Posted on 06/29/2004 1:05:21 PM PDT by demlosers
Instead of being concerned with the pestilence in the Parisian streets in his day, JeanDominique Cassini (16251712) continued studying the heavens. He discovered comets and planetary moons.
Saturn's rings were first viewed by Galileo Galilei in 1610, but he saw them from the edge and misidentified them as two moons. Forty-five years later, Dutch astronomer Christiaan Huygens, using a telescope superior to Galileo's, determined the two moons to be a ring around Saturn.
Another 20 years passed, and in 1675, Cassini discovered that Saturn's ring actually was divided into two rings. The large gap between them is still referred to the Cassini division. (Space probes have since determined Saturn has at least 1,000 rings.)
Sixty-five years lapsed between the time Galileo saw what he thought were two moons around Saturn and the time Cassini discovered there were really two concentric rings around the solar system's second-largest planet.
Given that time frame, the years that have elapsed since NASA launched the Cassini mission in October 1997 don't seem so long.
On Wednesday, scientists at the Jet Propulsion Laboratory in California will signal Cassini's thrusters to begin a 96-minute burn, slowing it enough to be captured by Saturn's gravitational pull. It will then embark on a four-year orbit of the planet to study Saturn's rings, its nearly two dozen moons, and its magnetic and radiation fields.
On Christmas Day, Cassini will launch the European Space Agency's Huygens probe, which will coast for 21 days before reaching the nitrogen-rich atmosphere of Titan, Saturn's largest moon -larger than the planets Mercury and Pluto. The Huygens probe will then parachute to the surface, collecting data and photos on the way down.
Shroud-wrapped Titan is of high interest to scientists. Other than the Earth, it is the only body in the solar system believed to have oceans and rainfall. The oceans are thought to be ethane and methane, which can still exist as liquids and gases in Titan's minus200-degree Fahrenheit climate and atmospheric pressure.
Even as bleak as the conditions may sound, "the potential for visual delight is enormous," according Carolyn Porco, an astronomer who heads the Cassini imaging team at the Space Science Institute in Boulder, Colo. "Hats off to the Mars rover team, but we're going to blow them out of the water in terms of interesting images." The Mars rovers have drawn attention away from the almost-forgotten Cassini-Huygens probe, but that may soon change.
Cassini was at center stage when it was launched nearly seven years ago. It carried 72 pounds of plutonium to power its radioisotope thermoelectric generators.
Although it wasn't the first time plutonium was launched in space, Cassini created a double fear: After launch, Cassini orbited the sun, then made a fly-by within 800 miles of the Earth in mid-1999. The Earth's gravitational pull provided the extra speed needed to reach Saturn. Both launch and flyby passed without incident.
For those agonizing over the use of plutonium in space, the late Carl Sagan, advisor to NASA as early as the 1950s, had an answer. The Galileo probe was also fueled with plutonium when it was launched aboard the Space Shuttle Atlantis in 1989. It would later be launched from Atlantis on a 14year mission to Jupiter. It, too, would swing by Earth to gain speed for its long trip.
"There are issues," Sagan wrote of the pending Galileo launch, "including nuclear winter . . . greenhouse warming, depletion of the ozone layer, AIDS, social and economic injustice, and the world population crisis, where the combination of probability and consequence are enormously more dangerous than for Galileo's plutonium. I would like to urge everyone concerned about the Galileo [nuclear-powered batteries] . . . to devote a proportionate amount of passion, wisdom and hard work to those activities (and inactivities) that really jeopardize the human family."
Fourteen years later, as Galileo disintegrated into Jupiter's atmosphere last September, Dr. Claudia Alexander summarized the mission: "We learned mind-boggling things. This mission was worth its weight in gold."
Cassini should begin sending back more of its nuggets soon.
There were RTGs on the Apollo missions as well. RTGs do not pose a danger. I am looking forward to this mission. :-)
It's already returning some really spectacular pics.
I was one of the people "Freeping" the anti-Cassini folks in front of the White House back before it launched. It's very gratifying to see it so close to orbit insertion.
Whoooooohoooooo! Good for you. :-)
I thank you for helping to save the mission. :-))))
bttt
"There are issues," Sagan wrote of the pending Galileo launch, "including nuclear winter . . . greenhouse warming, depletion of the ozone layer, AIDS, social and economic injustice, and the world population crisis, where the combination of probability and consequence are enormously more dangerous than for Galileo's plutonium. I would like to urge everyone concerned about the Galileo [nuclear-powered batteries] . . . to devote a proportionate amount of passion, wisdom and hard work to those activities (and inactivities) that really jeopardize the human family."
LOL! Sagan was such a goofball hippy!
Go Cassini! Can’t wait for more pictures.
I can't help but still like Sagan, lefty slant notwithstanding. He had a singular talent for expressing hard science in a soft, but still acccurate way. His political and cultural blindspots were legion, more's the pity.
Bump!
I remember the handwringing about the potential danger from the Galileo probe's plutonium if it were to hit the earth during the swing-by. We escaped that danger but instead must bear the guilt of polluting Jupiter's atmosphere with plutonium. Oh, the humanity!
You might find this amusing now, but when the Jovian death saucers appear in our skies, your mirth will soon come to an end.
Are you involved in any of the Cassini activities in Boulder?
Ah, shucks, I thought it read NASCAR runs rings around Saturns.
Definitely deserves a Bump for US engineering and science.
Sagan was excellent until he rotted his mind with pot.
So I reckon it will be something more visually interesting than static, chaos, randomness, and the like. Something for the eye to perceive. Something containing/communicating information to assess. But no intelligence or design or combination of the two. No way. Accidents do happen after all, and really big ones.
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