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Dig deeper to find Martian life
January 30, 2007Probes designed to find life on Mars do not drill deep enough to find the living cells that scientists believe may exist well below the surface of Mars, according to research led by UCL (University College London). Although current drills may find essential tell-tale signs that life once existed on Mars, cellular life could not survive the radiation levels for long enough any closer to the surface of Mars than a few metres deep - beyond the reach of even state-of-the-art drills.
The study, published in the journal 'Geophysical Research Letters' (GRL), maps out the cosmic radiation levels at various depths, taking into account different surface conditions on Mars, and shows that the best place to look for living cells is within the ice at Elysium, the location of the newly discovered frozen sea on Mars.
The lead author, Lewis Dartnell, UCL Centre for Mathematics and Physics in the Life Sciences & Experimental Biology (CoMPLEX), said: "Finding hints that life once existed - proteins, DNA fragments or fossils - would be a major discovery in itself, but the Holy Grail for astrobiologists is finding a living cell that we can warm up, feed nutrients and reawaken for studying.
"It just isn't plausible that dormant life is still surviving in the near-subsurface of Mars - within the first couple of metres below the surface - in the face of the ionizing radiation field. Finding life on Mars depends on liquid water surfacing on Mars, but the last time liquid water was widespread on Mars was billions of years ago. Even the hardiest cells we know of could not possibly survive the cosmic radiation levels near the surface of Mars for that long."
Survival times near the surface reach only a few million years. This means that the chance of finding life with the current probes is slim. Scientists will need to dig deeper and target very specific, hard-to-reach areas such as recent craters or areas where water has recently surfaced.
Dr Andrew Coates, UCL Department of Space & Climate Physics, said: "This study is trying to understand the radiation environment on Mars and its effect on past and present life. This is the first study to take a thorough look at how radiation behaves in the atmosphere and below the surface and it's very relevant to planned missions. The best chance we have of finding life is looking in either the sea at Elysium or fresh craters."
The team found that the best places to look for living cells on Mars would be within the ice at Elysium because the frozen sea is relatively recent - it is believed to have surfaced in the last five million years - and so has been exposed to radiation for a relatively short amount of time. H2O provides an ideal shield of hydrogen to protect life on Mars from destructive cosmic radiation particles. Ice also holds an advantage because it is far easier to drill through than rock. Even here, surviving cells would be out of the reach of current drills. Other ideal sites include recent craters, because the surface has been exposed to less radiation, and the gullies recently discovered in the sides of craters, as they are thought to have flowed with water in the last five years.
The team developed a radiation dose model to study the radiation environment for possible life on Mars. Unlike Earth, Mars is not protected by a global magnetic field or thick atmosphere and for billions of years it has been laid bare to radiation from space. The team quantified how solar and galactic radiation is modified as it goes through the thin Martian atmosphere to the surface and underground.
Three different surface scenarios were tested; dry regolith, water ice, and regolith with layered permafrost. The particle energies and radiation doses were measured on the surface of Mars and at regular depths underground, allowing the calculation of cell survival times.
The team took the known radiation resistance of terrestrial cells combined with the annual radiation doses on Mars to calculate the survival time of dormant populations of the cells. Some strains are radiation-resistant and are able to survive the effects because, when active, they successfully repair the DNA breaks caused by ionising radiation. However, when cells are dormant, such as when frozen as in the subsurface of Mars, they are preserved but unable to repair the damage, which accumulates to the point where the cell becomes permanently inactivated.
Mr Dartnell said: "With this model of the subsurface radiation environment on Mars and its effects on the survival of dormant cells we have been able to accurately determine the drilling depth required for any hope of recovering living cells. We have found that this suspected frozen sea in Elysium represents one of the most exciting targets for landing a probe, as the long-term survival of cells here is better than underground in icy rock. This could be crucial for the scientists and engineers planning future Mars missions to find life.\\\
University College London
"It just isn't plausible that dormant life is still surviving in the near-subsurface of Mars - within the first couple of metres below the surface - in the face of the ionizing radiation field. Finding life on Mars depends on liquid water surfacing on Mars, but the last time liquid water was widespread on Mars was billions of years ago. Even the hardiest cells we know of could not possibly survive the cosmic radiation levels near the surface of Mars for that long."
Survival times near the surface reach only a few million years. This means that the chance of finding life with the current probes is slim. Scientists will need to dig deeper and target very specific, hard-to-reach areas such as recent craters or areas where water has recently surfaced.
Dr Andrew Coates, UCL Department of Space & Climate Physics, said: "This study is trying to understand the radiation environment on Mars and its effect on past and present life. This is the first study to take a thorough look at how radiation behaves in the atmosphere and below the surface and it's very relevant to planned missions. The best chance we have of finding life is looking in either the sea at Elysium or fresh craters."
