- Email: [email protected]
Space rock strikes protected early life
This week
Space rock strikes protected early life Cockell’s team found that the altered crystal structure of the rocks absorbed and reflected UV rays. This suggests the rock could shield the bacteria while letting enough sunlight through to allow them to photosynthesise. Complex life evolved long before the crater formed, but
ASTEROIDS have a killer reputation, taking the blame for death and destruction on massive scales. But results fresh from a space experiment show ancient impacts may have been vital for cradling the first life on Earth. Several hundred million years after Earth formed, when life was emerging, our young planet had an atmosphere, oceans and primordial continents. But it did not yet have an ozone layer to shield the surface from the sun’s harshest ultraviolet rays. Because UV radiation can damage DNA, that would have made it difficult for any but the most extreme forms of life to survive. In 2002, a team led by astrobiologist Charles Cockell at the University of Edinburgh, UK, discovered a unique group of cyanobacteria in Haughton crater in northern Canada. The bacteria live in tiny pores and cracks of near-translucent rock, formed during the intense heat and pressure of the asteroid or comet impact that made the crater, about 23 million years ago.
Catching some rays may be addictive CAN’T resist sunbathing despite the risks? It might be more than a habit. That’s the suggestion from a study in mice showing that exposure to ultraviolet radiation causes similar affects to drug addiction. UV exposure significantly increases the risk of skin cancer, which is one of the most common and preventable cancers. Yet rates of this disease are rising faster than any other cancer – by 14 | NewScientist | 28 June 2014
Peter Essick/aurora photos
Ker Than
around 3 per cent every year. David Fisher at Harvard Medical School and Massachusetts General Hospital in Boston and his colleagues wanted to find out whether frequent tanning behaviour is driven by vanity or a biological addiction. The team exposed mice to UV light five times a week for six months. Each dose was comparable to a fair-skinned person spending 20 to 30 minutes in Florida’s midday sun. They found that the mice exhibited a response similar to addiction. For a start, they produced more feel-good hormones called beta-endorphins, which bind to opioid receptors – the
there have been countless space rock strikes in Earth’s history. “That raised a whole bunch of questions about whether the unique geology of impact craters could have been a good UV shield on the early Earth,” says Casey Bryce, a member of Cockell’s lab. Bryce and her colleagues got an unusual chance to test the notion in 2008. As part of the European Space Agency’s EXPOSE mission, the team sent some of the crater rocks to the International Space Station (ISS). Before lift-off, they grew samples of the cyanobacteria
either in plain glass discs or in discs of the impact-altered rock. Once in space, these discs were mounted on the outside of the ISS, where they were left exposed for nearly two years. The bacteria received radiation doses far more intense than conditions on early Earth. When the samples were returned to the lab, the microbes in the glass discs were dead. “However, when we cracked open the impact-shocked rocks we were able to detect chemical signals of life and rejuvenate the dormant cyanobacteria,” says Bryce. The team’s findings provide the first direct evidence that crystal cocoons formed by impacts might have been radiation-proof cradles for early life (International Journal of Astrobiology, doi.org/tcs). Alexandra Pontefract at the University of Western Ontario in Canada says the ISS experiment is a fantastic proof of concept. “Until now, we weren’t sure if any of these cells would remain viable in that type of environment.” Asteroid and comet impacts are ubiquitous in the solar system, so Pontefract thinks impacts could have helped kick-start life on rocky planets and then shielded whatever emerged. Crater rocks could provide refuges even now for life on other planets, such as –Rock-a-bye microbes– Mars, she says. n
same receptors that respond to heroin and related drugs (Cell, doi.org/tcq). They also showed signs of physical dependence, displaying classic withdrawal behaviours, including shaking and chattering teeth. This means UV light has a more powerful effect than previously thought, says Fisher. “We have a propensity towards seeking the most common carcinogen in the world,” he says. There might be a logical
“We have a propensity towards seeking the most common carcinogen in the world”
explanation. Fisher suggests that our UV light affinity evolved from a need to maintain levels of vitamin D, which the body synthesises using sunlight. Sunscreen is likely to help prevent UV-addictive behaviours because it protects from exposure, although this wasn’t tested in the study. Many researchers are wary of using the word addiction other than for extreme cases of substance abuse. Tighter control of tanning bed regulation might be in order anyway, Fisher says,“We need to treat it as more than just a cosmetic practice now that we know it is something that can modify behaviour.” n
Space rock strikes protected early life Cockell’s team found that the altered crystal structure of the rocks absorbed and reflected UV rays. This suggests the rock could shield the bacteria while letting enough sunlight through to allow them to photosynthesise. Complex life evolved long before the crater formed, but
ASTEROIDS have a killer reputation, taking the blame for death and destruction on massive scales. But results fresh from a space experiment show ancient impacts may have been vital for cradling the first life on Earth. Several hundred million years after Earth formed, when life was emerging, our young planet had an atmosphere, oceans and primordial continents. But it did not yet have an ozone layer to shield the surface from the sun’s harshest ultraviolet rays. Because UV radiation can damage DNA, that would have made it difficult for any but the most extreme forms of life to survive. In 2002, a team led by astrobiologist Charles Cockell at the University of Edinburgh, UK, discovered a unique group of cyanobacteria in Haughton crater in northern Canada. The bacteria live in tiny pores and cracks of near-translucent rock, formed during the intense heat and pressure of the asteroid or comet impact that made the crater, about 23 million years ago.
