The nearest place in the universe where extraterrestrial life could exist is Mars, and human beings are ready to try to colonize this next planet during the next decade. Before this happens, we must recognize that there is a very real possibility that the first human steps on the Martian surface will lead to a collision between Earth's life and the native biota of Mars.
If the red planet is sterile, the human presence would not create any moral or ethical dilemma in this front. But if life exists on Mars, human explorers can easily lead to the extinction of Martian life. As an astronomer who explores these questions in my book "Life on Mars: What to Know Before We Go", I answer that earthlings need to understand this scenario and discuss the possible results of colonizing our neighboring planet in advance. Maybe the missions that will take humans to Mars need a waiting period.
Where life could be
Life, scientists suggest, has some basic requirements. It could exist in any part of the universe that has liquid water, a source of heat and energy, and abundant amounts of some essential elements, such as carbon, hydrogen, oxygen, nitrogen and potassium.
Mars enabled, like at least two other places in our solar system. Both Europe, one of the great moons of Jupiter and Enceladus, one of the great Saturn's moons, seem to possess these prerequisites to house native biology.
I suggest that the way in which scientists planned exploratory missions to these two moons provides a valuable fund when considering how to exploit Mars without the risk of contamination.
Below its thick layers of shallow ice, both Europe and Enceladus have global oceans in which 4.5 billion years of primordial soup mix can allow life to develop and roots. NASA spacecraft have even imagined spectacular geysers that expel jets of water into the space of these underground oceans.
To find out if the moon is alive, planetary scientists are actively developing the Europa Clipper mission for the 2020 launch. They also hope to plan future missions that will be directed to Enceladus.
Take care not to contaminate
Since the beginning of the space age, scientists have taken seriously the threat of biological contamination from other worlds. Already in 1959, NASA held meetings to discuss the need to sterilize spacecraft that could be sent to other worlds. Since then, all planetary exploration missions have adhered to the standards of sterilization that balance their scientific goals with limitations of not damaging sensitive equipment, which could lead to failures in the mission. Today there is a NASA protocol for the protection of all bodies of the solar system, including Mars.
Since avoiding the biological contamination of Europe and Enceladus is an extremely well understood and priority requirement for all missions in the Jovian and Saturn environments, their moons continue to be untidy.
NASA's Galileo mission explored Jupiter and its moons from 1995 to 2003. Given the orbit of Galileo, there was the possibility that the spacecraft, once it was the rocket propeller and subjected to the whims of Jupiter's gravitational tugboats and Its many moons could hang up and pollute Europe.
Such a collision may not occur until many millions of years from now on. However, although the risk was small, it was also real. NASA paid close attention to the guidelines of the Committee of National Academies on planetary and lunar exploration, where serious national and international objections were observed about possible accidental removal of the Galileo spacecraft in Europe.
To completely eliminate this type of risk, on September 21, 2003, NASA used the last fuel in the spacecraft to send it submerged in the atmosphere of Jupiter. At a speed of 30 miles per second, Galileo vaporized in seconds.
Fourteen years later, NASA repeated this scenario of protection against the moon. Cassini's mission orbited and studied Saturn and its moons from 2004 to 2017. On September 15, 2017, when fuel went down, according to NASA's instructions, Cassini operators deliberately plunged the ship into the atmosphere of Saturn, where it disintegrated.
But what about Mars?
Mars is the objective of seven active missions, including two rovers, Opportunity and Curiosity. In addition, on November 26 NASA's InSight mission is scheduled to land on Mars, where it will perform measurements of the interior structure of Mars. Next, with planned launches of 2020, both the ESA ExoMars rover and NASA's 2020 Mars rover are designed to look for life tests on Mars.
The good news is that robotic robbers pose a bit of risk of contamination to Mars, since all spacecraft destined to land on Mars are subject to strict sterilization procedures prior to its launch. This was the case since NASA imposed "rigorous sterilization procedures" for the Viking Lander capsules in the seventies, as they would directly enter into contact with the Martian surface. These rovers have an extremely low number of microbial stirrups.
Any terrestrial biota that is able to deceive the rides on the outside of these rovers would have a very difficult time to survive the half-year journey from Earth to Mars. The vacuum of space combined with exposure to X-rays, ultraviolet light and cosmic rays would surely sterilize the exteriors of any ship sent to Mars.
Any bacteria that has stolen the rides within one of the rovers could reach Mars alive. But if one escaped, the thin Martian atmosphere would offer virtually no protection against high energy, sterilizing the radiation of space. Those bacteria would probably die immediately. Due to this harsh environment, life on Mars, if it exists at present, almost certainly must be hidden beneath the surface of the planet. Since no rover explored caves or dug deep holes, we still did not have the opportunity to come to the drill bit with possible Martian microbes.
Since Mars exploration has so far been limited to unmanned vehicles, the planet is likely to remain free of terrestrial contamination.
But when Earth sends astronauts to Mars, they will travel with vital support and energy supply systems, habitats, 3D printers, food and tools. None of these materials can be sterilized in the same way as the systems associated with the robotic spacecraft. Human settlers will produce waste, try to grow food and use machines to extract water from the soil and the atmosphere. Just living on Mars, human settlers will pollute Mars.
The clock can not be returned after the contamination
Space researchers have developed a careful approach to robotic exploration of Mars and a hands-on attitude towards Europe and Enceladus. Why, then, are we collectively willing to ignore the risk to Martian life of exploration and human colonization of the red planet?
The contamination of Mars is not an unforeseen consequence. A quarter century ago, a report from the National Research Council entitled "Mars Biological Pollution: Problems and Recommendations" stated that missions that carry humans to Mars will inevitably contaminate the planet.
I think it is essential that each attempt is made to obtain evidence of any past or present life on Mars well before future Mars missions that include humans. What we discovered could influence our collective decision or not send settlers there.
Although we ignore or do not care about the risks that human presence poses for Martian life, the question of bringing Martian life to Earth has serious social, legal and international implications that deserve the discussion before it is too late. What risks could Martian life have before our environment or our health? And any country or group has the right to risk contamination if Martian life forms can attack the DNA molecule and put all life on Earth at risk?
But public players: Mars 2117 project from NASA, United Arab Emirates and Private: SpaceX, Mars One, Blue Origin, already plan to transport settlers to build cities on Mars. And these missions will pollute Mars.
Some scientists believe that they have already discovered strong evidence of life on Mars, both the past and the present. If life already exists on Mars, then Mars, at least for now, belongs to the Martians. Mars is your planet and Martian life would be threatened by a human presence there.
Does humanity have an inalienable right to colonize Mars simply because we can soon do it? We have the technology to use robots to determine if Mars is inhabited. Does ethics demand that we use these tools to answer permanently whether Mars is inhabited or sterile before putting human footprints on the Martian surface?
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