baalke@mars.jpl.nasa.gov (Ron Baalke) (02/02/91)
Archive-name: astro/magellan/magellan-images/1991-02-01
Archive-directory: ames.arc.nasa.gov:/pub/SPACE/VICAR/ [128.102.18.3]
Original-posting-by: baalke@mars.jpl.nasa.gov (Ron Baalke)
Original-subject: Magellan Images
Reposted-by: emv@ox.com (Edward Vielmetti)
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MAGELLAN IMAGES
=================
I've placed six more Magellan images at the Ames site. You can get them
via anonymous ftp at ames.arc.nasa.gov (128.102.18.3) in the directory
pub/SPACE/VICAR. Again, thanks to Peter Yee for use of his disk space and
computer system.
There are now 8 Magellan images available, each one is about 1MB in size
and they are in VICAR format. I've also added the captions that go along
with each of the images. They are in a separate ASCII file with a .txt
extension with filename matching the corresponding image. The captions are
interesting to read by themselves, and I've appended them to the end of this
posting.
This weekend I will convert these same Magellan images into GIF format.
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GOLUBKINA.IMG
This three-dimensional representation of brightness variations in
a Magellan radar image of Golubkina crater enhances the structural
features of the crater. Golubkina is 34 km (20.4 miles) in
diameter, and is located at about 60.5 degrees north latitude,
287.2 degrees east longitude. Golubkina is characterized by
terraced inner walls and a central peak, typical of large impact
craters on the Earth, Moon and Mars. The terraced inner walls form
at late stages in the formation of an impact crater, due to
collapse of the initial cavity formed by the meteorite impact. The
central peak forms due to rebound of the inner crater floor.
=============================================================================
DSNALL.IMG
One of the most useful Magellan standard data products is the full
resolution mosaic, the F-MIDR (Full-Resolution Mosaicked Image Data
Record). These products are mosaics of about 500 km (300 mile)
segments of 30 or more individual image strips. This is a partial
F-MIDR made from orbits 376 to 399, obtained between September 15
and September 18, 1990, part of the first orbits in which the
Magellan flight team operated the radar system in the mapping mode.
The mosaic is centered at 27 degrees south latitude, 339 degrees
longitude, in the Lavinia region of Venus. Three large impact
craters with diameters ranging from 37 kilometers (23 miles) to 50
kilometers (30 miles) can be seen located in a region of fractured
plains. The craters show many features typical of meteorite impact
craters, including rough, radar-bright ejecta, terraced inner walls
and central peaks. Numerous domes of probable volcanic origin can
be seen in the southeastern corner of the mosaic. The domes range
in diameter from 1-12 kilometers (0.6-7 miles), and some have
central pits typical of volcanic shields or cones. Resolution of
the Magellan data is about 120 meters (400 feet).
=============================================================================
GUMBY.IMG
On September 15, 1990, the Magellan spacecraft started radar
operations for its mapping mission at Venus. This image is taken
from the first set of radar data collected in the normal operating
mode. These fault-bounded troughs were imaged by Magellan on orbit
147 on September 15, 1990. The image is of part of the Lavinia
Region of Venus at 60 degrees south latitude, 347 degrees east
longitude. The image is 28 kilometers (17 miles) wide and 75
kilometers (46 miles) long. This region is at the intersection of
two tectonic trends. An extensive set of east-west trending
fractures extends to the west (left) and a second set extends down
to the south-southeast (lower right). The lines of pits suggest
some igneous or volcanic activity accompanying the faulting. The
prominent trough trending diagonally across the image is 5
kilometers (3.1 miles) wide and is 100 to 200 meters (300 to 600
feet) deep.
=============================================================================
CHANNEL.IMG
This Magellan image covers a region 77 kilometers (46 miles)
wide and 85 kilometers (51 miles) high. This image shows part of
a long, open channel at 76.5 degrees north latitude, 335 degrees
longitude in the Vires-akka Chasma, about 100 kilometers (60 miles)
north of Freyja Montes, in the Denitsa Region of Venus. The
channel ranges in width from less than 1 kilometer (3300 feet) to
4 kilometers (2.4 miles). The portion of the channel visible in
this scene is over 120 kilometers (72 miles) long. Longitudinal
scour features are visible within the channel, particularly where
it makes abrupt turns. The channel may have been carved by very
low viscosity lavas that were able to remain fluid over great
distances and thermally erode pre-existing terrain due to the
extreme temperatures at Venus' surface.
