Living in the Universe

The Mars Rock Revisited

Third Week of January 2008

Back in 1995, a small lump of grayish rock from Mars made a big splash in the newspapers with the claim, put forward by NASA researchers, that it contained remnants of ancient life. This rock had a very interesting journey from the surface of Mars, being blasted off and spending millions of years in space before falling into the Antarctic tens of thousands of years ago. It was discovered in 1984. The rock was called Allan Hills 840001 and it has come to be known simply as the “Mars rock.” It’s one of several dozen Martian meteorites that have been found scattered over the surface of the Earth, mostly in the Antarctic because meteorites can easily be spotted there on the pristine ice surface.

NASA held a big press conference to highlight the claim of extraterrestrial life. Several strands of evidence were presented: small, elongated forms that looked a little like microbes, carbonate deposits, and a form of magnetite that’s often found associated with a metabolic process. Since the discovery, more research has cast doubt on the claims, and only a small number of researchers now believe there’s evidence for life in this particular rock.

Part of the reason this Martian meteorite is so interesting is that it contains organic compounds. Life is thought to have emerged on the Earth from a primordial soup of such compounds based on carbon, hydrogen, and oxygen, although we don’t exactly know how it happened. Scientists found little nodules of organic material in ALH 840001 that could have been created by life. Surrounding them were tiny traces of magnetite. There were also small, elongated forms that looked like tiny bacteria, but subsequent research has found that the elongated forms, perhaps the most compelling evidence at the time, could easily have been created by violent processes when the meteorite was blasted off the surface. They’re molten splatter remnants within the rock.

A team of researchers has returned to the issue of the carbonates, and they’ve just published their findings in Meteoritics and Planetary Science, which is a research magazine. There was also a claim at the time that life on Earth may have started on Mars, being born there and traveling to the Earth in rocks like ALH 840001. These are exciting possibilities, but the team from the Carnegie Institution of Washington decided to identify exactly which rocks and minerals the Allan Hills meteorite contains and then compare the results to rocks that formed definitively on Earth. They used a variety of techniques for their study. As the original researchers did, they found that the tiny spheres of carbonate material are surrounded by an iron oxide mineral called magnetite.

At the time ALH 840001 first hit the headlines, some true believers thought that the magnetite supported the cause of life in the meteorite. That’s because certain Earthly bacteria make small grains of the mineral in order to navigate their habitats using the Earth’s magnetic field, just as human navigators once used lodestone compasses made of magnetite to find their way around. However, most of the magnetite on Earth is not bacterial. It’s ejected in liquid form from volcanoes. If this magnetite cools in an environment rich in water and carbon dioxide, which is usually the case for terrestrial volcanoes, it can act as a catalyst for the formation of organic compounds from the carbon, hydrogen, and oxygen atoms in the raw ingredients.

Andrew Steele and his colleagues decided to compare the Mars rock with volcanic rocks collected from Svalbard, the northernmost territory of Norway. These rocks are thought to have formed when volcanoes erupted in freezing, pristine conditions a million or so years ago. They found that the terrestrial boulders also contained carbonates encircled by magnetite. Thus, they conclude that the organic materials in the Allan Hills meteorite were produced not by Martian microbes but rather by normal chemical reactions within the rock.

This may seem a disappointing conclusion to astrobiologists who hope to find life on other planets and hoped they might have found it on one of the nearest planets, but it does also offer them hope, because if Steele and his colleagues are correct then volcanic activity in a place other than the Earth has produced very interesting looking organic compounds that are indeed the raw materials for life. That means the building blocks of life may exist on cold, rocky, volcanic planets throughout the universe. And remember, the universe is a very big place.

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Dust Storms and the Mars Rovers

Fourth Week of July 2007

Dust storms on Mars have been in the news for the last few weeks. A series of severe Martian summer dust storms has blocked ninety-nine percent of the direct sunlight to the Opportunity rover, and its companion Spirit has been affected to a lesser extent. Both rely on solar panels to charge their batteries. Scientists think these storms could continue for several days or even weeks. Alan Stern, who is the associate administrator of the science directorate of NASA said, “We’re rooting for our rovers to survive these storms, but they were never designed for conditions this intense.” NASA says the rovers won’t be able to generate enough power to keep themselves warm and operating under reduced sunlight for much longer.

