by Richard C. Hoagland

from TheEnterpriseMission Website

On September 21, 2003 NASA deliberately directed its amazing, still-functioning Galileo spacecraft to make one final, 108,000 mph suicidal plunge into Jupiter’s vast atmosphere. Thus ended the incredibly successful eight-year unmanned NASA Galileo mission … which had returned against all odds an array of phenomenal new information on Jupiter and its “mini-solar system of moons”… in a literal, most fitting “blaze of glory.”


The intent of this unfortunate decision was to protect Europa, one of those Jovian moons. Galileo’s repeated Europa observations (below) over the course of its highly successful eight years have all-but-confirmed an extraordinary model, first proposed and published by this author in 1980:

that, beneath its several-miles-thick ice cover, Europa still harbors a liquid water ocean… an ocean potentially teeming with 4.5 billion year-old alien life!

NASA’s decision to finally terminate Galileo via a fiery plunge into Jupiter, was designed in 2002 to prevent any possible biological contamination of this remarkable environment from a future random collision with the spacecraft, once its fuel was exhausted. The recommendation, from the National Research Council’s Space Science Studies Board’s “Committee on Planetary and Lunar Exploration” to NASA re the Galileo “problem,” noted,

“This [procedure] is necessary to safeguard the scientific integrity of future studies of Europa's biological potential ….”


When NASA announced its “Galileo into Jupiter” option, among those to publish immediate, serious objections (and later to repeat them on “Coast to Coast AM”) was an engineer named Jacco van der Worp.


Van der Worp claimed that, plunging into Jupiter’s deep and increasingly dense atmosphere, the on-board Galileo electrical power supply – a set of 144 plutonium-238 fuel pellets, arrayed in two large canister devices called “RTGs” (Radioisotope Thermoelectric Generators – see image and schematic, below) would ultimately “implode”; that the plutonium Galileo carried would ultimately collapse in upon itself under the enormous pressures of Jupiter’s overwhelming atmosphere.


Triggering a runaway nuclear explosion!

Van der Worp further argued that this fission reaction might well initiate a much larger thermonuclear fusion reaction in the deuterium (heavy hydrogen) making up a significant percentage of Jupiter’s atmosphere – ultimately, igniting Jupiter as the solar system’s second sun!

Needless to say, NASA (and essentially all other observers, including myself!) thought these ideas “well beyond the fringe” ….

Fast-forward the film to almost one month later… October 19, 2003.

On that night, an amateur astronomer in Belgium, Olivier Meeckers, secured a remarkable composite “Webcam” image of Jupiter (place mouse on below image) through a small refracting telescope (inverted, as in a telescopic view, below).


On the image, a dark black “splotch” showed up on the southern edge of Jupiter’s well-known “North Equatorial Belt,” trailing a fainter “tail” southwest (image center).

Half an hour later Meeckers took a second set of frames, resulting in a second composite (below image).


The “splotch” clearly was still present, though Jupiter’s fast atmospheric rotation had obviously moved it several thousand miles further east.

Over the next few days, Internet stories began to appear regarding the “new Jovian mystery.” And, they contained key phrases like, “experts captivated” … and “researchers scratched their heads about what they'd found.”


From these reports, it was clear that seasoned amateur and professional astronomers alike were totally perplexed by the discovery… and didn’t have a clue as to the cause.

Almost ten years earlier – in July, 1994 – equally dramatic black markings had suddenly appeared in Jupiter’s atmosphere (below). Then, the cause was crystal clear:

- the impact of some 21 pieces of a stunning celestial object named “Comet Shoemaker/Levy 9.”

Unlike those clear cometary impacts, following Meecker’s images on October 19, 2003, astronomers immediately discounted “impact” as a likely explanation for the new “black splotch”; for one thing, unlike the case of the Shoemaker/Levy 9 fragments, nothing approaching Jupiter large enough to cause such a highly visible marking had been plotted by any observers in the months leading up to this sudden new appearance.

“It’s a shame,” I thought, “that Galileo isn’t around anymore… to take some really close-up measurements of this thing“.

Hey! I suddenly realized that everyone had apparently forgotten one well-known impact that HAD taken place… just a month before the appearance of this “splotch” - the plunge of the Galileo spacecraft into Jupiter, September 21, 2003!

