The DNA Files:
Unraveling the Mysteries of Genetics
As heard on National Public Radio
Life: How to Make a Cosmic Omelet
Genetics & Astrobiology
Hosted by John Hockenberry
2991 Shattuck Avenue, Suite 304
Berkeley, California 94705-1872
For further information about genetics and these programs, as well as the producers who brought you this series, visit the project web site at www.dnafiles.org.
Send your questions about genetics and this project to firstname.lastname@example.org.
Funding for this series was made possible by generous grants from The National Science Foundation and the Alfred P. Sloan Foundation.
Last reviewed for accuracy: February 2002.
JOHN HOCKENBERRY: Welcome to The DNA Files. I’m John Hockenberry. In this program, Life: How to Make a Cosmic Omelet, we’ll be looking at where life came from, and what genetic research is telling us about where else we might find it. The National Aeronautics and Space Administration—NASA—has dubbed the field Astrobiology, a marriage of sorts between astrophysics and biology. As we’ll see, it’s not the search for little green men, but rather the search for any sign of life at all. Even microscopic life. It may be one of the most difficult and most rewarding challenges facing science today, says physicist Paul Davies.
PAUL DAVIES: There can surely be no greater challenge than to understand how a mixture of non-living chemicals turn themselves spontaneously into the first living thing.
JOHN HOCKENBERRY: All this when we return with The DNA Files.
JOHN HOCKENBERRY: Yellowstone National Park. For most of us, it’s a spectacle of geysers and bison; for genetic scientists it’s a hotbed of microbial research, home to nature’s tiniest creatures. What scientists are learning here may help us unravel the biggest puzzles of all time: How did life get started? And what are the most extreme conditions in which it can survive? Joe Jordan has this story…
JOE JORDAN: Imagine the early earth, more than three and a half billion years ago. Boiling mud pools, toxic chemicals … big chunks of rock and ice crashing in from the sky. How could anything have lived through these conditions? For answers, scientists come to a place where our planet’s internal heat still leaks out, in scalding steam geysers and brilliantly colored hot springs teeming with life …
TIM MCDERMOTT: Welcome to Yellowstone National Park, Joe. G'morning; it's a great day to be here in Yellowstone, and it's a great place to work.
JOE JORDAN: That’s Tim McDermott, a soil microbiologist at Montana State University’s Thermal Biology Institute. He studies microbes that live here in the 200-degree Fahrenheit geothermal pools of Norris Basin, a volcanically active backcountry area of the park. Some of these microbes even live on arsenic – a poison to us, but one of several heavy metals found naturally here in Yellowstone.
TIM MCDERMOTT: Mercury, lead -- copper, zinc if it weren't a national park, at least places would probably be designated a super-fund site.
JOE JORDAN: At the edge of a bubbling hot spring, McDermott samples soil for microbes. Back in his lab, he’ll study variations among their genes for arsenic tolerance. Plotting where microbes live and what they eat helps color in the map of evolutionary relationships, from ancient to modern organisms. But most of what we know about microbes comes from being able to analyze their DNA, says University of Colorado molecular scientist Norm Pace.
NORM PACE: Imagine if our entire understanding of biology were based on a visit to the zoo ... And that's exactly the situation we've been at in the microbial world until really quite recently.
JOE JORDAN: In fact, an organism discovered here in Yellowstone gave scientists the enzyme used in most new gene sequencing techniques. Out in Norris Basin, Pace’s colleague, biologist John Spear studies the hydrogen diets of microbes in the crystaline turquoise blue, green and yellow waters. He takes DNA snapshots of whole microbial communities in their natural habitats.
JOHN SPEAR: What I'm doing is I hang a piece of glass -- just regular glass, like a window-pane glass -- I hang it in the pool and I'll come back and get it in 2 weeks or 3 months -- I'll give it an amount of time for it to get colonized with a bio-film.
JOE JORDAN: Spear uses a razor blade to scrape the microbial film off the glass into a tube that he freezes in liquid nitrogen. Then he takes it back to the lab, extracts the DNA and plots similarities and differences between groups of microbes. What starts to emerge is a map of the tree of life, of evolutionary relatedness. Spear’s wearing a tree-shirt today.
JOHN SPEAR: On this t-shirt we have a picture of a tree. It's a tree that has the 3 major groups, or domains, of life – the Bacteria, the Archaea and the Eukarya.
JOE JORDAN: Eukarya is where we humans are on the tree of life, along with all the animals, plants and fungi. Most of us know something about bacteria, too. But Archaea, A-R-C-H-A-E-A -- the name implies ancient heritage. Once thought to be among the bacteria, they've recently been revealed as a whole new category -- with significant differences between their DNA and that of all other modern life. They may be closely linked to the earliest life forms, near the root of the tree, explains Norm Pace.
NORM PACE: When you look at these high-temperature organisms -- particularly the high-temperature Archaea -- you see these very short line segments departing from the last common ancestor.
JOE JORDAN: Archaea turn up everywhere from oceans to the human gut. Among them are many "extremophiles,” organisms that can live in exotic conditions like heat, acid, salt and ice … places we never thought we’d look for life. Astrobiologist Jonathan Trent of NASA’s Ames Research Center in California studies how some of the heat-loving microbes beat the heat by making a heat-shock protein that appears to stabilize cell membranes. He reflects on how genetic adaptations like these are expanding the realm of the possible, opening whole new worlds, in our view of life.
JONATHAN TRENT: It’s probably comparable to the age of discovery that went on in the 19th century, where people were going around on ships and they were finding things living in the deep ocean, in places we had no way of ever visiting before … and now were going in that same direction with the inventories of DNA information that more and more organisms are being sequenced. And many people are now saying that the 21st century is going to be the age of biology.
JOE JORDAN: Now that we are beginning to map the range of extremes in which life can survive, what we learn in Yellowstone could help us plan where to look on upcoming missions to Mars and Europa, environments that now seem just a bit more likely to harbor at least some form of life…
For The DNA Files, I’m Joe Jordan.
