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For the first time in human exploration of Mars, the presence of a stable underground body of salt water (brackish) was strongly suggested by the data returned by the orbiter Mars Express from the European Space Agency. With the help of measurements taken by the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument, a team of Italian researchers announced this week the (likely) first discovery of a body of 39, stable liquid water on Mars. But with this discovery comes a host of questions regarding the future exploration of the red planet.
A mass of stable liquid water on Mars:
C is the word "stable" which is the historical and important element here
Before this week, the l & # 39; Liquid water on the surface of Mars had only been observed for very short periods. Brackish water droplets were observed briefly on NASA's Phoenix Polar Lander and orbital terrain images revealed new water-carved surface features that quickly disappeared.
Nevertheless, the presence of liquid water under the Martian polar ice caps has long been assumed. In fact, it was first suggested as "possible" more than 30 years ago, but conclusive data to prove or disprove the hypothesis remained elusive.
Mars Express in orbit of Mars. (Source: ESA)
Access to the Mars Express satellite of the European Space Agency (ESA), present on Mars since December 25, 2003.
Since then, he has been conscientiously studying the Martian terrain, including its mysteries underground, with Mars 'advanced radar for the underground and ionospheric sounding, or MARSIS, instrument – in particular, a region under Mars' Planum Austral (southern polar region) known as polar south polar deposits.
MARSIS Returned evidence of a persistent liquid The water deposit in this area was carried out during a terrestrial period of three and a half years between May 2012 and December 2015, during which MARSIS has carried out 29 different radar sweeps on a flat surface 200 km wide from Planum. Australe
The radar waves sent by MARSIS penetrated the upper layers of the Martian terrain, extending a few kilometers below the surface. These waves were then reflected back to MARSIS when they encountered various rocks, sediments and, in this case, liquid water
The MARSIS discoveries are reported by Dr. R. Orosie et al. . in the article "Radar evidence of subglacial liquid water on Mars" and was published in the journal Science can be read here.
(A) Shaded relief map of Planum Austral, Mars, south of 75 ° S latitude. The black square delineates the study area. (B) Mosaic produced using infrared observations by the Thermal Emission Imaging System (THEMIS), corresponding to the black square at (A). The red line marks the ground trace of the Mars Express 10.737 orbit. The area consists mainly of flat plains, with the exception of a few large asymmetrical polar escarpments near the lower right of (B). (Credit: R. Orosei and others Science 2018)
Specific discovery was made by measuring what is known as dielectric permittivity (or the strength of reflected radio waves) and via routine observations (c & # 39; ie stable) a reflective water deposit of 20 km wide (12 miles wide) and 1.5 km (0.9 mile) deep over an observation period of 3 , 5 years old
For this finding, the dielectric permittivity provides the information needed to understand that it's about liquid water In fact, other possible explanations of the yields high permittivity were explored but ultimately rejected on the basis of solid evidence.
In addition, the extremely strong evidence in the MARSIS. In fact, the stable liquid water also indicates that this deposit is extremely salty because the temperatures in the region are understood to be -68 ° C (-90 ° F), well below the freezing point of the temperature. Fresh water. [19659004] Therefore, the water deposit should be salty, because the more salty the water, the lower the freezing point.
On Mars, NASA's Phoenix Polar Lander found calcium, magnesium and sodium perchlorate The Curiosity rover of the US space agency operating in the equatorial region of Mars also found salt there perchlorate
It follows that these elements are also present in abundant quantities in the Austral Planum. And in fact, the presence of these salts would reduce the freezing point of any water present at -74 ° C (-110 ° F) – more than 6 ° C (20 ° F) colder than the temperature at the time of day. place of discovery However, if the liquid water highlighted by MARSIS is in the form of mud (salt water mixed with soils – for example, mud) or if it is purer, a salty pond resting on soils surface, will require follow-up. In addition, while MARSIS is limited in that it can detect in terms of the size of the liquid groundwater deposits (it can not detect very small water levels) – it is n & # 39; There is no evidence in the returned data that would lead in other words, although we still have a lot to learn about the March water cycle (hydrological cycle), this discovery shows the possibility that other stable (persistent) saltwater deposits exist just below the surface of Mars.
Color coded map o f radar reflections from MARSSI. The large blue area bounded in black corresponds to the main clear area. The value at each point is the median of all radar fingerprints crossing that point. (Credit: R. Orosei and others Science 2018)
And this could have important implications for future human missions to Mars as well as ongoing research to find out if Mars is currently harboring life.
The water is a huge part of any prospect of Martian colonization and human exploration, and the possibility of already having liquid water on the red planet and putting it at disposal (after desalinization) would be a boon for such human initiatives, especially since all projects are currently on the table the human exploration plans of Mars rely heavily on the almost complete recycling of the planet. 39 water, regardless of its form or origin.
