see if long-age believers can rescue Titan’s atmosphere from the evidence it is depleting rapidly (see 10/16/2003 headline).
    Cassini is poised to make major contributions to our understanding of the solar system and its age.  For now, enjoy the ride; it will be high adventure tonight at Saturn!

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Categories: Physics, Solar System

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