Chris McKay

Chapter 1 · 1954 – 1976 A Telescope Forgotten in a Closet

Christopher McKay was born in 1954 and grew up in South Florida. In high school he was interested in science “in some general sense,” as he would put it. He entered university to study physics, at Florida Atlantic University. It was there, by chance, that what would become his life began.

The Telescope in the Closet

In his third year, the university was short of graduate students to run the undergraduate labs; so, he relates, they took some of the taller undergraduates. In the lab, in the back of a closet, he found a ten-inch Newtonian telescope, about twenty-five centimeters. He took it out, fixed it, got it working. He borrowed a big astronomy textbook from the library, the “fat Abell,” as he calls it, and read it straight through over a whole weekend. Then he looked at Saturn and the Great Nebula in Orion.

One evening he set the telescope up in the campus parking lot. Passers-by came over and asked what he was looking at. He liked that, he says: both the science itself and explaining it.

The Last Saturn V

A roommate told him about a rocket launch. They went to watch it from the viewing area: it was, he remembers, the last Saturn V launch, the rocket of the Apollo missions. He would never forget it. Even years later, watching other launches, he would remember a power he had never imagined.

There was also, in the background, Star Trek, which he watched in the dorm’s TV room. It was the time of Watergate and the Vietnam War; much of what was going wrong was being blamed on science. He found refreshing the idea, carried by the show, that science and space exploration could be part of a positive future, and not only bombs and napalm.

He graduated in physics in 1975; he had also studied mechanical engineering. His first steps, he often tells students, came down to chance: had he not found that telescope, he might be doing particle physics today.

Sources: NASA Ames, “Interview with Chris McKay, Planetary Scientist of Planetary Systems Branch,” January 30, 2019 (Florida, physics, the labs in third year, the ten-inch telescope, the Abell book, Saturn and Orion, the parking lot, the last Saturn V launch, Star Trek, Watergate and Vietnam, chance and particle physics); English-language Wikipedia, “Christopher McKay” (born 1954, Florida Atlantic University, 1975 degree, mechanical engineering; tertiary source). The interview does not specify which Saturn V launch he saw.

Chapter 2 · 1976 – 1982 Viking, and an Office of Six Students

At the end of the summer of 1976, Chris McKay visited the University of Colorado and told a physics professor he would like to do graduate work there. The professor answered that a graduate student had just declined his place: could he start the following week?

A Hasty Departure

He said yes. He got in his car, raced back to Florida, put everything he owned in the back of his Toyota and drove back to Colorado. It was the first time he had left Florida, that flat land where, as one of his professors put it, there is not a rock within a thousand miles. Driving through Tennessee and the Appalachians, he finally understood, he says, why people are interested in geology.

The Shock of Viking

He started graduate school in August 1976. A month earlier, in July, the Viking 1 lander had touched down on Mars, at Chryse Planitia. It was the first landing on another planet, and its goal was to search for life. Results were coming in; speakers came to talk about them at the department’s symposiums.

He shared an office with five other graduate students, what he called the “graduate student ghetto.” At the next desk sat Carol Stoker. They asked themselves the question everyone was asking: was there life on Mars? It was not clear. The debate over the Viking results had not yet hardened into opposing camps. It was really exciting. At the time, he would say, he would have sworn it was just a passing interest, for a few months. Forty years later he was still working on the same question: why is there life on Earth and not on Mars, was there life on Mars, is there life elsewhere, how would we find it, and how would we send humans to look for it.

A Thesis on Air

His thesis dealt mostly with Earth’s atmosphere. His shift toward the planets came in the middle of his studies, partly because of Viking. He earned his doctorate in astrogeophysics from the University of Colorado in 1982.

Sources: NASA Ames, interview of January 30, 2019 (the visit to the professor, the empty slot, the Toyota, Florida without geology, Tennessee and the Appalachians, August 1976, Viking in July, the speakers, the “graduate student ghetto,” Carol Stoker, the question of life, forty years later); NASA in Silicon Valley, episode 57, August 31, 2017 (thesis on Earth’s atmosphere, shift toward the planets, Viking, the first landing on another planet with the search for life as its goal); NASA, “Chris McKay” page (Ph.D. in astrogeophysics, 1982). A caption accompanying the 2019 interview gives July 20, 1976 and Chryse Planitia for Viking 1.

