Water and the Search for Life on Mars (Springer Praxis Books / Space Exploration)

Mars has long been believed to have been cold, dead and dry for aeons, but there is now striking new proof that not only was Mars a relatively warm and wet place in geologically recent times, but that even today there are vast reserves of water frozen beneath the planet’s surface. As well as casting fascinating new insights into Mars’ past, this discovery is also forcing a complete rethink about the mechanisms of global planetary change and the possibility that there is microbial life on Mars. David Harland considers the issue of life on Mars in parallel with the origin of life on Earth. At the time the Viking instruments were designed, it was thought that all terrestrial life ultimately derived its energy from sunlight, and that the earliest form of life was the cyanobacteria with chlorophyll for photosynthesis. It was assumed the same would be the case on Mars and that microbial life would be on or near the surface that the Vikings had sampled. No sooner were the results from the Viking instruments in, than it was discovered that there was an even older type of microbial life on Earth when, in 1977 ‘black smokers’ were found in volcanically active parts of the ocean floor, at depths of several kilometres. Removed from sunlight, these archaea (literally, ‘the old ones’) live off the minerals released by the hydrothermal activity. Subsequently our view of life was further revised when ‘extremophiles’ were discovered thriving in acidic, salty, alkaline, very hot, very cold and radiation soaked environments previously considered lethal. Although the Vikings had found no sign of organics, and the surface was extremely hostile, suggesting that life had never gained a foothold, the discovery of microbes living far beneath the surface of the Earth raised the possibility of life below the surface of Mars, where there may be water-ice and/or hydrothermal activity. Perhaps, because the microbes were beyond the reach of the Vikings’ instruments, the negative result was premature. Following the negative tests for biological activity by the Vikings, NASA – in the belief that Mars was once warm and wet, as the erosional features on the surface suggest – decided to ‘chase the water’ in the hope of establishing that conditions on Mars were once suitable for life, although this would not prove that life had developed. The targets selected (from many) were what seemed to be an outflow channel, a dry lake and a patch of minerals emplaced by hydrothermal activity. In 1997 Mars Pathfinder landed in an outflow channel where it released the small Sojourner rover to perform chemical analyses of nearby rocks. NASA followed up in 2004 with the much larger Mars Exploration Rovers, which were equipped to act as mobile field geologists. One was landed in what seemed to be a dried up lake bed inside a crater, and the other set down in an area that a remote-sensing orbital survey had identified as haematite, a likely indicator of hydrothermal activity. Both of these missions have yielded evidence that conditions were once conducive to the development of life. In parallel with these NASA projects, the European Space Agency developed the Mars Express remote-sensing orbiter, which has detected traces of methane that may have been released by microbes. If microbial life is found on Mars, will it be based on DNA? Will this indicate that life developed independently? Or that it has characteristics in common with the most ancient forms of terrestrial life? If life is found on two planets in the same planetary system, this would favour the panspermia hypothesis. And if martian life is radically different, then in light of the discovery of planetary systems around other stars, this would, as remarked by Philip Morrison of MIT, "transform life from the status of a miracle to that of a statistic". These are all questions that the exploration of Mars for life are aimed to answer.

Mars has long been believed to have been cold, dead and dry for aeons, but there is now striking new proof that not only was Mars a relatively warm and wet place in geologically recent times, but that even today there are vast reserves of water frozen beneath the planet’s surface. As well as casting fascinating new insights into Mars’ past, this discovery is also forcing a complete rethink about the mechanisms of global planetary change and the possibility that there is microbial life on Mars.

David Harland considers the issue of life on Mars in parallel with the origin of life on Earth. At the time the Viking instruments were designed, it was thought that all terrestrial life ultimately derived its energy from sunlight, and that the earliest form of life was the cyanobacteria with chlorophyll for photosynthesis. It was assumed the same would be the case on Mars and that microbial life would be on or near the surface that the Vikings had sampled.

No sooner were the results from the Viking instruments in, than it was discovered that there was an even older type of microbial life on Earth when, in 1977 ‘black smokers’ were found in volcanically active parts of the ocean floor, at depths of several kilometres. Removed from sunlight, these archaea (literally, ‘the old ones’) live off the minerals released by the hydrothermal activity. Subsequently our view of life was further revised when ‘extremophiles’ were discovered thriving in acidic, salty, alkaline, very hot, very cold and radiation soaked environments previously considered lethal. Although the Vikings had found no sign of organics, and the surface was extremely hostile, suggesting that life had never gained a foothold, the discovery of microbes living far beneath the surface of the Earth raised the possibility of life below the surface of Mars, where there may be water-ice and/or hydrothermal activity. Perhaps, because the microbes were beyond the reach of the Vikings’ instruments, the negative result was premature.

