by Laura Woodmansee
All NASA spacecraft must be cleaned to prevent forward contamination, the corruption of alien life by Earth life. It turns out that this is a straightforward process. Technicians clean the spacecraft and then prove that it is clean by taking samples from the spacecraft. The samples are then studied to find out the number and type of spores, cells, and microorganisms left on the spacecraft.
NASA must use methods other than dry heat for sterilization of today's electronics and other materials. These products make the spacecraft lighter and smaller. This allows for the craft to be launched on today's smaller, cheaper launch vehicles. But these materials can't take the heat. Karen Buxbaum explains, "We have spacecraft materials that are not designed to withstand that type of dry heat environment. So our electronics are incompatible with heating, certain adhesives that we use, some of the optical surfaces, and synthetic materials that we use for spacecraft are ill suited for that type of approach."
Roger Kern agrees, "We can't imagine doing that to a modern spacecraft." This is why research and development efforts are looking into better ways of sterilizing spacecraft parts. Industry sterilization isn't enough. Roger Kern puts it this way, "The science of how to remove bacteria from surfaces is not something that a lot of people have been interested in to the level that we're interested in it. We have to obsess on it."
"What we're doing right now, part of our R&D is to develop and certify sterilization techniques which we can use to supplement the dry heat sterilization process for future missions," says Buxbaum.
One of the cleaning methods that engineers are studying is by using an ultrasonic toothbrush. "One way to look at it is to ask what industry out there would have been concerned with bacteria contaminating surfaces," Kern says. "And of course the dental sciences have been looking at that for a long time."
Preventing forward contamination is easy compared to the risks and difficulties in preventing backward contamination, the contamination of Earth's environment. Karen Buxbaum says this is because, "Back contamination has to do with every element of a project that could add risk to the issues of release of extraterrestrial material into the Earth's biosphere … our most demanding challenge in the next decade [is] containment [of samples of alien life]." In other words, it's hard to keep samples of alien life from escaping its container once it is brought to Earth. A mistake could endanger many Earth organisms, including people.
Perhaps the danger to Earth isn't as great as some speculate. The Earth is bombarded by rocks and dust from space every day. John Rummel says, "We get hit by stuff from Mars all the time. My favorite number is 40 kilograms a year, although some of the more enthusiastic people will say tons. It's a big planet. We get hit by one particle per square meter per day. It adds up."
The Mars rock, which was made famous in 1996, may of may not contain fossils of tiny Martians. But, scientists are positive that the rock did come from Mars, because trapped gas pockets exactly match the Martian atmosphere from Viking experiments. It is possible that a rock may arrive with life from Mars. There is no way to tell now if that life would be a danger to us. This is one reason why finding life on Mars is important to scientists. It may be that Mars and Earth exchange rocks, and life all the time. We may have cousins on Mars, and elsewhere.
The largest planet in our solar system is Jupiter. It has many moons, but perhaps the most fascinating is Europa. It has become the most important place in the solar system to scientists looking for life beyond Earth.
Europa is slightly smaller than our Moon. Data from the Voyager and Galileo spacecraft have led scientists to believe that Europa is covered with a thick crust of water ice floating on an ocean of liquid water. Cracks in the crust show that the moon is under constant gravitational stress from the huge planet Jupiter.
Many scientists believe that there may be life in Europa's oceans. But, the moon is bathed in radiation that would kill most Earth life. Life could survive such in the oceans beneath the ice because the thick ice acts as a radiation shield, protecting life in the oceans below.
In June 2000, the Space Studies Board, part of the National Academies, released a report called Preventing the Forward Contamination of Europa. The study concluded that Europa is the most likely place to find life in our solar system and that it must be protected from Earth organisms. It also found that NASA's current planetary protection methods are sufficient to send an orbiting spacecraft to Europa without endangering life in its oceans.
The study noted that microorganisms were able to survive for more than five years in deep space onboard the Long Duration Exposure Facility. So, scientists can't rely on the space journey alone to kill all the microbes.
In permafrost regions of the Earth, extremophiles have been found to survive for millions of years frozen in suspended animation. If a spacecraft were to crash on Europa, it's possible that microbes could survive for centuries until the craft made its way through the ice and reached Europa's ocean.
The radiation field surrounding Jupiter and Europa may help kill off any microorganisms that make it past NASA's planetary protection procedures. But, any organisms that survive and land on the planet could eventually get through the ice and thrive. And spread in the subsurface oceans. Therefore, NASA has made it a policy to be extremely careful about life on spacecraft going to Europa or anywhere in the area of Jupiter, allowing only a one in 10,000 chance of contamination.
Protecting Mars and Europa from Earth life may seem unimportant in our daily lives. But, think about it for a minute. In a century or two we may need these other bodies. Their resources, including possibly its native life forms, if any, may be necessary to understanding how humans can survive on other planets. What do they know about living in a high radiation zone that we need to learn?
However, what if there is life on Mars and WE put it there? Not on purpose, but because we just didn't know better. What we know today indicates that most Earth microbes will not survive on Mars, but it is possible that some could survive and even thrive. We were surprised to find microbes that live in the cores of nuclear reactors. We may be surprised again by the diversity and adaptability of life.
Astrobiology is a new field. If future experiments on Mars do find life, we must be able to tell if it originally came from Earth, or if it is native to Mars. That's why planetary protection is important.
Protecting life on other planets is not a new field. It is one that has advanced as our technology has advanced. Now that the new science of astrobiology has expanded the range under which life can survive, planetary protection is tougher to do and even more important.
Space exploration is a constant trade off. Experts balance the cost of exploration, the potential benefits to humankind, and the risks to both human and alien life. Planetary protection is one of these factors that increases costs, but minimizes risk. Both for us, and our alien cousins.
The stuff of life is available in the universe. The question is can we find it without destroying it first.
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