Wednesday, May 25, 2005
Life on Titan?
Scientists from the University of Arizona operating the Cassini spacecraft have been able to get some stunning surface pictures of Saturn' s perpetually clouded moon Titan.
But they've been baffled by a mysterious orange-colored spot near the moon's equator.
Members of the Cassini team have guessed that the 300-mile wide area might be a wound from a recent asteroid strike, or that the orange bruise is a mixture of water ice and ammonia oozing out of an ice volcano.
If that's the case, the spot might be a great place to start looking for extraterrestrial life.
In many ways, Titan, the second largest moon in the solar system after Jupiter's Ganymede, resembles the Earth some four billion years ago. It's the only known moon with a fully developed, planet-like atmosphere rich in nitrogen and methane. Such chemical brew could support the assembly of long organic molecules, similar to those, which preceded early RNA and DNA.
However, for life to be possible the moon "would need liquid water, which is not stable for long because Titan is too cold," said the Cassini scientists. (Titan's surface temperature averages -289F (-178C).) But "many of the large icy moons in the outer solar system host active water volcanism. Most of them contain a lot of liquid water, which flows across their surfaces in the same way lava does on Earth. Their internal heat initiates a melt that rises to the surface. These moons also contain various substances that are antifreezes (e.g. ammonia or formaldehyde). They are mixed into the water which lowers the density of liquid water and helps the water come up to the surface through the more dense icy crust."
Titan can also be heated with large asteroid impacts. "In the early 1990s, Carl Sagan and W. Reid Thompson of Cornell University suggested that impacts on the surface of Titan would melt the icy crust and produce liquid water," said Jonathan Lunine, professor of planetary sciences at the University of Arizona. He and a Russian colleague have been modeling impacts on Titan "to see what fraction of the crater would become liquid due to an impact." The couple computed that "an impact of a one-kilometer-diameter comet can turn about 5 percent of a crater's interior into liquid." Their simulations show that "the areas potentially containing organic matter would not be heavily shocked in an impact. Organic material survives such events and would be tossed in the crater where the liquid water would exist. When life on Earth originated about 4 billion years ago, large impacts were frequent."
But they've been baffled by a mysterious orange-colored spot near the moon's equator.
Members of the Cassini team have guessed that the 300-mile wide area might be a wound from a recent asteroid strike, or that the orange bruise is a mixture of water ice and ammonia oozing out of an ice volcano.
If that's the case, the spot might be a great place to start looking for extraterrestrial life.
In many ways, Titan, the second largest moon in the solar system after Jupiter's Ganymede, resembles the Earth some four billion years ago. It's the only known moon with a fully developed, planet-like atmosphere rich in nitrogen and methane. Such chemical brew could support the assembly of long organic molecules, similar to those, which preceded early RNA and DNA.
However, for life to be possible the moon "would need liquid water, which is not stable for long because Titan is too cold," said the Cassini scientists. (Titan's surface temperature averages -289F (-178C).) But "many of the large icy moons in the outer solar system host active water volcanism. Most of them contain a lot of liquid water, which flows across their surfaces in the same way lava does on Earth. Their internal heat initiates a melt that rises to the surface. These moons also contain various substances that are antifreezes (e.g. ammonia or formaldehyde). They are mixed into the water which lowers the density of liquid water and helps the water come up to the surface through the more dense icy crust."
Titan can also be heated with large asteroid impacts. "In the early 1990s, Carl Sagan and W. Reid Thompson of Cornell University suggested that impacts on the surface of Titan would melt the icy crust and produce liquid water," said Jonathan Lunine, professor of planetary sciences at the University of Arizona. He and a Russian colleague have been modeling impacts on Titan "to see what fraction of the crater would become liquid due to an impact." The couple computed that "an impact of a one-kilometer-diameter comet can turn about 5 percent of a crater's interior into liquid." Their simulations show that "the areas potentially containing organic matter would not be heavily shocked in an impact. Organic material survives such events and would be tossed in the crater where the liquid water would exist. When life on Earth originated about 4 billion years ago, large impacts were frequent."
