The Galileo probe, though at present its future is uncertain, would, if not sterilized, represent a good chance of contaminating Jupiter. Most scientists opposed to sterilizing the probe argue that to order the probe sterilized would be the death of the project, since sterilization would entail a reconstruction of the probe, and there are not enough funds to accomplish this. These scientists, however, are ignoring a relatively simple and inexpensive alternative to the traditional heat sterilization method. The main threat of contamination comes from Galileo's exterior surfaces: the shell of the probe and its parachute. The probe innermost components would not represent a threat since the probe is sealed. In light of the fact that only the exterior of Galileo would have to be sterilized, heat would not have to be used as a method of sterilization. Instead, various gas mixtures could be sprayed entirely over the probe and its parachute, gases which would kill any and all bacteria. This idea is more thoroughly examined

Garcia, Joe

English

NASA Technical Reports Server

THE POSSIBLE CONTAMINATION OF JUPITER Yf  
Joe Garcia 
Centuries ago, when the first Anglo pioneers invaded the shores of the Ameri- 
cas, they brought with them more than just the hope and will to survive that we nor- 
mally associate them with. They carried with them on their ships, their clothes, their 
cargo, unseen microorganisms, bacteria and disease. North America, and the Native 
Americans who inhabited it, being isolated from Europe by the Atlantic Ocean, had 
never before encountered these foreign bacteria. The "pilgrims," on the other hand, 
had not only coexisted with their domestic diseases, but had battled viciously with 
them and eventually built up an immunity which protected them from being overridden 
by bacteria. The Native Americans had no such defense system, and as a result of 
that, the bacteria thrived in the pure environment of the New World. Now keep in mind 
that these were not any bacteria of the complex sort; no, these were quite ordinary 
bacteria, predominantly just the common cold. But because these bacteria were in no 
way common to the uncontaminated Americas, the disease spread like wildfire and 
was responsible for more Native American deaths than any head-scalper. 
This contamination of North America was not planned. Man knew little of life 
invisible to the naked eye, and even less of the catastrophic reaction to these new 
microorganisms that the Native Americans displayed. The New World, as America 
was referred to in the first years of its "discovery," was a land full of mysteries to be 
solved. Explorers came from every land in an attempt to untangle and map out the 
unknown geography that North and South America represented. They came on a 
quest for knowledge, hoping to find a relative Garden of Eden and steal its forbidden 
fruits. 
Well, now it's 1986, and "The New World" is completely charted, its lands 
tamed. Satisfied with our knowledge of this now old world, we look beyond our own 
planet, into space, hoping to find newer worlds. There are at least eight others out 
there, future sites of expeditions and explorations, waiting for rocket-boosted Mayflow- 
ers to arrive. Space, perhaps the final frontier, a vast, uncharted sea. The days of 
exploring new continents are long over, and, as history repeats itself, the people of 
Earth enlarge their perspective to include other planets, the solar system, the universe. 
What a beautiful and pacifying new sea upon which will embark a new breed of 
explo re rs ! 
But like the pilgrims, will space explorations represent a threat of bacterial inva- 
sion? Bacteria are one of the most basic of Earth's organisms, hypothesized to be one 
of the turning points in our own evolution. It is said that the simpler things are, the 
better they are. Well, this is most certainly the case when we take into account the 
great capacity for survival which bacteria have. Temperatures much too hot for any 
human to survive in are no sweat (no pun intended) for most bacteria. Bacteria can 
survive in inhumanly cold temperatures just as easily, and are even able to exist on 
the outermost hulls of ships in the vacuum of space. 
29 
https://ntrs.nasa.gov/search.jsp?R=19890009012 2020-03-20T04:05:56+00:00Z
It is inconceivable to totally condemn the pilgrims for their contamination of the 
New World; they simply didn't know what they were doing. But now we know about 
bacteria, and we know that they will survive space travel. Contamination becomes 
less of a laboratory issue and more of a moral dilemma because we know what we are 
doing. Is it not the hope of NASA to someday discover other forms of life, perhaps 
intelligent life, on planets beside our own? And if the answer to this question is yes, 