JOHN HOCKENBERRY: Welcome to The DNA Files. I'm John Hockenberry. In this program we’ll meet scientists studying the origins of life on Earth and searching for the signs of life beyond Earth. For my own part, I want to know where I’m from. I mean I know where I was born, and where my parents were born and all that. But where am I really from? Where did any of us come from? We’ve asked this question as long as there have been humans to ask it.
VOICE: In the beginning, there were two realms. Muspell was in the south, and it was full of fire and blinding light. Niflheim, the home of fog, ice and snow, lay in the north. Between the two realms was a vast stretch of empty space called Gin-nun-ga-gap, or Yawning Gap.
JOHN HOCKENBERRY: There are probably thousands of stories that start with "in the beginning" and so on, to recount how life began. Every culture has at least one such tale. This one is from Iceland.
VOICE: The drips and drops started life growing…
JOHN HOCKENBERRY: To many ears, such tales sound far-fetched, if taken literally. But scholars of religion and folk traditions like Professor David Leeming say creation tales undoubtedly satisfy a universal human need for an answer to why we’re here. Dr. Leeming, is an emeritus professor of English and comparative literature at the University of Connecticut and author of the "Encyclopedia of Creation Tales."
DAVID LEEMING: Why did people in the Paleolithic dig their way down into caves and sit there in the darkness and then paint paintings, of animals and shamans or whatever? It’s as if we’re driven to tell the story of creation.
JOHN HOCKENBERRY: And it's not just storytellers and shamans who are driven to explain the origins of life, says Leeming.
DAVID LEEMING: And it’s also told by the scientist who says, "Hey, we are all the result of an explosion that took place in a billionth of a second billions of years ago.” There’s a relationship between what the old mythmakers were doing and what the scientists are doing.
JOHN HOCKENBERRY: Some scientists have theories that make the Icelandic story of Yawning Gap seem positively mainstream.
CARL SAGAN: With 400 billion stars in the Milky Way galaxy alone, could ours be the only one with an inhabited planet?
JOHN HOCKENBERRY: Take the late professor Carl Sagan, who used his public television program Cosmos to spread his conviction that advanced life must be common in the universe.
CARL SAGAN: Perhaps near one of those pinpoints of light in our night sky someone quite different from us is glancing idly at the star we call the sun and entertaining just for a moment an outrageous speculation.
JOHN HOCKENBERRY: Sagan was one of the country’s leading proponents of the search for extraterrestrial intelligence. He inspired a generation of scientists and science buffs dedicated to the quest for alien beacons. And he authored Contact the story of a scientist obsessed with finding extraterrestrial life. The book later became a major motion picture.
But many scientists say fishing for intelligent extra-terrestrials at the top of the galactic food chain is unlikely to be successful, even if there are aliens somewhere out there with transmitters trying to reach us. They say the scientific payoff is closer to home, on planets in our own solar system, looking for the simplest life forms possible—single-celled organisms like bacteria and yeast. Biologist Lynn Rothschild.
LYNN ROTHSCHILD: Where the interest is going to be is at the molecular and really the microscopic level. If we find anything that’s alive, no matter how microscopic, no matter how simple in a metabolic sense, that is the most exciting thing. It’s this whole question of life or non-life.
JOHN HOCKENBERRY: A scientist at NASA’s Ames Research laboratory in California, Rothschild says apart from such single-celled microbes, life is probably rare in the universe. The evidence comes from looking not up but down, at the Earth under our feet. On this blue ball we call home, single-celled life made its dramatic entrance some 3.8 billion years ago, but it wasn’t until about half a billion year ago multi-celled plants and worms and the like joined the cast.
CHARLES LIU: We’re here in the northwest corner of the Rose Center and we can see clearly the hanging and mounted models of the planets as we’ve displayed them...
JOHN HOCKENBERRY: To better understand the plot of this cosmic melodrama, we’ve made a visit to New York, to the Rose Center of the American Museum of Natural History.
CHARLES LIU: Earth in front of us here is about the size of a basket ball, Mars—with its red surface and white ice caps…
JOHN HOCKENBERRY: Physicist and museum curator Charles Liu is my guide. Models of electrons, protons, planets and stars illustrate the size of the universe and everything in it. A broad ramp called the Cosmic Pathway illustrates its age.
CHARLES LIU: And it is a 349-foot long spiral walkway--so it’s about as long as a football field plus one and a half end zones. Along this pathway, which describes the entire history of the universe, 13 billion years of cosmic evolution from the big bang to the present day.
JOHN HOCKENBERRY: Quite frankly, it’s a bit humbling to contemplate such vast scales of time and space as we follow the Rose Center’s cosmic pathway…
CHARLES LIU: As we walk down we see a pictorial history of the universe unfold…some quasars and galaxies and proto-galaxies. Followed by radio galaxies,
JOHN HOCKENBERRY: Liu says it’s not until two thirds of the way down the pathway that the sun, Earth and the other planets are created from a humongous cloud of gas. Six yards farther, microbes appear.
CHARLES LIU: We keep walking. Dinosaurs are just two steps—maybe three steps—away from the present day. Along this cosmic pathway we've walked a full length of a football field, and then we realize that all of human evolution, from when the first hominids began to walk on two feet, takes barely an inch and a quarter on this cosmic pathway.
JOHN HOCKENBERRY: Human civilization takes up barely the width of a human hair. Yikes! Seen in this light, life on Earth does seem insignificant. But looking at the flip side, you could say we’ve been 13 billion years in the making. How did the miracle of life occur? Michael Meyer, who has joined me at the Rose Center, says scientists have puzzled for generations about what mysterious process created life from almost nothing. Meyer is the top astrobiology scientist at NASA headquarters in Washington.
MICHAEL MEYER: Darwin’s idea of how life started on Earth is that it could have started in small ponds. You can imagine for instance, a splash pool on the edge of the ocean where big waves come up, you fill little puddles. You have some chemicals in there—whatever is in the ocean. It dries out, it concentrates everything. Concentration causes some chemical reactions. And you have the possibility of something getting more and more complicated, until at some point in time it's complicated enough so that you have something helping itself grow.
