Enceladus-3 (March 12, 2008) |
Enceladus-3 (March 12, 2008) |
Guest_AlexBlackwell_* |
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Excerpt from Cassini Significant Events for 02/16/06 - 02/22/06:
"As mentioned in previous weeks, the project has been working on adopting a new reference trajectory in order to raise the minimum Titan flyby altitude for various encounters. Today the project reached a decision to proceed with the 'optocc2' trajectory. Additional work is still to be performed before delivery of the final files. This will include minor tweaks that have been analyzed in other trajectories, adjusting orbit 68 timing, and capture of an Enceladus plume occultation on orbit 28." For the record, the new reference trajectory will result in an even more spectacular Enceladus-3 flyby [61EN (t) E3] on March 12, 2008. |
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Guest_BruceMoomaw_* |
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Unfortunately, as Jason noted back on his own (sorely missed) Titan blog, whenever Cassini flies by Enceladus it's also flying through the densest part of the E Ring, and has to keep its high-gain dish pointed in the direction of travel as a shield against any unusually large particles -- which means that they can't use image-motion compensation to deblur the craft's closeup photos of Enceladus. (This will certainly be the case if they're flying through the plume at such low altitude.) Thus such incredibly close-range photos would be so badly blurred that their overall resolution wouldn't be much better than the much wider-field photos taken several hundred km out. It's yet another loss resulting from the cancellation of the scan platform, although I don't think anyone could possibly have foreseen back then that Enceladus would turn out to be THIS interesting.
Am I correct in guessing that one of the main purposes of this flyby is to analyze the denser low-altitude portion of the plume, and thus get a better analysis of its trace components? At any rate -- just as we had to do with Europa (and Io) two decades ago -- we must now unexpectedly add another world to our high-priority list of Solar System targets, and start seriously thinking about followup missions. If this eruption has been going on for 100 million years or more, there is a genuine chance that it might be an environment in which life could evolve. Now that's a visionary statement. DOWN, boy! You can't call it "visionary"; but certainly when Ms. Clark and I raised it, it produced a considerable stir in Spilker's little subgroup, suggesting that they hadn't fully considered the consequences of such an Astrobiology Lander failure and thus the full extent of the need to try to make advance observations to minimize its chances of occurring. So I'll settle for "important" rather than "visionary". |
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Guest_Richard Trigaux_* |
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At any rate -- just as we had to do with Europa (and Io) two decades ago -- we must now unexpectedly add another world to our high-priority list of Solar System targets, and start seriously thinking about followup missions. If this eruption has been going on for 100 million years or more, there is a genuine chance that it might be an environment in which life could evolve. DOWN, boy! You can't call it "visionary"; but certainly when Ms. Clark and I raised it, it produced a considerable stir in Spilker's little subgroup, suggesting that they hadn't fully considered the consequences of such an Astrobiology Lander failure and thus the full extent of the need to try to make advance observations to minimize its chances of occurring. So I'll settle for "important" rather than "visionary". To maximise our chances of finding life (or at least active pro-life chemistry) I think an Enceladus probe should land very close to the vents where steam gets out, to have some chances of finding life particules. Any other place on Enceladus is covered with 100kms of pure ice... So I imagine the following scenario: 1) a probe satellises at a low altitude around Enceladus (It must be possible, but orbits may be unstable, so the mission has to be lead at a quick pace) 2) the probe examines the vent region to find holes, deposits, etc 3) a small lander is sent at an appropriate location. (Eventually we may consider two or several such landers, piggy-backed or sent separately) 4) How to get samples depends on how the vents look like. If there is a deposit cone around, the lander just have to land on it. But if we have to fiddle in a crater or hole, the landers should be able to get in. 5) make analysis, take microscopic images, see if the shapes reproduce... 6) fire the SAMPLE RETURN rocket. Actually it may be easier to get samples in an Enceladus vent than on Europa (even assuming that life chemistry could be present on the surface). And at least we are sure that Enceladus water is not some ammonia eutectic like on Titan, or filled with sulphuric acid, like maybe Europa: it is plain water, relatively pure, propicious for life. |
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