Because… I also now remembered something else: those bizarre “doomsday” warnings from Jacco van der Worp.

Could the new, totally unknown marking on Jupiter be the visible signature of precisely the kind of event van der Worp had warned about…a Galileo nuclear explosion? Could van der Worp, against all odds, actually have been right about Galileo’s “final mission?!”

I began to do some digging.



What van der Worp had suggested, in terms of Galileo, was merely a variant on the now well-known design of the “Fat Boy” plutonium nuclear weapon used against Nagasaki at the end of World War II - an “implosion” plutonium reaction (below).

In order to bring the sub-critical pieces of plutonium-239 together in a bomb fast enough for a catastrophic fission reaction to take place, in the original Los Alamos design Seth Neddermeyer (one of the Manhattan Project scientists), following on an idea by Richard Tolman at CalTech in 1943, began working on a novel but almost impossibly difficult idea (in 1943) for smashing plutonium pieces together in mere millionths of a second.


Such a device was called an “implosion mechanism,” and became the key to the success of the plutonium bomb. At its simplest, it consisted of several layers of carefully shaped high explosives, wrapped around the central sub-critical masses of plutonium (below).


When triggered, the resulting high energy explosive shock waves (below, right) drove these plutonium pieces closer together in a highly compressed, spherical configuration - resulting in a sudden transformation of the many plutonium pieces into a single “supercritical” mass… and a resulting runaway nuclear explosion.

The Fat Man bomb (named after Winston Churchill!), consisting of about 14 lbs of highly refined plutonium-239 - produced an energy equivalent (“yield”) of approximately 21,000 tons of exploding TNT, at an efficiency of approximately 17 % (analysis revealed that only about 4.5 lbs of the 14 lbs of plutonium actually fissioned on implosion, before the explosion itself drove the remaining plutonium apart).


The highly sophisticated geometry of the high explosives wrapped around the plutonium core, and the micro-second electronic circuitry needed for its precise detonation, were ultimately the determining factors for a successful chain reaction in this type of implosion plutonium weapon.

Van der Worp had argued that in Jupiter’s dense, high-pressure atmosphere, the creation of an implosion in Galileo’s plutonium capsules was almost naturally assured… without any complex high-tech explosive triggers or ancillary mechanisms.


He had written:

“…The plutonium pellets aboard are protected against unexpected pressures (not Jupiter’s atmospheric pressures though). Since the craft will be traveling so fast (107,000+ mph), the pressure will increase suddenly. The upper crust of Jupiter’s atmosphere is gaseous hydrogen and helium about 600 to 700 miles thick (2% of the radius of the planet), followed by a more liquid substance of the two, and much further in, a more metal version (so it is guessed).


At only 125 miles down the pressure is already 23 bars (Galileo would go from 1/2 bar to 23 bars in 4 seconds). If the craft is traveling at 107,000+ miles/hr, and the pellets (not the craft) last 20 seconds in Jupiter’s hostile atmosphere before imploding, they would have traveled approximately 500-600 miles inward if one accounts for the craft slowing down after entry. This is about the thickness of the more gaseous part of the atmosphere (this is assuming a perpendicular entry).


At this point, the pressure would be in the thousands of bars because the increase is exponential, not to mention the temperatures generated at this speed would be tremendous ….”

A quick survey of Internet nuclear weapons design sites indicated that a plutonium alloy (like the plutonium-238 dioxide ceramics carried in Galileo’s RTGs),

“undergoes a phase transition to the alpha state [highest density] at relatively low pressures (tens of kilobars, i.e. tens of thousands of atmospheres)….”

In other words, the physics of implosion dictates that extreme external pressures, reaching tens of thousands of Earth normal atmospheres (1 “bar”), can initiate supercriticality in certain plutonium alloys. In a weapon, this is achieved by a carefully shaped charge - to drive explosion shockwaves inward… imploding the metal to “supercriticality.”