JOHN HOCKENBERRY: Meyer says Darwin’s small ponds are only one place life could have appeared. Some researchers say it may have originated in hot springs deep under the ocean. Wherever Earth’s life first sprung up, scientists say it probably used the same simple chemical building blocks found in all known life today: twenty amino acids and some additional simple chemicals used to build DNA and RNA molecules. Today these important building blocks are made by living things. But before life could have started, these raw materials must have already been on hand. Most astrobiologists believe these chemicals were first cooked up in a primordial soup when the solar system was young.
Now somewhere on my desk here I have tape with a recipe for primordial soup. Hmm.
Excuse me. I haven’t tidied up in while.
No. That’s not it.
What’s this…no. Not chicken soup.
[sound of audio tapes being shuffled]
Ah. Here it is!
[sound of tape being put in machine.]
JULIA CHILD: Hello I’m Julia Child. I’m in my own kitchen today and I’m boiling up some primordial soup. We’re doing a recipe for the chemical building blocks of life.
JOHN HOCKENBERRY: [chuckle]. Julia is a fine cook, one of the best in the universe certainly but I just want the recipe. Let’s see.
JULIA CHILD: Then we have 24 grams of sodium chloride. That’s plain old table salt. And 24 grams is about a tablespoon and 3/4. Then we have 4 grams of sodium sulfate.
JOHN HOCKENBERRY: Julia Child of course is no astrobiologist, be she got that recipe from one. In fact, fhe first recipe for primordial soup was created by a chemist, Stanley Miller. You’ve probably heard about his famous 1953 experiment where he put a bunch of simple gases—methane, ammonia and hydrogen in a glass chamber with some water. He heated it and zapped the mixture with sparks to simulate lightening on a primitive Earth. Amazingly this simple apparatus produced a number of these amino acids building blocks. Based on new findings, scientists have refined the recipe for primordial soup many times over the years. Julia’s recipe, proposed by chemist Cyril Ponnamperuma contains about a dozen ingredients.
JULIA CHILD: 3, 4. Now take your wire whip. Stir it all up. There! And that’s all there is to your primordial soup.
JOHN HOCKENBERRY: Okay. So as far as anyone knows, amino acids and other building blocks of life were first created in some primordial soup. The soup’s broth was liquid water, which guaranteed that the ingredients would come into contact with each other. Carbon, an essential part of all known life today, was also an important ingredient in the soup. But the building-block products of primordial soup weren’t life. The next steps on the way to life itself are still very much in question.
JOHN HOCKENBERRY: Jack Szostak, a Professor of genetics at Harvard Medical School is researching one popular theory.
In his lab more than a dozen grad students, post docs, and lab techs here are busy operating equipment and pipetting solutions. All this activity is directed toward a single goal: to explain how complex molecules became life. Or, as some scientists say, how chemistry became biology. Jack Szostak.
JACK SZOSTAK: Cells nowadays—they’re the results of billions of years of evolution—and they are very complicated. So we have a complicated system where DNA encodes RNA, which encodes proteins, and the proteins make…
JOHN HOCKENBERRY: Whoa! I guess we're going a little too fast here. Let’s slow this the whole business down, because cell biology can get a bit technical. I’m taking off my journalist’s cap and put on my chef’s hat and apron because I’m going to do some cooking. And I’ve invited you into my kitchen today because in many ways what a cell does is just like cooking. A kitchen contains ingredients—let’s say eggs, milk and butter—to make something like your basic omelet. A cell like, say a yeast cell, takes simple sugars and makes alcohol and carbon dioxide. Both a kitchen and a cell need three essential things to function. Number one: a recipe.
A recipe of course is a list of instructions. In a cell, DNA is the cookbook. The genes, or segments of DNA, are the individual recipes. So DNA equals cookbook. Gene equals recipe. Got that? The second essential element in a kitchen is the chef…that’s me, Chef Jean...who uses the recipe to cook up a meal. I know you're following me. I’m going to start gathering up my ingredients. I need some of this, and some of that. That looks kind of bad... Eww, how long has that been in here.
A cell’s chef is RNA, a molecule that reads the DNA instructions to cook up materials to repair cells walls, make pigments like chlorophyll, digestive juices and other important chemicals in the life of a cell.
The third essential part of a kitchen are all the nifty gadgets like an eggbeater and pots and pans, and this garlic peeler over here. I mean these things are great. You've got to get one of these. A cell has nifty gadgets too, they're called enzymes. And if you’ll excuse me, I’m going to make my omelet while I keep talking. I’ve got guests coming soon…ok. Eggs…
A splash of milk…
Now beat …
[eggs pouring into a frying pan & sizzling of egg in pan]
Without my eggbeater and frying pan my milk and eggs would just sit there. In a cell, the same problem would occur, unless the cell’s cooking gear- the enzymes--make chemical reactions happen. Now there’s something interesting about how a cell works. As I’ve said DNA contains a cell’s recipes and RNA reads them. It turns out that RNA needs enzyme gadgets to be able read the recipes. It’s as if the first instruction for our omelet was to turn on the kitchen light. If the light’s not already on, the chef can’t read. It's this circular very basic, relationship between DNA, RNA and enzymes that makes it so hard to understand how modern cellular life began.
Okay. And now my omelet is done! So from Chef Jean…Bon Appétit!
JOHN HOCKENBERRY: Now let’s go back to what Harvard geneticist Jack Szostak was saying.
JACK SZOSTAK: And so we have a complicated system where DNA encodes RNA, which encodes proteins.
JOHN HOCKENBERRY: And by the way, when he says the word “encodes” he means “has the instructions for.”
JACK SZOSTAK: And then the proteins are enzymes, which are responsible for the synthesis of DNA and RNA. It’s a cycle and every part depends on every other part. It was very hard to imagine how that kind of cycle could have started.
