NASA is again threatening the lives of people on Earth.

On January 11, the window opens for a launch from Cape Canaveral of a rocket lofting a space probe with 24 pounds of plutonium fuel on board. Plutonium is considered the most deadly radioactive substance.

Once it separates from the rocket, the probe, on what NASA calls its New Horizons mission, would move through space powered by conventional chemical fuel.

The plutonium is in a Radioisotope Thermoelectric Generator (RTG) that is to provide on-board electricity for the probe's instruments-a mere 180 watts when it gets to its destination of Pluto.

Until after the probe leaves the rocket and breaks from the Earth's gravitational pull, the plutonium endangers life on Earth.

Because a fatal dose of plutonium is just a millionth of a gram, anyone breathing just the tiniest particle of plutonium dispersed in an accident could die.

NASA has divided the sequence into four phases before what it calls "escape" of the probe from the Earth's gravity. It is most concerned about the launch phase.

NASA's Final Environmental Impact Statement for the New Horizons Mission (EIS) says there is "about 6 percent probability" of an accident during launch.

If plutonium is released in a launch accident-and NASA says there is a 1-in-620 chance of that-it could spread far and wide. Some could drift up to 62 miles from the launch site at Cape Canaveral Air Force Station, says the EIS. And "a portion" of the plutonium could go well beyond that, says NASA, and "two-thirds of the estimated radiological consequences would occur within the global population."

That's because "fine particles less than a micron in diameter" of the plutonium "could be transported beyond 62 miles and become well mixed in the troposphere, and have been assumed to potentially affect persons living within a latitude band from approximately 20-degrees North to 30-degrees North," says NASA.

The troposphere is the atmosphere five to nine miles overhead. The 20- to 30-degree band goes through parts of the Caribbean, across North Africa and the Mideast and then India and China and Hawaii and other Pacific Islands and then Mexico and southern Texas.

But life elsewhere on Earth could be impacted if the plutonium-fueled probe falls back to Earth before its "escape" and flight on to Pluto.

NASA says the "probability of an accident" releasing plutonium "for the overall mission is estimated to be approximately 1 in 300."

An "enormous disaster" could result with the spread of the plutonium, says Dr. Ernest Sternglass, professor emeritus of radiological physics at the University of Pittsburgh School of Medicine. The issue is how much plutonium is released in respirable particles, he explains.

"The problem is it takes so little plutonium," says Dr. Sternglass.

The NASA EIS acknowledges that in the event of plutonium release "costs may include: temporary or longer term relocation of residents; temporary or longer term loss of employment; destruction or quarantine of agricultural products.land use restrictions which could affect real estate values, tourism and recreational activities; restrictions or bans on commercial fishing; and public health effects and medical care."

The EIS says the cost to decontaminate land on which the plutonium falls would range from "about $241 million to $1.3 billion per square mile."

But, it notes, compensation would be subject to the Price-Anderson Act, a U.S. law first enacted in 1957. It sets a cap on how much people can collect for property damage, illnesses and death resulting from a "nuclear incident." Under the Energy Bill passed this year, the cap in the United States was increased to $10 billion.

But the cap for damage from a "nuclear incident occurring outside the United States shall not exceed $100 million," the law stipulates. This is the limit in the original Price-Anderson Act. It has never been raised.

And it is in violation of the Outer Space Treaty of 1967, the basic international law on space-which the U.S. has signed and was central in drafting-which declares that "states shall be liable for damage caused by their space objects."

Demanding that the New Horizons mission be cancelled is the Global Network Against Weapons & Nuclear Power in Space (www.space4peace.org). Bruce Gagnon, its coordinator, says "one thing we know is that space technology can and does fail and when you mix deadly plutonium into the equation, you are asking for catastrophe."

NASA, he charges, is "playing nuclear Russian roulette with the public."

Indeed, NASA is planning a series of additional launches of plutonium-fueled space probes and other shots involving nuclear material. And under its $3 billion Project Prometheus program, the agency is working on nuclear reactors to be carried up by rockets for placement on the moon and the building and launching of actual atomic-propelled rockets.

Disaster may or may not strike on the New Horizons mission but if these nuclear missions are allowed to proceeded, some will inevitably result in accidents dispersing radioactive material.

Indeed, accidents have already happened in the U.S. space nuclear program. Of the 25 U.S. space missions using plutonium fuel, three have undergone accidents, admits the NASA EIS on New Horizons. That's a 1-in-8 record. The worst occurred in 1964 and involved, notes the EIS, the SNAP-9A RTG with 2.1 pounds of plutonium fuel. It was to provide electricity to a satellite that failed to achieve orbit and dropped to Earth. The RTG disintegrated in the fall, spreading plutonium widely. Release of that plutonium caused an increase in global lung cancer rates, says Dr. John Gofman, professor emeritus of medical physics at the University of California at Berkeley.

After the SNAP-9A accident, NASA pioneered the development of solar energy in space. Now all satellites-and the International Space Station-are solar-powered.

But NASA keeps insisting on plutonium power for space probes-even as the Rosetta space probe, launched this year by NASA's counterpart, the European Space Agency, with solar power providing all on-board electricity, now heads for a rendezvous with a comet near Jupiter.

Along with the U.S. military, which for decades has been planning for the deployment of nuclear-energized weapons in space, NASA seeks wider uses of atomic power above our heads.

In its New Horizons EIS, NASA maintains the risks to people from the mission are not so bad in view of a chart it presents titled "Calculated Individual Risk and Probability of Fatality by Various Causes in the United States." The chart lists the probability of getting killed by lightning or in a flood or by a tornado as higher than someone dying of cancer because of plutonium dispersed in New Horizons.

Of course, we can't control lightning or floods or tornadoes. These are involuntary assaults. NASA's space nuclear gamble using tax dollars (the cost of New Horizons: $650 million) is being carried out by choice.

An additional wrinkle: the Boeing machinists who were to install the New Horizons probe on the Atlas rocket that is to carry it up are on strike-and warning that the company's bringing in of replacement workers poses a safety risk. Because of the strike, other NASA missions at Cape Canaveral have been grounded. But NASA is continuing with the New Horizons launch. "If it's not safe to work on all the other projects with replacement workers, it's irresponsible to continue with New Horizons," says Robert Wood, a spokesperson for the International Association of Machinists and Aerospace Workers.

Gagnon says his organization is "building opposition to New Horizons and all missions that launch nuclear power in space. The public needs to know more about this issue and we need the grassroots to pressure Congress and NASA and others responsible. We say that NASA should be developing alternative, non-nuclear power sources for space travel."

Paul Gunter of the Washington, D.C.-based Nuclear Information and Resource Services comments: "The fact that both the planet Pluto and the manmade isotope plutonium are named after the god of hell lends bizarre insight into NASA's fascination with launching this hideous stuff into the heavens at the risk of fouling the very nest of all humankind."

New Horizons and the rest of NASA's deadly-dangerous nuclear space operations must be stopped.

If space is to be explored, let that be done safely. To destroy a portion of life on Earth to explore space makes no sense.

Karl Grossman, professor of journalism at the State University of New York/College at Old Westbury, is the author of The Wrong Stuff: The Space Program's Nuclear Threat To Our Planet (Common Courage Press) and wrote and narrates the TV documentary Nukes In Space: The Nuclearization and Weaponization of the Heavens (EnviroVideo, www.envirovideo.com).