" In October 1997, NASA plans to launch the Cassini probe to Saturn. Carrying 72.3 pounds of plutonium-238 fuelthe largest amount of plutonium ever used in space, the probe will sit atop a Lockheed Martin-built Titan IV rocket. This same kind of rocket has undergone a series of mishaps including a 1993 explosion in California soon after takeoff which destroyed a $1 billion spy satellite system and sent its fragments falling into the Pacific Ocean.
Plutonium has long been described by scientists as the most toxic substance known. It is "so toxic," says Dr. Helen Caldicott, founder of Physicians for Social Responsibility, "that less than one millionth of a gram is a carcinogenic dose. One pound, if uniformly distributed, could hypothetically induce lung cancer in every person on Earth." In addition to the specter of radioactivity spread by an accident on launch, another, potentially more lethal, scenario is causing concern. Because Cassini does not have the propulsion power to get directly from Earth to Saturn, NASA plans a "slingshot maneuver" in which the probe will circle Venus twice and hurtle back at Earth. It will then buzz the Earth in August 1999 at 42,300 miles per hour just 312 miles above the surface. After whipping around Earth and using its gravity, Cassini would then have the velocity, says NASA, to reach Saturn. But during that Earth fly-by, if Cassini comes in too close, it could burn up in the 75 mile-high atmosphere and disperse plutonium across the planet.
Dr. Michio Kaku, professor of nuclear pLysics at the City University
of New York, explains the catastrophic consequence of such a fly-by accident:
If there is a small misfire [of Cassini's] rocket system, it will mean
that [it] will penetrate into the Earth's atmosphere and the sheer friction
will begin to wipe out the heat shield and it will, like a meteor, flame
into the Earth's atmosphere ... This thing, coming into the Earth's atmosphere,
will vaporize, release the payload and then particles of plutoninm dioxide
will begin to rain down on populated areas, if that is where the system
is going to be hitting. [Pulverized plutonium dust] will rain down on people's
hair, people's clothing, get into people's bodies. And because it is not
water soluble, there is a very good chance that it could be inhaled and
stay within the body causing cancer over a number of decades. Indeed, NASA
says in its First Environmental Impact Statement for the Cassini Mission,
that if an "inadvertent reentry occurred" during the fly-by, approximately
five billion of the seven to eight billion people on Earth, "could receive
99 percent or more of the radiation exposure."