JOHN HOCKENBERRY: It’s hard to imagine because its one of those chicken and egg paradoxes, like the situation where the chef needs a light to read the instructions to turn on the light. Professor Szostak is a leading advocate of RNA World theory, which postulates that before life evolved today’s complicated division of labor, RNA somehow did all the work itself.
JACK SZOSTAK: One of the breakthroughs came with the discovery that the RNA molecules could be catalytic.
JOHN HOCKENBERRY: Meaning RNA that molecules could make reactions go. In the 1980’s researchers showed that RNA sometimes acts like an enzyme, a discovery that earned Thomas Cech and Sydney Altman a Nobel Prize. So enzymes weren’t the only molecules in the cells that could make reactions happen. It's as if they discovered a chef didn’t need any gadgets in order to make an omelet. Jack Szostak:
JACK SZOSTAK: What that showed in principle was that RNA might be able to actually catalyze its own synthesis.
JOHN HOCKENBERRY: In other words, maybe earlier life could actually have been simpler, needing neither DNA nor the enzymes. RNA would have done everything then, including storing the genetic information. The theory is hard to prove, however. If they ever existed, there are no such primitive cells left for scientists to study. The RNA world theory has many advocates in the scientific community. But some researchers say that before RNA could have appeared, early life must have developed a way to produce energy to fuel its chemical reactions. Carl Woese is a microbiologist at the University of Illinois.
CARL WOESE: There are two great aspects of living systems. And one is of course replication but the other is metabolism. And metabolism among other things provides you the building blocks with which to make RNAs, proteins, etc. I favor and a number of people favor that metabolism came first and replication grew out of it.
JOHN HOCKENBERRY: But others say that initially even before the primordial soup would have been too dilute for chemical reactions to have taken place. That what came first was neither RNA nor metabolism.
LOUIS ALLAMANDOLA: Imagine you are in a pond or a puddle or even a large sea. You might have all the ingredients there. But the probabilities and chances of all them getting together and then staying together long enough so that a third essential component might come along is very low.
JOHN HOCKENBERRY: So NASA Chemist Louis Allamandola says life needed a container to keep its ingredients corralled.
LOUIS ALLAMANDOLA: If these things started to happen in a little proto-cell, the odds of interesting chemistry—more complicated chemistry taking place—increase. And so once you have that kind of a proto-cell you could have chemistry taking place inside which is different from chemistry outside. It's considered an important step in this whole process of evolution from chemistry to biology.
JOHN HOCKENBERRY: One of the wilder theories about life on Earth is that it didn’t start on Earth at all. Remember primordial soup needs only water and a few other ingredients and all of these exist in many places apart from Earth. The only really important requirement for this early process to begin is that the temperature be warm enough so that the water isn’t frozen and cool enough so that it doesn’t turn to steam. Scientists call anywhere these conditions exist "the habitable zone.”
[sound of meteorite entering the atmosphere & people exclaiming about it]
JOHN HOCKENBERRY: That explosion is a sonic boom made when a meteorite entered the atmosphere over New Zealand in 1999. Very few meteorites this large ever encounter Earth. But many small meteorites do fall from the sky and more than one thousand tons of fine comet dust filter down every day. In the middle of the 19th some European physicists and biologists proposed that life on Earth—not just such raw ingredients, but life itself--originated deep in outer space, beyond the solar system. The theory, dubbed "Panspermia," postulated that microbes from distant stars seeded planets far and wide. The idea sounds more like science fiction than science. It has fallen into disfavor because many scientists believe living organisms couldn’t reach Earth from another star. But Australian physicist Paul Davies says the notion that microbes travel from one planet to another within our own solar system is not farfetched at all.
PAUL DAVIES: Cocooned inside a rock, say a meter or two across, a microbe would be shielded from the worst of the radiation and it would actually be perfectly comfortable. It would be a very good way to ride from one planet to another
JOHN HOCKENBERRY: Meteorites from Mars fall to Earth every year. One such rock might have been the source of life on Earth. The space agency NASA is sending a series of missions to Mars to see if there is or ever was life on the planet. In preparation the agency is conducting research at one of the most Mars –like regions of Earth. When we return a visit to the Arctic’s Haughton crater.
JOHN HOCKENBERRY: This is The DNA Files. I’m John Hockenberry. In this next segment, producer Robin White tells us about the search for life on Mars and how a group of scientists is going to the far reaches of Earth to find out more about our planetary neighbor.
ROBIN WHITE: Fourth in line for the sun, next to Earth in the habitable zone, Mars has always fascinated us Earthlings. We call it by the name the Romans gave it after their God of War. Maybe that’s why we’ve always been a bit leery.
ORSON WELLES: We know now that in the early years of the 20th Century this world was being watched closely by intelligences greater than mans'…
ROBIN WHITE: The 1938 radio drama broadcast of H.G. Wells’s War of the Worlds about a Martian invasion caused panic among listeners who took it for the truth. Early astronomers imagined canals on Mars and others fantasized great civilizations. But when we first sent a spacecraft in 1969 Mars seemed cold and barren. NASA scientist Chris McKay – sometimes called Mr. Mars – says 4.5 billion years ago, Mars was warmer but doomed.
CHRIS MCKAY: Imagine taking a large turkey and a small potato out of the oven - the small potato is going to cool faster even if they left the oven at the same temperature. In this analogy Mars is the small potato. Earth is the big turkey. Mars lost its heat much more quickly…
ROBIN WHITE: And McKay says when Mars cooled it lost its thick atmosphere. But when Mars was a warmer potato it probably had flowing water, lakes, oceans even.
CHRIS MCKAY: If Mars had water... even if only for a few hundred million years, that could well be long enough for life to appear there if Earth is any measure of the ability of life to appear on a planet.
ROBIN WHITE: Mars had the same primordial soup ingredients as Earth. So a few hundred million years could have been long enough for chemistry to start morphing into biology. But Mars’s warm period was over so long ago that if there was life, there’s only a slim chance anything’s left alive now. So we’re looking for traces – evidence - fossils. In 1996, some geologists at NASA’s Johnson Space Center in Houston thought they’d found just that in a meteorite from Mars called Alan Hills 84001.
