compiled by Dee Finney

This is not a new topic.  Proposals of what may happen at the end of Space Probe Galileo have been suggested for several years.

We've mentioned ourselves a few times as well over the years.

On our Sylvester the Cat page, we wrote:  Aug. 27, 2003. Mars is the closest to earth that its been in centuries, and at its brightest, it could mean a major war somewheres in the world. Mars comes to its closest point to earth at the same time it is at opposition, adding up to the brightest it has been since 1988. Note that around this time the world population reaches 6.3 billion, and in Revelation 6:3 the second horseman War starts to ride. So major wars in the world may begin then, possibly an India-Pakistan war or more trouble with Muslim wackos. Note that Uranus (Uranium?) is at opposition, its brightest, on Aug. 24. Nuclear weapons set off? Nuclear war? Note that in Sept. 2003, the Galileo spacecraft crashes into Jupiter; this could relate holographically to events on earth connected with the rise of the Antichrist.

We have also written about TWO SUNS - and wonder - how could Earth have two suns?

The topic hit the news back in the year 2000 as well:

Galileo mission may end in a blaze of glory

February 21, 2000

Web posted at: 3:26 PM EST (2026 GMT)

PASADENA, California (AP) -- NASA is considering a spectacular finish for Galileo's mission to Jupiter: A suicide plunge into the gaseous planet or one of its moons.

The probe was not designed to withstand such conditions for long, but it could send back a few minutes of valuable data before frying from radiation, melting under the pressure of Jupiter's atmosphere or crashing onto a moon, scientists say.

The alternative is to let the aging spacecraft run out of propellant or wait for a critical navigation component to fail, and either would turn it into a worthless piece of Jovian space junk.


Aging Galileo probe faces another dangerous encounter

Galileo must first survive Tuesday's close encounter with Io and the intense radiation in the vicinity of Jupiter's nearest moon. Two more encounters are being planned for the moon Ganymede through the end of the year.

The spacecraft could be given its final marching orders sometime next year, although details are still being worked out, said Duane Bindschadler, Galileo's manager for science planning and operations.

Plunging into Jupiter could shed new light on the planet's magnetic fields, Bindschadler said, although the amount of information received would be limited because Galileo sends back data at a slow rate.

"We would go into an environment where the radiation would be steadily and very quickly increasing, up to a certain point," he said. "If we survived past that point, we could probably send data as we were getting closer and closer (to the cloudtops)."

A probe that flew with Galileo took the plunge in 1995, sending data on the composition of the atmosphere before melting under the extreme pressure.

Galileo also could be sent into one of Jupiter's moons. Volcanic Io has been discussed.

Galileo won't be flying into Europa, where last month its instruments discovered the best evidence yet of a liquid ocean beyond Earth.

The reason? Galileo could still be carrying microbes, 11 years after its launch from the space shuttle Atlantis.

"We don't want to get anywhere near Europa, simply because of the possibility of life there," Bindschadler said.

"They don't want to crash this contaminated spacecraft into Europa," said Andrew Ingersoll of the California Institute of Technology.

A mission-ending plunge isn't unprecedented. Last year, NASA's Lunar Prospector dove into the moon in search of water. Telescopes in space and on Earth watched for the impact but saw nothing.

Regardless of how Galileo's mission ends, scientists say they will miss the spacecraft.

"It's not going to go on forever," Ingersoll said. "Everything has to end. It's going to be a sad day, though."

Copyright 2000 The Associated Press. All rights reserved.

Galileo has been flying around Jupiter since 1995

Galileo Reaches Jupiter

After a six-year, 2.3-billion-mile journey, the Galileo spacecraft reached Jupiter December 7, with the main spacecraft entering orbit around the solar system's largest planet as the probe plunged into Jupiter's atmosphere.

The Galileo Probe entered Jupiter's atmosphere at 5:04 pm EST December 7, transmitting data to the orbiter spacecraft as it descended into Jupiter's atmosphere. At 8:20pm EST the Orbiter's main thruster fired for 49 minutes, placing the $1.3 billion spacecraft into orbit around Jupiter.

On Sunday, mission controllers began playing back the Probe data. Officials estimate that the Probe returned data for at least 57 minutes before losing contact with the Orbiter. Using models of the spacecraft and the Jovian atmosphere, this time corresponds to a depth of 160 km (100 mi) below the visible cloud tops.

Data return continued until Thursday, December 14, when interference by the Sun made communication too difficult. Officials hoped to return up to 40 minutes of probe data by Thursday. The rest will be returned starting in late January, after the spacecraft passes behind the Sun and communications can be restored.

The next major event for the Galileo Orbiter is in late June, when the spacecraft makes its first close approach to Ganymede, the largest moon in the solar system. Galileo will flyby two other large Jovian moons, Callisto and Europa, during the next two years, as well as study the planet and its magnetic environment.

NASA officials were very pleased with Galileo's performance last week. "Is this a great day or what?" NASA administrator Dan Goldin said at a press conference December 7. "We are all absolutely ecstatic that our tremendously ambitious, first-ever penetration of an outer planet atmosphere has been so wonderfully successful," Bill O'Neil, Galileo project manager, said a few days later.

Interest in the mission from Internet users was very high. According to JPL's Ron Baalke, the Galileo home page at JPL,, was accessed 2.1 million times between December 1 and 11, with the peak on December 9. Even with an alternate site, reaching the home page became difficult during peak times during and after Galileo's arrival.

A press conference with the first science results from the Galileo Probe data has been scheduled for Tuesday, December 19.

As many of you may know, Sept. 21 the Galileo spacecraft's mission will be terminated when it crashes into Jupiter to prevent running out of fuel and crashing in to Europa, possibly contaminating any possible lifeforms in its ocean.

Since it arrived at Jupiter in Dec. 1995, it has overcome huge obstacles, including its main antenna not opening. But they have been able to use the secondary antenna, and while much slower transmit times, much useful data was collected. Also, it has withstood many times the radiation that it was built to take.

This is the main site for the Galileo mission, with information to keep you busy for a while

NASA to crash Galileo spacecraft

From a correspondent in California

September 15, 2003

NASA plans to crash its $US1.5 billion ($2.3 billion) Galileo spacecraft into Jupiter next weekend to make sure it doesn't accidentally contaminate the red planet's ice-covered moon Europa with bacteria from earth.

