Post-graduate geology student Leo Alvarado also witnessed the accident and telephoned the local Northern Catholic University. He spoke with Dr. Luis Barrera, director of the University's Astronomy Institute. It wasn't the only call Dr. Barrera got about the mysterious desert light. A group of geologists also reported an object burning-up in the sky, in the same location and at the same time. Dr. Barrera thought he knew what they had seen. He had been following the press and Internet accounts of the failed Russian Mars '96 space mission, including the revised U.S. Space Command estimate that the crippled probe may have come down over Chile or Bolivia, not the Pacific Ocean or Australia as first reported. Initial American press accounts said that the 200 grams of toxic plutonium, which the craft had been carrying as an on-board power source, would remain intact on reentry. But Dr. Barrera believes the eyewitness accounts of the object burning brilliantly and traveling in the shallowest of descents for several minutes, meant that the Alvarados and the geologists had probably witnessed the probe and its plutonium cargo vaporizing in the earth's atmosphere.
Aerosol plutonium particles drifting back to earth is bad news for the folks in Northern Chile. "That could be very serious for health," said Dr. John Gofman, a University of Berkeley physicist who worked on the Manhattan Project in the 1940's. "If it burned up and formed fine plutonium oxide particles, those particles are on their way down," he said. He notes that most of the fission products from the atomic bomb testing of the 1940's and 1950's fell to earth within a few years. "I would think people would be concerned with staying there," Gofman warned. "There would be an increased hazard of lung cancer."
The Mars '96 crash is also bad news for NASA. The world's attention is now firmly fixed on a planned launch in October of 1997, of a Titan IVA rocket carrying a probe to photograph Saturn and its moons. That Cassini mission will have 72.3 pounds of plutonium 238 on board, the largest volume of radioactive material ever placed into space. Like the Russian craft, the plutonium cargo is intended to provide onboard electrical power for the mission. There is mounting concern that a similar launch failure risks a global environmental disaster, and that using plutonium for Cassini is unnecessary given recent advances in solar power alternatives.
"If you liked Mars '96, you'll love Cassini," says John Pike, head of space policy at the Federation of American Scientists. He notes that in 1993 a similar Titan IVa rocket blew up a minute and a half out of California's Vandenburg Air Force Base, sending a billion dollar classified military satellite plunging into the Pacific Ocean. A similar failure following Cassini's blast off from the Kennedy Space Center in Florida, risks depositing, "a great steaming heap of plutonium, onto Disney world, right on top of Epcot Center," says Pike. He estimates the odds for failure of a Titan IV rocket are "between one in ten and one and twenty."
Even if Cassini safely escapes Earth's atmosphere, the risk of environmental disaster is not over. Because its Titan rocket will lack the power to send the probe to Saturn directly, NASA plans to have Cassini use the Earth's gravity in a special fly-by maneuver to "sling-shot" the craft into deep space. So in 1999, Cassini will approach Earth at some 42,300 miles per hour and pass within 312 miles of the planet's surface. The only previously controlled "gravity-assisted" fly-bys of Earth were conducted successfully by NASA's Galileo mission to Jupiter, in 1990 and 1992. That unmanned probe was carrying a similar, smaller plutonium cargo. But if NASA scientists misfire Cassini's steering rockets as it races towards Earth, the probe could reenter the planet's atmosphere, with potentially disastrous consequences. John Pike of the Federation of American Scientists says, "if you have a worst conceivable event, in which the plutonium burns up and is dispersed as a fine aerosol, then it is astonishingly hazardous, just grotesquely hazardous."
Despite the Russian Mars ‘96 accident, NASA remains determined to launch Cassini. A December 6th meeting of the project's principal partners at the Jet Propulsion Laboratory in California, including the safety and launch teams, confirmed that decision. "Why would we want to cancel it after the Mars ‘96 accident" said NASA spokesperson Mary Beth Murrill. She insisted that a similar accident was impossible. "You're assuming that in reentry these things break up. That's not what happens. They are designed to survive reentry."
But a catastrophe is possible. For 25 years, Dr. Horst Poehler worked as a senior engineer at the Kennedy Space Center for NASA contractors. After studying some 30 technical reports on the Cassini mission, he has concluded that it could produce, "the mother of all accidents." The iridium protective layer around the Radioisotope Thermal Generator (RTG) plutonium packs, he says, is only, "the thickness of your fingernail," and could burn through on reentry, or break up on impact with a hard surface. "I support NASA when they do right things," he said, but with Cassini, "they convict themselves with their own reports."
Even NASA's own Environmental Impact Statement (EIS) for the Cassini mission states that if "an inadvertent reentry occurred, "approximately five billion of the seven to eight billion people on Earth in 1999, could receive 99 percent or more of the radiation exposure." NASA concludes that the "health effects" from a reentry burn-up would be 2,300 deaths over a 50-year period and that these "latent cancer fatalities" would likely be "statistically indistinguishable from the normally occurring cancer fatalities among the world's population."
