Daily Archives: March 6, 2008

cassini, planetary science, planets

News from the Frontier

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Rhea May Have Rings

The Cassini spacecraft has uncovered something of a mystery at Saturn’s second-largest moon, Rhea. As the Cassini folk point out in their press release (accompanied by this spiffy “artist’s concept” of what the Rhea-ian system might look like), “Due to a decrease in the number of electrons detected by NASA’s Cassini spacecraft on either side of the moon, scientists suggest that rings are the likeliest cause of these electrons being blocked before they reach Cassini.”

Artist concept of Rhea's ring Now, that’s just darned cool. The spacecraft “saw” something on either side of Rhea. This is very much like the first time Galileo Galilei “saw” something he took to be “ears” or “handles” on either side of Saturn as it appeared through his telescope in 1610. So, it’s kind of fitting that a modern-day descendent of his telescope (albeit a different kind of detector) found rings around Rhea.

I happen to like rings and our solar system seems to be blessed with several nice sets in varying sizes and densities at Saturn, Jupiter, Uranus, and Neptune. In fact, Earth likely had a ring in the distant past, too. So, it seems, rings are things to have, if you’re a planetary system, that is.

Rhea is roughly 1,500 kilometers (950 miles) across. The debris disk that may be forming the possible ring is several thousand miles from end to end. The particles that make up this disk and the possible rings are most likely in a range between the size of small pebbles to boulders. An additional dust cloud may extend up to 5,900 kilometers (3,000 miles) from the moon’s center. This is almost eight times the radius of Rhea. Want to learn more about this find and other discoveries at Saturn? Visit the Cassini Mission web site for the latest.

geology, planetary science, surface geology

Evolutionary Earth

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Hawai’i Style

Last summer Mark and I and a group of science writers took an exciting hike across newly deposited lava flows on the Big Island of Hawai’i. To get to our hiking spot, we drove across flows that had been laid down over the past decade; fields of lava not 30 minutes from downtown Hilo. After gearing up (including plenty of water and food and safe clothing), we hiked out to live flows that originate at the Pu’u’ O’o vent on the flanks of Kileaua volcano. Our guide was noted volcano photographer and amateur astronomer Stephen J. O’Meara (in the image with me below).

That vent is still active, still pumping out lava each day, and recently it has been finishing the paving job it began when it first begain to engulf Kalapana Gardens subdivision more than a decade ago. If you take a look over at the USGS Hawaii Volcano observatory web page, you can see the latest action on the flanks of the volcano.

While we were hiking, we stepped across very live flows (like the one above) and took time to watch as slower flows moved leisurely across the already rocky and desolate fields. It’s hard to believe that this region was once a beautiful rainforest, dotted with homes. Not far from where we stood, there used to be a Park Service building and the site of an old heiau, a sacred site for the native Hawaiians.

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This recent picture (taken March 5, 2008) caught my eye because it shows the same road we drove over to get to our hike last summer with SteveO. As you can see, it doesn’ t matter to the lava whether it’s covering a road, a house, a forest, or dribbling into the ocean. It just keeps on flowing, a splendid example of the ongoing creation of new surface rock that planet Earth does with its volcanic eruptions.

If you ever visit the Big Island and take on the volcano, be warned that it’s not for the faint of heart. Earth-building processes aren’t delicate. The rock is hot, its action is incessant, and its a smelly and hazardous. But, it’s worth your while to confront the volcano. You can walk away from it knowing that you’ve experienced one of the most important surface-altering processes in the solar system. As one of the hiking cohort said last summer, what you’re seeing here are the most recent steps in the death of a massive star. If you think about it, that’s correct; and we were watching the NEWEST steps in the creation of our planet. You can see more of our pictures from last summer here.