After Galileo's orbit carries it behind Jupiter at 12.49pm PDT (7.49am AEST on Monday), the aging probe will plunge into the planet's stormy atmosphere at a speed of nearly 174,000kph.

The heat generated as it streaks through the atmosphere will vaporise the nearly 1350-kg Galileo and any microbes that may have been stowaways on the spacecraft since its 1989 launch.

The crash will ensure Galileo doesn't hit Europa and spill bacteria onto the ice that caps its enormous oceans.

Europa, a planet-sized moon, is widely believed to have the most promising habitat for extraterrestrial life within the solar system. Were earth bugs to gain a toehold on Europa, perhaps in pools of water warmed by radioactive plutonium the spacecraft uses to generate electricity, they could compromise future attempts to probe the moon for indigenous life.

"It seems like a good place where, potentially, you can have life and it also seems like a place where earth life would find it a nice place to live. So why hit it?" said John Rummel, planetary protection officer for the National Aeronautics and Space Administration.

NASA typically scrubs its spacecraft clean of microbes to prevent what it calls the "forward contamination" of other places in the solar system. That wasn't done with Galileo, which NASA originally intended to leave in orbit around Jupiter.

The crash will be the first since 1999, when NASA ploughed the Lunar Prospector orbiter into the moon. In 1994, NASA crashed the Magellan orbiter into Venus.

Satellites routinely crash to earth, as NASA's Compton Gamma Ray Observatory did in 2000.

Recent research has revealed the tenacity of microbial life and its ability to resist extremes of temperature and radiation. Even though Galileo has been buffeted by both, its shielded innards likely harbour viable microbes.

"We in our infinite wisdom thought nothing could survive in those harsh environments, but we are learning every day about things that can," said Claudia Alexander, Galileo's seventh and likely last project manager at NASA's Jet Propulsion Laboratory in Pasadena.

The 14-year mission has been among NASA's most successful, despite a litany of glitches. Its focus was to have been Jupiter itself, but the planet's quirky, diverse moons - including Io, the solar system's most volcanically active body - stole the spotlight.

NASA hopes to wring some scientific measurements from Galileo before its demise. When the end does come, 1500 people associated with the mission are expected to gather at the lab to mark the occasion.

"It will have some of the flavour of a wake," Alexander said.

The Associated Press

Jacco van der Worp says:  Could NASA Use Galileo to Create a Jovian Nagasaki?

YOWUSA.COM, 07-September-2003

The Radioisotope Thermal Generator (RTG)

The reason for crashing Galileo into the planet Jupiter on purpose is this: Galileo since its launch has been powered by Plutonium-238 in a RTG or Radioisotope Thermal Generator. Plutonium-238 decays via alpha and gamma emission, its daughter products are also highly radioactive for a long time. An RTG catches this radiation in a heat exchanging mechanism and there converts it into electricity. Duracell doesn’t make batteries like that. These RTG power units can power a satellite for many years. They powered the Pioneer and Voyager craft too or they would not have lasted three decades as they did.

Now, an independent researcher/writer by the name of J.C. Goliathan gathered some interesting information on the fuel load.

TIPS Report – August, 2003

J.C. Goliathan, July 30, 2003


The author believes the nuclear events reported here to be very unlikely and only remotely possible, but just as an asteroid impact with earth is remotely possible (and widely researched and reported on), the Jupiter impact issue deserves exposure also, because there is compelling evidence to suggest the feasibility of at least a temporary Jupiter ignition. Given the potential consequences of this, serious research is warranted. The author is a Geographer and Engineer, not a physicist. Further research is needed by more qualified individuals.

While Goliathan’s might be a bit technical for those outside of his field of study, as a physisict, I found it to be a brilliant piece of work and so will endevor to explain the critical aspects presented in his article in layman’s terms.

The Concerns Described in Goliathan’s Article

Theoretically the avalanche reaction described for the Pu-238 pellets aboard Galileo can take place setting off an implosion-induced nuclear detonation. Literally no one on Earth knows for certain what will happen when Galileo plunges into Jupiter. It may even trigger an on-going fusion reaction in the abundant hydrogen supply of Jupiter, creating a mini-star. We lack the in-depth knowledge on the atmospheric structure of the planet to accurately predict the outcome, yet we push ahead on the chosen path.

Physicists at NASA will undoubtedly tell you the danger is negligible and try and push this question into the realm of conspiracy-thinking. As a physicist, I’ve been trained in the safe application of radiation and I think we need to pay attention here, as we may be overplaying our hand by ignoring this possibility.

In my work I do risk analysis regularly. In such an analysis I divide potentially hazardous risks into a matrix. This type of matrix sorts risks by chance of occurring (on a 1 to 6 scale for likeliness) on one scale against the severity (on a 1 to 5 scale) on the other. The product of these two is known as the hazard of the event. Anything with a product of chance and severity above 12 requires ‘mitigating action’, but special attention is due also for the highest severity category, regardless of its chance.

This particular risk falls in that category of highest severity, it has to be looked at. Its chance is minute, but no matter how small the risk, its consequences are so severe and all-encompassing that we must not ignore it! I will tell a little more about why they are so great below.

About plutonium bombs

Critical mass

Critical masses can be calculated quite accurately. The important parameters are fission cross sections, the average neutron yield upon fission, and the mass density. The latter depends heavier on the integrity of the metal lattice than on the isotopic composition, since mass differences between the different plutonium isotopes are almost negligible.

Without a neutron reflecting shield, pure Pu-239 metal has a critical mass of 10 kg , and I have calculated that for a "reactor grade" isotopic mixture this would be 18 kg. Using a 15 cm U-238 shield, the Pu-239 critical mass is only slightly over 4 kg, while for LWR -produced plutonium (65% thermal fissile isotopes, fuel burn up around 40 MWd/kg HM) this is some 7 kg.

The critical mass of Plutonium-239 to start a chain reaction without help is about 10 kilograms. With that much Plutonium, the chance of a neutron from the middle hitting an atom on its way out is high enough to keep the reaction going or even speed it up. Plutonium is easy enough to gather, but you can’t control an amount like this at all. That is why in a bomb there is a layer of Uranium around it, this acts like a neutron mirror, it sends neutrons right back in for another pass through the Plutonium, only 2 to 4 kilograms of that is necessary this way. That by itself is still not enough though but keeps the Plutonium from going off by itself.

