Local inversion of magnetic anomalies: Implication for Mars' crustal evolution

Research areas:
Planet. Spa. Sci.
Martian magnetic anomalies have been revealed by
the Mars Global Surveyor (MGS) mission in the south
hemisphere of Mars. The present study models
anomalies located in the ancient Terra Sirenum area
between latitudes 261S and 401S and longitudes 1851E
and 2101E using forward and inverse
approaches. While the high-altitude measurements
reveal the presence of two main magnetic anomalies,
three are detected by low-altitude data. They are
modeled as uncorrelated dipolar sources. Forward
models predict large magnetizations between 30 and
60 A/m. A generalized non-linear inversion is used
to determine the characteristics of the dipoles,
based on different subsets of data. Low-altitude
measurements inversion leads to more reliable
results than those obtained by the inversion of
high-altitude measurements only. Inversion of both
low- and high-altitude data together provides with
three dipoles that explain more than 57% of the
signal, within this 106km2 area. All dipoles have
large magnetizations. Serpentinization of the early
martian crust can explain such remanent
magnetizations. Two resulting dipoles are 56km deep,
which suggests a locally thick martian crust. The
last one is shallower (31 km). This indicates
different origins and/or magnetization
processes. Paleomagnetic poles are calculated and
located around the Tharsis bulge. It suggests that
Tharsis formed at high latitudes and moved toward
its present location by polar reorientation.