Armando Azúa-Bustos is an astrobiologist collaborating with GAS in the LAREX (Low-cost AeRobiology EXpedition) campaign, devoted to characterizing the aerial transport of microbial organisms in the Atacama Desert, Chile. Atacama is one of the most Martian-like environments that can be found on Earth, and this study is aimed to extract conclusions that can be applied to the exploration of Mars, regarding the search for traces of life by the upcoming missions, and in particular to the operations to be carried out with HABIT instrument.
Azúa-Bustos is an expert in life in extreme environments, so we have taken advantage of the occasion to talk with him about some interesting aspects of the ongoing campaign, its implications for Mars research and some other bigger questions.
Armando was educated as an agronomical engineer, to specialize afterwards in molecular genetics and microbiology through his PhD, becoming eventually an astrobiologist currently working as Research Scientist at the Spanish Center of Astrobiology (CAB).
As he explains when asked why he shifted to astrobiology from his educational background, it was a “practical” matter: having got in touch with some NASA’s researchers as collaborator, he found a perfect chance to work in field in which he could apply his knowledge while satisfying his longstanding interest in space science. It happened, he tells “when astrobiology was acquiring its current strength, in the early 2000’s, and its foundations were being established in NASA”. The great questions raised within the discipline, such as the understanding of the origins of life or the possibility of finding life in other places of the universe were an irresistible lure for him.
Obviously, he thinks life is widespread throughout the universe as a mere “statistical matter. Only in our galaxy, he clears out, they could be one hundred billion potentially inhabited planets, and it is difficult even to imaging that in none of them life has arisen. As someone told once Life is a cosmic imperative [Christian de Duvé was who did it], so it is a consequence of the evolution of the universe itself. On Earth, he proceeds, life could have emerged several times until the lineage which gave place to the current biosphere was finally successful. He doesn’t see reasons why the same had happen in other worlds, including the further evolution leading to complex life”. In this latter event, the appearance of complexity, we mention the advent of the eukaryotic cell as the event which allowed the multicellularity to evolve, and that seems to have been a fortuitous one, an accident. Armando replies that, “ultimately, life is nothing but a series of accidents so, once it emerges, it probably will traverse the same paths everywhere”.
One of the pillars of astrobiology is the conception of life as a universal process, so we ask Armando if there is some key phenomenon that can be considered as the core essence of life. In particular, we pose the chemical disequilibrium between CO2 and H as the motor of life, which have been pointed by some authors lately.
The answer is clear and somehow disappointing: “There have been lots of attempts to fix a universal defining feature or even that can be established as a univocal property of life, but all of them have failed in doing it”.
In his opinion, the only way is “to focus on systems with a different level of entropy with relation to the environment maintaining them. The key point is to look for systems with a very low entropy state”. Indeed, Armando has participated together with some colleagues in the development of a method to search for life. “It is a model, based on fractal maths, intended to identify phenomena occurring in a given environment and whose entropy level is relatively low. The idea is to help selecting preferential targets to study”.
But, meanwhile it is possible to reach other places to perform direct investigations, the astrobiological research is driven on Earth, and the study of extremophilic life is the “practical way to study organisms living in similar conditions to those on other places in which it is thought that life could be found.
The finding of extremophilic life has changed gradually the idea of life itself. Initially, microbiology was developed in the health field, centred on organisms related to man and its environment, but little by little new life forms were discovered, living in conditions in which it seemed impossible for anything to thrive (extreme acidity or basicity, temperature, salinity, irradiation, etc). No matter how harsh it is, in any terrestrial environment organisms capable of living there have been found with no exception, and the idea of what is extreme has become relative”.
Martian-like landscape of Atacama and dishes to collect samples. Credits: Armando Azúa-Bustos
Therefore, the interest of Armando in the Atacama Desert lies in two bases. “First, the aim of going into depth in the understanding of the environmental limits of life, with special regard to the water availability and, on the other hand, the implications for posing the possibility of life on other places of the universe, and particularly on Mars.
Atacama, the oldest and driest desert in the world, is also a perfect Mars analogue in some of its environmental features:
As for the differences, the main one is the temperature, which is far higher on Atacama, though it does not mean a constraint regarding the validity of the results obtained in the biological sampling performed here when extrapolating them to Mars, since the typical temperature on the planet is not sterilizing, and it can be bearable for the organisms found in the desert".
LAREX campaign is intended to define the pattern of aerial transport of biomass throughout the desert as an example of what could happen on Mars, so it is an investigation within the field of Aerobiology, “a recent branch of biology”, as Armando explains, “focused on the study of the airborne organisms which started with the study of pollen, viruses, and pathogens, to extend to the study of the general movements of life on air. Microorganisms are carried in association with aerosols, and recently, it has been posed the possibility that air is not only a vector of transport, but also an ecological niche itself. There could be whole populations of organisms thriving in the upper layers of the atmosphere; it is a matter that is pending dedicated investigations.
LAREX campaign started with no foresight at all with respect to what could be found. We simply settle collectors on the ground along the direction of the prevailing winds, which blow from west to east (from the coastal mountain range inland), to see what is being transported”.
So, the next question is obvious: what has been found on Atacama so far? and, some of these organisms (or, for that matter, any other you know on Earth) could thrive on Mars?.
“They have been found a variety of bacteria and fungus whose DNA is under identification process. It is not clear which of them are thriving in Atacama because they are native of the area, and which have only been carried there. And then, we have to figure out how those found to be native manage to live on Atacama and how are their metabolisms like or their life pace, mostly with relation to the availability of water.
On the other hand, the only way of knowing what could survive on Mars is to carry it there and wait, what has not been done either on the surface or the subsurface. However, the subsurface of Mars offers a more hospitable environment, and maybe some of the organisms found in Atacama could survive there.
If life ever emerged on Mars, subsurface would be the environment in which the possible remnants could have survived, and indeed it is there where the foreseen missions are going to explore in search for signs of its presence".
It is difficult to imaging what kind of microorganisms could be the Martian ones, but Armando casts light on this matter according to his knowledge of the diversity of life though at last, the answer is rather speculative necessarily.
“Martian microorganisms would be some kind of chemolithotrophs feeding on certain minerals in the ground, and the possibility that some sort of photosynthesis is used as a source of energy cannot be discarded, since it is a metabolic path which evolved very quickly on Earth. The most favourable habitats would be the subsurface and caves, where populations would be protected from the high UV radiation, though I think that maybe photosynthetic Martian life, if some, could have even developed the metabolic tools to take advantage of this bandwidth of the electromagnetic spectrum for a living”.
A last question remains unsolved with respect to the one that probably is the most limiting requirement for life: the liquid water availability, precisely the matter HABIT is going to investigate on Mars. How could the presumed Martian organisms cope with the dryness of the planet? And what are your prospects with regards to the findings of the instrument?
“Martian organisms, like those living at Atacama do, could count on specific molecular mechanisms to counteract the effects of extreme desiccation.
As for HABIT, [apart from the confirmation of the occurrence of transient liquid water on the soil], it will provide crucial information about the metabolic activity level of possible organisms if they are there”.
The LAREX campaigns are funded by the HABIT project and the project "Investigation of transport of biomass and aerosols through the atmosphere in Mars analogues: implication for planetary protection during colonization and exploration", granted by the Dubai Future Foundation.