KATHIE THOMAS KEPRTA: I walked into Dave’s office and …I knew that something important was going on because David’s desk was all cleared off and it’s never cleared off.
ROBIN WHITE: Kathie Thomas Keprta remembers a meeting with her colleague Dave McKay
KATHIE THOMAS KEPRTA: … and David said I have something amazing to tell you and it can’t go any further than this office…he told me why ... because he thinks he’s seeing evidence of possible life forms... he was showing me pictures and I sat there and I looked at him and I thought “Oh my gosh I think he’s nuts."
ROBIN WHITE: It wasn’t living Martian bacteria flying through space - but possibly signs of dead ones. Keprta’s now convinced the rock does show traces of bacterial life from Mars that date back 3.9 billion years. Searchers on the National Science Foundation’s annual meteorite hunt found the grey-green fist-sized rock in Antarctica. It contains magnetite or iron oxide crystals. Some similar crystals are made on Earth by geological processes, but others are made by bacteria.
KATHIE THOMAS KEPRTA: They form them in a chain within their bodies and they use them as a little magnet to orient themselves using the Earth’s geomagnetic field lines. Now they want to make the best magnet that they can make because that’s going to improve their opportunity to survive.
ROBIN WHITE: And so they make very pure magnetites which look identical to those found in the meteorite. But even though the meteorite's crystals look right, how can we be sure they’re signs of life when they come from outer space? Laurie Leshin, Associate Professor of Geological Sciences at Arizona State University, is skeptical.
LAURIE LESHIN: It’s just a real question of whether or not there is such a thing as a uniquely biological shape - the shape of a mineral that would lead you to say "Aha! There’s no question that this was made by a bug." and we still don’t know the answer to that question.
ROBIN WHITE: Leshin says we need to go dig our own samples – perhaps in old Martian lakebed - to find out for sure. In 1997 the Pathfinder mission landed on Mars and millions of people watched on the internet as the Sojourner Rover explored the local rocks. Pathfinder didn’t find signs of life but didn’t rule it out. The current mission to Mars, the Odyssey orbiter, is looking for water. On future missions we’ll go get that soil and bring it back and then probably in twenty years we’ll see humans on Mars.
In preparation for that scientists are landing at the ends of the Earth - on Devon Island, in the frigid Canadian Arctic. Devon’s the largest uninhabited island on the planet and a polar desert with winter temperatures as low as -60 degrees centigrade.
VOICE: Looks like your weather is finally trying to clear up a bit.
ROBIN WHITE: The international scientific team comes here each year because the harsh, dry climate is similar to Mars. Also here is Haughton Crater, one of the best preserved impact craters on Earth. 23 million years ago an enormous rock crashed and left a hole the size of London. Charlie Cockell, chief biologist at the Haughton Mars Project says Mars is spattered with craters like this.
CHARLES COCKELL: The surface of Mars has been hit by asteroids and comets for 4.5 billion years now so the surface of the planet is essentially a shocked surface. It’s where the rocks have been pulverized by comets and asteroids over a long period of time…
ROBIN WHITE: In summer the Haughton Crater is piebald with snow patches and brown melted permafrost. Down inside the crater Cockell shows me enormous piles of blue-grey breccia - rock which was transformed by the thousand-degree heat from the meteor impact.
CHARLES COCKELL: Can you see that green?
ROBIN WHITE: Yeah?
CHARLES COCKELL: That's organisms living in shocked rocks.
ROBIN WHITE: The heat made the rock porous and microorganisms now live inside, protected from extreme freezing and thawing and high levels of polar ultra violet radiation. UV radiation is also abundant on Mars because Mars has no protective atmosphere. UV makes the strands of a cell’s DNA fuse together which causes the cell to die. When you’re a one-celled creature, that’s a problem.
CHARLES COCKELL: The best thing you can do is try and hide from UV radiation and you can do that two ways you can either screen yourself by producing ultraviolet screening compounds, essentially natural sun creams, or you can hide inside things like rocks.
ROBIN WHITE: Darlene Lim who studies geology at the University of Toronto, says another way microbes cope is to build a shell.
DARLENE LIM: Here of course we’re sitting at Haughton Crater, we’re cold, were putting on a lot of clothes to deal with our elements - well if you were on a planet that had a lot of incoming UV that could be damaging to whatever genetic code you may have then you may have to figure out strategies in order to deal with that and one possibility is that you may want to build some sort of exoskeleton or a shell that actually helps to shield yourself.
ROBIN WHITE: And if microbes on Mars had shells they might have left fossils for us to find in sediments on the planet’s surface. Gordon Osinski has found fossilized hot springs around the rim of the Haughton Crater. The University of New Brunswick geologist thinks we should look at hydrothermal vents as a possible haven for life on Mars – even to the present day.
GORDON OSINSKI: If there is life on Mars today, then hydrothermal systems there would pretty much be the only place that life could survive at the present time
ROBIN WHITE: But Martian hot springs wouldn't last forever. When one hot spring dies out, how does life move to the next when we know that nothing can live on the surface of Mars? Critics of the Haughton Mars Project say the scientists are just stabbing in the dark about life on Mars. But Mars scientists have a touch of the believer in them. The team members at Haughton Crater are even locking themselves into an isolated habitat to simulate a manned mission to Mars. Principal investigator at Haughton Crater, Pascal Lee, says looking for life on Mars touches something deep in the human soul.
PASCAL LEE: The fact that we’re interested in going to another planet to look for life is perhaps part of a process of life itself - a process whereby life seeks to expand from one planet to the next. It’s something that would allow it to have a foothold on more than one world. At the same time, it’s something that satisfies its appetite for knowledge and in a technological age it procures an evolutionary advantage. The more knowledge you have the more capable you are - the more likely you are to survive.