Before the dust storms, Opportunity’s solar panels had been producing about seven hundred watt-hours of electricity per day. The dust has reduced daily output to less than four hundred watt-hours, prompting the rover team to suspend driving and most observations. Last Wednesday, Opportunity’s solar output dropped even further to a measly hundred and thirty watt-hours. Remember, the rovers have been exploring Mars since landing in 2004 for a mission originally planned for only three months. So the rovers are being maintained on minimal life support as they fight conditions that stop them getting their precious lifeblood.

Meanwhile, scientists up the road from me at Arizona State University are using the thermal imaging system on NASA’s Mars Odyssey to monitor these large dust storms on the red planet. Their instrument, which is a multi-wavelength camera sensible to five different wavebands, provides scientists and spacecraft controllers with global maps that track the amount and the distribution of atmospheric dust obscuring the planet. The current dust storm erupted during the last week of June, and it’s affecting operations of all five spacecraft at Mars. The fleet currently includes two NASA rovers on the ground, Spirit and Opportunity, plus three orbiters, two of which belong to NASA, Mars Odyssey and Mars Reconnaissance Orbiter, and one to the European Space Agency, Mars Express.

Being on the surface of the planet, the rovers have been directly affected by the storm, and Opportunity has had to postpone its descent into Victoria Crater. Scientists are anxious to enter this crater because it will give them a chance to investigate the compositions and textures of exposed minerals in the crater’s depth for clues about ancient wet environments. These clues are an important step in determining whether or not the planet has supported life in its past. Beginning in Mars’ heavily cratered Southern Highlands the dust storm took a week to grow large enough, but it currently encircles the planet and dust has now drifted into the northern hemisphere as well.

This is the traditional time of the Martian year for dust storms. It’s summer in the southern hemisphere. That’s when Mars lies closest to the Sun, and the solar heating is the greatest. We can watch the weather fronts spreading and kicking up dust in a big way. As winds sweep dust into the atmosphere, the atmosphere gets warmer. This adds to the storm’s power, helping it pick up more dust, but the process does have a built-in limitation. When the dust becomes thick enough, it reflects sunlight from the atmosphere allowing the air near the surface to cool, and that’s why the dust storms eventually abate. As seen from orbit the dust storm has the effect of veiling surface features and sometimes econcealing them completely, which hasn’t yet happened.

This storm isn’t as big or as severe as one that occurred in 2001. All the other orbiters can still see the surface, but from the ground the dust in the air cuts the amount of sunlight and reduces the electrical power to the rovers. If you were standing next to the rovers, you’d see the sky looking tawny with haze. The Sun would appear as a sharp-edged disk, but the light level would be visibly lower. Luckily summer is a time when the rovers can best survive under reduced power. If the storm had struck during the local winter, the rovers might not get enough power during the day to stay alive through the cold Martian night. How long will this storm last? Nobody knows for sure, but its effects probably won’t disappear as quickly as the storm erupted and Mars is likely to remain dusty for a couple of months more.

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Mars Like You’ve Never Seen It

Second Week of June

Today I’ll talk about a story close to home, coming from the University of Arizona, and a press release just a couple of days ago. The mission called HIRISE has released twelve hundred images and launched a new viewer on its website. Anyone connected to the Internet can now see the planet Mars much better than at any time in history through the eye of HIRISE, the most powerful camera ever to orbit another planet. Of course you could also go out and in the evening sky see Mars approaching Jupiter, a nice view in its own right of naked eye astronomy.

Meanwhile, the Arizona based team that runs the High Resolution Imaging Experiment on the Mars Reconnaissance Orbiter has released these images. It’s about 1.7 terabytes of data, the largest single data set ever delivered to NASA’s space mission data laboratory, but also delivered in a user-friendly way for the public to see these images. Thanks to tools on their website, any Internet user can pull up and explore the same remarkable images that thrill and confound scientists. These images have been vital in understanding the history of liquid water on Mars and have yielded clues about the potential of life on the red planet. The mission principle investigator, Alfred McEwen of the University of Arizona’s Lunar and Planetary Lab says, “These images must contain hundreds of important discoveries about Mars. We just need time to realize what they are.”