In the Jovian context, this pressure naturally exists… beginning about 600 miles below the visible cloud decks - far in excess of anything Galileo was expected to encounter on entering Jupiter’s upper atmosphere in September, 2003, before being totally destroyed. Van der Worp, in proposing about a nuclear explosion after the first few seconds of Galileo’s entry, had apparently vastly underestimated the efficiency of friction in Jupiter’s increasingly dense atmosphere, which would slow the various components to a virtual standstill, long before they reached these critical “crush depths.”

So, even on reexamination, van der Worp’s ideas seemed irrelevant to the mystery of Jupiter’s new spot.

Until… I thought about the “time lag.”

Galileo slammed into Jupiter’s atmosphere September 21st. Meeckers photographed his mysterious “dark marking” October 19th. If Galileo, by creating an explosion, was somehow responsible for this new blemish… why the one month lag between these two events? Van der Worp’s scenario had a Galileo plutonium explosion happening almost as soon as the spacecraft hurtled into the Jovian atmosphere….

Suddenly, I realized that this was the missing puzzle piece - apparently not fully appreciated even by van der Worp; that time lag could be the key to resolving this entire “Galileo bomb” scenario… and the mystery of Jupiter’s “new spot.”

It all hinged on how far into Jupiter the spacecraft (or, more accurately, it’s plutonium canisters) would have to plunge - intact! - before encountering external atmospheric pressures sufficient for “implosion. In other words, how long would it have really taken Galileo’s plutonium - assuming it survived its fiery entry in the first place - to have fallen ~600 miles…?

I began to sketch out a possible scenario.

  • September 21st: Galileo enters Jupiter’s atmosphere at over 30 miles per second. It is traveling almost in the plane of Jupiter’s equator, at an angle of about 22 degrees to the horizontal (below).

  • As the more fragile parts of the spacecraft disintegrate from the enormous entry temperatures and pressures, its two 4-ft long, 124-lb RTGs - each containing 72 individual plutonium-238 capsules - separate from the main spacecraft.

  • Soon, the relatively fragile aluminum housing of the two RTG canisters also melts away, releasing the 144 individually sealed plutonium-238 capsules… to continue plunging deeper into Jupiter’s atmosphere on their own.

  • Because of their high-temperature, multi-layer containment, each capsule is clad in iridium (melting temperature 4435 F), encasing a floating boran-graphite membrane (melting temperature 6422° F), in which the plutonium-238 pellets are individually sealed - most of the plutonium capsules are NOT destroyed by Galielo’s violent entry, but in fact survive… and slow to an aerodynamic fall in the thickening Jovian atmosphere.

The multiple layerings of iridium and graphite have acted like individual heat shields [similar to the much larger (and heavier) Galileo Probe - which successfully entered Jupiter’s atmosphere December 7, 1995]. After slowing to sub-sonic speeds, the shielded capsules would have free-fallen through Jupiter’s increasingly dense atmosphere ... until the outside pressures inevitably caused them to implode.


The key question then became:

- how long would it take each free-falling iridium/graphite capsule to reach “crush depth” - the depth where the outside pressures are tens of thousands of atmospheres, ~600 miles below the clouds?

The depth where those pressures would cause the plutonium-238 capsules to undergo a sudden phase transition, to literally implode… initiating a violent nuclear reaction?



The rate of a free-falling object in a planetary atmosphere is governed by an elementary equation, known as “Stokes law”:

V = (2gr²)(d1-d2)/9µ


V = velocity of fall (cm sec-¹)

g = acceleration of gravity (cm sec-²)

r = "equivalent" radius of particle (cm)

d1 = density of particle (g cm -³)

d2 = density of medium (g cm-³)

µ = viscosity of medium (dyne sec cm-²)

What this translates to is this:

For a given atmospheric density, an object of a given mass and surface area, under a given gravitational acceleration, will fall at a given rate. Denser objects (less surface area for their given weight) fall faster than lighter ones (this is due to simple air resistance, and NOT any non-Newtonian aspects of the laws of gravitation!).


If the atmospheric density increases as an object falls to greater depths, the rate of free-fall is slowed in direct proportion to the increasing density. To a first order, increasing atmospheric pressure is approximately proportional to increasing atmospheric density, and thus a decreasing rate of free-fall.

In other words, the higher the outside gas pressure on Jupiter… the slower Galileo’s capsules would fall.