ROBIN WHITE: Lee hopes to be one of the first to go to Mars. The person who finds life on Mars, if it’s there, will go down in history. They’ll also answer an important scientific question which is whether life, if it exists on other planets, is genetically the same as life on Earth, or whether it had a second genesis. Charlie Cockell, says whatever the answer, it’ll be profound.
CHARLES COCKELL: If we find life on Mars and it’s like life on Earth, what that tells us is that life was transferred between Earth and Mars in the early history of our planet and in fact we have extinct relatives on Mars or possibly relatives still alive today in the subsurface of Mars.
ROBIN WHITE: It could also mean that life came to both planets from elsewhere, or that DNA is the only way to write the book of life given the chemistry in our solar system. If we find Mars life that’s different from us that could mean that life is common in the universe because it’s occurred twice in our neighborhood. And if we don’t find it at all, it means evolution is very special. For The DNA Files I’m Robin White.
JOHN HOCKENBERRY: Thank you Robin. I’m John Hockenberry. If there is life on Mars, will NASA researchers know it when they see it? You’d think it would be obvious whether something was alive or not. But when you are talking about microbes its not always that simple. Researchers are preparing themselves for the difficulty of identifying live organisms from Mars by learning the limits of life on our own planet. The bugs they're looking for are called extremophiles, microbes that live in places that humans, plants and animals would find uncomfortable if not downright fatal. Like boiling hot springs in Yellowstone - or in shocked rocks in Arctic craters. Compared with what we're used to it's a pretty strange menagerie.
CIRCUS ANNOUNCER: Welcome to the Bacterium and Bacillus Circus. Ladies and gentlemen step right up.
JOHN HOCKENBERRY: When people first hear about extremophiles there’s a temptation to think they’re freaks of nature, or perhaps stars of cable television. But scientists say even on Earth what’s "normal" for life may not be what we’ve always thought. For instance, some researchers suspect that pound for pound there may be more microbes living underground in rock than all life on the surface. In any event, I’ve come to this circus show to hear about some of the more far out microbes yet discovered.
CIRCUS BARKER: Stand back. Boys, girls, ladies and gentlemen. And now for the most incredible, most bizarre, the strangest... the most amazing microbe:
Folks Pyrolobus fumarii lives at the bottom of the sea... in hot springs... at the hell-defying temperature of 221 degrees Fahrenheit. Nine degrees above boiling water.
For our next act, feast your eyes. Folks, this bacterium is happiest in Antarctic brine pools at a frosty 25 degrees Fahrenheit, almost as cold as your freezer:
Ladies and Germs, the incomparable ferrosplama acidarmanus!
This feller calls home acid pools hundreds of times more burning, more deadly, more metal melting than acid in your car battery.
JOHN HOCKENBERRY: Hey... let’s get out of here before they start passing the hat.
They’re not called extremophiles for nothing! Research on these bugs help scientists learn about what to expect on other planets. Jack Farmer is a geology professor at Arizona State University and director of the school’s astrobiology program.
JACK FARMER: Twenty years ago when we headed off to Mars with the Viking Missions, we had a fairly limited and narrow perspective on what was possible for life. People pretty quickly abandoned the idea that there could be life there. Since that time, with all the advances in biology, with the advent of knowledge of extremophiles and this broader perspective on biology the door is opened up again pretty wide for many options for exploration on the planet Mars. An outcome of that is the origin of this new discipline called astrobiology.
JOHN HOCKENBERRY: If there’s life on Mars today its probably growing in protected springs or in caves, places the Viking mission didn’t visit. We sent producer Daniel Grossman to a cave on Earth where researchers are learning lessons that could help future Mars missions. He sent us this report from southern New Mexico.
DANIEL GROSSMAN A heavy steel grate marks the entrance to Spider Cave in Carlsbad, New Mexico. I’m joining a crew collecting samples from this cavern, a two-mile network of narrow passageways and bedroom-size chambers. But before we can we can enter, our guide Jim Werker must clear the way.
JIM WERKER: Yo, Bubba, where you at?
DANIEL GROSSMAN: A rattlesnake named Bubba, calls the entrance to Spider cave its home.
JIM WERKER: It looks like Bubba is in here.
DANIEL GROSSMAN: Jim Werker spots the rattler, but before he can nab it with a long stick, Bubba has slithered into a crevice. Lowering myself into the cave, I just hope the snake is more afraid of me than I am of it.
DANIEL GROSSMAN: We’re a team of 8, equipped with helmets, head lamps, rock cutting tools and sterile sample holders. One hundred feet below the blistering desert it’s cool and damp. Orange markers blaze a trail that weaves back and forth up and down past countless other passageways. Unlike the smooth, worn floor, the walls and ceilings are rough: like the surface of a well-cooked pan of brownies, colored in browns and grays.
JIM WERKER: I'm through…
DANIEL GROSSMAN: We stop in a long narrow chamber just high enough for me to stand without hitting the ceiling. University of New Mexico biologist Penelope Boston leads the today’s expedition. She takes out some bottles and tweezers and hands them to summer intern Katie Harris.
PENELOPE BOSTON: So Katie, you’ve probably not done anything like this before?
KATIE HARRIS: No. Not at all.
PENELOPE BOSTON: Well, the idea is to sterilize the tool we’re going to get the sample with. These are sterile inside. They’re not sterile outside. Neither are we.
DANIEL GROSSMAN: I expected the cave to have hard surfaces. But these walls are crumbly to the touch sort of like dry rotted wood. The comparison is apt because the researchers believe the rock is rotten—eaten by microbes. Boston holds a tweezers up and plucks a marble-size hunk of the brown crumbly rock.
PENELOPE BOSTON: Get right up under where you want and just kind of flick it in there. Did it go in? Yea? Good. Just put it in there. Some people have a real hard time with this.
DANIEL GROSSMAN: Until this team began their research, the crumbly crust found on cave walls like these was believed to be result of the chemical breakdown of the rock, a sort of rust build-up on the metal-rich stone. Penelope Boston and her team have shown that microbes are living in the rock, and she suspects that these bugs are actually eating it. If she can identify what these critters consume, the research could broaden the bounds of what conditions are known to support life. Penelope Boston.
