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| Chris McKay |
How did life begin? Are we alone? Where are we going?
These are the trivial concerns that preoccupy NASA planetary scientist Chris McKay. He believes that the vital clues to answer these questions may only be found when scientists can closely examine the world in our solar system most like our own… Mars. No one knows how life began on Earth and it’s possible that the answer can’t be found on this planet. The active geology of the Earth and the intense activity of life itself have effectively hidden the evidence of what this planet was like at the beginning. Mars, however, may have been much like the Earth in its early stages. Unlike the Earth, Mars has been effectively dead for over 4 billion years. No plate tectonics to recycle the surface, no running water to wash away the evidence. Mars could be an open book revealing chapters in life’s story long since erased from the Earth.
In his intense focus on planetary science for the last two decades Dr. McKay has crisscrossed the globe seeking extreme environments as close as possible to the conditions that may have existed on an earlier warmer and wetter Mars. This includes Siberia and the Canadian Arctic, super dry regions such as Chile’s Atacama Desert, and his favorite Mars analog environment, the dry valleys of Antarctica.
“It’s really the most amazing place I’ve been to. It’s like another world in terms of its interest and its connection to things I’m interested in like Mars. It’s like a frozen desert – that’s why I imagine it’s sort of like Mars.” Chris points out that Antarctica is one of the only places on Earth where you don’t see jet contrails in the sky. “It’s isolated and far away and you really get the sense of being out there”.
Life’s little hiding places
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| A rock from the Antarctic dry valleys |
But McKay isn’t just interested in getting away from it all. His research in Antarctica has revealed that organisms on Earth are capable of thriving in the most unlikely of places. One such environment is within the pores in permeable rocks lying on the surface in the dry valleys. The only precipitation in this area is a rare light dusting of snow. In the hottest part of the warmest days the surfaces of the rocks occasionally get a little bit above freezing and some of the snow melts into the rock. Since the rock is slightly translucent, tiny microorganisms find it possible to use the sun’s energy to drive photosynthesis. This is shown by a glance at a cross section of the rock, which reveals a greenish layer in the top couple of centimeters of the rock. “It’s practically balmy in there,” says McKay with characteristic humor.
Another fine place for bugs to hang out is deep in the water beneath frozen over lakes in these same dry valleys. Chris’s team has cut holes in the ice – no small matter when the ice is over 5 meters thick. The scientists then dive in and start looking around in the frozen twilight. Despite the ice’s thickness some light does make it through. This is because the ice crystals are so large and so pure that light can make its way to the liquid depths below. At the lake bottoms some organisms are doing quite well. There are macroscopic growths of coral-like structures that again thrive on photosynthesis and the basic nutrients available in the super cold water.
The presence of life in these extreme environments on Earth can provide important clues into what kind of conditions life needs to thrive on this planet and possibly others. What it seems to come down to is that if there is liquid water, even in minute quantities, and enough light for photosynthesis to take place, life springs forth. Some scientists, such as microbiologist Penny Boston, are finding that some kinds of life even thrive under conditions of complete deprivation of light deep beneath the Earth’s surface.
We now know life can hold on and even do well in these kinds of inhospitable locations, but could it originate there? Even a theorized warmer and wetter Mars in its early history wouldn’t be “balmy.”
How did we get here?
“The question of the origin of life was key”, Chris explains. “How did life get started? It is hard to understand a whole planet that’s like the polar regions versus the polar regions of a planet that’s rich in life. We don’t even know how life got started on Earth, so we have no idea how it got started on Mars if it did. These are questions that are beyond what we can do right now. As a result, our research has only been focused on the question of how does life survive in the polar regions today.”
“Sometimes I think we’re really close to knowing how life got started. Sometimes I think we’re missing something fundamental – that we’re no closer to it than Leonardo Da Vinci was to building a flying machine. It’s hard to say.”
It now appears probable that Mars had conditions capable of supporting life for a very long time early in its history. In fact, Mars had a couple of advantages that the Earth did not. One of these is that Mars didn’t have a Moon-forming impact early in its history like the Earth.
“A Mars-sized object slammed into the Earth and knocked a chunk of material off which condensed to form the moon. It was a major cataclysm that hit the reset button on life, for sure. Any life that had started on Earth would have been eliminated as of 4.5 billion years ago.”