Such is the power of the Internet and the public sharing of data by scientists that there’s a real possibility that amateur planet studiers will find something exciting in this data. Scientists simply can’t keep up with the high volume and high quality of CCD imaging data of Mars being produced by missions like this. The HIRISE camera takes images of a three and a half mile wide swath as the orbiter flies about eight thousand miles around a hundred and seventy miles above Mars’ surface. For the next eighteen months HIRISE will collect thousands of color, black and white, and stereo images of the Martian surface resolving features as small as forty inches across, about the size of an armchair, covering about one percent of the planet.

The team began releasing selected images on the Internet when science operations began back in November 2006. Since then they’ve been reprocessing all the images taken up to March using the improved calibration or image correction techniques. These are the images that are being released today. The planetary data systems node where the images will reside is used by scientists, students, textbook writers, and many others who simply want to follow the latest discoveries in planetary science. NASA started the archive two decades ago when planetary scientists needed a new system to keep up with the expanding volume of data from NASA missions in a form accessible at any time in the future. As computers evolve scientists always need to be able to access data, which is of course a national resource paid for by the taxpayer.

There’s also a special viewer, a tool to home in on any location within the huge data set and an individual image, which will often be a gigabyte across measuring twenty thousand pixels by fifty thousand pixels. The special tool which was developed by a startup in Boulder, Colorado, is called the IAS viewer. Users can download it free directly from the HIRISE website. The advantage of the viewer technology is that it transmits only the amount of data needed to render that portion of the image on your computer screen. That is, each time a user zooms in on an image they don’t have to download a completely new set of pixels. Instead, the user is downloading only the higher resolution parts of the image data which are added to the image data already downloaded. So the viewer ultimately renders the selected part of the image in high resolution by adding in more and more pixels. This tool has obvious defense, intelligence, and disaster management applications, and it delivers high quality images even on relatively slow Internet connections.

The HIRISE manager says, “I’ve run this at home with my little cable modem. The tool allows you to zoom in on small pieces of the image quickly without downloading all the information.” These images are already producing science results. Some tantalizing recent results include an image of a crater from an impact blast that triggered a hundred thousand little dust avalanches on the Martian surface, and exciting details on the fine layered sedimentary rocks on the plains next to Juventae Chasma which features intriguing repeating layers. The mission has also found buried sedimentary rocks exposed in ancient terrain in the southern highlands and a black hole, which is a possible cavern on Mars. HIRISE saw no detail in the shadow, which is consistent with a deep hole and overhanging walls. South polar geysers, possibly a result from the explosive release of carbon dioxide gas trapped under pressure beneath the carbon dioxide ice, have also been found. HIRISE also found spiders on Mars, a reference to David Bowie no doubt. The spiders are channels near the south pole that apparently converge and flow uphill.

HIRISE has been called the “people’s camera” because the team provides processed images directly to the world to stimulate learning, discussion, and investigation. The team encourages the scientific community and the public to help target and analyze images and give them advice where they should be looking for the next advances in Martian research.

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A Proxy for Europa

Fourth Week of May 2007

At a place called El Zacaton in Mexico, NASA is testing an underwater robot in one of the Earth’s deepest sinkholes as a first step towards searching for life on Jupiter’s icy moon Europa. El Zacaton is near the Gulf Coast of northeastern Mexico. It’s about three hundred and thirty feet wide and more than thirty-three hundred feet deep. It could easily hold the Washington Monument or the Eiffel Tower. Scientists plan to map and take samples in this dark water-filled fissure with the one and a half ton DEPTHX robot over the next two weeks, as a prelude to navigating Europa’s ice capped oceans in about twenty years.

That mission is the latest step in a four hundred year old endeavor to understand Jupiter and its distant moons. Chris McKay of NASA Ames Center in California says we’re so sure there’s water on Europa that the real question is whether there is also life, whether there’s something in the ocean that bugs can eat. The robot is the ideal way to search. The robot is lowered by a sixty ton crane, and it’s powered by batteries. It’s nicknamed Clementine for its round shape and orange color, and it’s going to make daily descents into the vertical cave known in Mexico as a cenote. In fact the cenotes known in this part of Mexico are often formed from the debris of giant impacts, and many were caused by the impact that extinguished dinosaurs and other mammals sixty-five million years ago.

