On January 14, 2005, a European space probe showed humanity for the first time what a world looked like more than 1,000 million kilometers from Earth. The ship Huygens it had been the first to break through the thick atmosphere of Titan, Saturn’s largest moon, and show its surface. The images taken during its descent revealed a world with canyons, rivers, lakes. Once landed, at about 170 degrees below zero, the ship portrayed a landscape of dirt and boulders. Titan’s looked like the most Earth-like landscape outside of Earth.
That image changed the life of Mike Malaska, a biochemist who had been working in the pharmaceutical industry for 20 years. His specialty was analyzing the chemical composition of a drug and modifying it to increase its effectiveness against cancer or parasitic infections. “When I saw the rounded rocks, the sand of that moon and I realized that Titan was a sedimentary world with organic compounds, basic elements for life, that blew my mind,” recalls this researcher, born 56 years ago in Seattle. (USA). Overnight, at age 45, he quit his job, applied for a NASA job offer, and joined the Jet Propulsion Laboratory, the center where NASA’s most ambitious robotic missions are designed. to search for life beyond Earth, where he has been working for more than 10 years.
Malaska has visited Spain to give several conferences at the Josep Comas i Solà astrobiology school of the Menéndez Pelayo International University, in Santander. In this interview, the researcher explains that several recent discoveries have forever changed current ideas about where life is most likely to be found in the solar system. It is no longer the subsoil of rocky planets like Earth or Mars, but the icy oceans of Titan or even the clouds of Jupiter or Saturn, where nothing prevents living beings from existing at the moment, he says.
Ask. Is there a connection between developing drugs and searching for life in the Solar System?
Response. Of course. I see everything from the point of view of chemistry. I try to understand the processes as the interaction of different compounds. When I think about the biology of planets or moons I see molecules interacting and I understand that well. There are other experts who see it on a large scale, from the geological processes that shape the territory. They are different scales that help us piece together the complete story of what is happening millions of kilometers from our planet.
P. Why is he so interested in Titan?
R. Part of my job is to study the geology and chemistry of Titan. On this moon there are karstic terrains similar to those on Earth, for example those in northern Spain in the Picos de Europa. We think there is karst on Titan. Instead of being water dissolving limestone rock, it is a rain of hydrocarbons [metano, etano] that dissolves organic material. The result is much the same: plains, canyons, valleys, and maybe caves.
The other part of my job is to study what might be inside the thick ice sheets that cover the saltwater oceans of Saturn’s moon Titan and Enceladus. We have very similar places on Earth: Greenland and Antarctica, where we know that there are microbes that literally live inside the deepest ice sheets.
P. In his lectures he mentions a finding that has changed the conception we have about life beyond Earth. What is it?
R. One of the great discoveries of the last 20 years is that there are microbes capable of living inside the ice. They are actually in little pockets that form at the intersection of ice grains. These bubbles are barely twice as wide as a human hair; enough to harbor one or two bacteria. Because of the way the different ice grains fit into those holes, there is a lot of food. This tells us that at enormous depths there may be tiny bubbles where microbes can live for thousands of years. We have discovered these microbes deep in the ice crust in Greenland, and it is quite possible that the same pockets of life exist on Titan or on Jupiter’s other moon Europa. In fact, given that there is no sunlight down there and the pressure and temperature are the same, if we took the terrestrial bacteria there they could live peacefully. This finding gives us a new way of thinking about life on other planets.
P. You repeat that it is one thing to determine that a planet is habitable and another to confirm that it is inhabited. How do we make that jump?
R. We need to develop very complex instruments to study the chemical compounds within the ice and estimate if any of them betray the presence of life. The problem is that Titan is riddled with organic compounds. One possibility is to search for amino acids, the basic building blocks of life. Some amino acids are very easy to find, they could be found on Mars and other planets, even in meteorites. Then there are others with a very complex structure, and those can only be assembled by living beings. An example is long fatty acids, which on Earth we can find in the outer membranes of cells. Finding these acids would be the strongest possible evidence that there is life outside of Earth.
“Titan is huge and there is a good chance that there are niches of life in the icy crust”
P. What is the most similar place to our planet in the Solar System?
R. Venus. At 30 kilometers from the surface you have the same temperature and pressure as on Earth. The atmosphere is the same. We don’t normally think of this planet as a habitable place, but it is.
P. In 2020 there was an announcement of possible organic compounds on Venus that later fell apart.
R. Yes, the phosphine. There’s something weird about Venus. A compound in its atmosphere is trapping ultraviolet radiation from the Sun and we don’t know what it is. I believe that many robotic missions will be sent to solve this puzzle.
P. Could it be a sign of life?
R. Yes. Although it is also possible that another unknown chemical process that has nothing to do with life is the explanation. In the 1970s, when the Viking mission landed on Mars for the first time, it also obtained results that could indicate the presence of life. Now we think that they could be geological processes that we did not understand well at that time. We’re probably going to have the same problems when we go to Titan and other icy worlds.
P. What do you think is the best place to find life beyond Earth?
R. Titan, without a doubt. It’s huge and there’s a good chance there are niches for life in the icy crust. There is organic material as food and there may be connections between the bottom and the surface. The problem is that there is an ice sheet 100 kilometers thick. Enceladus is also a good place and it’s easier to explore because it has geysers.
P. It seems that the rocky planets have lost interest in this aspect.
R. Yes. Partly it is because there is a problem. It is possible that life arose first on Mars and that it came to Earth aboard a meteorite. It can also be the other way around: it first appears on Earth and reaches Mars. So if we find life on the red planet, we may never know if it came from Earth. For Titan and Enceladus there is no such problem. It would be a second origin of life without a doubt.
P. You say that clouds are the next frontier in the search for extraterrestrial life.
R. That’s how it is. There is life in the clouds. Microbes. Until recently we thought that somehow they had been dragged there by atmospheric processes, and then fell back to the surface. Now, thanks to recent studies on Earth, we know that these microbes live in clouds and can stay there for thousands, millions of years, feeding almost exclusively on gases. This makes it possible for there to be life in the clouds of Jupiter and Saturn, in fact, nothing prevents it from happening.
“It is possible that in 20 years we will think that life is something inevitable in any place”
P. Do you believe that life is something common inside and outside the solar system?
R. It’s a great question. We have no idea. Before, we thought that a primordial soup was necessary, a kind of puddle that evaporates while increasingly complex molecules are assembled inside it. Then we discovered that this process can also happen at the bottom of the sea, in hydrothermal vents. More recently we have found out that it also happens inside the ice. The more we investigate, the more possibilities we discover. So it does seem that life is easier to assemble and preserve than we thought. It is possible that in 20 years we will think that life is something inevitable in any place.
P. What if we find out it’s not?
R. That would be terrifying because it would have to explain why we are so unique and special.
P. If it were discovered that there was a second origin of life on another planet, many religions would have to change their story.
R. I’m not sure. They could always adapt it and say that life started on Earth and then went somewhere else. Or that life arose on another planet, but it was just microbes and what counts are humans. I don’t think it’s such a brutal shock. When we think about the great discoveries of life in unthinkable places, like inside the ice or in hydrothermal vents, people are not so surprised. If we discovered life on Mars, people would simply say: OK. In fact, in my talks I meet audiences who believe that life has already been discovered on Mars, which is already proven. When I get them out of the error they shrug their shoulders and that’s it. I don’t think that discovering life on another planet is as radical a change as we think. We will say, well, a new thing that kids have to learn at school. Of course, for scientists it will be amazing; we will want to know everything about that life, but there will be thousands of questions and few answers. That’s the most exciting.
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