The team found that the best places to look for living cells on Mars would be within the ice at Elysium because the frozen sea is relatively recent - it is believed to have surfaced in the last five million years - and so has been exposed to radiation for a relatively short amount of time. H2O provides an ideal shield of hydrogen to protect life on Mars from destructive cosmic radiation particles. Ice also holds an advantage because it is far easier to drill through than rock. Even here, surviving cells would be out of the reach of current drills. Other ideal sites include recent craters, because the surface has been exposed to less radiation, and the gullies recently discovered in the sides of craters, as they are thought to have flowed with water in the last five years.
The team developed a radiation dose model to study the radiation environment for possible life on Mars. Unlike Earth, Mars is not protected by a global magnetic field or thick atmosphere and for billions of years it has been laid bare to radiation from space. The team quantified how solar and galactic radiation is modified as it goes through the thin Martian atmosphere to the surface and underground.
Three different surface scenarios were tested; dry regolith, water ice, and regolith with layered permafrost. The particle energies and radiation doses were measured on the surface of Mars and at regular depths underground, allowing the calculation of cell survival times.
The team took the known radiation resistance of terrestrial cells combined with the annual radiation doses on Mars to calculate the survival time of dormant populations of the cells. Some strains are radiation-resistant and are able to survive the effects because, when active, they successfully repair the DNA breaks caused by ionising radiation. However, when cells are dormant, such as when frozen as in the subsurface of Mars, they are preserved but unable to repair the damage, which accumulates to the point where the cell becomes permanently inactivated.
Mr Dartnell said: "With this model of the subsurface radiation environment on Mars and its effects on the survival of dormant cells we have been able to accurately determine the drilling depth required for any hope of recovering living cells. We have found that this suspected frozen sea in Elysium represents one of the most exciting targets for landing a probe, as the long-term survival of cells here is better than underground in icy rock. This could be crucial for the scientists and engineers planning future Mars missions to find life.\\\
University College London
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A team of NASA and university scientists has achieved the first definitive detection of methane in the atmosphere of Mars. This discovery indicates the planet is either biologically or geologically active.
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Artificial gravity: the next small step?
Dr Kevin Fong will talk about artificial gravity, one of the latest technologies being considered for human missions to Mars, in an event organised by the Royal Institution on 11 May 2004. The latest results from the Mars Rovers are impressive but the red planet will not yield its secrets easily. Investigation of the existence of Martian life, past or present, will ultimately demand that we embark upon human expeditions. But the protection of astronaut crews from the effects of long duration space flight presents formidable challenges. Prolonged weightlessness creates medical problems for the human skeleton, muscles, heart and nervous system. The hunt for solutions has generated many diffic
ESA prepares mission to search for life on Mars
Before humans can leave their boot prints on the dusty surface of Mars, many questions have to be answered and many problems solved. One of the most fundamental questions - one that has intrigued humankind for centuries - is whether life has ever existed on Mars, the most Earthlike of all the planets. Through its long-term Aurora Programme of solar system exploration, ESA is already preparing a series of robotic missions that will reveal the Red Planet's secrets and pave the way for a human expedition in decades to come. A major step towards the realisation of this ambitious robotic programme was completed this week with the selection of two industrial teams to carry out the detailed desi
Hitchhiking bacteria could compromise the detection of life on Mars
Is there life on Mars? It's possible, but it may not be Martian, say scientists. New research, published in the open access journal BMC Microbiology, suggests that conditions on Mars are capable of supporting dormant bacteria, known as endospores. This raises concern about future attempts to detect Martian life forms because endospores originating on Earth could potentially hitch a ride to Mars and survive on its surface. Soil on Mars is thought to be rich in oxidising chemicals that are known to destroy life. The high levels of ultraviolet radiation on the surface of the planet make it unlikely that any organism could survive. Ronald Crawford and colleagues from the University of Idaho hav
No place for life to hide from Mars Express
Of all missions sent to Mars only one, the Viking 26 years ago, has dared to search for life. Its only conclusive result was that finding proof of extraterrestrial life proved to be much harder than expected. Second attempts never followed. Until now. ESA`s Mars Express, the next mission to the Red Planet and the first European one, has an ambitious goal. To be launched in 2003, Mars Express will be the first spacecraft after Viking to search for direct and indirect evidence for past or present life on Mars. This time, scientists are equipped with more knowledge and insight in how to detect Martian life. The chances of success look very good. The expectations regarding life on Mars have ch
Search For Life On Mars?
ROYAL ASTRONOMICAL SOCIETY PRESS NOTICE Date: 9 November 1998 For immediate release
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