For a 6-foot, 200-lb human in Earth’s gravity, surrounded by its one bar atmospheric pressure, the final rate of fall is approximately 120 miles per hour - called its “terminal velocity.” On Jupiter, with a cloud-top gravity about 2.4 times Earth’s, and an upper atmospheric pressure less than a tenth of Earth’s, the initial rate of free-fall for an object with a similar mass-to-surface area (like Galileo’s RTGs) would be about 3000 mph.


But, by the time the RTGs had disintegrated and released their 144 plutonium individual capsules, the atmospheric density/pressure would have risen to several times the Earth’s, and the surface area to weight ratio of the smaller plutonium capsules (1.5-inch by 1-inch cylinders) is MUCH greater than for the RTGs themselves.


This would cut their free-fall velocity by a corresponding amount… to around 150 mph at this altitude.



  • As the capsules continue to fall deeper through the primarily hydrogen atmosphere, the surrounding pressure/density continues to rise, to thousands of times Earth’s surface density and pressure. The capsules are now falling at a constant rate, approximately one mile per hour… as the atmosphere transitions to an incompressible fluid, liquid hydrogen (below).

  • At this ultra-slow “terminal velocity,” it takes the Galileo plutonium-238 capsules on the order of 700 hours – a month! to fall to a depth inside Jupiter (~700 miles below the visible clouds) where the outside pressure of the surrounding liquid hydrogen literally crushes the plutonium capsules into a supercritical state

  • At this point, one of the capsules randomly implodes… and initiates, via the resulting shockwave and intense neutron shower, a runaway nuclear chain reaction in all the other surviving capsules, now spread in a spherical falling “cloud” a few tens of miles across ~700 miles below Jupiter’s visible “surface.” The resulting cascade nuclear detonation of all the surviving capsules totals several tens of kilotons….



A single month …

The simultaneous detonation of over 40 lbs of plutonium-238, over 700 miles below Jupiter’s cloud tops, instantly creates a superheated “bubble” of “million-degree plasma” deep inside Jupiter, tens miles across. Initially, this bubble has an expansion pressure of over fifty million atmospheres per square inch. Because the outside Jovian “mantle” pressure is approximately ten thousand atmospheres at this depth, the plasma sphere rapidly expands… to a diameter over fifty times as great... until the inside and outside pressures equalize.


Because of the extreme low density inside this super-heated sphere, and the higher Jovian gravity (2.4 times “Earth normal), the buoyancy forces are immense. The “bubble” immediately begins to ascend toward the visible surface, 600 miles above - rising at an extraordinary rate of several hundred miles per hour….

[In the “Ivy Mike” 1952 nuclear test in the Pacific (above image), the fireball rose to a height of 57,000 feet in only 90 seconds – which translates to a velocity of over 400 miles per hour! In the much higher pressure Jovian environment, the ascent rate of such a high-temperature, low density plasma bubble could well be ~1000 miles per hour, before slowing drastically as the “bubble” nears the top of the visible (lower density) atmosphere….]

At this rate of ascent, the bubble (also constantly expanding, as the surrounding atmospheric pressure lessens – until it is several thousand miles across) breaks the “surface” of the Jovian atmosphere within an hour or two of detonation.


The horizontal shear inside Jupiter’s atmosphere has also moved it north, away from the plane of Galileo’s entry, until it is trapped by the streaming atmospheric eddies that form the North Equatorial Belt (below image) - where it emerges as a visible phenomenon.

The intense temperatures of this nuclear plasma upwelling immediately dissociate the surrounding neutral molecular “contaminants” of Jupiter’s high altitude troposphere and stratosphere – water, ammonia and methane are instantly broken down into their component atoms. It is here that the unique “signature chemistry” which has revealed this incredible scenario takes place….

The carbon released from the dissociation of millions of tons of CH4 (methane) and other carbon-rich molecules floating at the highest levels in the vast Jovian hydrogen/helium atmosphere as “minor” constituents, with no significant reservoir of free oxygen available to turn it into CO2 (carbon dioxide), when it cools condenses into countless micron-sized pure carbon particles – “lamb black”… soot! Such particles, even though their total numbers are relatively trivial on the scale of Jupiter’s atmosphere, are extremely effective at absorbing visible wavelengths of light all across the spectrum….

