- Email: [email protected]
Looking for life on Mars? Try the salty bits
OPINION
It’s over there! The main reason we explore Mars is to find out if life ever existed there. But we’re looking in the wrong places, says Alfonso F. Davila WHEN searching for something, the first step is to look in the most likely location. That doesn’t always work. Things sometimes show up in unexpected corners. But most of the time the milk is in the fridge, the phone is on the table, and the keys are by the door. Why would searching for life on Mars be any different? The main reason we explore Mars is to determine if life ever arose on the planet. We have tried for centuries, starting with telescopes and lately with satellites, landers and rovers. We have searched for it directly (the Viking mission) and indirectly (every other Mars mission). No luck so far. Some think life has never been there. Others think it was there in the past but is now gone. Many think why bother, but that’s a whole different story. I think we are looking in the wrong places. Here is why. The surface of Mars is extremely cold and dry. Cosmic and solar radiation reach the surface unimpeded by the thin atmosphere, and the soil contains strong oxidants that destroy organic compounds. Fat chance for life. But it wasn’t always so. Early in its history Mars was warmer and wetter enough for the development of rivers, lakes and perhaps oceans. The atmosphere was thicker and the protective magnetic field was switched on. Mars might be uninhabitable today, but life would have been possible in the past. This is why future missions will focus on the study of ancient sediments, hoping to find fossilised evidence of life. 28 | NewScientist | 19 February 2011
But first we need to find a year to study the habitability and promising location, and that environmental history of a region means reconstructing Martian on Mars that contains sediments history. We need to find out if formed billions of years ago. there was flowing water, the time The MSL is the most advanced and extent of the water, what type robot ever sent to another planet. of minerals formed and if the Around 2018, a joint mission run geochemical conditions were by NASA and the European Space compatible with life. Once Agency will send two rovers to promising sites are identified, we the surface to pave the way for a need to find out if there are any Mars Sample Return mission physical or chemical processes beyond 2020. It will be the first that could have destroyed mission to collect and return fossilised evidence, and finally samples from another planet. Its search for that evidence. scientific value will be enormous, This is not easy, and this is “Salt and ice are excellent why the search is getting more substrates to preserve life ambitious, sophisticated and and there are salty and icy expensive. The Mars Science environments on Mars” Laboratory will launch this
but in the process it might swallow NASA’s planetary budget for the decade. Is this the best strategy? I think not. Let’s turn to our own planet for a second. On Earth, life is almost everywhere, but some places seem to be out of bounds. At first glance the Atacama desert in Chile and the Antarctic Dry Valleys appear lifeless, and until recently we thought they were. Atacama is the driest desert on Earth, with only an occasional shower every 10 years or so. The Antarctic Dry Valleys are the coldest deserts on Earth. Most of the water is frozen in the ground, and the little snow that falls sublimates before it can melt. In both places liquid water, the key ingredient for life, is extremely rare. These deserts are the closest analogues we have to the Martian surface and allow us to study what happens to life as environments become drier and colder. What happens is that life seeks refuge in niches where liquid water can still form, even if only for a short time every now and then. This occurs in two substrates, salts and ice. Salts absorb water vapour from the atmosphere and form liquid solutions at low relative humidities, a phenomenon called deliquescence. When ice is in contact with sediment particles, it melts and forms thin films of liquid water that are stable even at temperatures well below freezing. In other words, salts and ice expand the window of physical conditions in which liquid water is stable, and provide small habitable niches even when the
Comment on these stories at www.NewScientist.com/opinion
environment becomes generally uninhabitable. In the Atacama, where most of the water is in the atmosphere, life is found inside salt rocks, whereas in the Antarctic Dry Valleys it is found at the interface between ice or snow and sediments. It turns out that salt and ice are also excellent substrates for preserving life. Ancient salt and ice deposits on Earth contain organic compounds, complex biomolecules and even entire cells which have been preserved for millions of years. Hence, the last niches where life can retreat as an environment becomes drier and colder are also the niches where remnants of life are better preserved – a stroke of luck that plays in our favour. More good news: there are salty and icy environments on Mars. Large deposits of salts are widespread in the southern hemisphere; the northern polar cap has thick sequences of sediments and ice layers, and ground ice is near the surface at latitudes higher than 60° in both hemispheres. If there has ever been life on Mars, these are the niches where it could have retreated as the planet made the transition from wet and warm to cold and dry. These are also the places where fossil life would be best preserved. And these should be the first places we go searching. This could be done with small, low-cost missions. A small rover or lander could provide unambiguous proof of life, if equipped with technology to detect the complex biomolecules that are only synthesised by living organisms. The technology is readily available. A positive result would be a turning point in history. A negative result would be strong evidence against the presence of life and biomolecules anywhere on the planet. Not a small prize for a comparatively small investment. n Alfonso F. Davila is at the SETI Institute in Mountain View, California
One minute with…
Lily Cole