Chapter 3 · 1980 Eight Weeks That Decided Everything

One day another graduate student came by his office and showed him a tiny classified ad in the journal Science: NASA was starting, for the first year, a planetary biology summer intern program. “You ought to apply to this,” he said. Chris McKay applied and was selected.

An Internship That Changed Destination

He was told he would be sent to Florida, to Imre Friedmann, a researcher who studied in Antarctica organisms that live inside rocks. He knew his work, even if he was hardly keen on going back to Florida. He called Friedmann; his wife, Rosalie, answered: they would be in Europe all summer and could not host an intern. He then called Boston University, where Lynn Margulis was organizing the program. A couple of days later he was offered NASA’s Ames Research Center, in California. He accepted at once: he knew he would be working with Jim Pollack.

The next day Pollack called him and gave him a real exam over the phone. By chance, he was reading the only paper McKay had published as a graduate student. “Are you the Chris McKay that worked on this paper?” At the end of the conversation, he told him he could come.

An Organization Without Hierarchy

In the summer of 1980 Chris McKay worked with Jim Pollack, a leader in planetary physics, and met Brian Toon. He was struck by the atmosphere at Ames: here were some of the best people in the world, all working together, without a university’s hierarchy of professors and students. Right then and there he decided to come back for his postdoc. He would come, he relates, without applying anywhere else, something he would later advise every student against.

Antarctica

That same summer, Imre Friedmann visited Ames. He needed someone with a physics, math and computer background to work with him in Antarctica on those organisms hidden in rocks, the endoliths. Chris McKay agreed. Still a graduate student, he went to Antarctica with him in 1980. It was his first connection to fieldwork in extreme environments.

Two years later, his doctorate finished, he came back to Ames as a postdoc. He never left. He worked with Jim Pollack until Pollack died of cancer about ten years later, and later took over his old office. That eight-week internship, he would say, was his “gravity assist”: the push that still carries him.

Sources: NASA Ames, interview of January 30, 2019 (the ad in Science, the program’s first year, Imre and Rosalie Friedmann, Lynn Margulis in Boston, Ames, Jim Pollack’s call and the paper, summer 1980, Brian Toon, the level organization, the postdoc without other applications, Friedmann at Ames, Antarctica in 1980, the endoliths, Pollack’s death “about ten or twelve years later,” the office); NASA in Silicon Valley, August 31, 2017 (eight weeks, return two years later, “a leader in the field in planetary physics”); NASA, Gravity Assist, season 4, episode 8, May 29, 2020 (the internship as a “gravity assist”).

Chapter 4 · Since 1980 Under the Ice of Antarctica

Since that first trip in 1980, Chris McKay has kept going back to Antarctica. He seeks there what Earth can teach about Mars: how life lives, or stops living, when it is too cold and too dry.

Valleys Without Snow

The Dry Valleys of Antarctica look nothing like the usual image of the white continent. In their upper reaches, he explains, the landscape looks barren: rocks and dirt, very little ice. You have to hike to find drinking water. It is the coldest dry desert on Earth. As on Mars, the surface is dry and, beneath it, the ground is cemented by ice. For him it is the best Earth analog for the Martian polar regions, and his favorite spot for testing instruments and drills meant for Mars.

What his team finds there is troubling: in these high valleys, life seems to reach its limits of cold and dryness. In many extreme environments, he says, you arrive and find life everywhere, like the pink salt ponds or the hot vents of the deep sea. Here it is life itself that finds the environment extreme. Whether this means there could be life in the frozen ground of Mars remains an open question.

Diving Under Ten Feet of Ice

With Dale Andersen, the principal investigator of one of these projects, the team dives into ice-covered lakes. The ice is almost ten feet thick. A hole a meter across is drilled, and they go down, in dry suits, beneath the ice. It is, he says, like entering another world. There are no fish, no tadpoles: to the naked eye the water would seem lifeless. Yet it is teeming with microorganisms. On the bottom, they build mounds ten to twenty centimeters high. For such tiny beings, he points out, it is a project that makes the pyramids look easy.

