Fusion Crust Model
In order to better understand how the fusion crust was
created on the Frass Meteorite, I have
proposed
a simple model. Due to the very thin walls of the meteorite, the
greatest heating, and therefore the greatest melting, has occurred on those
surfaces closest to the exterior. As one moves into the meteorite, away
from the surface, one finds less melting. It appears that the rock never
melted more than about 1 centimeter deep, at any location. The
"bottom" of the meteorite suffered more melting than did the "top."
Any material that comes from space and finds its way to the surface of our planet must show the effects of heating that are consistent with a passage through the Earth's atmosphere. Most meteorites are the remnants of suns or planets that have gone before us, therefore they tend to be more dense than rocks made on the Earth. Very few have had vesicles, so most meteorites have flat surfaces of solid rock. This is the material exposed to heating upon entry into our atmosphere. But the Frass rock is very different. Since it was created on the surface of Mars, it is very light in weight and can dissipate heat very quickly and efficiently.
In order to
show how the Frass Meteorite is different than "normal" meteorites, I have
created the following set of diagrams. In diagram A, we see the rock as it
first begins to enter the atmosphere. Notice the sand and particles are still in
all of the vesicles. The air currents are shown by the arrows.
In diagram B, the process is continuing. Some of the outer
material of the
walls of vesicle 1 have begun to melt and to thicken. Some of the material is
blown from the rock as it heats up and the pressure of the atmosphere forces it
away from the rock, so vesicle 1 has lost most of its contents. Another thing to
notice is how complex the air currents would be for a rock of this type. Normal,
flat meteorites present a relatively simple aerodynamic profile to the
atmosphere, whereas the Frass meteorite would have been
composed of
countless tiny air currents, all helping to carry away the heat being generated.
Also, the loss of materials would help in the heat dissipation.
In diagram C we can see larger pieces leaving the rock.
The contents of vesicle 2 have now been eliminated and the outer wall to vesicle
3 has now been breached and its contents will soon begin to exit the rock. Many
of the outer walls have now been melted and are much thicker than they
originally were. The air currents have become even more complex
Diagram D represents the rock as it looks today, after its fall through the atmosphere. All of the outer vesicles have been cleared of sand and debris. The outer walls are thicker than the interior walls due to the heating by our atmosphere. Many of the vesicles show levels that are 2, 3, or 4 vesicles deep. The FC stands for Fusion Crust.