That estimate may be tragically wrong. NASA does not adequately address the fatal effects of low level radiation, says Dr. Ernest Sternglass, a professor emeritus of radiological physics at the University of Pittsburgh's School of Medicine. He has studied the low-level radiation health consequences produced by the atomic bomb tests of the 1940's and 1950's, and the nuclear power plant accidents at Three Mile Island and Chernobyl. The problem with NASA's Cassini risk estimate, says Sternglass, is that it is based on data derived from the Hiroshima and Nagasaki bombing, where low-level radiation was much less-well understood. Dramatic new scientific evidence suggests that low-level radiation is much more dangerous than once imagined. If Cassini's plutonium is widely dispersed in the atmosphere, catastrophic health consequences would follow, says Sternglass, because of the "logarithmic dose response" of human cells to low-level radiation. That means, he says, "that the curve rises very rapidly for tiny doses and flattens out at higher doses. Because of this, the small amounts of radiation from any kind of nuclear accident are hundreds of thousands of times more damaging than we suspected on the basis of the Hiroshima and Nagasaki data, which was obtained at very high doses." Soaring infant leukemia in Greece after Chernobyl, as reported in Nature earlier this year, and the 1996 Lancet account of increased congenital hypothyroidism in newborns in the United States following the Ukrainian reactor meltdown, confirm the danger of low-level radiation, says Sternglass. NASA may have underestimated the Cassini cancer risk alone by a factor of about 2,000 to 4,000 times, he says, adding, "we are dealing with the possibility of many millions of extra deaths over the next ten or twenty years following such an accident."
At least two earlier space accidents have also strewn radiation into the environment. In 1978, a Russian Cosmos satellite disintegrated over Northwestern Canada, leaving a 124,000-square kilometer swath of nuclear debris. And in 1964, an American SNAP-9a nuclear satellite burnt up on reentry, leaving radioactive debris, "present at all continents and all latitudes," according to a 1989 European OECD report.
Cassini may have already left a deadly trail. An Associated Press account this past July reported how nuclear contamination of workers and equipment at Los Alamos National Nuclear Laboratory in New Mexico had dramatically increased between 1993 and 1996. Laboratory officials blamed the increase on fabricating the Cassini RTG plutonium packs. With a half-life of only 88 years, the plutonium 238 used in the Cassini mission is roughly 300 times more toxic than plutonium 239 used in bomb making. The Laboratory reported that the number of incidents of contamination at its plutonium facility jumped 75 percent between 1993 and 1995, from 139 to 244. A second internal report found that the total amount of radiation the entire laboratory work force was exposed to in 1995, was the highest since 1980. Much of the increase was found on worker's clothing, according to Laboratory data.
NASA's game of nuclear Russian roulette with Cassini may be unnecessary. In April 1994, the European Space Agency (ESA) reported dramatic new advances in solar cells for "use in future demanding deep-space missions." ESA was studying solar power because the American nuclear RTG technology used on the NASA space flights was unavailable in Europe. The new silicon cells jointly developed by DASA in Germany and CISE in Italy, had a record 25% efficiency in the extreme cold and reduced sunlight of simulated deep-space conditions, ESA said. Last year, ESA physicist Carla Signorini told the newspaper Florida Today that, "if given the money to do the work, within five years ESA could have solar cells ready to power a space mission to Saturn."
But redesigning Cassini is unlikely. The mission is already over budget and overdue. Originally, Cassini was to have been launched on the Space Shuttle, but safety considerations in the wake of the Challenger accident instead placed the mission on a conventional rocket. (NASA's nuclear-powered Ulysses probe to the sun was to have been the next flight on the Challenger, before it exploded). Further delay of the $4 billion Cassini program for a multi-year, solar-power design might risk the entire venture. Explains John Pike, "maybe if I lived in Epcot Center I would have one view of it, but if I was a Cassini program manager and I had all these people working for me and they had kids, mortgage payments..."
The shadow of the Pentagon also darkens the Cassini mission. Three recent studies by the United States Air Force detail a continued enthusiasm for the military nuclearization of space. They make clear, says John Pike, that "there are a lot of space weapons that you need nuclear power for." The Air Force is currently ground-testing Russian-built Topaz II reactors at its Philips Laboratory in New Mexico. A flight test of Topaz II scheduled for December 1995 was canceled after protests from U.S. astronomers. Civilian use of nuclear power has a clear military agenda, says Pike. "The space nuke guys were obviously interested in getting the public desensitized to this stuff -- everybody's feeling that Galileo was okay, so if you like Galileo it is okay for us to fly Topaz II, or whatever..."
The momentum to nuclearize space continues. In 1991, NASA and the Department of Energy signed the Space Nuclear Power Agreement, restricting death or damage benefits from a U.S. space nuclear accident. That Agreement caps U.S. payouts at $7.3 billion, and assigns a mere $100 million for all damage to other countries and their populations. In 1993, the Clinton White House announced that "space nuclear power and propulsion systems can contribute to scientific, commercial and national security space missions." This January, a symposium at the University of New Mexico sponsored by the Defense Special Weapons Agency, NASA, the Department of Energy and the Air Force will include numerous ideas for space nuclearization, including a presentation from the Brookhaven National Laboratory on the "Disposal of Long Lived Fission Products Into Outer Space."
But there is growing unease even in the American scientific community over Cassini. Dr. John Gofman, formerly of the Manhattan Project, says the atomic bomb was a necessary evil of the Cold War, but he now opposes space nuclearization. Of Cassini, he says, "I pray that it has a good mission, but one of these things is not going to do too well one of these days. Doesn't the Russian failure tell you something about the nice assurances that we are never going to have one of these things come down?"
rhoffman@animatedsoftware.com