Manu
10-05-2001, 04:13 PM
From small things come great hope. Glass-eating microbes discovered 300 meters below the Earth's ocean floors have given scientists further evidence that life on Mars and Europa is a possibility.
The newly found microbes are literally at the rock bottom of the food chain. And they survive on a bare minimum: water, heat, and nutrients they digest from volcanic glass in the ocean floor. These lithoautotrophs, as they are called, are so bare bones they could easily exist on other less hospitable worlds.
"We now know the [minimum] requirements for life that have to be met," said astrobiologist Jack Farmer, referring to the glass-eating critters, "and it looks like a good possibility on Mars and on Europa that the right factors exist or have exited in the past."
A team of oceanographers from the Scripps Institution of Oceanography found that the microbes exist all around the world. The evidence is tiny trails burrowed in volcanic rock as far down as 4 miles (2.5 km) below the ocean floor. The rock is composed primarily of silica and is essentially glass created under high heat and pressure conditions.
The rock-munchers make the telltale tracks as they absorb the silica nutrients and release acid generated by their metabolic processes. The microbes' activities release substances that feed animals the next rung up on the food chain.
"It's a minimum of life," Staudigel said.
This minimalist approach to existence could prove the most enduring, however. Living safely below the ocean, these microbes most likely survived showers of space rocks that prevented more complex life forms from developing on Earth for its first few billion years. From these microbes' persistence, projects Staudigel, all life may have developed on Earth.
Farmer, the Principal Investigator of NASA' Astrobiology Program at Arizona State University, was not involved in the new study. But he and Staudigel both think this low-maintenance life form could have developed on Mars or Europa because the things the microbe needs to survive were likely there and may still be.
"If you translate the conditions they can survive in onto other planetary settings, life may have developed there as well," Staudigel said. "Then if there is no water, all that may be left are those traces [in the rock]"
A liquid ocean almost certainly exists underneath a layer of surface ice on Europa. Apparently the Jovian moon doesn't experience volcanic activity, but the water is warmed by the gravitational pull of Jupiter. Farmer believes a probe on Europa, which could perform and relay in-situ experiments, could determine if life in its lowest form survives there.
There is much speculation Mars once had water on the surface, and there may still be water below ground now. NASA's Mars Global Surveyor spacecraft has found important evidence to support these ideas. It confirmed that the Southern Martian hemisphere contains hematite, a mineral that develops below water, as well as glassy volcanic rock. Volcanic activity, water and glass would have provided the necessary heat, water and nutrients for these microbes to survive.
The spacecraft also found geologic evidence of an ancient ocean in the northern hemisphere, which is the flattest surface in our solar system. Channels that appear to have been carved by water scar large areas of the Red Planet.
Scientists may only have to explore the surface of Mars with orbiters and probes to find evidence of microbes. The critters on Earth are highly concentrated on the top layers of the ocean floor, where water can better circulate through the porous rock. This would correspond to the now dry Martian crust.
The Odyssey spacecraft will arrive at Mars later this month, carrying a higher-resolution thermal emission spectrometer than the one on Mars Global Surveyor, which still orbits Mars. This more powerful instrument will be able to clarify which areas have the most potential for harboring these microscopic life forms.
In 2003, twin rovers will be launched that will carry sophisticated microscopes which can look for the telltale rock channels of the microbes. Trial runs of similar rovers on Iceland have been able to pinpoint rocks with these features.
Both Farmer and Staudigel agree that the best evidence will come more than ten years from now, when samples will be returned from Mars.
The DNA of the Earth microbes could be compared to any that is found on Mars, revealing whether the life forms could have any common ancestry. www.space.com (http://www.space.com)
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Manu Narayan
The newly found microbes are literally at the rock bottom of the food chain. And they survive on a bare minimum: water, heat, and nutrients they digest from volcanic glass in the ocean floor. These lithoautotrophs, as they are called, are so bare bones they could easily exist on other less hospitable worlds.
"We now know the [minimum] requirements for life that have to be met," said astrobiologist Jack Farmer, referring to the glass-eating critters, "and it looks like a good possibility on Mars and on Europa that the right factors exist or have exited in the past."
A team of oceanographers from the Scripps Institution of Oceanography found that the microbes exist all around the world. The evidence is tiny trails burrowed in volcanic rock as far down as 4 miles (2.5 km) below the ocean floor. The rock is composed primarily of silica and is essentially glass created under high heat and pressure conditions.
The rock-munchers make the telltale tracks as they absorb the silica nutrients and release acid generated by their metabolic processes. The microbes' activities release substances that feed animals the next rung up on the food chain.
"It's a minimum of life," Staudigel said.
This minimalist approach to existence could prove the most enduring, however. Living safely below the ocean, these microbes most likely survived showers of space rocks that prevented more complex life forms from developing on Earth for its first few billion years. From these microbes' persistence, projects Staudigel, all life may have developed on Earth.
Farmer, the Principal Investigator of NASA' Astrobiology Program at Arizona State University, was not involved in the new study. But he and Staudigel both think this low-maintenance life form could have developed on Mars or Europa because the things the microbe needs to survive were likely there and may still be.
"If you translate the conditions they can survive in onto other planetary settings, life may have developed there as well," Staudigel said. "Then if there is no water, all that may be left are those traces [in the rock]"
A liquid ocean almost certainly exists underneath a layer of surface ice on Europa. Apparently the Jovian moon doesn't experience volcanic activity, but the water is warmed by the gravitational pull of Jupiter. Farmer believes a probe on Europa, which could perform and relay in-situ experiments, could determine if life in its lowest form survives there.
There is much speculation Mars once had water on the surface, and there may still be water below ground now. NASA's Mars Global Surveyor spacecraft has found important evidence to support these ideas. It confirmed that the Southern Martian hemisphere contains hematite, a mineral that develops below water, as well as glassy volcanic rock. Volcanic activity, water and glass would have provided the necessary heat, water and nutrients for these microbes to survive.
The spacecraft also found geologic evidence of an ancient ocean in the northern hemisphere, which is the flattest surface in our solar system. Channels that appear to have been carved by water scar large areas of the Red Planet.
Scientists may only have to explore the surface of Mars with orbiters and probes to find evidence of microbes. The critters on Earth are highly concentrated on the top layers of the ocean floor, where water can better circulate through the porous rock. This would correspond to the now dry Martian crust.
The Odyssey spacecraft will arrive at Mars later this month, carrying a higher-resolution thermal emission spectrometer than the one on Mars Global Surveyor, which still orbits Mars. This more powerful instrument will be able to clarify which areas have the most potential for harboring these microscopic life forms.
In 2003, twin rovers will be launched that will carry sophisticated microscopes which can look for the telltale rock channels of the microbes. Trial runs of similar rovers on Iceland have been able to pinpoint rocks with these features.
Both Farmer and Staudigel agree that the best evidence will come more than ten years from now, when samples will be returned from Mars.
The DNA of the Earth microbes could be compared to any that is found on Mars, revealing whether the life forms could have any common ancestry. www.space.com (http://www.space.com)
------------------
Manu Narayan