=============================================================================
X-CUT.IMG
This is a Magellan radar image mosaic of part of the Lakshmi
region of Venus. The mosaic is part of revolutions 390 and 391
acquired on September 17, 1990. The image is located at 30 degrees
north latitude, 333.3 degrees east longitude, and is about 37
kilometers (23 miles) wide and 80 kilometers (48 miles) long. On
the basis of Pioneer Venus and Arecibo data, it is known that the
region shown is located on the low rise separating Sedna Planitia
and Guinevere Planitia, and just to the west of Eistla Regio. The
image shows two sets of parallel lineations which intersect almost
at right angles. The fainter lineations are spaced at a regular
interval of about 1 kilometer and extend beyond the boundaries of
the image. The width of these faint lineations is at the limit of
resolution of the best Magellan images. The brighter, more
dominant lineations are less regular and appear in places to begin
and end where they intersect the fainter lineations. It is not yet
clear whether the two sets of lineations represent faults or
fractures, but in other areas outside the image, the bright
lineations are associated with pit-craters and other volcanic
features. This type of terrain has not been seen previously,
either on Venus or the other planets. Resolution of the Magellan
data is about 120 meters (400 feet).
=============================================================================
ODDIMPACT.IMG
On September 15, 1990, the Magellan spacecraft started radar
operations for its mapping mission at Venus. This image is taken
from the first set of radar data collected in the normal operating
mode. This Magellan radar image is of an impact crater in the Navka
Region of Venus. The image is a mosaic of data taken from orbits
376 and 377 on September 15, 1990. The crater is located at 334.5
E. longitude, 21.4 S. latitude, and is about 9 x 12 kilometers (5
x 7 miles) in size. This crater is very unusual, and is in some
ways different from anything seen elsewhere in the solar system.
It is fresh, with a sharp rim, terraces on the walls, and a well-
developed ejecta blanket. The rim, however, is distinctly kidney-
shaped rather than circular, and the crater's fresh appearance
suggests, that it formed with that shape at impact. The ejecta
blanket is markedly non-symmetric, with lobes extending to the
north (top) and south (bottom) of the image, and a major extension
stretching to the east (right). On the crater floor are several
smooth, flat, dark regions. The asymmetric shape of the ejecta
blanket has been observed on other planets and in impact
experiments, and probably indicates that the impactor struck the
surface at a low, oblique angle. The impactor would have been
moving from west to east, sending ejecta lobes off to either side
and a long streamer in the forward direction. The truly unusual
aspect of the crater is its shape. One possible explanation is
that the impactor broke up as it passed through the dense Venusian
atmosphere, causing several large chunks of material to strike the
surface almost simultaneously in an irregular pattern. The dark
patches on the crater floor may be solidified pools of molten rock
generated by the impact, or could be volcanic material extruded
some time after the crater's formation.
=============================================================================
DSNTALL.IMG
The first 3 days (24 orbits) of radar mapping from the Magellan
spacecraft have revealed the presence of a wide diversity of
geologic features on the surface of Venus. This full resolution
mosaic centered at 20 south latitude, 337.4 east longitude is
located between Navka and Lavinia Planitia and covers a region 475
kilometers (285 miles) wide and 545 kilometers (330 miles) long.
Analysis of this area from lower resolution Arecibo data show that
this area is part of an extensive region identified as bright
plains. The Magellan data reveal the detailed geologic
characteristics of different landforms in these plains. Located
along the left central edge of the image is a cluster of volcanic
domes which range from 1.5 kilometers to 7.5 kilometers in diameter
and cover a region 150 kilometers by 100 kilometers (90 miles by 60
miles). The domes and their deposits are located at the
convergence of radar-bright lineaments which are interpreted to be
faults and troughs. In some places the domes overlie the faults.
The faults and troughs extend into the lower part of the image
where they terminate against dark plains deposits and are cross cut
at right angles by additional faults. These relations indicate
that multiple episodes of faulting and volcanism have occurred. An
irregular shaped impact crater (11 kilometers by 8 kilometers) (7
miles by 5 miles) located in the lower left corner of the image is
interpreted to have formed by multiple impacts resulting from the
breakup in the atmosphere of a larger impactor. An extremely
radar-dark circular region located along the right central edge of
the image is interpreted as a possible region of sedimentary
deposits.
=============================================================================
PAN10.IMG
This image of the eastern edge of Alpha Regio, 30 degrees
south latitude, 11.8 east longitude, was acquired on November 7,
1990. It shows seven circular domical hills averaging 25
kilometers (15 miles) in diameter and maximum heights of 750 meters
(2475 feet). These features can be interpreted as viscous or thick
eruptions of lava coming from a vent on the relatively level ground
allowing the lava to flow in an even lateral pattern. The
concentric and radial fracture pattern on their surfaces suggests
if they are extrusive that a chilled outer layer formed then
further intrusion in the interior stretched the surface. The domes
may be analogous to volcanic domes on Earth. An alternative
interpretation is that the domes are the result of shallow
intrusions up-doming the surface layers. If they are intrusive,
then magma withdrawal near the end of the eruptions then produced
the fractures. The bright margins possibly indicate the presence
of rock debris or talus at the slopes of the domes. Fractures on
the surrounding plains are both older and younger than the domical
hills. Resolution of the Magellan data is about 120 meters (400
feet).
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | baalke@mars.jpl.nasa.gov
| | | | __ \ /| | | | Jet Propulsion Lab |
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