The 3,440 neutrons per gram per seconds of Pu-238 are the real reason for concern. If you compare them to the 0.03 neutrons that spontaneously come out of one gram of Pu-239 it will become obvious that the critical mass (the mass at which the reaction inside the Plutonium becomes self sustaining) is much smaller for Pu-238 than it is for Pu-239. Neutrons travel in every direction, as a result the difference in SF rate will work in all direction too. This leads to a critical mass of roughly 200 grams for Pu-238 only. This is why NASA used 144 pellets of 1/3 pounds (151 grams) to get the 48 pounds on board of Galileo. These pellets are shielded from one another to prevent them from going out of control. The crucial question is what will happen to these pellets and their shielding when the satellite plunges into the atmosphere of Jupiter. Will the shielding hold? Will the pellets stay together or wander apart? NASA appears to hope they wander apart or quickly burn up completely (what with, as there is almost no oxygen to burn them up?).

If the pellets stay together and are compressed ever stronger by the increasing atmospheric pressure they encounter (they will keep on falling until the outside specific weight or weight per volume matches that on the inside!!) each pellet will by itself go beyond the critical point density and chain-react. The true danger is if several ones or all of them were to go supercritical together. In that case you have 48 pounds of Pu-238 going into chain reaction.

If the chemical explosive is set off exactly simultaneously, a shockwave will travel inward, compressing the Uranium shell and the Plutonium so far inward that the atoms move much closer together. So much closer in fact that the two or three neutrons coming out of every atom splitting up split at least another atom of Plutonium. The reaction becomes self-sustaining. This principle is the principle by which a nuclear power plant works. By ‘catching away’ neutrons the balance point of one-splits-one is kept in-tact. The rest of the free neutrons will crash into water and gives of its energy boiling the water to steam.

If the shockwaves pushes further in still, then more than one other atom will be split by the resulting neutrons of an atom splitting up. An avalanche starts to build. This avalanche creates so much energy that a counter wave starts pushing outward overcoming the inward shockwave in an instant. The result is the notorious mushroom-shaped cloud we all so dread.

Chain Reaction

In the bombing of Nagasaki, the Americans used only 7 kilograms of Plutonium. 1.2 kilograms of that went into fission, which gave the explosion a equivalent force of 22 kilotons of TNT.

Not all of the Plutonium did fission, because after a small part of it had gone into fission, the outward pressure of that energy release caused the rest to become spread out, making it go sub-critical again. If you have a block of Pu-238 sinking into the atmosphere of Jupiter, the atmosphere will compress it ever stronger, the outward pressure will have a lot more trouble overcoming this compression, in the worst case all of the Pu-238 might go into reaction. If we extrapolate the table above linearly, about 18-20 ktons are released per kilogram of Plutonium fully fissioned, then a maxium explosive yield of some 400 ktons could come from 48 pounds or 21.7 kg of Plutonium.

Not all of the Plutonium will go of course, the explosive energy will be much lower, but 100 ktons lies well within possibility. In an explosion of that magnitude, what could be the temperature that is reached?

"The world enters the nuclear era" by Antonino Spoto

Planning, use and consequences of the first atomic bombs.

If in half kilogram of uranium every atom had to split up, the energy produced will be equal to the explosive power of 10.000 tons of TNT. In this hypothetical case, the efficiency of the explosion would be of 100%; in the first tests of the A bomb, this efficiency was never reached. For the detonation of the atomic bombs have been set more or less sophisticated launchings systems. In the simplest system, a bullet of fissile material is shot against a target of the same material, in way that the two masses are united in a supercritical whole. The atomic bomb exploded in Hiroshima on August 6 1945 was a weapon of this type, of the power of around 20 kilotons.

A most complex method, said "implosion", is used in a weapon of spherical conformation. The most external part of the sphere consists of a layer of lenses of common high potential explosive, prepared in way to assemble the explosion toward the center of the bomb (implosion). At the center, there is a core of fissile material that is compressed to the inside by the powerful wave of direct pressure; the density of the metal results increased with consequent production of a supercritical configuration. The bomb of the test of Alamogordo and also that dropped over Nagasaki on August 9 1945, both with a power of 20 kilotons, they were of the implosion type. Independently from the method used for getting a supercritical whole, the chain reaction proceeds for around a millionth of second, freeing enormous quantities of thermal energy. The so rapid liberation of such energy in a small volume increases instantly the temperature to about ten million of degrees. The rapid expansion and vaporization of the material that constitutes the bomb gives origin to an explosion of extreme power.

After only a millionth of a second, the pressure causing the implosion was overcome above Nagasaki. If such an explosion were to take place in the Jovian atmosphere instead of Earth’s, the outside pressure would resist the expansion a lot longer! The chain reaction could continue longer, up to three times as long perhaps, as high as 30-50% fission rate could be achieved instead of 16% and the reaction temperature could shoot up to beyond 100 million degrees.

The threshold temperature for sustained fusion is not as high as that. The exact conditions for fusion depend on a product of pressure, temperature and amount of atom nuclei able and ‘willing’ to fuse together (isotopes of hydrogen with neutrons in them and helium missing a neutron) into other atom nuclei.

The Sun is estimated to have a core temperature of 15 million degrees. It runs on fusion and the pressure inside amounts to millions of bars. Chemically, the Sun and Jupiter are not that different: the Sun also mainly holds hydrogen and helium. The pressure inside Jupiter will then determine if a fusion reaction can start up due to a nuclear explosion. If the product of pressure and temperature and number of fuseable nuclei is reached, a fusion reaction will start.

The moment fusion starts, all bets are off. There is no telling what will happen then, if the fusion will sustain itself or fizzle out again and how long that will take. Is Jupiter heavy enough to keep the reaction going? It is not heavy enough to have spontaneous fusion or we would have a binary star system already, but 200 ktons may provide the trigger it cannot provide itself.

NASA Is Taking an Titanic Risk

Let’s all keep in mind that NASA has lost two shuttle crews because of its own internal political problems. This is not an enviable track record and it would send any commercially viable international air carrier into immediate bankruptcy. However, NASA does not have to justify itself to paying customers and stockholders, and so the void between taxpayers and politically-minded administrators is both huge and dangerous.