The robot will take three dimensional images, collect rock samples, and using floodlight film nooks and crannies too deep for divers to reach. Plants, animals, fungus, microbes, and bacteria are the known forms of life, but there may be more branches to the tree of life on Europa. Learning more about life tells us about our own heritage and the benefits for health and medicine that it could bring, according to researchers in the project.

The idea of mapping Europa’s oceans with an automated robot was dreamed up by a Texas scientist called Marcus Gary at a barbeque in 2001. Two years later his team won NASA funding for the five million dollar project. Gary chose El Zacaton for the first major test of the robot, which is about the size of a small car, because its sheer depth at the site was an unknown quantity. In 1994, an American diver died trying to swim to the bottom. According to Gary, it’s an ideal testing ground because we can test the robot’s mapping powers in untried waters. Its great depth means that many of its microbes live without oxygen or light and could be similar to that which could exist on Europa.

Europa’s thought to have twice as much water as the entire Earth, and it’s intrigued scientists ever since Italian astronomer Galileo Galilei observed Jupiter’s large four moons for the first time in 1610. NASA has hopes to take the probe to Antarctica in November 2008 to test it in the much colder waters below the frozen ice that resembles Europa, and if funding can be found, the scientists could send a much smaller version of the robot to Europa in about twenty years. That’s a long time to wait for a measurement of life, but water much closer at hand features in another story from this week, further evidence of a wet past on Mars.

The Mars rover Spirit has uncovered possibly the strongest evidence that the planet was much wetter than previously thought, by analyzing a patch of soil in Gusev crater and finding it unusually rich in silica. The presence of water would have been necessary to produce such a large silica deposit, according to team scientists. Principle Investigator Steve Squyres of Cornell University said in a statement to the news media, “This is a remarkable discovery. It makes you wonder what’s still out there.”

Spirit previously found clues of ancient water in the crater through the presence of sulfur rich soil, water altered minerals, and explosive volcanism, but this latest find is compelling because of the high silica content, which raises the possibility that conditions may have been favorable for the emergence of primitive life. It’s not clear how silica deposits form. One possibility is that the soil mixed with acid vapors in the presence of water. Others believe the deposit was created from water in a hot spring surrounding. The durable Spirit and its twin Opportunity have been working on overtime since completing their primary three month mission all the way back in 2004. For eight months opportunity has explored the rim of Victoria Crater on the opposite side of the planet. Scientists are exploring for a safe opening to send the rover in. These missions are managed by NASA’s JPL laboratory, and we can expect further discoveries from these intrepid rovers searching for evidence of previous life and wet conditions on Mars.

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Life and Death on Mars

First Week of May 2007

This week saw the publishing of a report that showed that NASA can be faced with uncomfortable subjects when it considers life and death on Mars. A human mission to Mars is in the offing within the next decade or more, and NASA has suddenly had to realize that it hasn’t answered the questions like: how do you get rid of the body of a dead astronaut on a three year mission to Mars and back? When should the plug be pulled on a critically ill astronaut who’s using precious oxygen and endangering the rest of the crew? Should NASA use DNA testing to weed out astronauts who might get a disease on the long flight?

With NASA planning to someday land on Mars and the recent discovery of the most Earth-like planet ever that I covered last week, the space agency has been forced to consider some of these thorny practical and ethical issues posed by deep space exploration. In fact, the relevant document was obtained by the Associated Press after a Freedom of Information Act request, so NASA isn’t exactly putting it out there for everyone to see. It’s an uncomfortable subject. NASA doctors and scientists with help from outside bioethicists and medical experts plan to answer many of these questions over the next few years. At the moment, they’ve just raised them.