When these microorganisms die and the lake dries up, their structures and organic matter can be preserved. They give an idea of what might be found on Mars or in the rocks of the early Earth. Diving into these lakes, he says, feels like going back three and a half billion years, to a time when Earth held only microbes, and perhaps also like seeing what life on Mars was like when it, too, was only microbial.

Around the Campfire

What he loves about the field is being isolated together. At the end of the day everyone gathers to eat and talk science, as if around a campfire. He learned this tradition with Imre Friedmann, in tents in Antarctica, and has kept it. He also remembers those returns when you took your first shower in weeks.

Sources: NASA, Gravity Assist, season 4, episode 8, May 29, 2020 (the Dry Valleys, the coldest desert, ice-cemented ground, instrument tests, life at its limits, Dale Andersen, ice “almost 10 feet thick,” the one-meter hole, no fish, the mounds of 10 to 20 cm, the pyramids, the early Earth and Mars); NASA in Silicon Valley, August 31, 2017 (diving under the ice in a dry suit); NASA Ames, interview of January 30, 2019 (fieldwork, the metaphorical campfire, Imre Friedmann and the tents, the first shower).

Chapter 5 · Chile, Namibia, Mexico The Atacama, the Driest Place on Earth

Chile’s Atacama Desert had long been on the list of places Chris McKay wanted to go. It is the driest desert on Earth. But to go there, you have to convince people.

Three Proposals

A researcher, he points out, spends a great deal of time writing research proposals: a third of his time, depending on the season, with success rates sometimes below ten percent. For the Atacama, the first proposal was turned down; so was the second. The third was accepted: five years of funding, a big team bringing together people from Ames, the University of California at Berkeley and Louisiana State University. He does not regret writing it three times: with each version, the proposal got better.

A Year and a Half Without a Drop

On site, the team set up a state-of-the-art weather station able to record the tiniest rainfall. Their Chilean colleagues emailed them the readings. After a year and a half, Chris McKay thought the station was broken: it had not recorded a single drop. He went back to Chile with replacement kits and tested the station: it was working fine. It was just that dry. The place was drier by a factor of fifty than the next driest place they had ever studied, though they had been studying dry deserts for decades. They were, he says, the first to put a weather station in this hyperarid core.

He calls that not a failure but a surprise, and a surprise is a feature: that is how we learn. His team then sought to understand how the biology of the soils responds to this extreme dryness. In 2018, an international team that included him showed that even in the driest Atacama soils, indigenous microbial communities are present and become active during rare rain events.

A Test Bench for Mars

The Atacama matters in two ways, he explains. If we cannot figure out how to search for life there, we are not ready for Mars: it is a test of the biology and of the technology. Ames is in fact preparing a prototype rover there, under the ARADS project, which is to move, drill the soil and feed samples to life-detection instruments. And it is also a human test: living for weeks in a small camp gives a sense, he says, of what life will be like for an astronaut on Mars, far less romantic than in the movies.

Namibia and the Cave of the Crystals

He has worked in many other extreme places. Once, asking to go to the Namib Desert, he got a question from NASA’s John Rummel: is this a vacation or work? He answered that they would be sleeping in the dirt, eating dirt and digging in the dirt; you could call that a vacation if you liked. The travel was approved.

In Mexico he went down into the Cave of the Crystals, an underground chamber of giant crystals the size of telephone poles, formed over millions of years. The temperature is 55 °C and the humidity one hundred percent: the team wears cooling suits, and if they break down, there are five minutes to get out. He tested there a Raman spectrometer, to analyze the crystals without touching them, as you would study the Mona Lisa without damaging it. This approach, he says, was part of the logic that led to today’s focus on remote-sensing instruments on Mars rovers.

