Astro Bob A look at celestial happenings in the Northland and beyond Bob King View my profile Click here to view previous posts or additional resources

Out of this world Old Faithfuls

Cassini shot this photo on May 18 looking toward the shadowed side of Enceladus from 11,000 miles away. Three large plumes of water vapor are boldly backlit by the sun. The plumes' material comes from deeper within the moon and issues through large cracks in its surface. Credit: NASA

The Cassini Saturn probe made a close pass of the planet's icy moon Enceladus (en-SELL-ah-dus) two days ago and sent back the most amazing photos yet of the geyser-like plumes of water vapor shooting out of cracks in its surface. I mean, look at those guys -- would anyone have guessed a 300-mile-diameter ice ball nearly a billion miles from the sun could be so active?  A couple years back my friend Rick Klawitter took pictures of the geysers (right) at Yellowstone National Park in the moonlight that bear an eerie similarity to those at Enceladus. Those plumes originate when water deep beneath the surface is superheated by molten rock, expands explosively and bursts through a vent to the surface.

Enceladus' interior could be heated by the tug of Saturn's gravity or through the decay of radioactive elements within its core. Heat could melt ice beneath the surface and create one or more pockets of pressurized liquid water  which might escape through a vent to the surface much like the Yellowstone geysers. An alternative theory suggests that heat escaping from the moon's interior through vents near the south pole raise the temperature of the surrounding ice enough for it to vaporize directly into space as a plume. Fascinating stuff and yet another example of how similar geologic processes operate across the solar system. When we someday get to study an extrasolar planet up close, what do you think we'll find plenty of earthly analogs there ... perhaps including DNA and life.

Titan will be well to west of Saturn tonight and tomorrow night and appear as a bright star in a telescope. This illustration shows the scene with south up and west to the left, the way most telescopes view the sky. Illustration: Bob King

As long as we're on Saturn and its moons, tonight and tomorrow night Titan will be at maximum western elongation from the planet and especially easy to see in any small telescope. Titan takes almost 16 days to complete an orbit. When it's between us and the planet, it appears very close to Saturn, but tonight it's four ring-widths to the west and out of the Saturnian glare. Observers with telescopes 8 inches and up can see the pinkish-orange hue of its hydrocarbon-laden atmosphere. Watching the moon move from one side of the planet to the other makes a fun and easy observing project.

This artist's rendering depicts the Voyager 2 spacecraft as it studies the outer limits of the heliosphere, a magnetic 'bubble' around the solar system that's created by the solar wind. The probe is currently 8.6 billion miles from Earth. A radio signal traveling at the speed of light takes 12.7 hours to get there. Credit: NASA/JPL-Caltech

Voyager 2, the NASA probe that's been exploring the outer reaches of the solar system, has been in the news this past week because it began sending garbled nonsense data instead of scientific information. True believers and conspiracy lovers attributed the bizarre transmissions to aliens using the craft to send messages to Earth. While I like this idea it's complete fantasy. Turns out that a flip of one bit in Voyager's memory caused a change in the scientific data pattern. A "0" changed to a "1". Scientists reset the bit yesterday to see if that solves the problem. Voyager 2 is set to leave the sun's sphere of influence and enter interstellar space in about five years. That still leaves plenty of time for aliens to tinker.

The shadow of the Opportunity Rover stretches toward Endurance Crater in this photo taken in 2007. Two wheels are visible on the lower left and lower right. Larger image. Credit: NASA/JPL

The Mars Rover Opportunity will break the longevity record today for time spent in operation on Mars. The previous record of six years and 116 days was set by the Viking 1 lander which arrived in the planet in the summer of 1976. The Spirit Rover would have broken the record already since it landed on Mars three weeks before Opportunity, but it's been out of communication with Earth since March 22. Both rovers were designed for 90-day missions but have far exceeded expectations. Read the full story HERE.

Posted by: rking@duluthnews.com on 5/20/2010 at 8:22 AM | Comments (0) | Permalink | Edit

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