Catching some rays may be addictive CAN’T resist sunbathing despite the risks? It might be more than a habit. That’s the suggestion from a study in mice showing that exposure to ultraviolet radiation causes similar affects to drug addiction. UV exposure significantly increases the risk of skin cancer, which is one of the most common and preventable cancers. Yet rates of this disease are rising faster than any other cancer – by 14 | NewScientist | 28 June 2014
Peter Essick/aurora photos
Ker Than
around 3 per cent every year. David Fisher at Harvard Medical School and Massachusetts General Hospital in Boston and his colleagues wanted to find out whether frequent tanning behaviour is driven by vanity or a biological addiction. The team exposed mice to UV light five times a week for six months. Each dose was comparable to a fair-skinned person spending 20 to 30 minutes in Florida’s midday sun. They found that the mice exhibited a response similar to addiction. For a start, they produced more feel-good hormones called beta-endorphins, which bind to opioid receptors – the
there have been countless space rock strikes in Earth’s history. “That raised a whole bunch of questions about whether the unique geology of impact craters could have been a good UV shield on the early Earth,” says Casey Bryce, a member of Cockell’s lab. Bryce and her colleagues got an unusual chance to test the notion in 2008. As part of the European Space Agency’s EXPOSE mission, the team sent some of the crater rocks to the International Space Station (ISS). Before lift-off, they grew samples of the cyanobacteria
either in plain glass discs or in discs of the impact-altered rock. Once in space, these discs were mounted on the outside of the ISS, where they were left exposed for nearly two years. The bacteria received radiation doses far more intense than conditions on early Earth. When the samples were returned to the lab, the microbes in the glass discs were dead. “However, when we cracked open the impact-shocked rocks we were able to detect chemical signals of life and rejuvenate the dormant cyanobacteria,” says Bryce. The team’s findings provide the first direct evidence that crystal cocoons formed by impacts might have been radiation-proof cradles for early life (International Journal of Astrobiology, doi.org/tcs). Alexandra Pontefract at the University of Western Ontario in Canada says the ISS experiment is a fantastic proof of concept. “Until now, we weren’t sure if any of these cells would remain viable in that type of environment.” Asteroid and comet impacts are ubiquitous in the solar system, so Pontefract thinks impacts could have helped kick-start life on rocky planets and then shielded whatever emerged. Crater rocks could provide refuges even now for life on other planets, such as –Rock-a-bye microbes– Mars, she says. n
same receptors that respond to heroin and related drugs (Cell, doi.org/tcq). They also showed signs of physical dependence, displaying classic withdrawal behaviours, including shaking and chattering teeth. This means UV light has a more powerful effect than previously thought, says Fisher. “We have a propensity towards seeking the most common carcinogen in the world,” he says. There might be a logical
“We have a propensity towards seeking the most common carcinogen in the world”
explanation. Fisher suggests that our UV light affinity evolved from a need to maintain levels of vitamin D, which the body synthesises using sunlight. Sunscreen is likely to help prevent UV-addictive behaviours because it protects from exposure, although this wasn’t tested in the study. Many researchers are wary of using the word addiction other than for extreme cases of substance abuse. Tighter control of tanning bed regulation might be in order anyway, Fisher says,“We need to treat it as more than just a cosmetic practice now that we know it is something that can modify behaviour.” n