The changing surface of Comet 67P/C-G


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 ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit.

 
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

Changes on Comet 67P/C-G after outburst

More results from this week’s 50th Lunar and Planetary Science Conference in Texas! Two presentations today focused on showing the dramatic changes on the surface of Comet 67P/C-G that were documented by Rosetta. The first focused on the changes produced after massive outbursts during the comet’s closest approach to the Sun. The second documented several more evolutionary changes that changed more slowly.

The image to the right comes from the first paper, and shows the changes that took place on the surface following one massive outburst, with the numbers in red indicating unchanged features between the two photographs.

It appears an entire cliff section has disappeared, replaced by a single large giant boulder. Interestingly there is no obvious vent opening for the outburst. Instead, it appears that the eruption occurred below ground, and merely blasted part of the surface into space. As noted in the paper:

We report here on a third cliff collapse that occurred in the southern hemisphere in the Sobek region [7], which corresponds to the neck region in the 67P’s southern hemisphere. Due to the close alignment of the 67P’s
southern summer solstice with perihelion passage, the southern hemisphere is subjected to higher solar input, resulting in higher levels of activity and more intensive erosion. The location of the collapsing cliff in Sobek is consistent with the inferred source region of one of the strong outbursts [previously reported].

The paper also showed evidence of a large boulder more than a 100 feet across moving several hundred feet over a period of seven months.

The second paper showed various changes in a number of depressions and scarps on the smooth flat surfaces near the narrow neck that connected the comet’s two lobes. Examples of this terrain can be seen in high resolution pictures here and here and here and here.

From this data scientist suggest that the neck region is slowly dissolving away, its material in these flat areas flying away because the neck happens to be a region of low gravity.

Readers!
 

My July fund-raiser for Behind the Black is now over. The support from my readers was unprecedented, making this July campaign the best ever, twice over. What a marvelous way to celebrate the website's tenth anniversary!
 

Thank you! The number of donations in July, and continuing now at the beginning of August, is too many for me to thank you all personally. Please forgive me by accepting my thank you here, in public, on the website.
 

If you did not donate or subscribe in July and still wish to, note that the tip jar remains available year round.


 

Regular readers can support Behind The Black with a contribution via paypal:

Or with a subscription with regular donations from your Paypal or credit card account:


 

If Paypal doesn't work for you, you can support Behind The Black directly by sending your donation by check, payable to Robert Zimmerman, to
 
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

Leave a Reply

Your email address will not be published. Required fields are marked *