Mercury was shrinking for at least 3 billion years — and it still might be today

[Admin]

New research indicates that Mercury's thermal contraction was still occurring as recently as 300 million years ago.

Mercury was shrinking for at least 3 billion years — and it still might be today : Read more

 

[rod]

Mercury: Shrinking planet is still getting smaller, according to new research

Planetary scientists have long known that Mercury has been shrinking for billions of years. Despite being the closest planet to the sun, its interior has been cooling down as internal heat leaks away. This means that the rock (and, within that, the metal) of which it is composed must have...

phys.org

Widespread small grabens consistent with recent tectonism on Mercury, https://www.nature.com/articles/s41561-023-01281-5, 02-Oct-2023.

"...The identified grabens are about 10 to 150 m deep, tens of kilometres in length and generally less than 1 km wide. We find that the grabens occur as secondary tectonic features on larger compressional tectonic structures, which indicates continued activity of the parent structure. We estimate that they must be ~300 million years old or younger; otherwise, impact gardening would have masked their signature by burial and infilling. The widespread distribution of grabens and their young age supports the continued activity of Mercury’s shortening structures into geologically recent times and is consistent with thermochemical evolution models for a slowly cooling planetary interior and prolonged global contraction."

Okay, our best foot forward now to show Mercury is at least 4.5 billion years old it seems. Perhaps Mercury younger in age or much more recent catastrophism in the solar system

 

[billslugg]

Dear Abby:

"grabens...typically occur when the crust is stretched, an indicator of the planet's shrinkage."

I understand that grabens occur when crust is stretched, but the whole premise here is that the crust is shrinking.

Signed,
Confused

 

[Helio]

Dear Abby:

"grabens...typically occur when the crust is stretched, an indicator of the planet's shrinkage."

I understand that grabens occur when crust is stretched, but the whole premise here is that the crust is shrinking.

Signed,
Confused

Yeah, the stretching story seems a bit odd since a graben has two fault lines, where fracture due to stretching could be one fault line, I assume.

The link below shows a likely lunar graben, and it is described as a region that sank.

Rima Ariadaeus - Wikipedia

en.wikipedia.org

 

[billslugg]

That's not my point. The graben only occurs where the crust is stretching. On a shrinking planet with no plate tectonics there no place where the crust is stretching. It's impossible. Something is not adding up.

 

[Helio]

That's not my point. The graben only occurs where the crust is stretching. On a shrinking planet with no plate tectonics there no place where the crust is stretching. It's impossible. Something is not adding up.

Wouldn’t regional variations produce boundary stress with shrinkage?

 

[Classical Motion]

I think they are looking at the "wrinkle" point of view. The surface area must decrease, but we have to keep that area. A wrinkle is the solution, it's misdirects or misaligned some of the area into wrinkles....some of the area is pointed up and some of the area is pointed down. Slopes and grabens.

So a constant area stretched up and down to rest on reduced area. Wrinkled. The wrinkle is the stretch.

That's the only way I can figure it.

 

[billslugg]

Yes, this makes sense. If we look at the peaks of the ridges, they have crevasses from shallow, localized spreading to accomodate folding.

 

[Classical Motion]

I would have thought that Mercury would have achieved temperature equilibrium long ago.

 

[Classical Motion]

Perhaps it goes thru a temperature cycle.