Sources: NASA in Silicon Valley, August 31, 2017 (the Atacama, three proposals, five years, Ames, Berkeley and Louisiana State, the weather station, a year and a half, fifty times drier, the surprise, biological and human test bench, the cave at 55 °C, five minutes); NASA Ames, interview of January 30, 2019 (a third of his time, below 10 percent, the third proposal, Namibia and John Rummel); NASA Ames, “Microbial activity in Earth’s driest desert,” March 29, 2018 (Schulze-Makuch et al., PNAS 2018) and “Cooking up the World’s Driest Desert – Atacama Rover Astrobiology Drilling Studies,” June 20, 2018 (ARADS); NASA, Gravity Assist, May 29, 2020 (the Cave of the Crystals, the Raman, the Mona Lisa, remote instruments).

Chapter 6 · Field lessons What Matters Is the Team

From his years in extreme places, Chris McKay draws a lesson he did not expect. It concerns neither rocks nor microbes, but the humans who will one day go to Mars.

More Important Than the Gear

As an engineer and a scientist, he says, he expected success to depend on how good the gadgets and the gear were, on whether the tents were rated to minus twenty. That stuff is secondary. What matters most is how well the team comes together when things go bad, and they always go bad at some point. If the team holds together, obstacles can be overcome; if it fragments, it is hopeless. He is convinced it will be the same on Mars: no gadget will replace teamwork.

In places where the danger is immediate, under the ice of a lake or in the heat of a cave, the best safety feature is still the team: if someone is having a problem, the others notice. These moments, lasting only an hour or a day, give in his view a glimpse of what will have to be faced for a whole year on the surface of Mars, and of the mental discipline it will take.

He likes, in fact, the way the team is portrayed in the film The Martian: despite the problems, its members come together in adversity.

More Systematic Experiments

At first, attention to human factors was rather anecdotal: “five scientists in a tent.” Since then, simulations have become more rigorous and more relevant to future missions. He is a co-investigator on the BASALT project, which studies, at sites in Hawaii and Idaho, how crews might carry out their research; he has worked at the Idaho site.

Teachers in the Field

The accomplishment he is most proud of outside pure science is called Spaceward Bound. Around the early 2000s, with Liza Coe of the Ames Education Office, he invited teachers to join scientific field expeditions, so they could take the experience back to their classrooms. He feared the teachers would be uncomfortable with the unstructured nature of it, and the scientists with having them along. The opposite happened. In the evening a teacher would ask him what they would be doing the next day; he would answer that he had no idea and that they would discuss it together. The teachers understood that this is how field science is done, and they loved it.

A Human Being First

He tells young researchers that people work best when they are happy. He rejects the notion that you have to be a slave to the job: a researcher’s primary responsibility, he says, is to be a human being, not a cog in the science machine. He himself runs or swims every day, even if it means walking out of a meeting with the Center Director. And he advises reading history, exercising, spending time with family: you will do better science than by thinking only of Mars astrobiology twenty-four hours a day.

Sources: NASA in Silicon Valley, August 31, 2017 (the team more important than the gear, things going bad, Mars, immediate danger, mental discipline, The Martian, “five scientists in a tent,” BASALT, Hawaii and Idaho); NASA Ames, interview of January 30, 2019 (Spaceward Bound “about fifteen years ago,” Liza Coe, the teachers, “I have no idea,” happiness at work, “not to be a cog in the science machine,” running and swimming, reading history). “Around the early 2000s” is deduced from “about fifteen years ago,” said at the end of 2018.

Chapter 7 · 1984 – 1993 Preparing Humans for Mars

In the 1980s, researchers gathered to study seriously the means of sending humans to Mars. Chris McKay was one of them.

“The Case for Mars II”

In 1985 a volume titled The Case for Mars II appeared under his editorship, a collection of work on human Mars exploration. The topics show the group’s ambition: the political aspects of Mars exploration, preparatory missions before humans arrive, science programs for a base, mission strategies and spacecraft design, dirigibles to explore the surface, the power needs of a base, propellant manufacturing on site, water supply, and even psychological and interpersonal adaptation to life on Mars.

One already finds there the idea that would later make Mars Direct successful, making fuel on site, and the human questions he would meet again himself, years later, in the field.

