IPB

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
Huge rocks at Mons Hansteen
wildespace
post Jul 4 2013, 08:27 AM
Post #1


Member
***

Group: Members
Posts: 238
Joined: 15-January 13
Member No.: 6842



Greetings. What is your opinion on the origin of big rocks that are visible at this location at Mons Hansteen (also known as the "Arrowhead"). One of the rocks casts a particularly long shadow.

Could they be volcanic plugs, or simply hard rocks exposed through erosion? Would love to hear your take on this. Thanks.

Attached Image


--------------------
Go to the top of the page
 
+Quote Post
nprev
post Jul 4 2013, 08:50 AM
Post #2


Merciless Robot
****

Group: Admin
Posts: 8783
Joined: 8-December 05
From: Los Angeles
Member No.: 602



Um.

Well, they're certainly big rocks. Based on the Moon's general geological history they were probably fragmented & exhumed from an impact.

That's about it. There is no, and has not been over the history of the Solar System, any erosion on the Moon in the rapid terrestrial sense other then impacts from the micro to macro scale.


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
Juramike
post Jul 4 2013, 03:18 PM
Post #3


Senior Member
****

Group: Moderator
Posts: 2785
Joined: 10-November 06
From: Pasadena, CA
Member No.: 1345



Hansteen rocks are different than most normal basaltic moon rocks.
Check out: Hawke et al., JGR 108 (2003), E7,5069. http://www.spudislunarresources.com/Bibliography/p/78.pdf

This region has rocks that are unusual in that they are made of dacite, which is much more silica-rich lava than basalt. Dacite is a superfine-grained form of granodiorite. Since there is less manganese and iron in the chemical makeup of silica-rich lavas, the silicate-molecule tetrahedrons aren't as bound up by metal ions, so the silica units cling to each other more. (At least that is the simple explanation I have in my head). As a result, the silica-rich lavas are lumpy and flow like toothpaste. The more basaltic lavas are more runny and flow like maple syrup. Dacite and the even more silica-rich rhyolite (superfine-grained granite) form steep-sided plug domes. The plug dome in Mt. St. Helens formed in the 1980's was dacite (http://vulcan.wr.usgs.gov/Imgs/Jpg/MSH/Ima...9-13-84_med.jpg)

Other good candidates for silica-rich volcanic constructs on the Moon are : Marian domes, Oceanus Procellarum [41.4 N, 48 E]; Hansteen alpha, Oceanus Procellarum [12.3 S, 51 W]; Mons Gruithuisenen, Mare Imbrium [36.3 N, 40 W], and Compton-Belcovich Farside [61 N, 99.5 E].

If you poke around those areas, you'll also find some features that look like lumpy big-bouldered plug domes remnants. There is a great example of a big boulder pile just S of Beta dome in the Compton-Belkovic complex.







--------------------
Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
Go to the top of the page
 
+Quote Post
Fran Ontanaya
post Jul 5 2013, 05:32 AM
Post #4


Member
***

Group: Members
Posts: 293
Joined: 22-September 08
From: Spain
Member No.: 4350



I think the terrain just unevenly slopes down in the same direction as the shadows, making them longer by different amounts.
Go to the top of the page
 
+Quote Post
JohnVV
post Jul 6 2013, 10:54 PM
Post #5


Member
***

Group: Members
Posts: 890
Joined: 18-November 08
Member No.: 4489



without knowing the exact time the image was taken for that lat / long
And the exact pixel resolution < PPM> or <PPD>
knowing the exact position of the sun above the horizon for the location
i can not calculate the Height

If the Sun is right ON the horizon then they might be rather small .
Go to the top of the page
 
+Quote Post
wildespace
post Jul 6 2013, 11:56 PM
Post #6


Member
***

Group: Members
Posts: 238
Joined: 15-January 13
Member No.: 6842



QUOTE (JohnVV @ Jul 6 2013, 11:54 PM) *
without knowing the exact time the image was taken for that lat / long
And the exact pixel resolution < PPM> or <PPD>
knowing the exact position of the sun above the horizon for the location
i can not calculate the Height

If the Sun is right ON the horizon then they might be rather small .


I believe you can find those details when looking at the individual NAC strips, such as http://wms.lroc.asu.edu/lroc/view_lroc/LRO....0/M181494651LC or http://wms.lroc.asu.edu/lroc/view_lroc/LRO....0/M166182355RC

But the problem with using shadow length in calculations is that it's falling downhill, therefore being longer than if it were on flat ground.


--------------------
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 28th March 2024 - 08:46 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.