It is this unique, dark “carbon” signature - appearing as a dark black “splotch” in the highest levels of the Jovian cloud belts (below image) - which has given this entire, incredible scenario away….



Critics, of course, will raise all kinds of objections to this bizarre scenario. Many we have raised ourselves - like the low probability of Galileo’s plutonium even surviving entry - at 108,000 miles per hour! - to reach the necessary “crush depth” for implosion.

A far more serious objection is that the nuclear fuel Galileo carried - plutonium-238 - while ideal as a sustained heat source for making electricity via thermoelectric technology, is NOT traditionally viewed as a fissionable material appropriate for creating nuclear explosions. The plutonium isotope vastly preferred for the original “Fat Man” weapon was plutonium-239 - which, by not emitting an excess of neutrons prior to achieving supercriticality, allowed the construction of an actual implosion plutonium weapon.

However, a little-known US nuclear weapons test, carried out underground at the Atomic Energy Commission’s Nevada test site (now operated by the Department of Energy), demonstrated in 1962 that “reactor-grade” plutonium - a mix of isotopes, including plutonium-238 - could be successfully imploded.


Because of the extended Galileo mission, and the pre-production of the plutonium-238 fuel capsules before its launch (coupled with their unique design – which incorporated a layering of neutron-emitting uranium-234 into their construction), long-term creation of significant quantities of highly fissionable plutonium-239 across the fifteen years since the mission was launched cannot be ruled out of the eventual Galileo plutonium ceramics… by the time they were deliberately plunged into Jupiter.

So, did any of this really happen?

The deliberate destruction of Galileo to “save” Europa, and the sudden appearance of “a mysterious dark splotch” on Jupiter just one month later - precisely time enough to get the entering plutonium down to a depth where it could catastrophically implode - is truly a remarkable “coincidence.”


Admittedly, this is strictly a case of circumstantial evidence: radioactive debris can’t be analyzed in Jupiter’s atmosphere remotely; no one has demonstrated that plutonium-238 can make a “bomb” under Jovian conditions; and there are major questions regarding the capsules even having sufficient mass for a runaway nuclear reaction, that is, if they survived entry… let alone falling intact to a depth sufficient to implode.

But, television is replete these days with highly publicized legal cases where a defendant is tried - for murder, no less – based on strictly circumstantial evidence alone… like, a single strand of hair. The case for “something extraordinary” happening to Jupiter - with NASA inadvertently behind it - is based on a chain of far more solid evidence at this point.

And then, there is the troubling absence of key evidence….

One of the lingering mysteries surrounding the sudden appearance of Meecker’s “new dark splotch” has been the seeming total non-curiosity exemplified by the professional astronomical community.

In 1994, a new “white spot” suddenly appeared in the clouds just north of Saturn’s equator. Within days, professional astronomers world wide were imaging the new disturbance with an eye toward understanding its origin and evolution – culminating in a stunning time lapse movie acquired by the Hubble Space Telescope itself (see below video).

a frame of above video


Where are any of the scores of professional astronomical images - including those from HST - which should be flooding the Internet over this discovery, documenting the “enigmatic new phenomenon” that just appeared on Jupiter?!

High quality, early observations of remarkable astronomical events are standard operating procedure, especially in the case of planetary atmospheric phenomena - which can rapidly change, or even disappear entirely if early observations aren’t secured in the first few days. Yet, by all accounts, for this new phenomenon on Jupiter, all observations have been left totally to the amateur community….


Is it possible that the professional “insiders,” those at the major observatories (which get most of their funding from NASA anyway) - including NASA’s own Space Telescope Institute - know perfectly well how this atmospheric spot arrived on Jupiter… and have been quietly told not to “immortalize” another monumental miscalculation by NASA… particularly, at this politically sensitive time?



Finally, if you discount all these ideas as simply “too far out,” there is one final scenario which neatly fits the evidence currently at hand… conceived many years ago in “2010 - Odyssey Two”… from the fertile imagination of my old friend, Arthur Clarke.

For those fans of Arthur who love a good “conspiracy” - especially if it involves our favorite space agency (anyone we know..?) - these observers may now discern the completion of a long-term, hidden goal in this enigmatic Jovian data… here.