The other big advantage on Mars had to do with something we don’t often associate with modern Mars – the presence of oxygen. The development of complex lifeforms on Earth had to wait until there was sufficient oxygen generated by early anaerobic (non-oxygen breathing) lifeforms. This process took about 700 million years. On Mars, due to a variety of factors such as a greater initial quantity of volatiles including water, the lower gravity letting more hydrogen escape, less volcanic outgassing, and the lack of plate tectonics as on Earth, all combine to create a situation in which Mars could have become sufficiently oxygenated to allow development of multicellular life in only 10 to 100 million years. With these kinds of advantages, how advanced could life have become on Mars before the surface became uninhabitable?
“It could have been as advanced as small animals and plants – if evolution was faster on Mars. It could have gone up to the Precambrian level – trilobites and palm trees; fern trees would have been possible. That’s not saying that they’re there, but theoretically it’s possible. We should include in our research the ability to be able to see fossils of things like that.”
Better than fossils
The next big question McKay ponders is, where did the life on Earth and possibly Mars come from? Finding any kinds of fossils on Mars would provide great clues. Even better, would be finding the lifeforms themselves – not necessarily alive – but frozen intact in the deep permafrost. This is another reason Chris has spent significant amounts of time in Earth’s polar regions. On a recent expedition to Siberia, McKay’s team drilled into 3 million-year-old frozen tundra and found frozen lifeforms capable of being brought back to life. On Mars it is suspected that there may be ices that are billions of years old and these may contain the frozen corpses of Mars life. Could they be brought to life?
“Not likely,” says Chris. “These organisms would have probably accumulated many lethal doses of radiation from background emission of naturally occurring radioactive elements. Although non-viable, they would be largely intact and suitable for phylogenetic analysis.”
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| The 'tree of life' |
Such analysis could provide evidence of what to Chris is the Holy Grail of planetary biological research – a second genesis of life on Mars. All life that has been found on this planet has evolved from a common ancestor. This is apparent from the “tree of life” which indicates that the basic building blocks of life are the same in all creatures here on Earth. If life had a second genesis on Mars, these basic building blocks would be completely different. If we find corpses of life in the Martian ice, we can determine whether or not we’re all one big family or not. Since we still don’t really know how life formed on Earth – it has never been successfully replicated in the laboratory – it could also have been formed on Mars in parallel with Earth life.
“However life originated on Earth, either from external sources or from local processes, we might expect that the same events could have occurred on Mars since the environments available on Earth would also have been available there.”
Life from other worlds
What kind of “external sources” could there be for Earth life? There are two distinct possibilities: interplanetary transfer via asteroid bombardment, and arrival from distant stars, a process known as panspermia. Throughout the early history of our solar system, but especially during the early history of both Earth and Mars, material has frequently been exchanged between the two planets. Several meteorites have been discovered on Earth that have been proven to have originated on Mars and it can be assumed that the opposite case is also true – lots of Earth rock is now on Mars. Some types of bacteria are capable of withstanding the force of such a catastrophic impact and remaining dormant for great lengths of time deep within these rocks as they make their way between planets. This means that life on Mars could very well be transplanted Earth life. If the conditions for the origin of life on Mars were even better than those on Earth, the opposite could also be true. In this case, we could all be Martians!
Panspermia is an even more intriguing possibility. According to this theory which has been elucidated by Mars Society president Robert Zubrin, “astronautically adapted” bacteria could have traveled from star to star through transfer between stellar Oort clouds – the extended shells of frozen volatiles out beyond the farthest planets. In such a way, proto-cometary bodies in our Oort cloud could have become impregnated by interstellar travelers and periodically descended toward the sun to impact with Earth and Mars, bringing the seeds of life from the distant cosmos. Zubrin believes this is the most likely origin for life on Earth and he fully expects to find the same basic kinds of life on Mars, since it would all have had a common ancestor.
How do we get there?
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| Chris McKay |
Then there is the question of where are we going in the future. What would be the best way to uncover Mars’ secrets? McKay salivates at the thought of how to attack this problem.