The campaigning model is helping to promote a pioneering elephant conservation project in India You are best known from the world of fashion and film, so how did you come to be involved in elephant conservation ? Through a friend, I got involved with the Emeralds for Elephants campaign for the conservation charity World Land Trust. They invited me to India, where they have been working with the Wildlife Trust of India (WTI) to establish corridors of land along traditional elephant migration routes. These corridors link national parks and other protected areas so that the elephants can walk the routes they have used for hundreds of years. Conflict between humans and animals is reduced by enabling local NGOs to buy land in the corridors and offering the villagers living there houses and larger plots of land nearby. On your visit to India you saw some of these land corridors. Are you convinced they are a good strategy for conservation? In Kerala we visited an area within a corridor where a village had recently existed. The evidence of elephants moving through the area – cut markings on the trees, trampled gates – suggested that, ordinarily, there would have been conflict here between villagers and elephants. In India in the past decade, some 3200 people and 1150 elephants have died due to these conflicts. What about the social implications of moving an entire village? What did you see of this? We met villagers who used to live in the corridors but who were now resettled locally through a WTI initiative. One man said how glad he was to be able to sleep with his family at night now. Before, he had to keep watch in case elephants came. Are there any other benefits for conservation from the creation of land corridors? They are used by other wildlife, such as tigers and monkeys. It was fantastic to see these efforts, which benefit humans but also promote biodiversity and harmony between species. There is no reason for conflict between humans and animals if the wildlife and their patterns of living are understood and respected.
Profile Actress and model Lily Cole was the youngest English model to appear on the cover of British Vogue. Last year she helped to launch the Emeralds for Elephants fund-raising exhibition for the conservation charity World Land Trust. She is studying the history of art at the University of Cambridge
What other memorable things did you see on your visit? I was particularly affected by the extraordinary landscape of the Himalayas. It took my breath away and made me feel so appreciative of this wonderful planet we live on. I know it sounds hideously hippy, bit it reiterated to me how much trees need protecting. We depend on forests to survive, so it is quite unbelievable, when you consider it logically, how blindly we cut down many forests each day. I say “we”, as I think we are globally accountable for deforestation, whether it is happening now or happened in the past. Celebrity involvement in environmental causes seems to be on the rise. Do you think it can make a difference? The more paths that can be created towards the same destination – environmental sustainability – the more hopeful it is that we will reach it. Interview by Roger Highfield
19 February 2011 | NewScientist | 29
It’s over there! The main reason we explore Mars is to find out if life ever existed there. But we’re looking in the wrong places, says Alfonso F. Davila WHEN searching for something, the first step is to look in the most likely location. That doesn’t always work. Things sometimes show up in unexpected corners. But most of the time the milk is in the fridge, the phone is on the table, and the keys are by the door. Why would searching for life on Mars be any different? The main reason we explore Mars is to determine if life ever arose on the planet. We have tried for centuries, starting with telescopes and lately with satellites, landers and rovers. We have searched for it directly (the Viking mission) and indirectly (every other Mars mission). No luck so far. Some think life has never been there. Others think it was there in the past but is now gone. Many think why bother, but that’s a whole different story. I think we are looking in the wrong places. Here is why. The surface of Mars is extremely cold and dry. Cosmic and solar radiation reach the surface unimpeded by the thin atmosphere, and the soil contains strong oxidants that destroy organic compounds. Fat chance for life. But it wasn’t always so. Early in its history Mars was warmer and wetter enough for the development of rivers, lakes and perhaps oceans. The atmosphere was thicker and the protective magnetic field was switched on. Mars might be uninhabitable today, but life would have been possible in the past. This is why future missions will focus on the study of ancient sediments, hoping to find fossilised evidence of life. 28 | NewScientist | 19 February 2011
But first we need to find a year to study the habitability and promising location, and that environmental history of a region means reconstructing Martian on Mars that contains sediments history. We need to find out if formed billions of years ago. there was flowing water, the time The MSL is the most advanced and extent of the water, what type robot ever sent to another planet. of minerals formed and if the Around 2018, a joint mission run geochemical conditions were by NASA and the European Space compatible with life. Once Agency will send two rovers to promising sites are identified, we the surface to pave the way for a need to find out if there are any Mars Sample Return mission physical or chemical processes beyond 2020. It will be the first that could have destroyed mission to collect and return fossilised evidence, and finally samples from another planet. Its search for that evidence. scientific value will be enormous, This is not easy, and this is “Salt and ice are excellent why the search is getting more substrates to preserve life ambitious, sophisticated and and there are salty and icy expensive. The Mars Science environments on Mars” Laboratory will launch this