then wouldn't any type of bacterial invasion deeply risk reducing our chances? 
The only way to avoid contaminating an alien environment with terrestrial 
organisms is either to completely sterilize any and all equipment/persons that come 
into contact with the environment, or else simply not to come into contact with it. If we 
must come into contact, then it is the logical and responsible choice to sterilize as best 
we can. It takes only one bacterium to start an epidemic. Sterilization has been met 
with much skepticism and much dislike. Not only does the present method of extreme 
heat cost a great deal, but it also forces the developers of space exploration to face 
new problems. Bacteria can survive high temperatures which can ruin the most intri- 
cate and complex parts of a space vessel, such as its circuit boards. So when 
designing landers and probes, scientists must be extra careful that their final product 
will survive the heat of sterilization. The early Ranger series, intended for exploring 
the moon, met with this difficulty and could not be made to function properly after 
sterilization. 
The Viking mission, however, is a testimony to our ability to sterilize spacecraft 
without creating malfunctions. It's true that Viking took a great deal of money, time, 
and more money, but the final product passed the test. Though it was proven that 
Viking was not totally sterile, it was a cornerstone in space sterilization. 
Recently, there has been much concern regarding the fact that the Galileo 
probe, though its fate is now uncertain, will be the first probe ever which will not be 
sterilized. Designed to enter into the atmosphere of Jupiter, the probe will simply take 
readings and measurements as it falls to its eventual death. It was thought that the 
Galileo probe need not be sterilized, for Jupiter was considered to be an environment 
where the chances of contamination are "nil." Most assumed that no terrestrial life 
could live on the planet, but is that an accurate assumption? 
BACKGROUND INFO ON THE MODEL 
Jupiter, to the best of our knowledge, is completely composed of gases. Like 
Earth, its temperature increases as one gets closer to the center, its core an inferno. 
There are various vertical layers in Jupiter's atmosphere, and particles can travel from 
one layer to another by two primary means. The first way is simply by gravity; the par- 
ticles are pulled to a lower layer by Jupiter's own gravitational force. Countering the 
effects of gravity on Jupiter are conditions such as winds, turbulence, and heat, all of 
which cause particles to rise to a higher level. This process of rising and falling is 
known as "mixing." 
The main argument against bacteria surviving on Jupiter is that it is believed 
that there will be little, if anything, for the microorganisms to eat. Without substantial 
30 
nutrients, bacteria cannot multiply and will eventually be pulled down by gravity to a 
layer whose temperature is too high and will cause combustion. If bacteria can get 
enough food to multiply and reproduce, then, even though some bacteria will perish in 
lower-layer infernos, others will survive and reproduce more, continuing the legacy of 
bacteria. If there is enough food, the bacteria will reach a point of equilibrium in their 
reproduction; this point is achieved when the number of bacteria being produced is 
equal to the number which are being destroyed, thus yielding a constant number of 
bacteria. 
Well, is there food for bacteria on Jupiter? Yes, there are substances known as 
"tholins" which have been proven to be a good carbon source for bacteria. Tholins are 
organic compounds which are produced by mixing gases, such as methane and 
ammonia, and then exposing this mixture to some form of energy. The energy trans- 
forms the simple ammonia-methane mixture into complex chains of molecules (amino 
acids) which bacteria can then live on. Jupiter has gases in its atmosphere which will 
mix, and, when exposed to energy such as lightning or sunlight, produce tholin, which 
the bacteria can then use as food. But will there be enough food to allow enough 
bacteria growth to overcome the loss of many bacteria in the gravitational pull? In 
other words, will the bacteria be able to reproduce faster than the rate at which they 
will be killed? 
Due to the varying temperatures of the Jovian atmosphere, bacteria growth is 
limited to a certain atmospheric region. This area is known as the habitable zone. 
Characteristically, it is bounded by temperatures ranging from 0 to 100 degrees Cel- 
sius, since those are the parameters within which water is in its liquid form, a necessity 
if bacteria are to grow. Bacteria can only grow while in the habitable zone, and 