Richard Williams, NASA’s chief health and medical officer, says, “As you can imagine it’s a thing that people aren’t really comfortable talking about. We’re trying to develop the ethical framework to equip future commanders and mission managers to make difficult decisions.” One topic that’s too hot to handle: how do you cope with sexual desire amongst healthy young men and women during a mission years long? We’ve just seen a very recent love triangle involving a crazed astronaut dressed in a diaper traveling halfway across the country to deal violently with a rival. What could happen on a three-year mission to Mars? Hormones will fly. Tempers will flare. Emotions will run strong. Crazy things could happen. But sex is not even mentioned in the NASA document; it is essentially a taboo topic at NASA. That’s pretty short sighted. They’re going to have to face this eventually. Williams said the question of sex in space is not a matter of crew health but a behavioral issue and will have to be taken up by others at NASA. So he basically punted on that one.

Bioethicist Paul Wolpe at the university of Pennsylvania, who’s advised NASA for six years says, “A decision is going to have to be made about mixed-sex crews, and there’s going to be a lot of debate about it,” especially given recent news. But the document does spell out some health policies in detail such as how much radiation astronauts can be exposed to. The answer? No more than the amount that would increase the risk of cancer by three percent over an astronaut’s career. Also, the number of hours crew members should work each week: no more than forty-eight.

But on other topics, such as the steps for disposing of the dead or cutting off an astronaut’s medical care if he or she cannot survive, the document merely says that these are issues for which NASA needs a policy. Here’s Wolpe again, “There may come a time in which a significant risk of death has to be weighed against mission success. The idea that we will always choose a person’s well being over mission success, it sounds good, but it doesn’t really turn out to be necessarily decisions will always be made.” For now astronauts and cosmonauts who become critically ill or injured at the international space station, something that’s never happened, can leave the orbiting outpost, it’s only two hundred and twenty miles above Earth, and return home within hours aboard a Russian Soyuz space vehicle. That simply wouldn’t be possible if a life or death situation were to arise on a voyage to Mars where the nearest hospital is a hundred million miles away. Moreover, Mars-bound astronauts will not always be able to rely on expert advice and instructions from mission control since it might take nearly half an hour for a question to be asked and the answer to come back by the radio.

Astronauts going to the Moon and Mars for long periods of time must contend with basic health risks from space travel multiplied many times over, and those include radiation, loss of muscle and bone, and the psychological challenges that go along with extreme isolation. NASA will consider whether astronauts must undergo preventative surgery such as appendectomy to head off medical emergencies during a mission, and whether astronauts should be required to sign living wills with end of life instructions. The space agency must also decide whether to set age restrictions on the crew and whether astronauts of reproductive age should be required to bank sperm or eggs because of the risk of genetic mutation from radiation exposure during the long trip. These are pretty heavy things to consider.

Already NASA is considering genetic screening in choosing crews for the long duration missions, something that’s currently prohibited. Taking a longer view, NASA’s three major tragedies resulted in seventeen deaths: Apollo 1, Challenger, and Columbia. But they were all caused by technical rather than medical problems. NASA has never had to abort a mission because of health problems, although the Soviet Union has had three such episodes, and some people think the U.S. space agency, coming to these issues so late and so hesitantly, has simply not adequately prepared for the possibility of death during a mission. Listen to former astronaut Story Musgrave, a six-time space shuttle flyer who has a medical degree. “I don’t think they’ve been great at dealing with this type of thing in the past. I guess it’s nice they’re considering it now.” Life and death on Mars: one of the things we’ll have to consider when we look for life in the nearby universe.

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Fossil-Hunting on Mars

First Week of March 2007

Mars still represents our nearest and best opportunity for finding life beyond the Earth, and we have a number of missions that are heading there in the next decade. Recent news stories reflect two missions that are heading there. The first is the Mars Science Laboratory, due to launch in 2009.

MSL will have on it a rover that will have the capability to look for existing or fossilized life forms. Jack Farmer, a professor of geological sciences at ASU, up the road from me in Phoenix, gave a talk at the annual meeting of the American Association for the Advancement of Science in San Francisco last week. He said, “Searching for extraterrestrial life must follow two alternative pathways, each requiring different approach and tools. If we are to look for living organisms we’re doing exobiology, but if we’re seeking traces or biosignatures of ancient life, it’s better to call it exopaleontology. Unfortunately,” as he notes, “for the next decade, technological limitations will force us down the exopaleontology path. To find living organisms on Mars, you need to find liquid water, and because liquid water is unstable on the surface today, that means going deep under the subsurface.”

