Mars One / Bryan Versteeg
The closest place in the universe where extraterrestrial life could exist is Mars, and humans are ready to try to colonize this planetary neighbor in the next decade. Now, before such a thing happens, we must know that there is a very real possibility that the first human steps on the Martian surface will produce a collision between terrestrial life and the native biota of Mars.
If the red planet is sterile, human presence would not pose any moral or ethical dilemma in this area. But if there is life on Mars there would also be the possibility that human explorers easily cause the extinction of any form of activity. As an astronomer who explores these issues in my book Life on Mars: what to know before going, I argue that we Earthlings must know this possible scenario and discuss in advance the potential consequences of colonizing the neighboring planet. Maybe the missions that would take humans to Mars require a waiting time.
Where could there be life
Life, the scientists suggest, has some basic requirements. It could exist anywhere in the universe where there is liquid water, a source of heat and energy and abundant quantities of a few essential elements, such as carbon, hydrogen, oxygen, nitrogen and potassium.
Mars fulfills these requirements, as do at least two other places in our solar system: both Europe, one of the great moons of Jupiter, and Enceladus, one of Saturn's great moons, seem to possess these prerequisites for harboring native biology. .
I suggest that the way scientists planned the exploratory missions to these two moons provides a valuable background when considering how to explore Mars without risk of contaminating it.
Under the thick layers of ice on the surface, both Europe and Enceladus harbor oceans in which it is possible that, after four and a half billion years of stirring up the "primordial soup", life has developed and taken root. The spacecraft of NASA have even captured spectacular images of geysers that expel water columns from these underground oceans into space.
To find out if there is life in either of these two moons, planetary scientists are actively developing the "Europa Clipper" mission to launch in the 2020-2030 decade. They hope to be able to also plan future missions to Enceladus.
Be careful not to contaminate
Since the beginning of the space age, scientists have taken seriously the threat of human biological contamination: in 1959 NASA already organized meetings to discuss the need to sterilize spacecraft that could be sent to other worlds. Since then, all planetary exploration missions have been subjected to sterilization standards to balance their scientific objectives with the limitations of not damaging sensitive equipment, which would entail the potential risk of failing the mission. Currently there are protocols of NASA for the protection of all bodies of the solar system, including Mars.
Precisely because the avoidance of the biological contamination of Europe and Enceladus is a high priority, and extremely well understood, requirement of all missions sent to the environments of Jupiter and Saturn, the moons of these two planets remain unchanged.
NASA's "Galileo" mission explored Jupiter and its moons from 1995 to 2003. Given the "Galileo" orbit, there was a possibility that the spacecraft, once out of the rocket engine and subject to cravings of the gravitational pulls of Jupiter and its many moons, could one day collide with Europe and contaminate it.
Such a collision may not occur for many millions of years. However, although the risk was not very high, it was real. NASA paid great attention to the guidelines of the Committee on Planetary and Lunar Exploration of the National Academies, which indicated serious national and international objections to a possible accidental spillage of the spacecraft "Galileo" on the moon Europa.
In order to completely eliminate such a risk, on September 21, 2003, NASA used the last small remaining fuel left in the spacecraft to launch it into Jupiter's atmosphere. At a speed of more than forty-eight kilometers per second, the "Galileo" evaporated in a matter of seconds.
The Cassini mission ended with the spacecraft burning in Saturn's atmosphere.
Fourteen years later, NASA repeated this scenario of protection: the mission "Cassini" orbited and studied Saturn and its moons from 2004 to 2017, and September 15 of that last year, when there was little fuel remaining and following the instructions From NASA, the operators of the "Cassini" deliberately launched the spacecraft into Saturn's atmosphere, where it disintegrated.
But what about Mars?
Mars is the target of seven active missions, among which are two rovers, the "Opportunity" and the "Curiosity". Also, this coming November 26, the NASA "InSight" mission is scheduled to land on Mars, where it will make measurements of the interior structure of the red planet. Then, with the launches planned for 2020, both the ESA's "ExoMars" scout vehicle and NASA's "Mars 2020" are destined to seek life tests.
The Curiosity was tested in clean conditions on Earth before its launch to prevent contaminants.
NASA / JPL-Caltech, CC BY
The good news is that these robotic rovers pose little risk of contamination, as all the spacecraft destined to land on this planet are subject to strict sterilization procedures before launch. This has been the case since NASA imposed, in the decade of the seventies of the last century, "rigorous sterilization procedures" for the "Viking" landing capsules, which came into direct contact with the Martian surface.
Thus, it is likely that the number of microbial stowaways carried by these scout vehicles is negligible. Any terrestrial biota that resisted the procedures and finally managed to travel outside of them would have very difficult to survive the half-year trip from Earth to Mars, since the vacuum of space together with the exposure to implacable X-rays, ultraviolet light and cosmic rays would almost certainly sterilize the exteriors of any spacecraft sent to the red planet.
Any bacteria that sneaks into one of the rovers could reach Mars alive, but if, once there, it left the ship, the fine Martian atmosphere would offer virtually no protection against high-energy, sterilizing radiation. coming from space, that would strike her instantly.
Because of this arduous environment, life on Mars, if it exists, is almost certain to be hidden beneath the surface, but since no spacecraft has explored caves or excavated deep holes, we have not had Still the opportunity to meet with any possible Martian microbe.
Given that the exploration of Mars has been limited to unmanned vehicles so far, it is likely that the planet remains 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 the systems of robotic spacecraft. Human settlers will produce waste, try to grow food and use machines to extract water. By the simple fact of living on Mars, human settlers will pollute the planet.
There is no going back after pollution
Space researchers have developed a thorough approach to the robotic exploration of Mars and a non-intervention attitude towards the Europa and Enceladus moons. So, why are we collectively willing to overlook the risk to human life of the exploration and human colonization of the red planet for Martian life?
The contamination of Mars is not an unforeseen consequence. A quarter of a century ago, a report by the US National Research Council entitled "Biological contamination of Mars: issues and recommendations" stated that missions that carry humans to Mars will inevitably contaminate the planet.
I believe it is crucial that every effort be made to obtain evidence of any past or present life on Mars long before future missions that include human presence. What we discover could influence our collective decision about sending settlers or not.
Even if we ignore or do not care about the risks that human presence would entail for Martian life, the question of bringing that life back to Earth also has serious social, legal and international implications that deserve to be discussed before it is too late: What risks could Martian life pose to our environment or our health? Is there any country or group that has the right to risk a "counter-contamination" if those Martian life forms could attack the DNA molecule and, with it, put at risk all forms of life that are on Earth?
But there are already public actors – NASA, the "Mars 2117" Project of the United Arab Emirates – and private actors – "SpaceX", "Mars One", "Blue Origin" – who plan to transport settlers to build cities on Mars. And these missions are going to pollute the planet.
Scientists hold the hypothesis that narrow, dark veins were formed by salty liquid water – necessary for life – that flows through the walls of a crater on Mars.
NASA / JPL-Caltech / Univ. of Arizona, CC BY
There are scientists who believe they have already discovered conclusive evidence of the existence of life on Mars, both past and present. If life already exists on Mars, then, Mars, at least for the moment, belongs to the Martians: it is your planet, and Martian life would be threatened by human presence.
Does humanity have the inalienable right to colonize Mars simply because we will soon be able to do so? We have the technology to use robots that can determine if Mars is inhabited. Does ethics require that we use these tools to obtain a definitive answer to the question of whether Mars is inhabited or is a sterile planet before putting a human foot on its surface?
David Weintraub, Professor of Astronomy, Vanderbilt University
This article was originally published in The Conversation. You can find it in the following link.