In 1975, NASA’s Viking 1 spacecraft entered orbit round Mars, carrying a mission to unlock the secrets and techniques of the Pink Planet. Quickly, it launched twin landers that drifted towards the Martian floor and ultimately made historical past as the primary American spacecraft to the touch down on the world.
For over six years, Viking 1 continued to orbit Mars’ Chryse Planitia area whereas its landers collected soil samples utilizing robotic arms and onboard laboratories, marking a groundbreaking chapter in humanity’s exploration of the Martian setting.
On the time, nevertheless, little was recognized about environmental situations of the Pink Planet, and the Viking life detection experiments have been modeled after culturing strategies generally used to determine microbes on Earth. These strategies concerned including water and vitamins to these aforementioned soil samples, then monitoring for any indicators that recommend microbes may be residing within the samples. Such indicators have been related to responses to the components — primarily an inflow of elements wanted to finish regular life cycles as we all know them — and included issues like progress, copy and the consumption of meals for vitality.
In the future, each Viking landers reported a possible optimistic detection of microbial exercise of their soil samples, and the findings naturally sparked a long time of intense debate. Had we lastly discovered proof of life elsewhere within the universe? Nevertheless, most scientists now imagine the outcomes have been damaging or — at finest — inconclusive. They suppose it is extra seemingly that the optimistic readings have an alternate clarification.
However that is most scientists.
In response to Dirk Schulze-Makuch, an astrobiologist on the Technische Universität Berlin in Germany, there could also be one other side to this thriller that hasn’t but been thought of: Viking might certainly have found life on Mars, however the water-based nature of its life-detection experiments might need unintentionally killed it.
In a current commentary printed within the journal Nature Astronomy, titled “We could also be on the lookout for Martian life within the mistaken place,” he argues that as a result of Mars is even drier than probably the most arid locations on Earth, the Atacama Desert, the place microbes acquire water via salts that draw moisture from the ambiance, any analogous Martian life could be extremely delicate to the addition of liquid water. Even one drop an excessive amount of might threaten their existence.
But, the Viking experiments have been carried out underneath the belief that Martian life would require liquid water, like most life kinds on Earth. Thus, Schulze-Makuch believes, the outcomes of the experiments may be finest defined not because the absence of natural life, however because the human-driven destruction of arid microbial organisms uncovered to an excessive amount of water.
If the assumptions about organisms thriving in Mars’ hyperarid situations are correct, Schulze-Makuch argues that NASA ought to rethink its longstanding “comply with the water” technique for locating life past Earth. As a substitute, he suggests adopting a “comply with the salts” method.
Area.com sat down with Schulze-Makuch to debate this intriguing tackle the Viking experiments, how the group has reacted to it, and what it’d imply for life-seeking experiments going ahead.
The interview has been edited for size and readability.
What sparked your curiosity in re-examining the Viking experiments on Mars?
I’ve all the time been intrigued by the Viking life detection experiments. It is unlucky that they haven’t acquired extra emphasis as a result of, in the end, they’re the one direct life detection experiments we have carried out on one other planet. And sure, the outcomes have been complicated, however for scientists, that type of ambiguity is fascinating — it often indicators that there is one thing deeper to know.
Now, practically 50 years later, we are able to reexamine these experiments with a a lot better grasp of Mars’ setting — its complexities — and the way sure reactions might unfold there. We have additionally gained invaluable insights into extremophiles on Earth — organisms that survive in essentially the most inhospitable situations — and the way they perform. That information helps us interpret the Viking information with a brand new perspective.
Why do you suppose the Viking experiments might need truly encountered and inadvertently killed Martian life?
I did a number of work within the Atacama Desert, which is an analog setting to Mars. And we obtained some “Blues Clues” about how organisms survive there. From there, it wasn’t that tough to place it collectively.
I introduced this concept a couple of yr in the past at a particular assembly on life in the universe, hosted by the King of the Netherlands. Many European Space Agency scientists have been there, and I believed afterwards I could get some backlash, however they took it surprisingly effectively.