In fact, it’s not even clear how deep we will have to go to find liquid water. Certainly at the higher latitudes in the poles, water exists in the frozen form only a few inches below the surface, but it’s possible that liquid water would be miles deep. There’s no way we can reach that. In practical terms, robotic drilling being limited to a couple of yards, we’re going to look for fossilized or ancient life forms rather than living germs. Finding the signature of an ancient biosphere means exploring old rocks that preserve traces of life for millions or billions of years.

Farmer says the best places to look on Mars are the deposits left by springs and former lakes in the heavily cratered highlands. These rocks date from a period in Martian history when liquid water was common at the surface and conditions on Mars were actually similar to those on the Earth at the same time. He says, “Besides water, life also requires energy sources and organic building blocks.” The Mars Exploration Rover Opportunity found ample evidence for water in the ancient rocks at Meridiani Planum, but the rover’s instruments can’t detect organic materials. Farmer notes that recognizing a Martian fossil could be very difficult. As he puts it, “We’re not talking about stumbling over dinosaur bones.”

In fact the most likely biological formed structures in these sediments will probably be stromatolites like those found on Earth. These are distinctive structures that form in shallow oceans or lakes or streams were microbial colonies trap sediments to form thin, repeating layers. Stromatolites also contain microscopic cellular remains and chemical traces left by the microbes that form them. Taken together, these colonies are already the primary source of evidence for life on ancient Earth, and they may well become the best evidence for ancient life on Mars.

The second Mars story involves a mission that’s even further off. It’s the ExoMars rover, with greatly increased capabilities compared to the rovers we currently have roaming around Mars. It’s not due for launch until 2013, but last week NASA selected one instrument, called Urey or more formally the Mars Organic and Oxidant Detector, for instrument development funds at a level of three quarters of a million dollars. That’s a good sign that this mission is going to go ahead. The European Space Agency is running this mission, and it plans to use the ExoMars rover to grind up samples of the Martian soil into a fine powder and then deliver them to a suite of analytic instruments, including Urey, that will search for signs of life. Each sample will consist of about a spoonful of material dug from the underground by a robotic drill, but of course not very far below the surface as already noted.

Urey is of course named after Harold Urey, the scientist and chemist who developed the famous “life in a bottle” experiments in the 1950s. The Urey experiment is designed to look for organic molecules such as amino acids at incredibly low concentrations, as low as a few parts per trillion. All life on Earth assembles chains of amino acids to make proteins. However amino acids can be made either by living or non-living means. This means it’s possible that Mars has amino acids but has never had life. So how do we distinguish between biological and non-biological amino acids?

The Urey instrument team is going to make use of the knowledge that most types of amino acids can exist in two different forms: left-handed and right-handed. In other words these are molecules that have shapes and they’re distinct just as the hands of a human are distinct between right and left. The right hand of a human mirrors the left, and so the two forms of amino acids mirror each other. Amino acids from non-biological sources come in a fifty-fifty mix of right-handed and left-handed forms. Life on Earth, from the simplest microbes to the largest plants and animals including us, makes and uses only left-hand amino acids, with very rare exceptions. That’s probably because life conserves energy, which made it a favorable choice to pick one handedness and then stick to it for all its chemical functions. Comparable uniformity, either all left or all right, is expected in any extraterrestrial life using building blocks that have mirror image versions because a mixture would complicate biochemistry and make it more inefficient.

According to Dr. Allen Farrington, the Urey project scientist, “The Urey instrument will be able to distinguish between left and right-handed amino acids.” If Urey were to find an even mix of the mirror image molecules on Mars that would suggest life as we know it never began there. All left or all right would be strong evidence that life now exists on Mars, with all right dramatically implying an origin separate from Earth life, which is all left.

It’s also possible that life moved from the Earth to Mars or vice versa being carried by meteorites. Something between fifty-fifty of left and right and uniformity could result if Martian life once existed, because amino acids created biologically gradually change towards an even mixture in the absence of life. Urey is a beautifully designed experiment. Looking at the handedness or shape of molecules can distinguish between current biology, former biology, and no biology at all. It’s going to be hard to wait almost a decade to learn the results.