Following the negative tests for biological activity by the Vikings, NASA – in the belief that Mars was once warm and wet, as the erosional features on the surface suggest – decided to ‘chase the water’ in the hope of establishing that conditions on Mars were once suitable for life, although this would not prove that life had developed. The targets selected (from many) were what seemed to be an outflow channel, a dry lake and a patch of minerals emplaced by hydrothermal activity. In 1997 Mars Pathfinder landed in an outflow channel where it released the small Sojourner rover to perform chemical analyses of nearby rocks. NASA followed up in 2004 with the much larger Mars Exploration Rovers, which were equipped to act as mobile field geologists. One was landed in what seemed to be a dried up lake bed inside a crater, and the other set down in an area that a remote-sensing orbital survey had identified as haematite, a likely indicator of hydrothermal activity. Both of these missions have yielded evidence that conditions were once conducive to the development of life.

In parallel with these NASA projects, the European Space Agency developed the Mars Express remote-sensing orbiter, which has detected traces of methane that may have been released by microbes. If microbial life is found on Mars, will it be based on DNA? Will this indicate that life developed independently? Or that it has characteristics in common with the most ancient forms of terrestrial life? If life is found on two planets in the same planetary system, this would favour the panspermia hypothesis. And if martian life is radically different, then in light of the discovery of planetary systems around other stars, this would, as remarked by Philip Morrison of MIT, transform life from the status of a miracle to that of a statistic. These are all questions that the exploration of Mars for life are aimed to answer.

"Why explore Mars? The simple answer is, we’re going to Mars to search for life. We’re following the water because on Earth where you find liquid water, organic material, and energy, you find life." u find life" Ed Weiler, NASA's Associate Administrator for Space Science Ear where you find liquid water, A century ago, the world was enthralled by Percival Lowell’s vision of a Mars criss-crossed with the canals of a dying civilization distributing water from the polar caps. Later, Mars was thought to have been cold, dead and dry for eons, but striking new evidence suggests the planet was relatively warm and wet in geologically recent times, and that even now there are reserves of water frozen beneath the planet’s surface. Today, robot spacecraft maneuver across the Martian surface while others orbit overhead seeking evidence of water, ice, and landing sites for further exploration. In recent years, the very possibilities for life have dramatically expanded as discoveries by biologists and oceanographers have revealed bizarre life forms where none would have been expected. And as the growing evidence that water flowed on Mars becomes indisputable, more spacecraft are soon to follow. This highly absorbing book relates how NASA and ESA have sought evidence of life on Mars. ‘Follow the water’ with noted science writer David Harland as he assembles and weighs the evidence in this timely and compelling book. It contains what you need to know behind today’s, and possibly tomorrow’s, headlines, including details of the Mariner, Viking, and Pathfinder missions and evolving theories of Martian geology and climate. It explains how the search accelerates with the Mars Orbiter and Mars Exploration Rovers Spirit and Opportunity. Harland sets this within the broader perspective of the likely nature of life on Mars as compared to primitive life on Earth. Finally, he analyzes the implications of there being life on both planets. Join the scientific adventure of a lifetime in this well-researched and thoroughly engrossing true account. "This book relates how NASA and ESA have sought evidence of life on Mars. Science writer David Harland assembles and weighs the evidence in this timely and compelling book. It contains what you need to know behind today's, and possibly tomorrow's, headlines, including details of the Mariner, Viking, and Pathfinder missions and evolving theories of Martian geology and climate. It explains how the search continues with the Mars Express orbiter and Mars Exploration Rovers Spirit and Opportunity. Harland sets this within the broader perspective of the likely nature of life on Mars as compared to primitive life on Earth. Finally, he analyzes the implications of there being life on both planets."--Jacket Provides a comprehensive account of the recent Spirit and Opportunity Mars Exploration Rover missions. Relates how NASA/ESA have sought evidence of life on Mars, with the prevailing mood sometimes being optimistic and sometimes pessimistic. Details an account of the rationale for the tests for life carried out by the Viking missions in 1976, with an account of the debate over their results. A concise primer for readers wishing to bone up when NASA next sends a lander explicitly to seek life on Mars. Discusses the nature of life on Mars in terms of the most primitive forms of life on Earth, and reviews the implications of there being life on both planets. This volume relates how NASA and ESA have sought evidence of life on Mars, with the author assembling and then weighing the evidence. It contains details of the Mariner, Viking, and Pathfinder missions and evolving theories of Martian geology and climate. It explains how the search continues with the Mars Express orbiter and Mars Exploration Rovers Spirit and Opportunity. The author sets this within the broader perspective of the likely nature of life on Mars as compared to primitive life on Earth. Finally, he analyzes the implications of there being life on both planets Front Matter....Pages i-xix Peering at Mars....Pages 1-30 A close look....Pages 31-52 The Vikings....Pages 53-74 What is life?....Pages 75-94 A multiplicity of missions....Pages 95-112 The water dilemma....Pages 113-137 Spirit....Pages 139-182 Opportunity....Pages 183-222 Future prospects....Pages 223-229 Back Matter....Pages 231-239