That being said, NASA decision to hurl the spent Galileo spacecraft along with its plutonium could be the worst. Sending Galileo into an environment mankind does not know enough about is equal to playing Russian roulette on a planetary scale. This to me is truly unbelievable, it should be unacceptable to everyone in the world!

NASA does not know, nor can it know, how long the satellite will last in the Jovian atmosphere, how high the pressure on the Plutonium will rise and whether the Plutonium will be crushed together to form one mass or stay apart in pellets. Still they are taking the risk of plunging Galileo into Jupiter. There cannot be a scientific base for it other than guesswork.

So, what if nothing happens. After all the statistics favor NASA’s decision – for now.

There is only one bullet in the pistol cylinder but if you pull the trigger often enough, you’ll die, for sure. NASA has pulled the trigger a few times already , so far nothing happened. The Plutonium bullet however may now be up in the chamber. If this goes wrong, even though the chance of it is remote at best, it will affect all of us, not just NASA.

The Possible Result of a Jupiter Ignition

If Jupiter ignites, it may throw out a portion of its atmosphere in a shockwave as most starting stars do. This starting star however will then be too close for comfort. A portion of that shockwave will then hit Earth too, its results will be beyond imagination. Millions of tons of hot hydrogen will impact the atmosphere hitting it with 1000 km per second. It will result in an ELE category event at best due to intense global aurora and a bombardment of X-rays everywhere that may last for days to weeks. The survivors will be sterile or die from all kinds of radiation-induced diseases.

See: for more details



Despite scientific warnings of a possible disaster, NASA is pursuing plans to launch the Project Galileo shuttle space probe which will carry enough plutonium to kill every person on earth. Theoretically, one pound of polutonium, uniformly distributed, has the potential to give everyone on the planet a fatal case of lung cancer. Galileo will have 49.25 pounds of plutonium on board, most of it plutonium 238, a radioisotope 300 times more radioactive than the one used as fuel for atomic bombs. Critics of the plan, such as Dr. John Gofman, professor of medical physics at the University of California, Berkeley, and Michio Kaku, professor of nuclear physics at the City University of New York claim that putting Galileo's plutonium payload into space is both risky and unnecessary.



DISCLAIMER:  I am not a doctor, so my personal opinions are not on this page. All you will see are links to other pages where the people are experts on this topic.
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The plutonium will be used to fuel "radioisotope thermoelectric generators" which keep instrumentation warm. Although NASA and the DOE say there are no alternatives, professor Kaku asserts that the latest advances in solar cells make it possible to generate solar electricity even as far away as Jupiter, Galileo's destination. NASA downplays the possibility of the release of plutonim in an accident, stressing that the substance will be encapsulated in "clads" made from iridium alloy in a graphite shell. The DOE contends that clads can withstand explosive pressures up to 2,200 pounds per square inch. However, a DOE safety analysis report on the Galileo mission obtained under FOIA states that from the viewpoint of potential nuclear fuel release, the most critical accidents would occur on the launch pad. Launch pad accident scenarios, such as "tipovers" and "pushovers" are estimated to generate explosive pressures as high as 19,600 psi.

Once in space, Galileo is still potentially danglerous. Since the solid-fuel rocket substituted for the highly volatile liquid-fuel Centaur rocket used in the Challenger does not have the power of the Centaur, NASA devised a plan to use the earth's gravitational pull to increase the rocket's momentum sufficiently to reach Jupiter. During the "flyby" orbits around the earth, Galileo would at times be only 277 miles overhead. A 1987 NASA report estimates the chance of Galileo inadvertently reentering the earth's atmosphere to be less than one in a million, and, as such, an accident scenario is deemed not credible.

NASA set the probability figures for the chance of a shuttle accident at one in 100,000 for thhe Challenger. Investigation following the crash put the figure at closer to one in 25. While "The Lethal Shuttle: Plutonium Payload Scheduled" was one of the top 10 overlooked stories cited by Project Censored in 1986, the continued failure of the media to draw attention to the potential risk of Project Galileo fully warrants its renomination for 1987.

SOURCES: THE NATION, 1/23/88, "The Space Probe's Lethal Cargo," by Karl Grossman;, pp 1, 78; L.A. TIMES, 2/6/86.




by  Carl Sagan

[An edited version of this article, amounting to cuts of about 20 percent of the text, was published as "Benefit outweighs risk: Launch Galileo craft," in USAToday, Inquiry Page, Tuesday, October 10, 1989.]


Late this August the Voyager 2 spacecraft flew within 3000 miles of the south pole of the planet Neptune, triumphantly concluding its exploration of all four giant planets with phenomenal interplanetary marksmanship. Our knowledge of the solar system has been decisively rewritten. Our species has visited what is now the outermost known planet. Voyager's place in human history is secure.

Now that we have completed the preliminary reconnaissance of the solar system, it makes sense to explore selected worlds in greater depth. The next step is Galileo -- to be launched aboard the shuttle, nominally in October or November. It's to be the first space vehicle to go into orbit around Jupiter, the largest planet in the solar system. If all goes well, it will explore, in much greater detail than Voyager, multicolored Jupiter, its four large moons -- one with active volcanoes, another with a possible underground ocean -- and its vast magnetic field; Galileo will also drop a scientific probe directly into the atmosphere of Jupiter and radio back what it finds. It is a trailblazing mission.

However, Galileo, launched from the comparatively enfeebled present space shuttle configuration, can't simply make a beeline for Jupiter. Instead, it must execute a set of caroms through the inner solar system -- first to Venus for a gravitational assist that then flings it back to the Earth, which swings it around the Sun once more to the Earth, where it receives a third boost and is finally on its way to Jupiter. It is scheduled to begin operations there in late 1995. While it's careening past worlds, Galileo will be gathering data -- about Venus, about the Moon, about two worldlets named Gaspra and Ida, about the interplanetary gas . . . and about the Earth. It will help determine the worldwide distribution of greenhouse gases, the present status of the ominous hole in the ozone layer over Antarctica, and the water content of the upper atmosphere -- central for understanding the ozone problem. Furthermore, its investigations of the atmospheres of Venus and Jupiter promise to improve our knowledge of our own fragile envelope of air. Galileo will not only be exploring other worlds; it will help us to understand and safeguard this world. Galileo is a worthy successor to Voyager.

