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Once people get there, Mars will be contaminated by earthly life. Credit: NASA / Pat Rawlings, SAIC, CC BY
The closest place to the universe where extraterrestrial life could exist is Mars, and humans are on the brink of attempting to colonize this planetary neighbor over the next decade. Before this happens, we must recognize that it is very likely that the first steps of man on the Martian surface will cause a collision between life on earth and biota originating in 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 could easily lead to the extinction of Martian life. As an astronomer who explores these issues in my book "Life on Mars: What to Know Before You Go," I argue that we, Earthlings, must understand this scenario and debate the possible consequences of colonizing our planet. neighboring planet. Maybe the missions that transport humans to Mars need a waiting period.
Where life could be
Scientists suggest that life has basic requirements. There can be anywhere in the universe where there is liquid water, a source of heat and energy, and a large amount of some essential elements, such as the carbon, hydrogen, oxygen, nitrogen and potassium.
Mars qualifies, as do at least two other places in our solar system. Europa, one of the great moons of Jupiter, and Enceladus, one of Saturn's great moons, seem to possess these prerequisites for harboring aboriginal biology.
I suggest that the way scientists have planned the exploratory missions in these two moons is a valuable background for exploring how to explore Mars without the risk of contamination.
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Cassini photographed this false-color image showing jets emerging from the Enceladus Southern Hemisphere on November 27, 2005. Source: NASA / JPL / Institute of Space Science, CC BY
Beneath their thick layers of surface ice, Europa and Enceladus both have a global ocean in which 4.5 billion years of churning of the primordial soup may have allowed life to grow and develop. 'root. NASA spacecraft have even taken pictures of spectacular geysers ejecting plumes of water in space from these underground oceans.
To determine whether one or the other of the two moons has life, planetary scientists are actively developing the Europa Clipper mission for a launch to 2020. They also hope to plan future missions that will target Enceladus.
Taking care not to contaminate
Since the beginning of the space age, scientists have taken seriously the threat of biological contamination from other worlds. As early as 1959, NASA held meetings to discuss the need to sterilize spacecraft that can be sent to other worlds. Since then, all planetary exploration missions have adhered to sterilization standards that balance their scientific goals with limitations designed not to damage sensitive material, which could potentially lead to mission failures. Today there are NASA protocols for the protection of all bodies in the solar system, including Mars.
As avoiding the biological contamination of Europa and Enceladus is an extremely well understood and high priority requirement of all missions in the Jovian and Saturnian environments, their moons are not contaminated.
NASA's Galileo mission explored Jupiter and its moons from 1995 to 2003. Because of its orbit, it was possible that the spacecraft, once released from the rocket booster and subjected to the whims of the gravitational tugs of Jupiter and his many moons, may one day crush against contaminate Europa.
Such a collision might not occur for many millions of years. Nevertheless, even though the risk was low, it was also real. NASA paid particular attention to the advice of the National Academy's Planetary and Lunar Exploration Committee, which noted serious national and international objections to the possible accidental disposal of the Galileo spacecraft on Europa.
To completely eliminate this type of risk, on September 21, 2003, NASA used the last amount of fuel from the spacecraft to send it to the atmosphere of Jupiter. At a speed of 30 miles per second, Galileo is vaporized in seconds.
Fourteen years later, NASA repeated this "protect the moon" scenario. The Cassini mission orbited and studied Saturn and its moons from 2004 to 2017. On September 15, 2017, when fuel was down, on instructions from NASA, Cassini operators deliberately plunged the satellite into the atmosphere of Saturn, where he disintegrated.
But what about Mars?
Mars is the target of seven active missions, including two rovers, Opportunity and Curiosity. In addition, on November 26, NASA's InSight mission is expected to land on Mars, where it will conduct measurements of Mars' inner structure. Next, with launches planned for 2020, ESA's ExoMars rover and NASA's March 2020 rover are designed to look for evidence of life on Mars.
The good news is that robotic robots pose little risk of contamination to Mars because all spacecraft designed to land on Mars are subjected to strict sterilization procedures before launch. This has been the case since NASA imposed "rigorous sterilization procedures" on Viking Lander capsules in the 1970s, as they would come into direct contact with the Martian surface. These rovers probably have an extremely low number of microbial stowaways.
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The Curiosity rover has been tested on Earth before launch, under clean conditions, to prevent stowaways. Credit: NASA / JPL-Caltech, CC BY
Any terrestrial biota that manages to snatch from the outside of these vehicles would have a hard time surviving the journey of half the Earth between Mars and Earth. The vacuum of space combined with exposure to rigorous X-rays, ultraviolet light and cosmic rays would almost certainly sterilize the outside of any spacecraft sent to Mars.
Any bacteria that would infiltrate one of the rovers could arrive on Mars alive. But if it escaped, the thin Martian atmosphere would offer virtually no protection against high energy, which would sterilize the radiation of space. These bacteria would probably be killed immediately. Because of this hostile environment, life on Mars, if it exists now, must almost certainly hide beneath the surface of the planet. As no mobile vehicle has explored caves or dug deep holes, we have not yet had the opportunity to face face to face with possible Martian microbes.
Since Mars exploration has so far been limited to unmanned vehicles, the planet is probably free of terrestrial contamination.
But when 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. Human settlers will produce waste, try to produce food and use machines to extract water from the soil and the atmosphere. By simply living on Mars, human settlers will contaminate Mars.
Can not go back after contamination
Space researchers have developed a cautious approach to robotic exploration of Mars and a passive attitude towards Europa and Enceladus. Why, then, are we collectively disposed to neglect the risk that human life and the colonization of the red planet represent for Martian life?
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Scientists speculated that narrow, dark trails were formed by salty liquid water – necessary for life – flowing along the walls of a crater on Mars. Credit: NASA / JPL-Caltech / Univ. from Arizona, CC BY
The contamination of Mars is not an unintended consequence. A quarter of a century ago, a report from the National Research Council entitled "Biological Contamination of Mars: Issues and Recommendations" stated that missions carrying humans to Mars would inevitably contaminate the planet.
I think it is essential that everything be done to obtain evidence of past or present life on Mars well before future missions on Mars including human beings. What we discover could influence our collective decision to send settlers.
Even if we ignore or do not care about the risks that a human presence could pose to Martian life, the issue of bringing Martian life back to Earth has serious social, legal and international implications that deserve to be addressed. to be discussed before it is too late. What risks could Martian life pose to our environment or our health? And does a country or a group have the right to risk contamination by return if these Martian life forms could attack the DNA molecule and thus endanger all life on Earth?
But public actors – NASA, UAE Project Mars 2117 – and private – SpaceX, Mars One, Blue Origin – are already planning to transport settlers to build cities on Mars. And these missions will contaminate Mars.
Some scientists believe they have already uncovered solid evidence of life on Mars, past and present. If life already exists on Mars, then Mars, at least for the moment, belongs to the Martians. Mars is their planet and Martian life would be threatened by a human presence.
Does humanity have the inalienable right to colonize Mars simply because we will soon be able to do it? We have the technology to use robots to determine if Mars is inhabited. Does ethics require that we use these tools to definitively determine if Mars is inhabited or sterile before placing footprints on the Martian surface?
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