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Mapping the Red Planet

Third Week of February 2007

Mars is in the news once again, and it’s all about water. Scientists have long debated whether water flowed on the red planet, and the evidence has been increasing steadily in recent years. The presence of water would increase the possibility of at least some form of subsurface life existing on the red planet. This past week images from a camera aboard NASA’s Mars Reconnaissance Orbiter have showed a region of alternating layers of dark and light toned rock in a giant rift valley. Within the deposits are a series of linear fractures called joints that are surrounded by halos of light toned bedrock.

This work was done by a team at my university, the University of Arizona, and their findings have just been published in the journal nature. Their lead author Chris Okubo says, “The halos indicate areas where fluids, probably water, pass through the bedrock. Minerals in the fluids strengthen and bleach the rock leaving some areas more resistant to erosion than others.” He says, “On Earth bleaching of rock surrounding a fracture is a clear indication of chemical reactions between fluids circulating within that fracture in the host rock.” The researchers also said that layered outcrops can indicate cycles with materials deposited by regular episodes of water, wind, or volcanic activity.

You’ll recognize that this evidence is not completely direct. It’s based on the interpretation of geological features, evidence that is always slightly suspect because there may be alternative explanations. But these are experts not only in planetary geology but in terrestrial geology, and there’s no question that the features they’ve identified are most easily explained by water.

Just last December scientists reported that water may be flowing through Mars’ rigid surface when the Global Surveyor showed changes in craters providing evidence that water moved through them as recently as several years ago and may be doing so now. The Surveyor had previously spotted tens of thousands of gullies that scientists believed were geologically young and carved by fast moving water coursing down cliffs. That water eventually freezes and quickly evaporates. Liquid water cannot exist on the surface of Mars right now. But it can be spurred from interior activity, and it could exist under pressure under the surface. In addition, two craters in the southern hemisphere that were photographed in 1999 and 2001 were examined again in 2004 and 2005, and the images showed changes consistent with water flowing down the crater walls.

The summary of all this is that, as with the case of global warming, another topic in the news recently, there’s steadily accumulating evidence for water, evidence that cannot really be refuted. Each individual piece of evidence may have an alternative explanation, but taken together they are starting to make a compelling case for water at some times under the Martian surface. And where water goes, we think that life follows. That’s the big speculation. So we are itching to get back to Mars and see what’s really happening.

A second piece of news on Mars in the past week was the release of data from the HRSC experiment aboard ESA’s Mars express. This spacecraft has produced what are called the first hiker’s maps of Mars giving detailed high contours and the names of geological features. These maps are going to become the standard reference for future Martian research. They’re being called topo maps because they use contour lines to show the heights of the landscape. They are taken by a high-resolution stereo camera which gives the altitude information. On Earth the same kind of maps are used by hikers and planning authorities. They are called ordinance survey maps in the U.K. where I come from.

The researchers chose the Iani Chaos region for the release of these first maps because of its major topographical interest. It’s covered in huge blocks and hills that form a chaotic pattern across the landscape. These islands of rock are likely all that remains of a previous surface of Mars. The areas in between the islands collapsed when cavities formed below the surface. Initially these cavities may have been supported by the presence of ice which melted due to volcanic heat. As water flowed out to the Ares Vallis towards the northern lowlands of Mars the landscape collapsed and formed the Iani Chaos region we see today. This is not geologically recent; some of the activity happened over a billion years ago, but it’s yet more evidence for ancient water on the surface of Mars.

Topo maps are a demonstration of the kind of tools that we will need when we go back to Mars for detailed exploration. The HRSC is on the way to providing enough data to create such maps over the whole of Mars, over ten thousand particular map sheets, each covering an equal area of the Martian surface. The majority of the maps will be on a scale of one to two hundred thousand. That’s a resolution of ten meters, meaning all features about the size of a large room will be identified. Particular interesting regions will be surveyed to a scale of one in fifty thousand meaning everything larger than two meters, about the size of a sofa, will be identified. This kind of detail is really required to send spacecraft to Mars with the best possible information, and such spacecraft are coming. There will be a virtual armada of spacecraft heading to Mars in the next five to ten years.

