Solid matter is not solid. A material which is solid is Neutronium, a mass of pure neutrons. Ordinary matter consists of atoms. Atoms are a Nucleus and some electrons, all the rest is space. The appearance of solid matter is created by linking the electron shells of atoms. By increasing the amount of pressure upon a volume of normal matter its volume can be decreased. In atomic weapons the volume of the critical mass (HEU) is squeezed down (with explosives) to about 40% of normal. So ignoring reality, I could create a path through Mars that could contain both the compressed asteroid and the compressed mass of Mars without either touching along the asteroids path. In a more complicated process that is what partially happens.
There is a picture of C4 (the plastic explosive) being detonated, surrounded by glass beads. You would think that the explosion would produce a spherical boundary, but it does not. It produces a giant symmetric pin cushion. The explosion produced a boundary which maximized the velocity of the glass beads. Minor instabilities at the beginning of the explosion are amplified as more and more glass beads running into open air resistance are deflected into neighboring glass paths. Following in the wake of another particle the air resistance is less.
http://www.technologyreview.com/view/425794/the-puzzle-of-particle-jets-and-blast-waves/
The boundary instability is driven by the difference in directional/kinetic velocity of the glass beads across the boundary. The glass beads do not move in an exact line leading from the center of the blast, they encounter air resistance and drift toward one side or the other. Eventually they may encounter the path of a previous bead and follow the lowered air resistance in its wake.
A slow velocity asteroid impact produces molecules which have kinetic energy that is only slightly greater than the shocked molecules of the target in that it strikes. The forces/energies are nearly balanced producing much less boundary instability. Slow impacts tend to push matter ahead of it while a hyper-velocity impact produces a complex boundary which channels the asteroid material past the compressed target material.
Only partial and localized compression of the target is achieved as the leading edge of high velocity asteroid molecules are channeled along a pathproducing right angle compresseion of both asteroid and target material. This is not a homogenous process. There are channels where the asteroid molecules are freely moving past islands of target material. These isolated islands will be swept up into the kinetic soliton which is a catch all phrase for all the matter possessing kinetic energy or storing energy by compression.
With the impact of a high velocity asteroid a boundary consisting of two radically different structures interspersing into each other. One structure is a channel of high velocity asteroid molecules. The other structure (separating the channeled asteroid material) are fingers of compressed Martian rock. Once the process instability begins, it feeds back on itself and increases. This process is self optimizing. The size of channels and the fingers of target material are dependent on the area of the boundary, the density of the target material and asteroid, and the velocity of the asteroid. The high amount of kinetic energy compresses both the asteroid and Martian material so that they can temporarily occupy the same volume.
Asteroid molecules cannot be dammed up, (or pause), until an opening forms, the asteroid molecules continue forward deflecting and pushing past target molecules. The least resistive boundary shape wins the contest between possible boundary structures. As the asteroid goes deeper it has more Martian material mixed with into a conical column of material. This column has a complex internal structure of asteroid molecular channels, accelerated and compressed islands of Martian material, and new fingers of Martian material. This conglomerate of structures can be called the asteroids kinetic soliton.
At some point the fast asteroid molecules can no longer generate new channels. At this point the energy of matter following in the soliton begin to reach the front boundary and can move it forward some more. The kinetic soliton slows down enough that it has a smooth regular boundary and it is best described by shockwave dominated forms of modeling.
(Using a heavy construction equipment analogy)
A slow asteroid acts like a bulldozer continuously compressing target mass in front of it. A fast asteroid acts more like a scraper, moving and compressing material out of its path.
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