Debates with Robert Zubrin

Chris McKay also works with the Mars Society of Robert Zubrin, his friend. In 1993 the two together modeled the energy it would take to turn into gas the frozen carbon dioxide of Mars’s south polar cap, a possible first step in warming the planet. But on the ethics of such warming they disagree, and they have often debated it in public. The next chapter tells of this disagreement.

With the Planetary Society

He has also served on the board of directors of the Planetary Society, and he writes and speaks widely on space exploration and on transforming Mars.

Sources: NASA Technical Reports Server, C. P. McKay (NASA Ames), The Case for Mars II, 1985 (list of topics, summarized); English-language Wikipedia, “Christopher McKay” (work with the Mars Society, board of the Planetary Society, writing and speaking, public debates with R. Zubrin) and “Terraforming of Mars” (modeling by Zubrin and McKay in 1993); tertiary sources. The sentence on Mars Direct is the author’s remark; propellant manufacturing on site appears in the 1985 list of topics. Robert Zubrin has his own biography in this collection.

Chapter 8 · 1987 – 2020 Making Mars Habitable?

Can Mars be transformed to make it habitable? The question sounds like science fiction. Yet Chris McKay studied it as a scientist from the late 1980s on, and made it one of the threads of his career.

Making an Earth of Mars

In December 1987 he published in the Planetary Society’s magazine an article titled “Terraforming: Making an Earth of Mars.” The first step, he writes, would be to determine the amount, distribution and chemical state of the water, carbon dioxide and nitrogen on Mars. The process would then divide into two steps: first warm the planet with a thick carbon dioxide atmosphere, then convert that carbon dioxide and the soil nitrates into the desired mix of oxygen and nitrogen. He concludes that life would play a major role in any terraforming, and that it would be a gradual, evolutionary process duplicating the early evolution of life on Earth.

Two Habitable Mars

In 1993 he refined the idea in an article with a telling title: “Restoring Mars to habitable conditions: Can we? Should we? Will we?” He distinguishes there two possible states. The first, with an atmosphere of one to three bars of carbon dioxide, would suit plants and microorganisms. The second, with a breathable atmosphere, would suit humans. In 1999 he estimated that Mars might be warmed by selectively introducing trace gases that enhance the greenhouse effect, and that this would take on the order of a century; producing a breathable atmosphere would take much longer. That long-term goal, determining whether a self-sustaining biosphere can exist on Mars, seems to him worthy of human exploration.

Life First

But he also raises the moral question. His position, described as moderately “biocentric,” puts life itself at the center. Mars must first be thoroughly explored to find out whether there is any microbial life. If any is found, even hidden or dormant, we should in his view remove all Earth life and alter Mars to help this Martian life spread. Robert Zubrin, for his part, holds a moderately human-centered position. The two have debated it publicly several times.

In 2020, questioned by Jim Green, he spelled out his thinking. If life were discovered on Mars, we would have to proceed very, very carefully. First remove from Mars all the spacecraft sent there, because they all harbor, at some level, dormant Earth organisms. Then ask: do we still send humans? Do we leave Mars alone? Or do we help the life that is there? As “an advocate for life,” he favors the last: study that life, understand what it needs, then help it spread over the whole planet and build its own biosphere. Jim Green reminds him that Carl Sagan wanted, in such a case, to leave Mars to the Martians. McKay sums up his position with a quip: “We’re from the government. We’re here to help.”

Sources: NASA Technical Reports Server: C. P. McKay, “Terraforming – Making an earth of Mars,” Planetary Report, December 1987 (abstract); “Restoring Mars to habitable conditions: Can we? Should we? Will we?,” 1993 (abstract); “Bringing Life to Mars,” Fifth International Conference on Mars, July 1999 (abstract); English-language Wikipedia, “Christopher McKay” (biocentric position, removal of Earth life, debates with Zubrin; tertiary source); NASA, Gravity Assist, season 4, episode 8, May 29, 2020 (proceeding carefully, removing the spacecraft, the three options, “advocate for life,” Sagan, “We’re from the government. We’re here to help”).

