IPB

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
Mercury's molten core
Guest_AlexBlackwell_*
post May 3 2007, 05:37 PM
Post #1





Guests






The embargo won't be lifted for a few more hours, but note that the May 4, 2007, issue of Science will have an interesting paper Margot et al. (and accompanying Perspectives piece by Sean Solomon) regarding Mercury and a possible molten core, a paper that also makes the cover.
Go to the top of the page
 
+Quote Post
Guest_AlexBlackwell_*
post May 3 2007, 06:48 PM
Post #2





Guests






Mercury has molten core, Cornell researcher shows
By Lauren Gold
Cornell University Chronicle Online
May 3, 2007

Surprise Slosh! Mercury's Core is Liquid
By Ker Than
Staff Writer, Space.com
posted: 03 May 2007
2:00 pm ET
Go to the top of the page
 
+Quote Post
Guest_AlexBlackwell_*
post May 3 2007, 07:52 PM
Post #3





Guests






NASA Antenna Cuts Mercury to Core, Solves 30 Year Mystery
NASA/JPL
May 3, 2007
Go to the top of the page
 
+Quote Post
nprev
post May 4 2007, 12:29 AM
Post #4


Merciless Robot
****

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



Hmm...sulfur enrichment needed...Mercury migrated inward? Wonder if some planet we know might be missing a moon after all... huh.gif


--------------------
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
Guest_AlexBlackwell_*
post May 4 2007, 06:02 PM
Post #5





Guests






For those who don't have access to Science, or who cannot comprehend the paper, check out Emily's blog entry on the subject, which is a fairly decent summary, and without all the messy numbers.
Go to the top of the page
 
+Quote Post
Guest_AlexBlackwell_*
post May 4 2007, 09:35 PM
Post #6





Guests






MESSENGER PI Discusses Significance of News That Mercury Has Molten Core
MESSENGER Mission News
May 4, 2007
Go to the top of the page
 
+Quote Post
nprev
post May 5 2007, 04:56 AM
Post #7


Merciless Robot
****

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



What I find most mysterious is how Mercury could have such a disproportionately large and at least partially still liquid core yet have a thick crust with no evident prior surface activity and apparently little in the way of a mantle.

Does this perhaps suggest that Mercury did indeed form further out, cooled rapidly, yet had a rapid rotation rate and was re-heated during its orbital migration inward by dynamic tidal braking as it settled into the 3/2 spin resonance and significantly eccentric orbit while its core "re-melted"? Sort of like a thick-skinned Io in some ways...

Another point to consider is Venus' rotational resonance with Earth. Something very interesting and not at all obvious may have happened to all three planets in the early days.


--------------------
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
mchan
post May 5 2007, 06:17 AM
Post #8


Member
***

Group: Members
Posts: 599
Joined: 26-August 05
Member No.: 476



QUOTE (AlexBlackwell @ May 4 2007, 02:35 PM) *

Kind of sucks the links here are for a pay to view only. At least they could have linked the NASA press release.
Go to the top of the page
 
+Quote Post
edstrick
post May 5 2007, 06:52 AM
Post #9


Senior Member
****

Group: Members
Posts: 1870
Joined: 20-February 05
Member No.: 174



When they discovered Mercury's mag field from Mariner 10, besides the absolute magnetic moment (something like field strength*volume) of the field, the other major observation was that the field was off center, tilted and distorted in ways that magnetosphere pressures on the field couldn't explain. Similar things are seen at Uranus and Neptune.

The inference was that the field was being generated in a rather shallow shell, rather than deep inside, far from the surface. In Mercury's case, plausible modles had the core frozen to maybe 2/3 of it's radius with a solid inner core and a convecting outer core.

The question was how could a core of a small and geologically inactive world stay partially molten over 4.5 billion years. A generally plausible model was that refined calculations of lower thermal conductivity in a heavily fractured megaregolith (like the moon's) and the even lower thermal conductivity of a deep, old regolith, could significantly reduce global heat flow and extend the life of a molton core. My recollection is that that was marginal, and models of some additional heating than just that from inner core freez-out would help keep enough core molton to provide a dynamo.
Go to the top of the page
 
+Quote Post
Jeff7
post May 5 2007, 03:42 PM
Post #10


Member
***

Group: Members
Posts: 477
Joined: 2-March 05
Member No.: 180



Could the heating be a result of tidal forces? As I recall, Mercury has a fairly elliptical orbit. It might not be nearly as severe as what Io experiences, but it still might be enough to liquefy the core.
Go to the top of the page
 
+Quote Post
Guest_AlexBlackwell_*
post May 7 2007, 10:48 PM
Post #11





Guests






QUOTE (Jeff7 @ May 5 2007, 05:42 AM) *
Could the heating be a result of tidal forces? As I recall, Mercury has a fairly elliptical orbit. It might not be nearly as severe as what Io experiences, but it still might be enough to liquefy the core.

Bruce Bills had an LPSC abstract on this a few years back. See also Correia and Laskar [2004].
Go to the top of the page
 
+Quote Post
Rob Pinnegar
post May 22 2007, 07:51 PM
Post #12


Member
***

Group: Members
Posts: 509
Joined: 2-July 05
From: Calgary, Alberta
Member No.: 426



QUOTE (edstrick @ May 5 2007, 12:52 AM) *
The question was how could a core of a small and geologically inactive world stay partially molten over 4.5 billion years.


I haven't read the new papers, but off the top of my head, a growing inner core might well be made of solid iron which would tend to enrich the sulfur concentration of the remaining outer mantle. This could help keep it molten.
Go to the top of the page
 
+Quote Post
edstrick
post May 23 2007, 05:33 AM
Post #13


Senior Member
****

Group: Members
Posts: 1870
Joined: 20-February 05
Member No.: 174



"Could the heating be a result of tidal forces? As I recall, Mercury has a fairly elliptical orbit."

Tidal heating involves dissipation of energy. The result is that the orbit would circularize over time. Io and Enceladus are in resonances that keep re-ellipticizing <new word?> their orbits. I don't know the timescale for plausible orbital ellipticity evolution at Mercury, but that it hasn't gone circular over 4.5 billion years argues that the crust is pretty rigid and does not dissipate energy. A fluid core is so fluid that it doesn't dissipate tidal energy efficiently.
Go to the top of the page
 
+Quote Post
Marz
post Oct 30 2008, 12:32 AM
Post #14


Member
***

Group: Members
Posts: 311
Joined: 31-August 05
From: Florida & Texas, USA
Member No.: 482



Looks like more clues to a molten core:

http://www.nasa.gov/home/hqnews/2008/oct/H...er_Mercury.html

with this AP article:

http://news.yahoo.com/s/ap/20081029/ap_on_sc/sci_mercury
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 19th March 2024 - 09:53 AM
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.