PENELOPE BOSTON: All of the work that we are doing in these many different caves are allowing us to approach some of the kinds of problems that we are going to be facing looking for life on other planets. The first, of course is the fact that it’s not obvious life. This is very cryptic stuff. You look at it and it looks like rock, and it looks like dirt and mud.
DANIEL GROSSMAN: When not crawling through cave passages, professor Boston conducts laboratory research at the University of New Mexico in Albuquerque. One of her colleagues Diana Northrup is showing me electron microscope pictures of cave samples. One picture shows a curious object Northrup discovered not long ago.
DIANA NORTHRUP: I was actually running the scope that day. And I went, "Look what we've got!” And there were just like these chains and chains. It wasn’t an isolated one. If you look at some of this there 's chains all over the place. Penny was up in Boulder. I called her up and said, "Whoa, you won't believe what we found.” I was like, this is definitely an organism.
DANIEL GROSSMAN: It was unlike any mineral like she’d ever seen. And it had a suction cup-like structure resembling parts of certain bacteria. Visually it appears to be a living thing, but proving that isn't easy. Northrup has found DNA molecules in this rock, but they could come from other underground organisms. If she could grow the strange object in the lab that would be the most conclusive proof. But so far she's had no luck. Penelope Boston says the difficulty of making sense of cave samples from earth teaches an important lesson for investigators of life elsewhere.
PENELOPE BOSTON: If we here with all our laboratories and big teams of people have a hard time convincing people that this stuff has living organisms in it, it's going to be that much more difficult to demonstrate a biogenic character to something that we find on another planet.
DANIEL GROSSMAN: For The DNA Files, I’m Daniel Grossman
JOHN HOCKENBERRY: Thank you Dan. I'm John Hockenberry. Hard as it will be to figure out if we're actually looking at extraterrestrial life, it might be even harder to make sure our search for it doesn't have the unintended result of contaminating other pristine worlds. We’d, in that case, end up looking at our own footprints, so to speak, rather than something truly extra-terrestrial. Besides Mars, one of the places we’re most interested in exploring is Jupiter’s moon, Europa. Robert Pappalardo, of the University of Colorado at Boulder says Europa might have an ocean under its intriguing icy surface.
ROBERT PAPPALARDO: What Europa looks like from afar is somewhat like a cracked eggshell – or perhaps like a bloodshot eye - it's criss-crossed by lines - dark lines and bands somewhat reddish in color. When you zoom in on Europa, you see that these lines become ridges that crisscross the surface, sort of like looking at a plate of spaghetti that's been scrambled up.
JOHN HOCKENBERRY: The double ridges in the ice are probably cracks formed by warmer ice pushing up from down below. The fact that Europa rotates and also is so close to the giant planet Jupiter causes its ocean and ice sheet to be flexed and heated by a tremendous tidal pull.
With a possible tidal change of up to 30 meters, the ice cracks every half hour and it probably sounds something like this earthly ice sheet.
The possibility of an ocean and hydrothermal vents or even underwater volcanoes makes Europa another good candidate for harboring life. But how do we sample it without contaminating it? Some of the suggestions seem almost wacky
ROBERT PAPPALARDO: It’s been said that the best way to search for life on Europa could be to look for freeze dried fish in orbit.
JOHN HOCKENBERRY: The idea is that something crashing into the ice – a meteor or perhaps a ball dropped from a spacecraft - could spray detritus into orbit. The spacecraft could then check it for it for fish - or microbes - or whatever’s there without ever landing.
At the moment Europa’s being photographed by the Galileo spacecraft and there are plans to send another orbiter to map the whole surface. But what happens when these spacecraft end their missions? Galileo is scheduled to crash into the harsh environment of Jupiter. But the next orbiter is going to end its life on Europa itself.
ROBERT PAPPALARDO: There’s been a recommendation that the Europa orbiter receive a certain critical dosage of radiation so that the orbiter will have to live a certain number of days in orbit before it receives a total dosage enough to effectively sterilize the spacecraft. If any Earth organism is on board that spacecraft we’ll have to know that it’s dead before we allow it to crash into Europa.
JOHN HOCKENBERRY: And we can’t be too careful because any Earth bug could spread all over Europa in its ocean currents. The threat to Europa if contaminated by Earthly microbes is serious, but a concern closer to our hearts is the possibility of contamination going the other way: that some alien species in goop brought from other planets could run rampant on Earth. In the 1971 Robert Wise film, The Andromeda Strain, a satellite falls to Earth contaminated with microbes from outer space. A recovery team is sent to find the satellite in a small New Mexico town.
VOICE 1: the signals from the satellite are getting very strong…
VOICE 2: Sir! See that, lieutenant?
VOICE 1: See what, Frank?
VOICE 2: Over there by the fence — it looks like a body.
JOHN HOCKENBERRY: It is a body and there are others as well. To prevent the kind of plague depicted in the Andromeda Strain, NASA actually has a program to prevent microbes that might be brought back in samples from other planets from contaminating Earth. The agency says any soil samples brought to Earth will be secured in sealed containers. And to prevent anything live from hitchhiking back on the exterior of returning spacecraft, the agency plans to sterilize the vehicles in space, or transfer sealed sample containers from contaminated landers to clean spacecraft that would return to Earth.
NASA insists alien microbes are no cause for concern.
I'm back at New York's Museum of Natural History to chat with astrobiologist Michael Meyer. Dr. Meyer, you see, was once NASA's planetary protection officer.
MICHAEL MEYER: The job of Planetary Protection Officer has the coolest title of any job I ever had. It worked at parties. It worked at bars. Yes I am the Planetary Protection Officer. It was great.
JOHN HOCKENBERRY: You had a badge that said Planetary Protection Officer on it?
