Geoscience Reference
In-Depth Information
(a)
(b)
Figure 5.9
Aeolian features on Venus captured by
Magellan
radar imagery: (a) possible yardangs centred at 9 N, 60.7 E; image
width
∼
95 km; (b) wind streaks and transverse dunes, part of the Fortuna-Meshkenet dune field; image width
∼
37 km. NASA
images courtesy of R. Greeley.
surface consists of rocky material, with loose regolith in
the minority (Figure 5.10). The surface of Venus as re-
vealed by the various missions displays surface properties
as variable as on Earth or Mars, which can be summarised
on a mission-bymission basis.
Venera 9
landed on the eastern side of the highlands of
Rhea Mons and recorded the first images by any spacecraft
from the surface of another planet. The image revealed
scattered slightly flattened to equidimensional, angular to
subangular rocks. Possible layering, picked out by differ-
ential weathering, was seen in several rocks. The rocks
were resting on or were partly buried by a poorly sorted
granular regolith.
The landing site for
Venera 10
is south of
Venera 9
on the southwestern side of Theia Mons. The surface is
composed of large flat slabs of rock with wavy fracture
patterns separated by patches of very dark granular re-
golith. Textures similar to terrestrial sandy corrosion and
cellular weathering can be seen (Florenskii, Basilevskii
Landings sites for
Venera 13
and
14
probes were the
eastern flanks of the highlands of Phoebe Regio, with
Venera 14
to the east of
Venera 13
.The
Venera 13
im-
age resembled that of
Venera 10
, except the fine regolith
was only slightly darker than the bedrock but more abun-
dant. The higher resolution images returned by these mis-
sions showed that the loose regolith was composed of very
poorly sorted angular fragments.
Venera 14
imaged a flat plain almost completely cov-
ered by slabby bedrock. Fractures are linear to scalloped,
and loose regolith is minor. Possible dirt cracking (
senso
,
Ollier, 1965) is visible. Areas in the distance with more
extensive loose regolith are visible.
5.7.3
Rock breakdown
Radar data (Greeley, 1994) suggest that only a quarter of
the surface is composed of loose material. This is con-