Data starting to come in from Cassini's most recent flyby of Enceladus

Wednesday, August 13, 2008

Enceladus' size compared to the United Kingdom

Just a few more hours now and we should have the first preliminary results (=pretty pictures) from the most recent Enceladus flyby performed by Cassini:
"We are happy to report that Cassini's begun sending data home," said Julie Webster, Cassini team chief at JPL. "The downlink will continue through the night and into tomorrow morning."

Closest approach occurred at approximately 3:21 p.m. PDT, while Cassini was traveling at a swift 17.7 kilometers per second (40,000 miles per hour) relative to Enceladus.

During the flyby, Cassini focused its cameras and other remote sensing instruments on Enceladus with an emphasis on the moon's south pole where parallel stripes or fissures dubbed "tiger stripes" line the region. That area is of particular interest because geysers of water-ice and vapor jet out of the fissures and supply material to Saturn's E-ring. Scientists hope to learn more about the fissures and whether liquid water is indeed the engine powering the geysers.

"There is a lot of anticipation and excitement about what today's flyby might reveal" said Bob Pappalardo, Cassini project scientist, also of JPL. "Over the next few days and weeks, the Cassini teams will be analyzing the photos and other data to tease out new clues about this tiny, active world."
This is certainly not the last either:
Two more Enceladus flybys are planned for October. The first of those will cut Monday's flyby distance in half and bring the spacecraft to a remarkable 25 kilometers (16 miles) from the surface. Enceladus measures about 500 kilometers (310 miles) in diameter--just one-seventh the diameter of Earth's moon.
For Cassini updates, see its page here, and if you want to see raw images you can see them here. One thing I like about NASA so much is how it puts so much raw data up for anybody to see and analyze.

The interesting thing about Enceladus of course is that it has cryovolcanism in spite of being such a small body. Wikipedia goes into much more detail on that. One other interesting part of the article is what the sky would look like for anyone on its surface:

Seen from Enceladus, Saturn would have a visible diameter of almost 30°, sixty times more than the Moon visible from Earth. Moreover, since Enceladus rotates synchronously with its orbital period and therefore keeps one face pointed toward Saturn, the planet never moves in Enceladus' sky (albeit with slight variations coming from the orbit's eccentricity), and cannot be seen from the far side of the satellite.

Saturn's rings would be seen from an angle of only 0.019°, and would appear as a very narrow, bright line crossing the disk of Saturn, but their shadow on Saturn's disk would be clearly distinguishable. Like our own Moon from Earth, Saturn itself would show regular phases, cycling from "new" to "full" in about 16 hours. From Enceladus, the Sun would have a diameter of only 3.5 minutes of arc, nine times smaller than that of the Moon as seen from Earth.

An observer located on Enceladus could also observe Mimas (the biggest satellite located inside Enceladus' orbit) transit in front of Saturn every 72 hours on average. Its apparent size would be at most 26 minutes of arc, about the same size as the Moon seen from Earth. Pallene and Methone would appear nearly star-like. Tethys would reach a maximum apparent size just above one degree of arc, about twice the Moon as seen from the Earth, but is visible only from Enceladus' anti-Saturnian side when it is at closest approach.


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