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Killing Life on Mars

Second Week of January 2007

I want to present you with a detective story that took place thirty years ago on the planet Mars. The story was reported at the recent meeting of the American Astronomical Society being held in Seattle. The scientist involved is Dirk Schulze-Makuch, and he has presented the idea that when the Viking probes visited Mars in 1976 and 1977, they may have found alien microbes on the red planet and inadvertently killed them.

That would be extraordinary. What’s the evidence? It’s basically the idea that a more expansive view of where life can take hold and its biochemical basis opens the possibility that these Mars probes were simply looking for the wrong kind of life, because they were looking for life that’s too similar to the Earth’s. In the 1970s the Viking missions apparently found no sign of life, but they were looking for Earth-like life forms in which salt water is the internal liquid of living cells. Given the cold conditions of Mars, life would have evolved on Mars with a key internal fluid consisting of a mix of water and hydrogen peroxide, according to Dr. Schulze-Makuch. That’s because a hydrogen-water peroxide mix stays liquid at very low temperatures, minus seventy degrees Fahrenheit, and doesn’t destroy cells when it freezes. It can suck water vapor out of the air.

The Viking experiments from the 1970s wouldn’t have noticed hydrogen peroxide-based life, and in fact they would have killed it by drowning and overheating the microbes. One Viking experiment seeking life on Mars poured water onto soil that it took into the instrument. That would have essentially drowned the hydrogen peroxide-based life. Another experiment heated the soil to see if something would happen, which would have baked the Martian microbes. The fundamental problem is that we don’t know what life might be like in strange environments, and we’re stuck looking for life the way it is on Earth. It limits our ability to say that life doesn’t exist if it has a different chemical basis.

Dr. Schulze-Makuch even points out that Earth has something related. He points to an Earth bug called a bombardier beetle that releases a boiling hot spray that’s twenty-five percent hydrogen peroxide as a defense weapon. The researcher acknowledges he can’t prove that Martian microbes exist but given the Martian environment and how evolution works, he thinks it makes sense. In recent years scientists have found life on Earth in conditions once thought much too harsh such as in ultra-acidic rivers in Spain and California and ice covered lakes in Antarctica.

Another group working for the National Research Council is looking at the possibilities of extreme life. They’re nicknamed the weird life committee. We won’t ask what they get up to when they’re not on the committee. The group worries that scientists may be too Earth-centric when looking for extraterrestrial life. As Katherine Freeman, one of the reviewers of the NRC work says, “You only find what you’re looking for.” This is a big problem because upcoming Mars missions are built around instruments designed to look for life the way we find it on Earth. Of course, it’s possible that life is similar to Earth and these fears are misguided. Another member of that committee cautioned against just-so stories about what is possible. Either way it’s a fascinating possibility that life on Mars was strange enough that thirty years ago we killed it while looking for life that was like life on Earth.

And a minor side note for this week. I point out that Pluto has been chosen as the 2006 word of the year by the American Dialect Society at its annual meeting on Friday. In this usage, Pluto is a verb and to Pluto is to demote or devalue something, much like what happened to the former planet last year when the general assembly of the International Astronomical Union decided that Pluto didn’t meet its definition of a planet. Society president Cleveland Evans said, “Our members believe the great emotional reaction of the public to the demotion of Pluto shows the importance of Pluto as a name. We may no longer believe in the Roman god Pluto, but we have a personal sense of connection with the former planet.” Plutoed won in a runoff against climate canary which was defined as an organism or species whose poor health or declining numbers hint at a larger environmental catastrophe on the horizon.

The hundred and seventeen year old American Dialect Society comprises linguists, grammarians, historians, and independent scholars. They conduct their vote for fun and not in any official capacity. However, we should note that the society chose truthiness as its top word last year. Truthiness is credited to Comedy Central satirist Steven Colbert who defines it as truth that comes from the gut not books. It took until this year for Time Magazine to declare truthiness the word of the year. So maybe we should pay attention to the American Dialect Society, and maybe we can expect to find the verb Plutoed to work its way into our everyday vocabulary.

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