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Fountains of Optimism for Life Way Out There
By GUY GUGLIOTTA
Published: May 9, 2011
For those who hunt for life on other worlds, water in its liquid form is perhaps the leading indicator. Life as we know it on Earth is based on water and carbon. And if organisms can prosper here in nasty environments — in geysers, in the depths of the sea, in toxic waste, in water that is too hot, too cold, too acidic or too alkaline — why could they not prosper out there?
Enlarge This Image
NASA/JPL-Caltech
A REFRESHING ICY DIP Ontario Lacus is a large lake on Saturn's moon Titan.
Scientists for years regarded liquid water as a solar system rarity, for there was no place apart from Earth that seemed to have the necessary physical attributes, except perhaps Jupiter’s ice-covered moon, Europa, which probably concealed a subterranean ocean.
The past 20 years of space exploration, however, have caused what the astrobiologist David Grinspoon calls a sea change in thinking. It now appears that gravity, geology, radioactivity and antifreeze chemicals like salt and ammonia have given many “hostile” worlds the ability to muster the pressures and temperatures that allow liquid water to exist. And research on Earth has shown that if there is water, there could be life.
On Mars and Venus, on Saturn’s moons Enceladus and Titan, and even on two outer-belt asteroids, researchers have shown that the presence of liquid water is possible and even likely. Proof of life, of course, will come only when something — or someone — puts a drop of alien water under a microscope and sees a microbe.
“Water and carbon-based life works well,” Dr. Grinspoon said. “That doesn’t mean it’s the only way, but it’s the only way we know, and it gives us something to look for.”
Finding water in space, in the form of ice, has never been a problem. Hydrogen is the most common element in the solar system, and oxygen is not far behind. When the solar system formed about 4.5 billion years ago, a spiraling disc of dust and gas spun out from the Sun to produce the planets, their moons, and an enormous cloud of comets, planetoids and other bits of cosmic flotsam. Nature endowed much of this debris with a generous helping of water ice.
Liquid water is another matter. The heat of the Sun may melt the ice, but in the vacuum of space there is little or nothing on the surface of most solar system objects to keep the heated molecules together, so they flash instantly away as water vapor. This process is called sublimation.
The physics of sublimation are unforgiving. Liquid water needs a delicate balance of temperature and pressure. Ice must be able to melt without boiling off, but the water must stay warm enough that it does not refreeze. On Earth, with a sea level atmospheric pressure of 14.7 pounds per square inch, water is liquid between 32 and 212 degrees Fahrenheit. On the unshadowed parts of our Moon, where the atmospheric pressure is zero and daytime temperatures can exceed 260 degrees Fahrenheit, the surface ice is long gone.
Ice survives at very low temperatures, however, and the chunks of debris that linger in the chill reaches of deep space beyond Neptune make up the biggest source of water in the solar system today. These dirty snowballs re-enter the planetary system periodically as comets. When they get close enough to the Sun, the ice begins to sublimate, giving the comets their characteristic tail of dust and water vapor.
Many scientists say it is likely that much of the ice in the inner solar system came from comets. On Earth, cometary impacts early in the planet’s history could have provided this raw material, and the Sun and atmospheric pressure would have done the rest. Earth is the only place in the solar system so far discovered where liquid is the default state of surface water. And Earth is where life proliferates.
But it is maybe not the only place. Dr. Grinspoon has theorized that Venus, whose spectacular volcanism boiled off all its surface water long ago, nevertheless harbored liquid moisture in the noxious clouds of sulfuric acid that cloak the planet. In 2008 the European Space Agency’s Venus Express orbiter measured water vapor in the clouds. About 30 miles above the surface in the Venusian mist, where temperatures are about 70 degrees Fahrenheit, extremophiles could find a comfort zone.
Another improbable venue for liquid water is the outer limits of the asteroid belt between Mars and Jupiter. There, using infrared telescopes, two teams of astronomers working separately in 2008 and 2009 found water ice on the surface of the asteroid 24 Themis, about 280 million miles from the Sun. Last year, the teams joined forces and found ice on a second asteroid, 65 Cybele, which, with a diameter of 180 miles, was about 1.5 times as large as 24 Themis and 45 million miles farther out.
For ice to endure on like objects with no atmosphere that close to the Sun, there must be a mechanism to replenish what is lost to sublimation. Humberto Campins, a University of Central Florida astrophysicist and leader of one of the discovery teams, suggested that the patchy ice was a thin coating of frost from a reservoir hidden below the asteroids’ topsoil regolith.
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A version of this article appeared in print on May 10, 2011, on page D1 of the New York edition with the headline: Fountains of Optimism For Life Way Out There.
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Fountains of Optimism for Life Way Out There
By GUY GUGLIOTTA
Published: May 9, 2011
- Recommend
For those who hunt for life on other worlds, water in its liquid form is perhaps the leading indicator. Life as we know it on Earth is based on water and carbon. And if organisms can prosper here in nasty environments — in geysers, in the depths of the sea, in toxic waste, in water that is too hot, too cold, too acidic or too alkaline — why could they not prosper out there?