Because Voyager had to fly so far from the Sun (which appears virtually as a bright point of light from the distance of Neptune), it could not rely on sunlight for energy. Instead, it was powered by heat from the radioactive decay of plutonium -- all this occurring safely, without the slightest mishap, in a component of the spacecraft called an RTG, for "radioisotope thermoelectric generator."

Galileo also will be powered by radioactive plutonium. There is no alternative. To power Galileo by solar panels, the spacecraft would have to be as big as a house; to power it by batteries would add so much weight that the mission would never fly -- at least on any U.S. launch vehicle in existence or now under development. But plutonium can be deadly, and the Galileo RTG's have now begun to alarm many people. A lawsuit has been filed in Federal District Court in Washington, D.C. -- by the Washington-based religiousaffiliated Christic Institute and other organizations -- to stop the Galileo launch on the grounds that it may pose a serious danger to public health. Meanwhile, the White House, after considering the dangers, has given the go-ahead for launch.

I'm a scientist working on Galileo with a long-time involvement in planetary exploration. I'm also a long-term supporter of the Christic Institute. I admired their successful suit on behalf of the estate of Karen Silkwood against the Kerr-McGee Corporation -- accused of shameful negligence in protecting industrial workers from the dangers of radioactive waste. (I also admired the Christic Institute's early warnings about what later came to be known as the Iran-Contra fiasco.) Concern about the environment and, especially, about the threat of nuclear war has been a thread woven through my life. I was a member of the team that discovered nuclear winter; I've twice been arrested at the Nevada Nuclear Test Site for demonstrating against continued American testing of nuclear weapons in the face of the Soviet unilateral moratorium; I opposed Ronald Reagan's Star Wars scheme from the moment he proposed it -- on grounds that are now widely accepted; for the past decade I've been speaking out around the world to warn about greenhouse warming and depletion of the ozone layer. At the very least, you can't charge me with uncritical acceptance of high technology. Twenty years ago, I also played a role in the NASA decisions to quarantine astronauts returning from the Moon against the unlikely contingency that they might bring back disease microorganisms. It turned out as we had expected: there was not a trace of pathogens. But we had to balance the low probability of their existence against the enormous conceivable public health danger that might follow had we been wrong and such bugs did exist. I would do the same today.

I've felt torn on the Galileo RTG issue for years. I still do. Four years ago, I arranged for the Planetary Society, the largest space interest group in the world, to commission an extensive article presenting both sides of the issue (David Salisbury, "Radiation Risk and Planetary Exploration -- The RTG Controversy," The Planetary Report, May-June 1987). I believe there is nothing absurd about either side of this argument. Many people have urged me to make public my thinking on this matter, and I here take the opportunity to do so:

How dangerous is plutonium? The authoritative Handbook of Physics and Chemistry in its various editions calls plutonium "a very dangerous radiological hazard" and "one of the most dangerous poisons known." Robert Oppenheimer, the Director of the Manhattan Project, reminisced in February 1960: "If the plutonium had ever caught fire, there would not have been anyone left in Los Alamos and probably in much of New Mexico, it is so terribly toxic. It burns in oxygen." (This remark is true for plutonium the metal, but not the ceramic form aboard Galileo.) A microgram of the stuff -- a particle much too tiny to see -- if breathed into your lungs may, over a period of decades, give you cancer. Since Galileo carries 50 pounds of plutonium into space, it is hypothetically carrying a cancer fatality for everyone on Earth. This is an impossibility in fact, because it requires the plutonium to be funnelled directly into the lungs of everyone on Earth, instead of being dispersed in and diluted by the Earth's atmosphere. But this is where much of the concern (including real anguish in many letters I've received) is focussed. Understandably. Why didn't we hear similar concerns voiced about the launch of Voyager or Viking (which also carried RTG's)? Because that was in another epoch -- before Chernobyl, before Challenger, before the revelations about Rocky Flats, before we got serious about protecting the planet. One year before the Chernobyl disaster a Soviet Deputy Minister of the power industry announced that Soviet engineers were confident that you'd have to wait 100,000 years before the Chernobyl fission reactor had a serious accident. Less than a year before the Challenger explosion, NASA spokesmen and contractor personnel assured us that at the then current rate of launch, you'd have to wait ten thousand years before a catastrophic launch failure. Hundreds of FBI agents descending on the Department of Energy's Rocky Flats facility in Colorado has raised justifiable fears of criminal carelessness by the U.S. government where public health and nuclear energy intersect. The Department of Energy and the Department of Defense have systematically minimized the dangers of nuclear power and of nuclear weapons. These cases rouse valid skepticism about government-sponsored probability estimates which are intended to calm the public. Skepticism about government credibility is, in my view, healthy. You can't maintain a democracy without it. I'd like to see much more of it.

What are the actual dangers concerning Galileo's plutonium? First of all, it can't explode. Given the configuration and amount of plutonium, there is no conceivable danger of a nuclear explosion. Secondly, if the Challenger explosion happened all over again with Galileo, there would be no plutonium danger. It would fall to Earth in solid lumps contained within their protective shields. Nobody would breathe it. The danger comes when the plutonium is ground down into very tiny breathable particles, or when it's vaporized -- converted into atoms. Are there any plausible circumstances in which this could happen?

There are some failure modes -- explosions just after launch, for example, in which pieces of metal, improbably, go sheering through the protective graphite shields and iridium clads that surround the lumps of plutonium -- that I'll ignore here because they release much less plutonium than the most worrisome potential failure: the possibility that the plutonium is vaporized during a fiery accidental reentry of Galileo into the Earth's atmosphere.

On its second pass by the Earth, Galileo is scheduled to miss our planet by as little as 200 miles. What if the trajectory is a little bit off and it hits the Earth? Then, entering the Earth's atmosphere at 30,000 miles per hour, it might burn up; it's not guaranteed, it may even be unlikely, but there's a chance that all 50 pounds of plutonium would be vaporized. Some of the plutonium would quickly settle out; some of it would be carried widely by the winds and the general circulation of the Earth's atmosphere. It would be enormously diluted in the air. Some people would breathe in more plutonium and some less over the next 50 years, but no one is likely to get as much radiation from this source as in a single dental X-ray. But there's a tiny chance that you can get cancer from such an X-ray. In our ignorance, we don't know what these low radiation doses would do. In the worst case, you might have an incremental chance of around one in 10 million of getting cancer were all of Galileo's plutonium to vaporize in the upper air. That's the equivalent of producing bone and other cancers in roughly a thousand people worldwide. Or there might be no health effects at all. We simply don't know. (Remember, these people are at risk only if, improbably, Galileo burns up in the Earth's atmosphere on its way back from Venus.)

