8.3: History of Mercury
- Page ID
- 110552
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Mercury History
Formation
Inner part of nebula
Metal rich materials
Early impact or solar flares
Giant impact that stripped away some of crust and mantle? -
reformed crust and mantle would be low on volatiles (like the Moon)
Hollows on surface show slow sublimation of volatiles
Inner solar nebula depleted in volatiles due to activity of young Sun
Check recent research of planet formation?
Openstax Astronomy 2.0
The problem with understanding how Mercury formed is the reverse of the problem posed by the composition of the Moon. We have seen that, unlike the Moon, Mercury is composed mostly of metal. However, astronomers think that Mercury should have formed with roughly the same ratio of metal to silicate as that found on Earth or Venus. How did it lose so much of its rocky material?
The most probable explanation for Mercury’s silicate loss may be similar to the explanation for the Moon’s lack of a metal core. Mercury is likely to have experienced several giant impacts very early in its youth, and one or more of these may have torn away a fraction of its mantle and crust, leaving a body dominated by its iron core. A recent alternative explanation suggests that, early on, heat from the young Sun evaporated much of the lighter, more volatile, silicates in the material that formed Mercury, leaving the planet with a majority of metals.
oday, astronomers recognize that the early solar system was a chaotic place, with the final stages of planet formation characterized by impacts of great violence. Some objects of planetary mass have been destroyed, whereas others could have fragmented and then re-formed, perhaps more than once. Both the Moon and Mercury, with their strange compositions, bear testimony to the catastrophes that must have characterized the solar system during its youth
Heavy Cratering
Heavy cratering
Crater age of surface?
Mercury gravity higher so eject travels 65%
Inter crater plains occurred during heavy bombardment
Near end of HB – Caloris
Smooth plains may come from Caloris impact?? Or occurred at same (geologic) time?
Interior Cooling
cooling of interior => shrinking of surface => scarp
Apparently, at some point in its history, the planet shrank, wrinkling the crust, and it must have done so after most of the craters on its surface had already formed.
Erosion on Mercury
No plate tectonics
Mostly old surface
Micrometeorite gardening
Larger impacts forming rayed craters
Extreme heat and cold breaks down rocks