The science idea on this case is that salts, and organisms with the assistance of the salts, can pull water straight from the ambiance. There’s additionally an impact the place, as water is eliminated, there’s a kind of delay — a hysteresis — as a result of the system resists crystallization. This implies water can stay in a salt longer than anticipated, which is essential as a result of it raises the water exercise on a microscopic degree, making it accessible to microbes. Life is superb at profiting from these bodily or chemical results. There are many examples in biology, which is superb at utilizing these sorts of results — I’d practically name them methods as a result of they’re utilizing this sort of quirky physics or chemistry.
In fact, I can’t say there’s undoubtedly an organism on Mars exploiting these results. However Mars, nearly 4 billion years in the past, was a lot like Earth, with considerable water. Because it grew to become drier, shifting towards its present desert state, these are the sorts of diversifications I’d count on any remaining life to develop.
How do organisms in Earth’s deserts survive by pulling water out of the salts?
It’s the identical factor if you consider rice in a salt dispenser, the place the rice grains are inside to maintain the salt dry — in any other case it might grow to be all clumpy. The rice grains are extra hygroscopic than the salt grains, in order that they appeal to extra water from the ambiance.
It’s the identical factor we see within the Salars, the place historic salt lakes dried up, forsaking salt deposits, however there’s nonetheless just a little moisture within the ambiance above these deposits. Relying on the kind of salt, it could actually appeal to and take in moisture. We name this course of hygroscopicity, and it permits the salt to grow to be damp, ultimately forming a brine, which is then referred to as deliquescence.
We see this even with widespread desk salt — it could actually attract sufficient moisture from the air to create a brine, by which sure micro organism thrive, even in absolutely saturated sodium chloride options. Whereas extra advanced salts like perchlorates or chlorates are more durable environments, some organisms can tolerate pretty excessive concentrations. The primary salt on Mars seems to be sodium chloride, which implies this concept might work.
Do you imagine the belief that life requires water hinders our understanding of extraterrestrial life and the way we search for it?
Typically, I’d agree with that — however not for Mars. Mars and Earth are a lot alike, and you’ve got a number of the identical type of minerals, although not the identical selection on Mars that Earth has as a result of there are a number of minerals on Earth which might be shaped by biology. However they’re in any other case very, very comparable.
They’re each terrestrial planets, considerably comparable of their distances away from the sun. If we count on life on Mars, we might expect that dependence on water as effectively. I believe when you would search for life, for instance, on Titan, the place floor situations differ vastly, then I’d agree that this requirement for water would hinder our search. However for Mars itself, I do not see an issue.
How may the Viking experiments have led to a false damaging outcome that life does not exist on Mars?
Think about one thing comparable occurred to you [as a human]. For instance, if there was an alien in a spaceship coming right down to Earth and located you someplace within the desert. Then they mentioned ‘OK, look, that is a human and it wants water,’ and places you straight in the course of the ocean. You would not like that, proper? Though that’s what we’re. We’re water-filled baggage, however an excessive amount of water is a foul factor, and I believe that is what occurred with the Viking life-detection experiments.
There was one research carried out within the Atacama Desert the place there was torrential rain and it flooded an enormous space. Afterwards, the scientists discovered that 70-80% of the indigenous micro organism died as a result of they could not deal with that a lot water so instantly. This actually suits into the identical image.
How would you design a brand new experiment that will take this into consideration and will possibly detect these life kinds?
I believe crucial factor is that one experiment by itself can not permit us to decide. For instance, one may assume that Martian organisms have precisely the identical DNA as these on Earth, and so we would devise an experiment to go on the lookout for that materials. However what if it’s totally different? You’d then should have a number of totally different experiments to check this out and make a certain conclusion.
Within the case of the Viking life-detection experiments, these folks weren’t silly and I believe the method was proper at that time, however the scientists did not actually know something concerning the Martian setting. What they have been doing was very refined for the time. And now, we’ve got a lot better instruments and a lot better insights and higher methodologies.