There are two ways of looking at this: One chance in 10 million is very long odds -- safer over 50 years, for example, than taking a single commercial airline flight is for a few hours. By such a standard, the risk is negligible. But when I fly on an airplane, I do so voluntarily and presumably fully aware of the dangers. It's no business of the government, or some Jupiter-obsessed scientists, to diminish my life expectancy without even consulting me. Roughly 1000 deaths, over 50 years, in a world population that will by then be 10 billion people, seems very small. But if anyone dear to me is one of those people, I no longer find the odds comfortably small. So then I have to ask myself: why should it matter whether it's someone dear to me? Shouldn't I have the same concern for the health of everyone on Earth?

But we haven't yet asked how likely it is that Galileo, instead of swinging by the Earth, will accidentally collide with it. Here I believe the probability estimates are reliable. They are not made by the Department of Energy or NASA contractors, but by NASA's Jet Propulsion Laboratory (JPL), run by the California Institute of Technology. On the one hand, JPL -- responsible for the Galileo project -- has an enormous vested interest in seeing the spacecraft successfully launched. On the other hand, JPL's record on risk assessment is excellent. These are the people responsible for Voyager and most other American robotic missions to the planets, the people with the most experience on Earth in interplanetary navigation and the inventors of the gravity assist. The safety program for containing the plutonium in the Galileo RTG's and for understanding the risks has cost NASA about S50 million.

The JPL engineers have listed the remote contingencies: The spacecraft might be hit by a meteorite in interplanetary space and by accident redirected towards the Earth. There might be a programming error so the spacecraft veers much closer to the Earth than had been planned. There might be an accidental firing of the onboard rocket motor that would have the same effect. There are many possibilities. Every one of them is extremely unlikely. Even if they occur, there is little danger, because unless Galileo itself is crippled in some way, the spacecraft can be commanded to alter its trajectory. When the JPL engineers add up all conceivable sources of trajectory error and their probabilities, plus the likelihood that the error will make the spacecraft hit the Earth rather than miss it by a bigger distance, plus the probability that simultaneously the spacecraft will be unresponsive to commands from the Earth, they derive an overall estimate of the probability of accidental impact. This number is 1 chance in 2 million.

So there's only 1 chance in 2 million that instead of swinging by the Earth and being flung on to Jupiter, Galileo will plummet in flames into the Earth's atmosphere, fragment, burn up and release its fuel as plutonium dioxide vapor into our atmosphere. If that happens, only then is there a chance that around 1000 people would get cancer over the next 50 years -- although, in our ignorance, it might be that not even one person is injured.

There is no such thing as absolute safety. To assess risks, we are required to assess probabilities. If there were a SO50 chance that even one person would die because of the Galileo launch, I would be against it. But there must come some point where I conclude that the risk is so minimal that it becomes acceptable. Different people may well draw that line in different places. One chance in a million that 1000 people would die is, in a certain sense, like one chance in a thousand that one person would die. This is somewhere around my threshold. That's why I find the Galileo decision so agonizing. But taking account of the past history of government incompetence or worse in matters of public health, considering the likely scientific findings (including the possibility that many more lives might be saved because of Galileo's findings), and evaluating the low magnitude of the risk, my personal vote is to launch.

My assessment for spacecraft in Earth orbit is quite different. Here sunlight is strong enough to provide power. Here chemical sources of energy can be carried up. And here -where the plutonium is guaranteed to come down sooner or later -- lies the greatest danger. The attitude of the spacefaring nations on this issue has often been irresponsible. In 1964 a U.S. Department of Defense satellite carrying an RTG did enter the Earth's atmosphere and dispersed plutonium-238 at high altitude; but this was no accident -- it was designed to disperse its plutonium worldwide. So no protective covering was included to minimize the plutonium dispersal. No official thought seems to have been given to the possibility that it might be a bad idea to distribute deadly plutonium all over the planet. An even more serious danger than RTG's is power reactors -- in which nuclear fission is occurring in Earth orbit. The chief offender here has been the Soviet Union, especially its radar satellites designed to follow the activities of U.S. warships worldwide. Their failed Cosmos 954 satellite distributed plutonium pellets all over Western Canada. The Washington-based Federation of American Scientists, the Moscow-based Soviet Scientists Against War and the Nuclear Threat, and House bill H.R. 966, introduced this year, all propose, in the words of the House bill, a "ban on the use of nuclear power sources in orbit around the Earth," although "nuclear power sources for a Moon base or deep space scientific and exploration missions should not be curtailed." The FAS, the Chairman of the Soviet group, and Rep. George Brown, sponsor of the House Bill, unanimously support the launch of Galileo.

I end with a plea for consistency. There are issues -including nuclear war (accidental and deliberate), 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 RTG -- including the scientists, engineers and government officials who for the first time have been forced to think seriously about this matter because of public protest -- to devote a proportionate amount of passion, wisdom and hard work to those activities (and inactivities) that really jeopardize the human family.

Copyright 1989 by Carl Sagan


published by WISE News Communique on November 23, 1990

Space probe, flying reactors and Star Wars

The Ulysses space probe, a joint effort of the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA) to explore the sun, was launched in October - in the face of litigation and demonstrations.

(342.3420) WISE Amsterdam - The launch was the second in a series of plutonium-fueled space probe flights which began last year with the Galileo mission (see WISE News Communique 320.3214). It is also part of a much larger scheme involving placing nuclear reactors in space to provide the power for "Star Wars" and the launching of rockets that would be propelled by nuclear power.

Both probes could impact on the lives of large numbers of people. It takes less than a millionth of a gram of Pu to induce fatal lung cancer. The Galileo probe carries 49.25 pounds of Pu, the Ulysses 23.7 pounds. Thus each carries enough radioactive plutonium to give every person on Earth a fatal dose of lung cancer if it were to be dispersed in an accident. (The plutonium is used in electric generating systems to supply electricity - 570 watts on the Galileo, 284 watts on the Ulysses - to instruments.)

