Martian Cataclysm: Impact energy analysis in support of the origin of multiple anomolies on Mars (cont.)
by Gary R. Spexarth
5. Formation of the Northern Lowlands
The Northern region of Mars is a topic of much interest because it is 5 km below datum ("sea level") and the Tharsis Bulge is 10 km above datum . Why is almost half of the planet so much lower in elevation than the rest?
The Tharsis Bulge and the Northern Lowlands can be seen in the topography map and globe produced by MOLA (Figures 1 & 6). These two features have not been previously thought to be directly related. However, one must consider the possibility that the Northern Lowlands are actually a direct result of the planet bulging to create the Tharsis Montes.
The following analysis will show that "bulging" at Tharsis Montes may have actually "pulled" the adjacent region inward, thus forming the Northern Lowlands. Referring to Figure-8, the following arc-lengths are defined as:
A1 = Original arc-length of Tharsis Region (at original elevation of Mars Datum)
A2 = Arc-length of Tharsis Region after formation of bulge
B1 = Original arc-length of Northern Lowlands (at original elevation of Mars Datum)
B2 = Arc-length of Northern Lowlands after formation (due to formation of Tharsis Bulge)
Rdatum = 3375 km = Average diameter of Mars
A1 is 4000 km, which is the diameter of the Tharsis Bulge base .
Since the Lowlands occupy approximately 90o of the Mars surface, B1 can be calculated to be 5300 km.
Similarly, by knowing A1=4000 km, the Tharsis angle is calculated to be 68o.
By knowing the angle of the Tharsis Bulge (68o), and its elevation of 10 km above datum, the final arclength of the Tharsis Bulge (A2) was determined using a Computer Aided Design (CAD) program, and was found to be 4008 km. Therefore, the increase in length of the Tharsis region is 8 km.
Assuming that this increase in arc-length of the Tharsis Region is taken up by the deformation of the Northern Lowlands, 8 km can be subtracted from B1 to determine B2.
5300 km - 8 km = 5292 km = B2 (26)
The reduction in elevation due to the decrease in arclength of the Northern Lowlands can now be calculated.
Rnew = The radius of the Northern Lowlands due to the reduction of arc-length.
Rdatum - Rnew = 5 km, which is the average elevation that the Northern Lowlands lie below datum.
Therefore, the increase of arc-length required to form the Tharsis Bulge (A2-A1) corresponds exactly to the reduction of arc-length of the Northern Lowlands (B1- B2) as well as the lower elevation of the Northern Lowlands, as shown in Figure-8 where A1, A2, B1, and B2 are arc-lengths.
Thus, the Northern Lowlands may, in fact, be a direct result of the "bulging" of the Tharsis region! In other words, as the Tharsis Region "bulged" outward, the adjacent region was "pulled" inwards, thus forming the Northern Lowlands.
Figure-8: The increase of Arc-length in the Tharsis Region corresponds to the reduction of arc-length in the Northern-lowlands, (A2- A1)=(B1-B2). The solid line is the shape of Mars prior to impact. The dashed line is the exaggerated, deformed shape of Mars after the impact.