but in the process it might swallow NASA’s planetary budget for the decade. Is this the best strategy? I think not. Let’s turn to our own planet for a second. On Earth, life is almost everywhere, but some places seem to be out of bounds. At first glance the Atacama desert in Chile and the Antarctic Dry Valleys appear lifeless, and until recently we thought they were. Atacama is the driest desert on Earth, with only an occasional shower every 10 years or so. The Antarctic Dry Valleys are the coldest deserts on Earth. Most of the water is frozen in the ground, and the little snow that falls sublimates before it can melt. In both places liquid water, the key ingredient for life, is extremely rare. These deserts are the closest analogues we have to the Martian surface and allow us to study what happens to life as environments become drier and colder. What happens is that life seeks refuge in niches where liquid water can still form, even if only for a short time every now and then. This occurs in two substrates, salts and ice. Salts absorb water vapour from the atmosphere and form liquid solutions at low relative humidities, a phenomenon called deliquescence. When ice is in contact with sediment particles, it melts and forms thin films of liquid water that are stable even at temperatures well below freezing. In other words, salts and ice expand the window of physical conditions in which liquid water is stable, and provide small habitable niches even when the
Comment on these stories at www.NewScientist.com/opinion
environment becomes generally uninhabitable. In the Atacama, where most of the water is in the atmosphere, life is found inside salt rocks, whereas in the Antarctic Dry Valleys it is found at the interface between ice or snow and sediments. It turns out that salt and ice are also excellent substrates for preserving life. Ancient salt and ice deposits on Earth contain organic compounds, complex biomolecules and even entire cells which have been preserved for millions of years. Hence, the last niches where life can retreat as an environment becomes drier and colder are also the niches where remnants of life are better preserved – a stroke of luck that plays in our favour. More good news: there are salty and icy environments on Mars. Large deposits of salts are widespread in the southern hemisphere; the northern polar cap has thick sequences of sediments and ice layers, and ground ice is near the surface at latitudes higher than 60° in both hemispheres. If there has ever been life on Mars, these are the niches where it could have retreated as the planet made the transition from wet and warm to cold and dry. These are also the places where fossil life would be best preserved. And these should be the first places we go searching. This could be done with small, low-cost missions. A small rover or lander could provide unambiguous proof of life, if equipped with technology to detect the complex biomolecules that are only synthesised by living organisms. The technology is readily available. A positive result would be a turning point in history. A negative result would be strong evidence against the presence of life and biomolecules anywhere on the planet. Not a small prize for a comparatively small investment. n Alfonso F. Davila is at the SETI Institute in Mountain View, California
One minute with…
Lily Cole
The campaigning model is helping to promote a pioneering elephant conservation project in India You are best known from the world of fashion and film, so how did you come to be involved in elephant conservation ? Through a friend, I got involved with the Emeralds for Elephants campaign for the conservation charity World Land Trust. They invited me to India, where they have been working with the Wildlife Trust of India (WTI) to establish corridors of land along traditional elephant migration routes. These corridors link national parks and other protected areas so that the elephants can walk the routes they have used for hundreds of years. Conflict between humans and animals is reduced by enabling local NGOs to buy land in the corridors and offering the villagers living there houses and larger plots of land nearby. On your visit to India you saw some of these land corridors. Are you convinced they are a good strategy for conservation? In Kerala we visited an area within a corridor where a village had recently existed. The evidence of elephants moving through the area – cut markings on the trees, trampled gates – suggested that, ordinarily, there would have been conflict here between villagers and elephants. In India in the past decade, some 3200 people and 1150 elephants have died due to these conflicts. What about the social implications of moving an entire village? What did you see of this? We met villagers who used to live in the corridors but who were now resettled locally through a WTI initiative. One man said how glad he was to be able to sleep with his family at night now. Before, he had to keep watch in case elephants came. Are there any other benefits for conservation from the creation of land corridors? They are used by other wildlife, such as tigers and monkeys. It was fantastic to see these efforts, which benefit humans but also promote biodiversity and harmony between species. There is no reason for conflict between humans and animals if the wildlife and their patterns of living are understood and respected.
Profile Actress and model Lily Cole was the youngest English model to appear on the cover of British Vogue. Last year she helped to launch the Emeralds for Elephants fund-raising exhibition for the conservation charity World Land Trust. She is studying the history of art at the University of Cambridge
What other memorable things did you see on your visit? I was particularly affected by the extraordinary landscape of the Himalayas. It took my breath away and made me feel so appreciative of this wonderful planet we live on. I know it sounds hideously hippy, bit it reiterated to me how much trees need protecting. We depend on forests to survive, so it is quite unbelievable, when you consider it logically, how blindly we cut down many forests each day. I say “we”, as I think we are globally accountable for deforestation, whether it is happening now or happened in the past. Celebrity involvement in environmental causes seems to be on the rise. Do you think it can make a difference? The more paths that can be created towards the same destination – environmental sustainability – the more hopeful it is that we will reach it. Interview by Roger Highfield
19 February 2011 | NewScientist | 29