The nearest place in the universe where extraterrestrial life can exist is Mars, and the people are ready to try to colonize this planetary neighbor in the next decade. Before that happens, we must realize that there is a very real possibility that the first human steps on the Mars surface will lead to a collision between Earthly and biota native to Mars.
If the red planet is sterile, a human presence would not create any moral or ethical dilemma on this front. But if life exists on Mars, human explorers can easily lead to the extinction of Martian life. As an astronomer exploring these issues in my book "Life on Mars: What To Know Before We Go", I say that we strawberries need to understand this scenario and debate the possible results of colonizing our nearby planet in advance. Perhaps missions that would carry people to Mars need a timeout.
Where life could be
Life, researchers suggest, have some basic requirements. There can be somewhere in the universe that has floating water, a source of heat and energy and large amounts of some essentials, such as coal, hydrogen, oxygen, nitrogen and potassium.
Mars qualifies as well as at least two other places in our solar system. Both Europe, one of Jupiter's great moons and Enceladus, one of Saturn's great moons, seems to have these conditions for host to domestic biology.
I suggest that scientists planning exploratory missions for these two moons provide a valuable background when considering how to explore Mars without risk of pollution.
Under their thick surface layers, both Europe and Enceladus's global oceans where 4.5 billion years of churning of primordial soup may have allowed life to develop and root. NASA spacecraft has even depicted spectacular geysers that pour out water plants into space from these underground oceans.
To find out if either moon has life, planetary scientists actively develop the Europe Clipper mission for a 2020 launch. They also hope to plan future missions that will target Enceladus.
Take care not to contaminate
Since space age began, scientists have taken the threat of biological pollution of other worlds seriously. As early as 1959, NASA held meetings to discuss the necessity of sterilizing spacecraft that can be sent to other worlds. Since then, all planetary exploration missions have followed sterilization standards that balance their scientific goals with restrictions not to impair sensitive equipment, potentially leading to missions for mission purposes. Today, there are NASA protocols for the protection of all solar system bodies, including Mars.
Because avoiding the biological contamination of Europe and Enceladus is an extremely well-considered high priority for all missions in the Christian and Saturnian environments, their moons remain untouched.
NASA's Galileo mission explored Jupiter and its moons from 1995 to 2003. Given the path of Galileo, it was possible that the spacecraft, once taken out of rocket drift and subject to the lusts of gravity forces from Jupiter and its many moons, could ever crash into and thereby polluting Europe.
Such a collision can not happen until many millions of years from now on. But even though the risk was small, it was also true. NASA paid particular attention to guidance from the National Academies Committee on Planetary and Lunar Exploration, which noted serious national and international objections to the possible unintentional disposal of Galileo spacecraft in Europe.
To completely eliminate such a risk, September 21, 2003, NASA used the last bit of fuel on spacecraft to send it to Jupiter's atmosphere. At a speed of 30 miles per second, Galileo evaporates within seconds.
Fourteen years later, NASA repeated this protection against the moon scenario. The Cassini mission circled and studied Saturn and its moons from 2004 to 2017. On September 15, 2017, when the fuel had gone low, on instructions from NASA Cassini's operators, the spacecraft intentionally ran into Saturn's atmosphere, where it was destroyed.
But what about Mars?
Mars is the goal of seven active missions, including two robbers, opportunity and curiosity. In addition, on November 26, NASA's InSight mission is scheduled to land on Mars, where it will make measurements of Mars's interior structure. Then, with planned 2020 launches, both ESA's ExoMars rover and NASA's Mars 2020 rover are meant to search for evidence of life on Mars.
The good news is that robot robots represent a small risk of contamination to Mars, as all spacecraft destined to land on Mars is subject to rigorous sterilization procedures prior to launch. This has been the case since NASA introduced "rigorous sterilization procedures" for the Viking Lander capsules in the 1970s, as they would directly contact the Mars surface. These robbers probably have an extremely low number of microbial stewards.
Any terrestrial biota capable of hitching on the outside of these robbers would have a very difficult time to survive half-year trip from Earth to March. The vacuum space in combination with exposure to hard X-rays, ultraviolet light and cosmic rays would almost sterilize the outside of every spacecraft sent to Mars.
Any bacteria that sneaked rides inside one of the robbers can come to Mars alive. But if someone fled, the thin atmosphere would offer almost no protection against high energy, sterilizing radiation from space. Those bacteria are likely to be killed immediately. Because of this harsh environment, life on Mars, if it exists, will almost certainly hide under the surface of the planet. Since no robber has examined caves or dug deep holes, we have not yet had the opportunity to come and drill with some possible martian microbes.
Given that the exploration of Mars so far has been restricted to unmanned vehicles, the planet is likely to be free from terrestrial pollution.
But when the Earth sends astronauts to Mars, they will travel with life support and energy supply systems, habitats, 3D printers, food and tools. None of these materials can be sterilized in the same way as systems associated with robotic spacecraft. Humanists will produce waste, try to grow food and use machines to extract water from the ground and the atmosphere. Just by living on Mars, human colonists will contaminate Mars.
Can not reset the clock after contamination
Space scientists have developed a cautious approach to Mars's robotic exploration and a hands-off attitude towards Europe and Enceladus. Why are we then collectively willing to overlook the risk of the Martian life of human exploration and colonization of the red planet?
Polluting Mars is not an unforeseen consequence. A quarter ago, a National Research Council entitled "Biological Pollution of Mars: Questions and Recommendations" claimed that missions carrying people to Mars will inevitably pollute the earth.
I think it is critical that any attempt is made to get evidence of any past or present life on Mars in good time before future missions to Mars that include people. What we discover may affect our collective decision as to whether we will transfer colonists at all.
Even if we ignore or do not care about the risks that a human presence would imply for martian life, the question of bringing martian life back to earth has serious societal, legal and international consequences that deserve discussion before it's too late. What risks can Martian life be for our environment or our health? And does any country or group have the right to risk contamination if the Mars lifestyles could attack the DNA molecule and thus risk the entire life of the earth?
But players both public – NASA, United Arab Emirates March 2117 projects – and private – SpaceX, Mars One, Blue Origin – are already planning to transport colonists to build cities on Mars. And these missions will pollute Mars.
Some researchers believe that they have already discovered strong evidence of life on Mars, both earlier and present. If life already exists on Mars, Mars currently belongs at least to the Martians. Mars is their planet, and Marsh life would be threatened by a human presence there.
Does humanity have an unforgivable right to colonize Mars simply because we will soon be able to do it? We have the technique of using robots to determine if Mars is inhabited. Please note that we use these tools to definitely answer if Mars is inhabited or sterile before we place human footprints on the Mars surface?
David Weintraub, Professor of Astronomy, Vanderbilt University
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