Post by Wes on Feb 21, 2010 0:15:19 GMT 10
"Earth May Not Be the Center of the DNA-Based Universe"
Increasing evidence, such as the low temperature transfer of microbes via the Allen Hills meteorite (ALH 84001) and theoretical calculations suggest that objects capable of carrying life have been transferred between solar system bodies with significant frequency. In addition, extremophiles have been discovered in Earth environments with high radiation and frozen conditions which, while not as extreme as those on Mars and other planets, demonstrate the incredible adaptability of microbes and suggest that habitable zones are much broader than previously thought. Together these facts raise the possibility that life could have been transferred between Earth and Mars perhaps early in the history of the solar system, and could survive on Mars to the present day.
Compelling new data that chemical and fossil evidence of ancient microbial life on Mars was carried to Earth in a Martian meteorite is being elevated to a higher plane by the same NASA team which made the initial discovery in 1984 in Victoria Land, in the Eastern region of Antarctica, at the end of the Transantarctic Mountains range, where numerous meteorites have been discovered.The new data are providing a powerful new case for the Allen Hills Meteorite to have carried strong evidence of Martian life to Earth -- evidence that is increasingly standing up to scrutiny as new analytical tools are used to examine the specimen. It is about 4.5 billion years old and is thought to have been blasted off of Mars by a meteor impact about 16 million years ago. A possible microfossil, found in a sample of the meteorite, measures less than 1/100th the width of a human hair. This microfossil has caused much debate about whether or not it is evidence for past life on Mars.
The latest findings are the product of new research using more advanced High Resolution Electron Microscopy than was in existence when the initial findings were made and announced by NASA and the White House in 1996. Those laboratory sensors were focused directly on carbonate discs and associated tiny magnetite crystals present inside the meteorite Allen Hills ALH 84001.
Now, 16 years after the Martian meteorite life story emerged, the science team finally feels vindicated. Their data shows the meteorite is no smoking gun but is full of evidence that supports the existence of life on the surface of Mars, or in subsurface water pools, early in the planet's history.
The distinct environments of the two planets at present might not allow an organism adapted to one planet to grow on the other. But meteoritic exchange in the solar system was 100 to 1000x more intense during the heavy bombardment stage 4 billion years ago. There are signs of numerous fluid flows a possible ancient ocean, and sedimentary formations that suggest a warmer and wetter Mars 3 to 4 billion years ago, an environment more similar to Archean Earth.
Thus at the time of maximal meteoritic exchange 3.5-4 billion years ago, microbial life on Earth may have already possessed a shared core of 500 genes, including the 16S ribosomal RNA gene. The last common ancestor with life on Mars may have also shared this core of genes. Thus at the point of high meteoritic exchange, there may have been microbial life on Earth detectable by 16S gene PCR and an environment on Mars more similar to Earth than today.
The environments on Mars and Earth have diverged: the appearance of oxygen on the Earth 2 billion years ago led to decreased UV radiation, while Mars lost its atmosphere as its magnetic field decayed causing an increase in UV flux, cooling of the surface, and loss of surface water. Current life on Mars would need to survive temperatures and pressures below the triple point of water, high UV flux and the oxidizing surface chemistry induced by UV radiation.
www.dailygalaxy.com/my_weblog/2010/02/earth-may-not-be-the-center-of-the-dnabased-universe-harvard-team-seaches-for-extraterrestrial-genom.html#more
Increasing evidence, such as the low temperature transfer of microbes via the Allen Hills meteorite (ALH 84001) and theoretical calculations suggest that objects capable of carrying life have been transferred between solar system bodies with significant frequency. In addition, extremophiles have been discovered in Earth environments with high radiation and frozen conditions which, while not as extreme as those on Mars and other planets, demonstrate the incredible adaptability of microbes and suggest that habitable zones are much broader than previously thought. Together these facts raise the possibility that life could have been transferred between Earth and Mars perhaps early in the history of the solar system, and could survive on Mars to the present day.
Compelling new data that chemical and fossil evidence of ancient microbial life on Mars was carried to Earth in a Martian meteorite is being elevated to a higher plane by the same NASA team which made the initial discovery in 1984 in Victoria Land, in the Eastern region of Antarctica, at the end of the Transantarctic Mountains range, where numerous meteorites have been discovered.The new data are providing a powerful new case for the Allen Hills Meteorite to have carried strong evidence of Martian life to Earth -- evidence that is increasingly standing up to scrutiny as new analytical tools are used to examine the specimen. It is about 4.5 billion years old and is thought to have been blasted off of Mars by a meteor impact about 16 million years ago. A possible microfossil, found in a sample of the meteorite, measures less than 1/100th the width of a human hair. This microfossil has caused much debate about whether or not it is evidence for past life on Mars.
The latest findings are the product of new research using more advanced High Resolution Electron Microscopy than was in existence when the initial findings were made and announced by NASA and the White House in 1996. Those laboratory sensors were focused directly on carbonate discs and associated tiny magnetite crystals present inside the meteorite Allen Hills ALH 84001.
Now, 16 years after the Martian meteorite life story emerged, the science team finally feels vindicated. Their data shows the meteorite is no smoking gun but is full of evidence that supports the existence of life on the surface of Mars, or in subsurface water pools, early in the planet's history.
The distinct environments of the two planets at present might not allow an organism adapted to one planet to grow on the other. But meteoritic exchange in the solar system was 100 to 1000x more intense during the heavy bombardment stage 4 billion years ago. There are signs of numerous fluid flows a possible ancient ocean, and sedimentary formations that suggest a warmer and wetter Mars 3 to 4 billion years ago, an environment more similar to Archean Earth.
Thus at the time of maximal meteoritic exchange 3.5-4 billion years ago, microbial life on Earth may have already possessed a shared core of 500 genes, including the 16S ribosomal RNA gene. The last common ancestor with life on Mars may have also shared this core of genes. Thus at the point of high meteoritic exchange, there may have been microbial life on Earth detectable by 16S gene PCR and an environment on Mars more similar to Earth than today.
The environments on Mars and Earth have diverged: the appearance of oxygen on the Earth 2 billion years ago led to decreased UV radiation, while Mars lost its atmosphere as its magnetic field decayed causing an increase in UV flux, cooling of the surface, and loss of surface water. Current life on Mars would need to survive temperatures and pressures below the triple point of water, high UV flux and the oxidizing surface chemistry induced by UV radiation.
www.dailygalaxy.com/my_weblog/2010/02/earth-may-not-be-the-center-of-the-dnabased-universe-harvard-team-seaches-for-extraterrestrial-genom.html#more