Radar Exploration of Mars: Recent Results and Progresses - Planetary Exploration and Science: Recent Results and Advances - page 88

Fig. 5.10 MARSIS and SHARAD Mars north pole radargrams

For each orbit, it has been produced a radargram. Figure 5.10 shows a radargram
generated with MARSIS data along with a radargram generated with SHARAD
data for comparison. As mentioned before, SHARAD has the capability to better
discriminate subsurface interfaces, revealing Martian superficial stratigraphy, while
MARSIS signal can penetrate deeper into Martian surface achieving information
even of the basal unit (BU) structure. This peculiarity of MARSIS data suggested to
study the feasibility to produce a three-dimensional representation of north pole ice
cap along with the underlying basal unit.
Each radargram can be considered as a cross section of the Martian crust
(Fig. 5.11 ). Composing the radargrams in a three-dimensional structure, Frigeri et al.
( 2012 ) generated three-dimensional images in which there are easily recognizable
Olympia Undae, Gemina Lingula, and Chasma Boreale (Fig. 5.12 ).
The peculiarity of this approach is the possibility to study Martian north pole
from different perspectives and even to discriminate the ice polar cap (in cyan) and
the basal unit (in yellow) (Fig. 5.13 ). This study revealed a cavity under Olympia
Cavi, 80 km wide and 400 km long, buried under upper layered deposits (Fig. 5.14 ).

5.5.2 Mars Total Electron Content Evaluation

Mars has strong local magnetic fields (up to 1,600 nT at 90 km of altitude), con-
nected to characteristics of the Martian crust (Acuna et al. 1999 ; Nielsen et al. 2006 ),
as the data collected by Magnetometer/Electron Reflectometer (MAG/ER) onboard
Mars Global Surveyor (MGS) proved. But the Red Planet is not characterized by an
appreciable global magnetic field. Therefore, its ionosphere is not protected from
direct interaction with the solar wind which can directly interact with it altering its
local properties.