Enlarge This Image
NASA/JPL-Caltech
A REFRESHING ICY DIP Ontario Lacus is a large lake on Saturn's moon Titan.
Scientists for years regarded liquid water as a solar system rarity, for there was no place apart from Earth that seemed to have the necessary physical attributes, except perhaps Jupiter’s ice-covered moon, Europa, which probably concealed a subterranean ocean.
The past 20 years of space exploration, however, have caused what the astrobiologist David Grinspoon calls a sea change in thinking. It now appears that gravity, geology, radioactivity and antifreeze chemicals like salt and ammonia have given many “hostile” worlds the ability to muster the pressures and temperatures that allow liquid water to exist. And research on Earth has shown that if there is water, there could be life.
On Mars and Venus, on Saturn’s moons Enceladus and Titan, and even on two outer-belt asteroids, researchers have shown that the presence of liquid water is possible and even likely. Proof of life, of course, will come only when something — or someone — puts a drop of alien water under a microscope and sees a microbe.
“Water and carbon-based life works well,” Dr. Grinspoon said. “That doesn’t mean it’s the only way, but it’s the only way we know, and it gives us something to look for.”
Finding water in space, in the form of ice, has never been a problem. Hydrogen is the most common element in the solar system, and oxygen is not far behind. When the solar system formed about 4.5 billion years ago, a spiraling disc of dust and gas spun out from the Sun to produce the planets, their moons, and an enormous cloud of comets, planetoids and other bits of cosmic flotsam. Nature endowed much of this debris with a generous helping of water ice.
Liquid water is another matter. The heat of the Sun may melt the ice, but in the vacuum of space there is little or nothing on the surface of most solar system objects to keep the heated molecules together, so they flash instantly away as water vapor. This process is called sublimation.
The physics of sublimation are unforgiving. Liquid water needs a delicate balance of temperature and pressure. Ice must be able to melt without boiling off, but the water must stay warm enough that it does not refreeze. On Earth, with a sea level atmospheric pressure of 14.7 pounds per square inch, water is liquid between 32 and 212 degrees Fahrenheit. On the unshadowed parts of our Moon, where the atmospheric pressure is zero and daytime temperatures can exceed 260 degrees Fahrenheit, the surface ice is long gone.
Ice survives at very low temperatures, however, and the chunks of debris that linger in the chill reaches of deep space beyond Neptune make up the biggest source of water in the solar system today. These dirty snowballs re-enter the planetary system periodically as comets. When they get close enough to the Sun, the ice begins to sublimate, giving the comets their characteristic tail of dust and water vapor.
Many scientists say it is likely that much of the ice in the inner solar system came from comets. On Earth, cometary impacts early in the planet’s history could have provided this raw material, and the Sun and atmospheric pressure would have done the rest. Earth is the only place in the solar system so far discovered where liquid is the default state of surface water. And Earth is where life proliferates.
But it is maybe not the only place. Dr. Grinspoon has theorized that Venus, whose spectacular volcanism boiled off all its surface water long ago, nevertheless harbored liquid moisture in the noxious clouds of sulfuric acid that cloak the planet. In 2008 the European Space Agency’s Venus Express orbiter measured water vapor in the clouds. About 30 miles above the surface in the Venusian mist, where temperatures are about 70 degrees Fahrenheit, extremophiles could find a comfort zone.
Another improbable venue for liquid water is the outer limits of the asteroid belt between Mars and Jupiter. There, using infrared telescopes, two teams of astronomers working separately in 2008 and 2009 found water ice on the surface of the asteroid 24 Themis, about 280 million miles from the Sun. Last year, the teams joined forces and found ice on a second asteroid, 65 Cybele, which, with a diameter of 180 miles, was about 1.5 times as large as 24 Themis and 45 million miles farther out.
For ice to endure on like objects with no atmosphere that close to the Sun, there must be a mechanism to replenish what is lost to sublimation. Humberto Campins, a University of Central Florida astrophysicist and leader of one of the discovery teams, suggested that the patchy ice was a thin coating of frost from a reservoir hidden below the asteroids’ topsoil regolith.
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Next Page »
A version of this article appeared in print on May 10, 2011, on page D1 of the New York edition with the headline: Fountains of Optimism For Life Way Out There.
Advertise on NYTimes.com
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Quality Water Distillers
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www.nutriteam.com
Citro Landscapes & Ponds
Ponds, Waterfalls, Fountains Affordable Designs & Installations
www.citrolandscapes.com
Water Flow Meter
Find water flow meter suppliers. Compare suppliers online & save.
www.ArchitectureAlley.com
Custom Water Features
Residential & Commercial Fountains, Water Walls, Bubble Panels & more.
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Ads by Googlewhat's this? CUNY Online Degree
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