therefore growth is limited by how much tholin enters this zone. The process of 
"mixing" plays a key role in the bacteria's survival. Wi.1 the bacteria, at the mercy of the 
mixing process, stay within the zone long enough to encounter tholin (another traveler 
dependent on the mixing process), eat it, and produce more bacteria? How much time 
do the bacteria have to find food, eat, and then double before they are swept away? If 
the mixing process does not allow the bacteria enough time to complete this cycle, 
bacteria will not be able to exist on Jupiter. However, if there is an adequate amount 
of time in which the bacteria can fulfill their survival obligations, then bacteria will more 
than likely thrive. 
THE MODEL ITSELF 
A computer model simulates Jupiter's conditions. It regards two things when 
testing to see if bacteria will survive: 1. altitude (are the bacteria in the habitable zone, 
how much has drifted out of the zone), 2. time (have certain bacteria been in the zone 
long enough or too long, at what time should they naturally be mixed out of the zone). 
Not only are these two dimensions applied to the bacteria, but to the tholins as well. 
(How much tholin is in the biozone, did it all get consumed by the bacteria, is there an 
excess, how much tholin has left the zone, how much has entered.) 
The simulation program suggested that bacteria would indeed exist and multi- 
ply within Jupiter's atmosphere, and that the point of equilibrium would be reached 
31 
. -  
approximately one year after the initial contamination occurred. Once bacteria enter 
Jupiter, there is no getting rid of them. Total colonization by the bacteria would be 
achieved. 
Two notable errors in the program's simulation are: 
1. The time step between each mixing occurrence was too large. It allowed too 
much time for the bacteria to eat and reproduce. 
2. It was assumed that the tholin which entered the habitable zone would be 
consumed if needed by the bacteria. No consideration was given to the fact that the 
tholin must come in contact with the bacteria for them to eat it. 
Regardless of these flaws in the initial simulation, bacteria would still, most 
likely, thrive in the Jovian atmosphere. The point of equilibrium may not be reached in 
the time given by the initial simulation, but the point would be reached. Also, the 
quantity of bacteria, which was phenomenally large, would be reduced, of course. 
CONCLUSIONS AND AFTERTHOUGHTS 
The Galileo probe, though at present its future is uncertain, would, if not steril- 
ized, represent a good chance of contaminating Jupiter. Most scientists opposed to 
sterilizing the probe argue that to order the probe sterilized at this point would be the 
death of the project, since sterilization would entail a reconstruction of the probe, and 
there are just not enough funds to accomplish this. These scientists, however, are 
ignoring a relatively simple and inexpensive alternative to the traditional heat steriliza- 
tion method. The main threat of contamination comes from Galileo's exterior surfaces: 
the shell of the probe and its parachute. The probe's innermost components would not 
represent a threat since the probe is sealed. In light of the fact that only the exterior of 
Galileo would have to be sterilized, heat would not have to be used as a method of 
sterilization. Instead, various gas mixtures could be sprayed entirely over the probe 
and its parachute, gases which would kill any and all bacteria. Though this method 
could fit in the Galileo budget, it is being overlooked. Why? Certainly the avoidance of 
contamination is worth the small amount of time and money that this alternative steril- 
ization would cost. Isn't it? 
Bacteria appear to have played a key role in our evolution. Jupiter, a planet 
which appears to be in a far more primitive state than ours, may be involved in its own 
evolution. Surely any terrestrial bacteria would jeopardize this evolution by either 
eating or destroying any domestic microorganisms, or by producing mutant bacteria 
and new breeds, interfering with the original destiny of Jovian evolution. And how 
would we know, many years after the contamination, if any life we then discover on 
Jupiter is its own, or simply our own unrecognizable mutant leftovers? We have a 
responsibility to make moral decisions when dealing with space exploration. Is that 
not one of the main aspects to space exploration in the first place, to learn about other 
worlds and hopefully other beings? The information that the Galileo probe would fur- 
nish is not enough to take such a risk. Contamination is too possible. 
32 


The possible contamination of Jupiter

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