The Galileo was taken up on a shuttle in October 1989 and sent from it on a mission to explore Jupiter. But this year, in December, it is on its way beck towards Earth for the first of a pair of unusual "flybys". The rocket carrying Galileo does not have the power to take the probe straight to Jupiter, so NASA devised a scheme which would first send the probe to Venus, then hurtling back towards Earth. On 8 December it is to pass the earth at a distance of 625 miles. Then it is to be sent back into space again, to return on 8 December 1992. At that time it will be only 185 miles from Earth, flying at more than 30,000 miles per hour. The idea is to use the Earth's gravitational pull to increase the velocity of the probe, so that after the two flybys it will have the power to get to Jupiter. The idea, however, has never been tested at such a low altitude. Certainly not with a space probe containing plutonium.

If radio contact is lost with the Galileo probe, if it collides with a meteorite altering its trajectory, or any number of miscalculations occur, and it crashes into the Earth's atmosphere on either of the flybys and disintegrates, Earth is in for a disaster. According to Dr. John Gofman, Professor Emeritus of Medical Physics at the University of California at Berkeley, "the amount of radioactivity released would be more than the combined plutonium radioactivity returned to Earth in the fallout from all the nuclear weapons testing of the United States, the Soviet Union, and the United Kingdom." Gofman calculates that these have already caused 950,000 lung cancer fatalities.

The reason the plutonium radio-activity would be so intense, says Gofman, is because the plutonium isotope used on space probes is Pu-238 which is 300 times more radioactive than the Pu-239 used in atomic bombs.

Even General Electric Co. (GE), the manufacturer of the plutonium-fueled electric generating system on both probes (a radioisotope thermal generator, or RTG), admits that the danger of contamination on Earth from the plutonium on the two RTG's on the Galileo will only be over when the last flyby is over, in 1992. A "Final Safety analysis" on the Galileo done by 3E and obtained from NASA under the US Freedom of Information Act by Karl Grossman, a journalism professor at the State University of New York, Old Westbury, states:

"At this point, with a successful and correct burn of the IUS, escape of the spacecraft from the Earth's gravitational pull will be effected, and the RTG's will no longer present a potential risk to the Earth's population."

Other documents reveal that the use of plutonium on the Galileo, Ulysses and other space probe missions is not needed -that the risk being taken is unnecessary and that solar-generated electricity would be adequate (see WISE News Communique 337.3369.)

According to one NASA-contracted report by the Jet Propulsion Laboratory (JPL) released to Grossman photovoltaics can replace RTG's on several NASA missions on which plutonium power was proposed. These included what is now the next proposed plutonium-fueled space probe shot, the Comet Rendezvous Asteroid flyby (CRAF) mission, scheduled for 1995.

NASA's dismissal of the solar alternative and preference for nuclear power in space has much to do with a new role it has taken on: providing delivery service for Star Wars. NASA, notes Dr. Michio Kaku, Professor of Nuclear Physics at the City University of New York, has been reshaping itself in recent years to use its shuttle fleet as a service for the orbiting nuclear power plants that are to provide power for the laser cannons and particle beams of Star Wars. Faced with tight budgets since its moon landings, NASA has joined in what he calls an "unholy alliance" with the military in order to receive larger new sources of money - and the plutonium-fueled space probe flights are a part of this.

GE is currently developing what are to be 100 or more space nuclear reactors - it calls its design the SP_100 - designed to be small enough to be launched on NASA shuttles and which, orbiting overhead, are to provide power for Star Wars. In addition, four other types of space nuclear power systems are being developed for the Star Wars program.

Not to stop there, NASA has revived an old Atomic Energy Commission scheme: development of rockets actually propelled by nuclear power. Concerns about the consequences if a nuclear-powered rocket crashed back on Earth led to the cancellation of the scheme in the late 1970s after some US $ 2 billion had been spent. No nuclear-powered rocket ever got off the ground. But now NASA is seeking funding to build nuclear-powered rockets to be ready as early as 2005. Says Gary Bennett, manager of government studies for NASA on the subject, " If we're going to Mars to stay and colonize, we'll need some type of nuclear propulsion."

The Florida Coalition for Peace and Jusitce, which ahs engaged in protest including civil disobedience at the Kennedy Space Center, vows to continue opposition to NASA's attempt to "nuclearize space". The Coalition is a plaintiff in a lawsuit brought in US federal court to block both the Galileo and Ulysses launches. Part of that suit is still to be decided as it calls for halting the flybys. The Coalition's coordinator, Burce Gagnon, says NASA's new nuclear-powered rocket plan "confirms what we have been saying all along - the nuclear industry is continually working to develop more dangerous kinds of nuclear power for space use. When these reactors start dropping out of the sky, they're going to fall anywhere. Those who are concerned about toxic contamination had better pay a lot more attention to the space/nuclear issue."

Sources: The above is a summary of an article by Karl Grossman.

Contact: Florida Coalition for Peace and Justice, PO Box 2468, Orlando FL 32802, USA, tel: 9407) 422-3479

Karl Grossman, Box 1680, Sag Harbor NY 11963, USA.



The following two excerpts are from recent press releases from NASA and Sky and Telescope Magazine concerning the Galileo Spacecraft:

"The Amalthea encounter was Galileo’s final flyby. The spacecraft has nearly depleted its supply of the propellant needed for pointing its antenna toward Earth and controlling its flight path. While still controllable, it has been put on a course for impact into Jupiter next September. The maneuver prevents the risk of Galileo drifting to an unwanted impact with the moon Europa, where it discovered evidence of a subsurface ocean that is of interest as a possible habitat for extraterrestrial life." 1

"To eliminate any potential that the spacecraft could someday contaminate Europa, a moon that may harbor primitive life, Galileo will be directed to fall into Jupiter's atmosphere on September 21, 2003, when it will plunge into the Equatorial Zone at 48 km per second." [Approx. 107,000 mph]2

Elements present in the Atmosphere of Jupiter

Jupiter is mostly composed of hydrogen and helium, in various gas, liquid, and metallic forms. The inner core may be composed of a somewhat solid rocky material. The average density of Jupiter is much less than that of Earth, but the pressure in the atmosphere of Jupiter, and below it, is intense. The probe that Galileo launched into the atmosphere relayed data for about an hour. At that point it was overcome by pressure exceeding 23 times that of Earth at sea level at only 125 miles in. Towards the core of Jupiter it is estimated that the pressure could be millions of times that of Earth at sea level.

