"How's bout them holes in the moon.When it orbits low, we can reach up to
harvest the cheese, and retrieve,
all our things back from them holes."
by That 1 Guy
Phase of the Moon Today: Waxing Gibbous 60% of Full. I saw the Moon again today as well as yesterday.
Impact craters can be divided into two categories: simple and complex. The formation of these craters is characterized by three distinct stages that include contact and compression, excavation and modification. The first stage is when the projectile makes contact with the ground surface to about half its diameter. The kinetic energy of this projectile is transferred to the surface and converted into shockwaves radiating outward into the planetary body. The projectile becomes compressed and some of the shockwaves make their way to the rear of the projectile. Once this happens it will be reflected as a rarefaction transforming the projectile into melt and vapour. The vapourized portion may expand out of the crater and the melt may be mixed into the breccias below.
The second stage, excavation, is characterized by the impact crater opening up. As some of the shockwaves travel upward their energy is converted into kinetic energy. This kinetic energy exceeds the mechanical strength of the target rocks and ejects fragments into the atmosphere. The movements of these rocks create a bowl-shaped depression called a transient crater. The area under the impact site has material that continues to be driven downward and outward.
The final stage is the modification stage. This stage begins when the transient crater has grown to its maximum size and the shockwaves no longer play a role in crater formation. The crater is modified by gravitational forces and rock mechanics. Once all of the remaining material falls and stops the stage is complete.
The second stage, excavation, is characterized by the impact crater opening up. As some of the shockwaves travel upward their energy is converted into kinetic energy. This kinetic energy exceeds the mechanical strength of the target rocks and ejects fragments into the atmosphere. The movements of these rocks create a bowl-shaped depression called a transient crater. The area under the impact site has material that continues to be driven downward and outward.
The final stage is the modification stage. This stage begins when the transient crater has grown to its maximum size and the shockwaves no longer play a role in crater formation. The crater is modified by gravitational forces and rock mechanics. Once all of the remaining material falls and stops the stage is complete.
Complex crater formation follows the same stages as the simple crater but with some noted differences. This includes the uplift that occurs at the end of the excavation stage to begin the modification stage. This is characterized by the deep seated rocks beneath the center of the transient crater forming a central uplift. This process is accompanied by the peripheral material collapsing and draping the original uplifted rocks. As the modification stage ends a central uplift is present and surrounded by a terraced rim.
signing off
kb
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