This type of water recycling is already used aboard the International Space Station, where urine is converted into clean drinking water.
More so, this discovery is enticing in that a stable saltwater body is precisely where life has developed and been nurtured on Earth.
rs is quite different – and not the least in its radiation environment – from the Earth, the building blocks of life were found by Curiosity in Mount Sharp in areas that were flowing with rain. liquid water.
This graph shows comparisons between the amount of organic chemical chlorobenzene detected in the "Cumberland" rock sample by NASA's Mars Curiosity rover over time. (Credit: NASA / JPL-Caltech)
And here on Earth, scientists have found simple organisms that live in incredibly salty water (much saltier than the terrestrial oceans) that exists in liquid form at temperatures up to -50 ° C (-58 ° F) – such as the Don Juan Pond, a hypersaline lake in Antarctica .
Therefore, if life developed on Mars billions of years ago in the presence of liquid water, it is possible that despite the radiation environment of Mars current that life could still exist on the red planet in a pool / saltwater deposit like the one highlighted in the MARSIS data
If (and it's a big "if") the life was to be discovered in a He would raise ethical and biological issues of interest to human exploration and colonization of our nearest second planetary neighbor.
One of the principles of interplanetary exploration is to prevent contamination of another world with microbes and bacteria
International Treaties currently set permissible levels of microbial contamination on robotic explorers sent to Mars – and these standards of cleanliness are different depending on where the robot must land on Mars. the wetter areas that have a greater chance of sustaining the current life on Mars have stricter standards. And to date, only NASA's Viking landing gear has reached these higher standards.
But we can decontaminate a robot. We can not decontaminate a human because we need the host of microbes and bacteria that live on and in us to survive – microbes and bacteria that could potentially invade and destroy native Martian life.
So if we were to follow the water "And find conclusive evidence that life – indigenous Martian life – exists, what are the implications for future explorations and human colonization initiatives already underway? [19659004] On Earth, where there is water, there is life.If this is true on Mars, then any human presence on the red planet could devastate the life that already exists just on the simple fact that humans should bring microbes and bacteria with us to Mars.
And if we were to definitively prove that there is a life on Mars before sending humans to the planet, would we then a moral and ethical obligation to protect this life – to let it flourish without potentially eradicating it by Earth microbes and bacteria – could greatly infect an ecosystem of Mars, no matter how primitive, as soon as it is over. man would put foot on the pl red anete?
NASA's March 2020 robot will specifically and directly look for signs of life on Mars. (Credit: NASA / JPL-Caltech)
In other words, if we find life on Mars, would we have the ethical and moral obligation to never set foot on the planet and to to let this life follow its natural course? and / or the continuous robotic presence?
Human history is an exploration and discovery – to want to know what is beyond the horizon. As European explorers crossed the oceans, they brought with them microbes and bacteria that the indigenous life of the Americas did not have biological immunity. And this indigenous life was greatly – and negatively – affected by this interaction.
At first, it was an accident. But with this knowledge, and if we find life on Mars, what should we be of the colonization of the red planet?
Should we stop and guess our desire to live in another world? Would we have equal value on the native Martian life – as simple as ours?
The artist's design of a future plan to terraform Mars. (Credit: SpaceX)
Or Would We Decide That It Was Correct To Contaminate (And Potentially Disappear) Any Native Martian Life Because Of The Safety Of Survival That A Dual Planetary Existence Would Provide To l & # 39; humanity?
Examples where this last decision (in these cases, the multi-continent dwelling) was taken.
More so, if we find life on Mars in or around saltwater deposits as indicated by the MARSIS data is present, we would need to make sure that it does not occur. is not dangerous or deadly to humans before sending dozens or hundreds of people on the planet.
But just as important: and what if we do not find conclusive evidence about current life on Mars? of Mars (something that seems less and less likely but that is no less a possibility) – before sending humans?
Rendering of the artist of a future colony of Mars established by SpaceX. (Credit: SpaceX)
In other words, what happens if the possibility of the present life exists but is not proven at the moment when humans arrive there? With growing evidence of the past and present habitability of Mars, should not we take every possible precaution to protect all life there even though we have not found it by the time we get there?
After the meticulous contamination of Mars with our robotic explorers, this type of contamination would be inevitable as soon as humans reached the red planet.
Currently, there are no answers to these questions. And these answers will certainly not be easy to obtain.
But these are necessary questions for a conversation that must take place now that convincing evidence of a stable saltwater deposit has been found – especially given SpaceX's plans to send the first wave of human settlers to Mars in a decade (a mission that, apart from our collective response to the above issues, will be the most significant achievement in the history of humanity).
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