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Readers!

 

It is now July, time once again to celebrate the start of this webpage in 2010 with my annual July fund-raising campaign.

 

This year I celebrate the fifteenth anniversary since I began Behind the Black. During that time I have done more than 33,000 posts, mostly covering the global space industry and the related planetary and astronomical science that comes from it. Along the way I have also felt compelled as a free American citizen to regularly post my thoughts on the politics and culture of the time, partly because I think it is important for free Americans to do so, and partly because those politics and that culture have a direct impact on the future of our civilization and its on-going efforts to explore and eventually colonize the solar system.

 

You can’t understand one without understanding the other.

 

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A look inside Comet 67P/C-G

The Rosetta science team has determined that Comet 67P/C-G has no voids or large caverns in its interior, and that its low density is because its dust and water ice have mixed to produce a “fluffy” density.

In a new study, published in this week’s issue of the journal Nature, a team led by Martin Pätzold, from Rheinische Institut für Umweltforschung an der Universität zu Köln, Germany, have shown that Comet 67P/Churyumov-Gerasimenko is also a low-density object, but they have also been able to rule out a cavernous interior. This result is consistent with earlier results from Rosetta’s CONSERT radar experiment showing that the double-lobed comet’s ‘head’ is fairly homogenous on spatial scales of a few tens of metres.

The most reasonable explanation then is that the comet’s porosity must be an intrinsic property of dust particles mixed with the ice that make up the interior. In fact, earlier spacecraft measurements had shown that comet dust is typically not a compacted solid, but rather a ‘fluffy’ aggregate, giving the dust particles high porosity and low density, and Rosetta’s COSIMA and GIADA instruments have shown that the same kinds of dust grains are also found at 67P/Churyumov-Gerasimenko.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

 

The print edition can be purchased at Amazon. from any other book seller, or direct from my ebook publisher, ebookit. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.


The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
 

"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News

One comment

  • steve mackelprang

    It seems odd to me that the general topology isn’t more smoothed and less sharp edges everywhere. Why is it that sublimation leaves a different “geography” than melting ? At a gross level, melting would also give a certain small amount of “erosion” which would increase the smoothing , but I think sublimation being temperature dependent and acting over the whole surface, would leave a more rounded surface than what appears to be the case.

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