“If I was in charge of the Mars program and had no budget constraints I would first do a sample return mission. Then I would go after Gusev crater looking for fossils. Follow that with drilling in the south polar region looking for organisms preserved in the permafrost. That would be the near term. In the long term – establishment of a base. I would use the Antarctic as a model. United States put a base in Antarctica, McMurdo Station, in 1957 with the intention of it being a permanent base and there have been people at that base since then continuously.”
The Antarctic is frequently sited as a potential model for a future Mars exploration effort. While at first this idea may lack the glamour of the notion of settling a new world, it could well be the most practical way to begin such an effort.
“A lot of people assume that the first people who go to Mars are going to be like settlers to the new world – a wagon train, there to homestead and build a farm – but I just don’t see that happening. It’s hard to imagine. The New World was easy because it wasn’t really new, there were already people living here. It was already a place that was user-friendly compared to Mars. I don’t see how the hardy pioneer striking out for the open frontier is going to work on Mars, so I think the Antarctic model is a better one. A small research base”
There are, however, differences that would force a Mars settlement to be more independent than Antarctica. All food consumed in Antarctica, for instance, is grown in more temperate climates and shipped there. The cost of shipping food and other renewable resources to Mars would be astronomical. It would make much more sense to grow them locally. This could create the foundation for a sustained community. There’s also the commute to consider.
“I’ve been working with people in Antarctica for twenty years, but I certainly wouldn’t live there because I could come home. I’d much rather live here and commute there, just like I don’t live in this office. I commute to this office. But if it were far enough away, where the commute took two years, maybe I would live there for a longer period. It’s hard to predict. I think it’s one of the things we’ll just have to wait and see.”
Can we afford to wait?
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| Admiral Zheng's ship of the Ming Dynasty fleet |
Science fiction author Gregory Benford is among some of those concerned that there may me a real urgency to getting humans to Mars for societal reasons. In
a recent interview on New Mars, Benford stated “Unfortunately, I don’t think it’s 100% obvious that we’ll ever do it. There’s a chance we’ll never go to Mars and that’s what terrifies me. That’s why I introduced the Chinese analogy.”
The “Chinese analogy” is a reference to the Ming Dynasty of China. In 1500 AD they were by far the most powerful nation on Earth and, with a huge and capable armada, were on the threshold of discovering and profitably interacting with the western world. A conservative wave quenched their exploratory zeal and they were effectively halted in their tracks. “It’s not crazy to think of it happening to this culture,” Benford muses. “So seize your opportunities when you can.”
McKay disagrees. “I don’t see those arguments as compelling. I don’t think that the chance to do it will go away. It may be true, but I don’t think that space exploration is that fragile that we’ll stop doing it if we don’t go right away. People who follow that logic sometimes say that if we don’t go in the next five years we’ll never go. I don’t find any of those arguments compelling. Obviously I’d like to go sooner than later, but I think that later will happen. I don’t think that there’s any window that will close. In fact I see everything pointing to the opposite, that it gets easier and easier, better and better to go. You can even imagine nanotechnology and micromachines making it easier and easier to go. Self-repairing mechanisms and feedback controls based on computers will make it simpler to imagine building a base for people. I don’t think it’s going to get to a point where we can’t go.”
Countering Chris’s faith in humanity is the trend of the manned space program over the past forty years. In the sixties we went from practically nothing to having astronauts walking on the moon. For the last three decades we’ve failed to get beyond low Earth orbit. Do we still have the cultural vitality to duplicate those achievements, let alone go on to even grander heights? Recent polls suggest that ordinary Americans rank the space program as pretty low on their list of priorities, and Mars is just not on most folks’ radar at all. One wonders if it would be this way if most people could grasp the significance of what amazing discoveries may lie in wait on the red planet. Humanity has struggled to carve out a niche on this planet for millions of years, but it is our generation that has the opportunity to find out the answers to questions like: where did we come from? and, are we alone?
The boldest question of all may be… where are we going, and when?
This article drew extensively from a recent interview with Dr. McKay. View the full transcript.
Joel McKinnon currently works as a User Interface Engineer for a
software company in Half Moon Bay, California. In 2001, he helped to organize a fundraiser for the Mars Society which attracted filmmaker James Cameron, Robert Zubrin, Pascal Lee, and Chris McKay and raised well over $100,000. Joel has had a deep fascination with the planet Mars since childhood.
Posted in Articles at 07:51 PM on 25/06/02