I believe, from my perspective, the secret’s to not depend on one experiment to make a conclusion. My analysis group, for instance, is at present engaged on reside detection based mostly on motility, the attribute motion of microorganisms, which additionally makes use of water by the best way, however in very small quantities. We take a look at how the organisms or the sediment particles transfer within the drop of liquid, for instance. If it is a bacterium, it has a sure type of sample that is determined by the type of micro organism and may be distinguished from a sediment particle as a result of a sediment particle would transfer in a different way. With AI, we are able to monitor the motion mechanically to say this can be a microbe, and that may be a sediment particle. We predict that we are able to distinguish even an alien microbe from a sediment particle. That may be an attention-grabbing experiment to conduct.
The purpose is, there are quite a few methods to [search for life on Mars]. Ideally, it might be good to have a microscope on Mars, however this poses challenges — although I believe it’s attending to be about time that we use one for looking for life on different planets.
However to make an extended story quick, we might wish to have a number of totally different sorts of life-detection strategies which might be unbiased of one another, and from there, we might provide you with extra convincing information.
Have you ever noticed a shift since Viking in how scientists are on the lookout for life on Mars? Have the strategies developed a bit or taken this into consideration?
Sure, there are many totally different strategies accessible now and there are, in fact, benefits and downsides to every. Gasoline chromatography and [mass spectrometry] is without doubt one of the extra refined [methods] and would permit scientists to take a look at the natural compositions of samples.
We might then evaluate to samples from Earth. For instance, you’d see particular patterns and peaks for sure proteins and their amino acids — these we all know and will count on. You could possibly additionally search for merchandise of abiotic synthesis, the sort that occurs at first, earlier than life, and could be indicative with excessive ranges of small natural molecules.
Primarily, we do have fairly a number of methodologies that will be actually attention-grabbing to check out.
Within the context of this speculation, what particular salts or mineral compositions could possibly be prioritized? You talked about sodium chloride, however are there any others?
Sure, you’d must search for hygroscopic salts. Not all soils possess this property; as an example, some sulfur salts, like gypsum, aren’t hygroscopic because the mineral construction comprises a number of water and wouldn’t be appropriate.
Sodium chloride might be the most typical alternative, together with potassium chloride. In my analysis group, we’re additionally chlorates and perchlorates, which we’ve discovered to be fairly efficient. Chlorate (ClO₃) and perchlorate (ClO₄) are the kinds we’re all for, though perchlorates could be a bit problematic for all times as we all know it; they are often tolerated solely in sure quantities, and an excessive amount of may be dangerous. Alternatively, chlorates appear to work a lot better.
One benefit of chlorates and perchlorates is that they keep liquid at a lot decrease temperatures in comparison with sodium and potassium chloride. That’s vital as a result of if the setting will get actually chilly, having salts that stay liquid at colder temperatures might present a extra appropriate habitat for microbial life.
So, whereas sodium chloride is a high precedence, I’d additionally recommend contemplating chlorates and perchlorates. In areas just like the Southern Highlands of Mars, excessive concentrations of chloride have been detected.
Do you suppose this take is controversial?
Sure, absolutely it is controversial. In science, difficult the prevailing paradigm is all the time powerful. Colleagues typically assessment work from a place that displays their present beliefs, and egos can complicate the method as effectively. Finally, although, I imagine science prevails. There is not a top-down method; even essentially the most esteemed scientists may be mistaken, and all of us perceive that. My purpose has all the time been to current our findings and let the scientific group interact with them as potential hypotheses.
Nevertheless it’s essential to place out a speculation out to see if we are able to provide you with a logically sound resolution to it. I have no idea whether or not there are actually microbes on Mars, however I really feel assured that my proposed resolution might work and may reveal life. Future missions ought to undoubtedly examine this additional. I may be mistaken, however I may be proper — we received’t know till we attempt.
Ultimately, we’ll get the proof, a method or one other, and that is good. I’m okay if I used to be mistaken. I believe both means, this was an attention-grabbing thought — even when some folks do not suppose so. However we’re in the end trying to uncover life, and to take action, we’ve got to suppose outdoors the field.