Chapter 9 · 2008 – 2011 Viking Reread in the Light of Phoenix

Viking’s biology experiments in 1976 had decided Chris McKay’s vocation. More than thirty years later, he took part in rereading them.

An Unexpected Salt

Chris McKay is a co-investigator on the Phoenix mission, the lander set down near the north pole of Mars in 2008. In August 2008 Phoenix found perchlorate in the Martian soil, a salt that becomes a strong oxidizer when heated above 200 °C. Now, to search for organic molecules, one of Viking’s instruments heated the soil samples. Viking had not concluded that organic matter was present, but both its landers had detected chloromethane and dichloromethane.

The Desert Experiment

A team led by Rafael Navarro-González of the National Autonomous University of Mexico, which included Chris McKay, redid the experiment on Earth. It added a little perchlorate to soil from the Chilean desert containing organics, then analyzed it the way Viking had. The result, published in December 2010: perchlorate destroys organic molecules when heated, and produces precisely chloromethane and dichloromethane, the same compounds found by both Viking landers. If the Martian soil contained perchlorate like that at Phoenix, Viking may itself have destroyed the organic molecules it was looking for. Chris McKay estimated that the organic content of the Martian soil may have been higher than had been believed.

Klaus Biemann published a commentary critical of their paper; they replied; the exchange appeared in December 2011. The question of whether Viking found organic compounds was open again.

Curiosity, Titan

Chris McKay is also a co-investigator on the Mars Science Laboratory mission, the Curiosity rover. In 2017, four years after the rover’s arrival, he said the team still had surprises, long telecons and big arguments about what the data meant, all in fun. In 2020 he co-authored a study on whether ice-covered lakes could have persisted in Gale Crater during an ancient period of Mars, the Hesperian. He was also a co-investigator on the Huygens probe, sent to Titan, Saturn’s large moon.

Sources: English-language Wikipedia, “Viking lander biological experiments” (perchlorate found by Phoenix in August 2008, oxidizer above 200 °C, chloromethane and dichloromethane, R. Navarro-González’s team at UNAM, Chilean desert soil, publication of December 2010, McKay’s estimate of the organic content, Biemann’s critique and the reply published in December 2011; tertiary source) and “Christopher McKay” (co-investigator on Huygens, Phoenix and MSL; tertiary source); NASA in Silicon Valley, August 31, 2017 (Curiosity, four years, surprises and arguments); NASA, “Chris McKay” page (A. M. Kling, R. M. Haberle, C. P. McKay et al., “Subsistence of ice-covered lakes during the Hesperian at Gale crater, Mars,” Icarus, 2020).

Chapter 10 · 2014 – 2020 Breaking the Ice of Mars

Where should we look for life on Mars? Chris McKay has a preference: the polar regions, and what they hide below the surface. “I like it cold,” he says.

Microscopic Mammoths

Ice, he explained in 2020, is very good at preserving the biomolecules life is made of. In the frozen ground of the Martian polar regions, one might find not just fossils, but the actual frozen remains of biological molecules. He thinks of the woolly mammoths preserved in Siberian ice: what he wants on Mars is their microscopic, ancient equivalent.

At the site where Phoenix landed, at 68 degrees north latitude, the ground is cemented by water ice just below the surface. A few million years ago, when Mars was more tilted on its axis, that ground could have become muddy in summer, like the Arctic on Earth. Life would then have found liquid water.

Icebreaker

The problem is technical. Drilling into that mix of dirt and ice is like drilling into concrete; it is hard enough on Earth, much harder on Mars, where summer is short and the sunlight weak. Chris McKay is the principal investigator of a proposed mission called Icebreaker, which aims to return to the Phoenix site and drill into the ice to search for traces of life. His team tests the drills in the high Dry Valleys of Antarctica, his favorite analog for the Martian poles.

Elsewhere on Mars, he also dreams of drilling deeper. If he had a little rocket ship at his disposal, he said in 2017, he would go to Gale Crater, where Curiosity roams, with a drill able to go ten meters down, bring back some of what lies there and ask the lab folks whether there is life in it.

