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A Surprise for Astronomers
When Voyager flew by Enceladus in 1980 it photographed a moon with unusual tectonic activity for such a tiny moon. There was clearly geologic activity occurring, which railed against current theory for a body so small—only 314 miles in diameter.
It wasn’t until the Cassini probe arrived on scene in 2004 that the real surprise was revealed.
Flying much closer to the tiny moon than Voyager had, Cassini photographed a phenomenon that caused researcher’s jaws to drop. Near the south pole, geysers of what appeared to be ice and water vapor were being emitted into space.
That required a retooling of the mission. Researchers had to collect samples of the emissions to determine exactly what they were. They reprogrammed Cassini for a closer approach and flew it right through the plumes.
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What’s in the Water?
Now researchers wanted more data. What was in the water? Was it fresh water, salt water? Were there perhaps primitive life forms living beneath the surface?
The geysers are coming from a part of the moon that is hotter than the rest of the body. In fact, the heat signature of the area forms what researchers call ‘tiger stripes.’ But hotter on Enceladus is a relative term. The average temperature of the surface is -330 degrees F. The stripes are a sizzling -135 degrees F.
It is from these tiger stripes that the geysers originate. So there is water and heat. Researchers had to get more data, so Cassini was sent within 30 miles of Enceladus to fly through the plumes again.
The results were even more astounding.
The water was salt water, and it contained hydrocarbons. Was there a subterranean ocean beneath the moon’s surface, with, if not life, the building blocks?
This meant more flights through the plumes to refine the data. Today, it appears the salt may be coming from rocks beneath and under surface lake. The salt and other minerals detected in the geysers is being leached from the rocks and mixes with the water as the geysers are ejected into space by tectonic forces. But a few researchers continue to contend the water is an ocean. It may take a lander to solve the puzzle completely.
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As fascinating as the geysers are, what they result in as they spew into space is equally amazing. Enceladus orbits within Saturn’s E ring, the outermost of its rings. It is extremely diffuse and consists of tiny particles of ice and dust. The ice almost assuredly came from Enceladus’ geysers. The moon’s escape velocity is so low and the geysers emit their water at such a high velocity most of it escapes into space to create the ring.
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Sources and Credits
Reference and all Cassini photos:
NASA Cassini site: http://www.nasa.gov/mission_pages/cassini/media/cassini-20090624.html