MICHAEL MEYER: I couldn’t figure out the paper work to get a badge. I thought it would have been proper to have one just in case I had to arrest someone for violating planetary protection protocol--although nobody knows what that is. Except NASA.
JOHN HOCKENBERRY: Which brings me to the question, what does the planetary protection officer do?
MICHAEL MEYER: Planetary Protection Officer. Reason why it's created is the concept that we’ll be exploring other planets. We should do that responsibly. What does that mean? One of them is, when you start talking about bringing a sample back from another planetary body where there’s even remote chance that there might be something living or have been alive on it, then you should make sure if you are going to bring that back that you don’t contaminate Earth. And when you go out and look at some other place that you don’t contaminate the world that you’re trying to study.
JOHN HOCKENBERRY: When we think about something coming from somewhere else being a contaminant what would be something we would fear most?
MICHAEL MEYER: Certainly the concern is that if you brought something back from another planet that you'd bring back something living. And somehow think wow! This is tasty! What a great Earth! And that it would take over. It's very far-fetched. But it's something where we know how to contain dangerous things. We can do it, and we know how to do it, so it would be stupid not to go through planetary protection.
JOHN HOCKENBERRY: I’ve been focusing on life on Earth and in our solar system, because that is the only life we’re ever likely to come in contact with, at least for the next hundred centuries or so. But many scientists believe that microbes, if not intelligent aliens, are living on planets orbiting distant starts. This speculation has gained considerable momentum since 1995 when the first extra-solar planet was discovered. Since then nearly 100 more have been reported. Paul Butler is one of the world’s leading extra-solar planet hunters. He says so far researchers have detected primarily two varieties.
PAUL BUTLER: They’re either the so called "hot Jupiters" that have these radical four-day orbits, they orbit a hundred times closer to their star than Jupiter does to the sun and as such they’re boiling hot; and then the other class of planets are Jupiter-like planets that are in oblong, or egg-shaped orbits. Both these types of planets are quite stunning, quite startling.
JOHN HOCKENBERRY: With existing rockets it would take tens of thousands of years to send a mission to get a look at even the nearest of these planets. Even so, Butler is certain the hot Jupiters are completely sterile, orbiting so sizzingly close to a star. The planets with eccentric orbits are another story. They are more temperate, though they alternate between quite hot and quite cold. Paul Butler.
PAUL BUTLER: So the fact that planets are in wacky orbits and might have extreme conditions probably doesn’t rule out the possibility of simple, single-celled creatures. We know how hardy they are. It probably does rule out the possibility of highly advanced creatures--multi-cellular organisms.
JOHN HOCKENBERRY: There may be planets out there with just the right orbit for complex life--relatively circular at just the right distance from a star. When I gaze up in the sky, I may be staring at one. But so far telescopes aren’t sensitive enough to detect a planet like ours. NASA is proposing to launch a flotilla of Planet-Finder satellites that could detect Earth-like planets, though it will probably be another generation before the project is launched. These satellites will also be able to gather spectral data from light coming from those distant planets, possibly detecting the first evidence of life beyond our solar system.
VOICE: After they had formed the earth, Odin, Vili, and Ve took the blood that was left from Imir and made the ocean in a ring. The three brothers lifted the skull of Imir and made the dome of the sky. They placed a dwarf at each of the four corners to support the sky high above the Earth…
JOHN HOCKENBERRY: In a little less than an hour, we’ve come a long way from creation tales like the Icelandic legend of Yawning Gap. Or have we? Brother Guy Consolmagno a Jesuit priest and a staff member of the Vatican Astronomical Observatory says searching for microbes on Mars, the origins of DNA, or life on the planets of distant stars is how scientists make sense of the awesome scale of the universe and the incredible wonder of creation.
GUY CONSOLMAGNO: These are all questions that are part of a great puzzle, a great game--and by playing this game I become a in some way little more intimately connected with the fellow at the other side of the board who’s been setting up the puzzles for me. And that’s God, that's the creator.
JOHN HOCKENBERRY: We may not all believe in a creator, but physicist Paul Davies says the need to explain creation may very well be one attribute that makes us human.
PAUL DAVIES: The search for the origin of life in some sense is a search for ourselves—who we are and what our place is in the great cosmic scheme of things. This is one of the big questions of existence.
JOHN HOCKENBERRY: Astrobiology—the search for life beyond Earth and the study of its origins—is inching forward with new findings about the great wonder that began some 13 billion years ago with the big bang. And even though knowing the answers won’t necessarily cure hunger or raise the standard of living, it gives me pleasure each time I learn a little more about where I’m from in this universe we call home. How about you? I’m John Hockenberry. Thank you for listening to The DNA Files.
This series, The DNA Files, was produced by SoundVision Productions with funding by the National Science Foundation and the Alfred P. Sloan Foundation.
This program, Life: How to Make a Cosmic Omelet — Genetics and Astrobiology, was produced by Daniel Grossman and engineered by Jane Pippick. The features on Europa and the Houghton Mars Project were produced by Robin White and engineered by Robin Wise. The program editor was Loretta Williams, and our host was John Hockenberry.
Special thanks to Hathfor Ingveson, Daniel McCallum and the Houghton Mars Project.
The opening feature, “Life in Hell,” was produced by Joe Jordan, and edited by Gemma Hooley.
The DNA Files is: Managing Editor, Rachel Ann Goodman. Science Consultant, Sally Lehrman. Research and Production support by Adi Gevins and Noah Miller. Technical and Music Director, Robin Wise.
Original music composed by Jesse Boggs and performed by the Stanford Woodwind Quintet, Anton Schwartz, Tom Hayashi, and Jesse Boggs.
Project Director, Jude Thilman. Marketing by Murray Street Enterprise. Legal services by Walter Hansel. and Spencer Weisbroth.
You can visit our website at www.dnafiles.org. Send your responses and letters to email@example.com. For tapes and transcripts, call 866-DNA-FILES (866-362-3453).
The Executive Producer is Bari Scott.
This has been a SoundVision Production, distributed by NPR, National Public Radio.