Re: Relevant - Plate Tectonics Might Only Occur on 0.003% of Planets. That Makes Earth Very Special Indeed.

On 7/5/2024 8:57 PM, Dimensional Traveler wrote:
> On 7/5/2024 11:00 AM, Cryptoengineer wrote:
>> On 7/4/2024 10:25 PM, Dimensional Traveler wrote:
>>> On 7/4/2024 4:49 PM, a425couple wrote:
>>>> On 7/4/24 12:33, Dimensional Traveler wrote:
>>>>> On 7/4/2024 9:54 AM, a425couple wrote:
>>>>>> Big DEAL !!
>>>>>> So many times greats like Heinlein and Silverberg have written
>>>>>> about us going to exoplanets, and it being like Earth.
>>>>>> Sorry,,,, NO!
>>>>>>
>>>>>> from
>>>>>> https://www.universetoday.com/167659/plate-tectonics-might-only-occur-on-0-003-of-planets-that-makes-earth-very-special-indeed/
>>>>>>
>>>>>> Plate tectonics: Image Credit: NASA/Goddard Space Flight Center 
>>>>>> Scientific Visualization Studio
>>>>>> POSTED ONJULY 2, 2024 BY SCOTT ALAN JOHNSTON
>>>>>>
>>>> -----------snip-------
>>>>>>
>>>>>> Go to the citation for the rest ----.
>>>>>
>>>>> I went to the citation but couldn't find if that 0.003% is of ALL 
>>>>> exo-planets or just the Terrestrial/Super-Terrestrial types.
>>>>>
>>>>
>>>> "the rest" of the citation, did not give a lot of specific information.
>>>> Hopefully we will see a lot more on this research in the future.
>>>>
>>> I also think there's a flaw in their basic assumptions.  If you have 
>>> a rocky planet with a liquid core/mantle, you are going to have plate 
>>> tectonics.
>>
>> Venus, Mars, and Mercury suggest otherwise.
>>
> I believe Mars and Mercury's cores have solidified.  Venus has ... other 
> issues but does have active vulcanism.  And considering how many it has 
> may make up for the locked crustal plates.

If you trust wikipedia, all 3 that liquid cores. I was a little
suprised myself.


>> My impression is that the existance of a (relatively shallow)
>> water ocean is critical. There's also a suggestion that a major
>> meteor impact may have been involved in starting the process.
>>
> Theia was a bit more than a meteor and yes, liquefying the entire planet 
> a second time might have an effect.

Wasn't thinking of Theia, but something much later, which still make a 
big enough hole in the early crust that subduction got kickstarted, then 
spread.

pt