Monday, November 23, 2009

Links on Extinctions and Enceladus

I'm slow getting around to this, but Jacquelyn Gill of UW-Madison and others had an important paper in the November 20th Science on megafauna extinction-Younger Dryas-Clovis culture-cometary impact research. (I touched on the topic in the introduction to this post.) Gill et al.'s abstract is here, and you can find an excellent summary of the popular press coverage at the Knight Science Journalism Tracker, here. If you're not familiar with that website, they provide consistently thorough and usually insightful reviews of popular science journalism. On the research itself: Gill and her coauthors use spore counts and other paleobiological data from lake sediment cores to posit that the megafauna went into a steep decline 800-1900 years before the proposed impact and climate cooling. Yet again, the search for a single smoking gun for a mass extinction comes up short.


Plumes on Enceladus. (Credit to NASA/JPL/SSI, mosaic by Emily Lakdawalla, from her post here.)

In other news, The Planetary Society blog posts some amazing images from Cassini's second flyby of Enceladus -- here, here, and here. The resolution of the vapor/ice plumes is amazing. I link to that site often (we bloggers are a parasitical bunch) so if you're interested in this kind of think you should follow it directly.
Posted by at 8:09 AM
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4 comments:

  1. The photos from Cassini have been breathtaking. Combined with the Galileo mission we've got enough data to keep folks like you busy for a long time.

    Any hope for a similar mission to Uranus or Neptune in our lifetime?
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  2. Cassini has been and should continue to be a very successful mission.

    I don't know of any planned robotic craft heading out to Uranus or Neptune. New Horizons will miss them on its trip to Pluto and the Kuiper Belt. I think we'll have to rely on Voyager 2 data and ground- and Earth orbit-based instruments for a while.
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  3. The image is spectacular, but is clear that these are not volcanic vents or plumes as previously discussed. These are in fact electrical arcs in nature and more closely related to the Earth's Aurora than volcanic activity. You can see the current sheet clearly as is separates and intertwines into the classical twisted tornadic Birkeland current filaments that are so prevalent in space as measured directly by the NOAA THEMIS probe and others.
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  4. I've familiar with the electric arc internet talk. I appreciate your interest and welcome your comments, but I your alternate proposal is unconvincing. We have lots of reasons to think it should vent, we see the vents, we can successfully model why they happen, and we've analyzed the particulates that spew out. Why invoke another whole paradigm? Especially one at odds with so much of what we know?

    Sometimes ideas totally outside the current paradigm turn out to be true, but I don't see much traction with yours.

    cheers,
    CM
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