A Curious Aspects of Topography of Mars: Impact volcanism?
Generated by the Mars Orbiter Laser Altimeter (MOLA), an instrument aboard
NASA's Mars Global Surveyor, the high-resolution map represents 27
million elevation measurements gathered in 1998 and 1999. The data serves
as a basic reference book for Mars scientists , and inspires a variety
of insights about the planet's geologic history.
The data were assembled into a global grid with each point spaced 60
kilometers apart at the equator, and less elsewhere. Each elevation point
is known with an accuracy of 13 meters in general, with large areas of
the flat northern hemisphere known to better than two meters. The
full range of topography on Mars is about 30 kilometers
The Curious Aspects of the Topography of Mars
Lowlands-highlands
The one well-known curious aspect of the topographic map is the striking
difference between the planet's low, smooth Northern Hemisphere and
the heavily cratered Southern Hemisphere, which sits, on average,
about three to five kilometers higher than the north. One clue is
that the boundary between the terrains is roughly circular. See fig.
1
One questionable explanation is that a giant impact hit the north
early in the history of the planet, thereby lowering it. But as one can
see from the fig. 2 of crustal structure, the terrain continues to
slope beyond the lowland-highland boundary:
Additional analysis of the topography and gravity indicates that the
northern lowlands was likely a zone of high heat flow early in Martian
history, relecting vigorous convection of the Martian interior[1].
This rapid heat loss could have released gases trapped within
the planet to the atmosphere and underground ice or water to thesurface,
helping to produce an ocean in the Northern Hemisphere. If this process
was axial symmetrical so one can find the place of the old poles from the
fig 1. : 65 North and 170 West. The old equator :
The Mars with magnetism inscriptions in the same position :
Impact Volcanism
Hellas Basin - Alba Patera
The massive Hellas impact basin in the Southern Hemisphere is another striking
feature of the map. (Nearly nine kilometers deep and 2,100 kilometers acros
the basin is surrounded by a ring of material that rises about two kilometers
above the surroundings and stretches out to 4,000 kilometers from the basin
center.)
But what impressed me the most is the fact, that there is another striking
feature of Mars on the exact opposite point of the Mars globe: The crater
of Alba Patera. (The Alba Patera a 6 km high volcano with a territory of
1200x1600 km).
The Point of Cataclysm
The Isidis Planitia's counter point (the "Point of Cataclysm") is a very
interesting place: It is on the Tharsis bulge, which is unique in the solar
system and rises to 10 km above the "Marsian see level". The Point
of Cataclysm is in the center of a system of tectonic features that covers
the entire western hemisphere. It is at the beginning of Valles Marineris
and near to the top of the bulge in Noctis Labyrinthus which were formed
when the crust was pulled apart in extension, radiating out from a center.
Everything is here the largest in the solar system and appears to have
reulted from adjustment in the outer layer of the planet caused by impact
tectonics:
Argyre impact basin- Elysium Mons
The Elysium mons is 1000-1200 km far from the counter point. Why this difference?
Or where supposed the Argyre impact basin to be? See the figure.
On the next figure one can see three place of rotation . All three
rotation clockwise and has the same value:29 degrees plus/minus 2 degrees.
The rotation of Lunae Planum and Valles Marineris is evident from the pictures.
The third constructed in the following way: We hawe to place, the Argyre
basin, and a point where it shuld be. If this difference is coused by rotation
so the centre of rotation should be on the normal bisector of the
line between these two points. What is very interesting, the "point of
cataclysm" will be on the bisector. So I took the point of cataclysm as
centre of rotation. So reconstructing the events: the Argyre impact
came first and with it the Elysium volcanos om the other side and
secondly the Isidis impact made to rotate the Argyre basin around a its
counter-point as centre with ~29 degree.
Conclusions
The longevity and vigor of internal geologic activity of terrestrial planets
correlates roughly with size. (This is understandable, considering that
most geologic and tectonic processes are driven by the heat engine of a
planet.)
As the Mars is a one-plate planet, where nothing goes down, there will
be nothing to drive the volcanism. So where did those violent tectonic
events come from? Mars is just large enough to became active with the help
of giant impacts, but not so active that all records of its early history
be destroyed. My hypothesis is that the huge impacts are the causes of
volcanism and cataclysmic movement of huge part of crust. Time to time
the planetary billiard revived the volcanism of an inactive Mars and the
events connected to it. And the explosive volcanic eruptions and
cataclysmic movement of crust , fueled colossal floods that carved some
of the gorges and gouges found on the Red Planet.
This idea came to me seenig the picture PIA02035 (Maps of the Mars
Topography, site photojournal.jpl.nasa.gov) in Apr. of 2000 and induced
me to send a message to the discussion web site of CNN [2]. Afterwards
I developed the program "PlanetScape" to study Mars and other planets.
PlanetScape was used to generate all but two figures.
In the Tharsis region the tectonic events include clockwise rotation
of the Lunea Planum, Valles Marineris and Argyre Planitia.
In the end I should like to say, that it is the most unfortunate thing
that no topogrphic data for the Moon, though it would be not too
expensiv to put a laser altimeter arond the Moon
By Marton ZSENEI
[1] Zuber, M.T., S.C. Solomon, R.J. Phillips, D.E. Smith, G.L. Tyler,
O. Aharonson, G. Balmino, W.B. Banerdt, J.W. Head,
C.L. Johnson, F.G. Lemoine, P.J. McGovern, G.A.
Neumann, D.D. Rowlands,
S. Zhong,
Internal structure and early thermal evolution of
Mars from Mars Global
Surveyor topography and gravity, Science, 287, 1788-1793,
2000.
[2] Marton ZSENEI - Sunday, 04/23/00, 8:14:28am (#1979 of 1980)
Discussion web-site "Destination Mars"