"Jupiter's atmosphere consists of about 81 percent hydrogen and 18 percent helium. If Jupiter had been between fifty and a hundred times more massive, it might have evolved into a star rather than a planet. Our solar system could have been a binary star system, meaning that we would have two suns. Besides hydrogen and helium, small amounts of methane, ammonia, phosphorus, water vapor, and various hydrocarbons have been found in Jupiter's atmosphere." 4

"Jupiter has similar relative abundance of hydrogen and helium to the Sun itself. However, its core temperature…is too low a value to trigger nuclear fusion." 5

Where will this event be visible from Earth, if it occurs?

Unless the date and time changes, the craft is impacting Jupiter on September 21, 2003 at about 2:38pm EDT, image reaching earth at 3:30 (Jupiter is visible pre-dawn from Japan to Australia at this time). Early September occurs shortly after the next conjunction of Jupiter-Sun-Earth (when Jupiter is obscured by the Sun), and Jupiter will start to become visible again just before dawn around September 1st. Look in the eastern sky, low to the horizon, right under the constellation Leo. The entry of the craft will be completely unnoticeable if no reaction occurs. If Jupiter ignites, however, a tremendous flash or series of flashes would be seen. (the actual impact would have taken place 52 minutes prior due to speed of light lag). Jupiter is visible for 1 to 2 hours in the early morning in September, 2003.


The Henry Holt Guide to Astronomy, David Baker, 1990 USA

Compton’s Interactive Encyclopedia, 1999

Merriam-Webster’s Collegiate Dictionary – Tenth Edition

The Independent Public Service Report

TIPS Report – August, 2003

J.C. Goliathan



Galileo Heads for Fiery Death

NASA Probe to Take Kamikaze Plunge into Jupiter

Listen to Weekend Edition - Saturday audio

Image Gallery: Galileo's Greatest Hits

An illustration depicting Galileo in front of Jupiter.

Provided by: JPL/NASA

Jupiter's volcanic moon Io, as seen by Galileo.

Provided by: JPL/NASA

"We spent the month of July with no way to get Galileo to Jupiter, and for a time it looked like the only place we could get it to was the Smithsonian. And we weren't entirely kidding."

Galileo Project Manager Bill O'Neil

Sept. 20, 2003 -- Scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif., will listen in Sunday as the Galileo spacecraft sends its final signals. After orbiting Jupiter for nearly eight years, mission managers decided it was best to destroy the spacecraft by crashing it into the giant planet. NPR's Joe Palca, who has been covering the Galileo mission for 17 years, reports on the mission and its accomplishments.

Galileo was a big success, Palca says. Its cameras returned thousands of pictures of Jupiter and its large, icy moons. Galileo's magnetometers found evidence that liquid oceans still exist under the ice of Europa. Other instruments analyzed Jupiter's turbulent atmosphere.

But Galileo was very nearly a flop, Palca says. It was constantly flirting with disaster, even before it left Earth.

"When the project started in 1977," says Bill O'Neil, one of Galileo's project managers, "the idea was that it would be launched in January 1982 and would arrive at Jupiter in the middle of July 1985. So it turns out that we actually arrived at Jupiter a little more than a decade later, in December of 1995, and launched seven-and-a-half years after we were originally scheduled to launch."

The problem was with NASA's brand new space shuttle that was to carry Galileo and its booster rocket into orbit.

A launch date was finally set for May 1986. But in January that year, the space shuttle Challenger blew up. After reviewing the safety of all future missions, O'Neil says NASA decided it was too dangerous for Galileo's powerful booster to fly on the shuttle even when flights resumed.

Without the booster, Galileo couldn't leave Earth's orbit and make it to Jupiter. The summer of 1986 was a bleak time for O'Neil and colleagues.

"We spent the month of July with no way to get Galileo to Jupiter, and for a time it looked like the only place we could get it to was the Smithsonian," he says. "And we weren't entirely kidding when we used to talk about that."

O'Neil says NASA would only let the shuttle carry a far less powerful booster, one that didn't have the power Galileo needed. System engineer Roger Diehl solved the problem in the nick of time:

"It was just on that last Friday in July that Roger had this brainwave to come by the Earth twice to get the gravity assist we needed to get to Jupiter," O'Neil explains.

So in what has to be one of the most counterintuitive flight plans of all time, the mission to the outer planet Jupiter actually started off flying to the inner planet Venus, then back for two loops around Earth. Finally, six years after it launched, Galileo arrived at Jupiter in December 1995 and began taking pictures and measurements of the Jovian system.

Galileo's main mission ended in 1997, but NASA has kept the project going -- until now.

Claudia Alexander, Galileo's final project manager, says NASA officials worried that the spacecraft's orbit could send it crashing into Europa. They didn't want to risk contaminating a moon that might harbor life, so they decided a suicide plunge into Jupiter would be best.

Alexander says Galileo is scheduled to work right up to the end. "We are hoping, with fingers crossed, that we can go past the orbit of Amalthea and continue collecting science data," she says. "I actually don't think that's going to happen. I don't think the spacecraft is going to be able to handle that radiation environment."

But with Galileo, says Palca, you have to be prepared for pleasant surprises.

Galileo Probe Ends in Deliberate Dive


Sunday, September 21, 2003; 5:02 PM

WASHINGTON - NASA's Galileo space probe ended its eight-year mission to Jupiter Sunday as expected in a fiery collision with the largest planet as the space scientists celebrated back on Earth.

The space agency's Jet Propulsion Laboratory in Pasadena, Calif., lost contact with the spacecraft slightly after 3:40 p.m. EDT, 2 minutes and 36 seconds before expected, laboratory spokesman D.C. Agle said.

More than 1,000 people who worked on the Galileo program gathered at the Laboratory to celebrate the end of the mission, Agle said.

Galileo was low on propellant and six years past its original end date. Launched from space shuttle Atlantis in 1989, Galileo traveled about 2.8 billion miles .

Galileo orbited Jupiter 34 times and obtained the first direct measurements of its atmosphere by sending a descent probe parachuting down toward the planet in 1995.

It detected evidence of underground salt water oceans on Jupiter's moons Europa, Ganymede and Callisto, and examined the lively, intensely hot, volcanoes on the moon Io.