Leave No Stone Unturned

Below the surface, life might be more abundant than on it, on Earth and on Mars. Our knowledge of the Martian subsurface is so limited, he says, that we must look everywhere: aquifers, ice that may have melted millions of years ago, minerals rich in water. We should, in his phrase, leave no stone unturned; and Mars has a lot of stones.

Hope and Doubt

He does not hide his doubts. In June 2014, interviewed by the National Geographic website, he said his hope of finding life on Mars was dimming, and that even if life were found, it might be related to us. He also works on projects to Europa, Enceladus and Titan, and refuses to say which he prefers.

Sources: NASA, Gravity Assist, season 4, episode 8, May 29, 2020 (“I like it cold,” ice preserving biomolecules, the mammoths, the Phoenix site at 68° N, obliquity, ice like concrete, Icebreaker, the short summer, the Dry Valleys, the subsurface, “leave no stone unturned”); English-language Wikipedia, “Christopher McKay” (principal investigator of the proposed Icebreaker Life mission; tertiary source); NASA in Silicon Valley, August 31, 2017 (Gale and the ten-meter drill); NASA, press summary of June 30, 2014 (“McKay Is Losing Hope In Finding Life On Mars,” after National Geographic).

Chapter 11 · 2005 – 2020 Beyond Mars: Enceladus and Titan

When Chris McKay first became interested in life elsewhere, the field was limited to Earth-like planets: Earth, Mars, Venus. Exploring the outer solar system changed everything.

A Soup Spraying into Space

In 2005, he relates, the Cassini spacecraft, exploring the Saturn system, discovered water jets spraying out of Enceladus, a small moon only five hundred kilometers across. Under its ice lies an ocean, which escapes through cracks. Cassini flew through these jets and found organic molecules in them, nitrogen, and chemicals some microbes feed on, such as hydrogen and carbon dioxide. “I like to call it a soup,” says Chris McKay. Is it a soup in which life could emerge?

If he had a little rocket ship to go wherever he wanted, he says, he would head straight for Enceladus, fly through the plume, bring back samples and ask the lab scientists whether there is life in them. Then he would go to Mars, then to Europa, Jupiter’s icy moon, and finally to Titan.

A Mission for Several Generations

A mission to Enceladus takes nine or ten years of flight, and the data would not come back for twenty years. So, he explained in 2017, one has to think across generations: recruit young researchers now, and plan to bring in students who are in middle school today and will one day analyze the results. When he speaks to middle schoolers, he thinks some of them may one day analyze the data of the mission he is working on.

He also explains why Cassini was deliberately steered into Saturn at the end of its mission: the spacecraft carries Earth microbes, and there could be no risk of it someday crashing into Enceladus and contaminating its habitable ocean.

A Second Genesis

Titan, Saturn’s large moon, is in a category by itself. It is, besides Earth, the only world with beaches, but its liquid is not water: it is liquid methane. If life were found there, it would necessarily be unrelated to ours: a “second genesis.” How would such life be recognized? All life on Earth uses left-handed amino acids in its proteins, though they also come in a right-handed form. If biological molecules made of right-handed amino acids were found on Mars, that would be for him persuasive evidence of an independent life, one that “drives on the other side of the road.” And for Titan, he says, with only Earth to compare, we would not even know who is the weird one.

In 2015 he received the Nevada Medal.

Sources: NASA in Silicon Valley, August 31, 2017 (Earth, Mars and Venus at first, Enceladus 500 km across, the ocean, the jets, the organics, “I like to call it a soup,” the four trips, nine or ten years, twenty years, the middle schoolers, Cassini’s end); NASA Ames, interview of January 30, 2019 (Cassini and the discovery of the plumes in 2005); NASA, Gravity Assist, season 4, episode 8, May 29, 2020 (redox couples, nitrogen, Titan and its methane beaches, the second genesis, the amino acids, “drives on the other side of the road,” “who’s the weird one”); English-language Wikipedia, “Christopher McKay” (Nevada Medal 2015; tertiary source).