Newsgroups: comp.archives
Path: utzoo!news-server.csri.toronto.edu!ox.com!msen.com!emv
From: baalke@mars.jpl.nasa.gov (Ron Baalke)
Subject: [graphics] Magellan Images
Message-ID: <1991Mar13.224558.20484@ox.com>
Followup-To: comp.graphics
Keywords: Magellan, JPL
Sender: emv@msen.com (Edward Vielmetti, MSEN)
Reply-To: baalke@mars.jpl.nasa.gov (Ron Baalke)
Organization: Jet Propulsion Laboratory, Pasadena, CA.
References: <1991Mar13.213459.1452@jato.jpl.nasa.gov>
Date: Wed, 13 Mar 1991 22:45:58 GMT
Approved: emv@msen.com (Edward Vielmetti, MSEN)
X-Original-Newsgroups: comp.graphics

Archive-name: astro/magellan/magellan-images/1991-03-13
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@msen.com (Edward Vielmetti, MSEN)

                            ===================
                              MAGELLAN IMAGES
                              March 13, 1991
                            ===================

     I've placed two more Magellan images in VICAR format and 11 in GIF format
at the Ames SPACE archives, bringing the Magellan total to 14 VICAR images and
28 GIF images.  They can be obtained via anonymous ftp from ames.arc.nasa.gov
(128.102.18.3), and are in the pub/SPACE/VICAR and pub/SPACE/GIF directories,
respectively.  The two new VICAR files are called pancakes.img and bahet.img.
All of the VICAR images have a corresponding caption files (with a .txt
extension) which contains detailed descriptions of the image.  Make sure
you are in binary mode when transferring the image files, and in ASCII mode
when transferring the text files.  The two new caption files are appended to
the end of this message.

     The VICAR images can be viewed on an IBM PC computer with the IMDISP
program stored in a zip file called imdisp56.zip, located in the
pub/SPACE/IMDISP directory.  The VICAR format is the format used by the Image
Processing Lab (MIPL) at JPL.  Most of the VICAR images are in 1024x1024
pixel resolution and are 1MB in size.

     The pancakes.img image is the image showing the 7 pancake volcanoes.
The pan10.img file that I had uploaded earlier shows 3 of the 7 volcanoes.

     I've converted all of the Magellan VICAR images into GIF format in 640x480
resolution.  The new GIF files are:

     saca1.gif          pancakes.gif
     saca2.gif          pancake1.gif
     saca3.gif          bahet.gif
     saca4.gif          bahet1.gif
     saca5.gif          bahet2.gif
     saca6.gif

     The saca GIFs were all derived from the original saca.img file which I
placed at the Ames site earlier.  The original file is quite large at
2.8 MB.  This saca.img file had to be reduced by a factor of 4 in order for
it to fit in the 640x480 GIF resolution.  The six new saca GIF files are
closeups of various parts of the saca.img with no detail loss.  The
pancakes.gif was converted from pancakes.img, with pancake1.gif zooming
in on 4 of the volcanoes.  Likewise, bahet.gif was converted from bahet.img,
with bahet1.gif and bahet2.gif being subsections of bahet.img, showing it in
greater detail.
============================================================================
PANCAKES.TXT (same as PAN10.TXT)

     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).
============================================================================
BAHET.TXT

     This mosaic of Magellan data in the Fortuna region of Venus,
centered at 49 degrees north latitude, 2 degrees longitude, shows
two coronae.  Coronae are large circular or oval structures first
identified in Soviet radar images of Venus.  The structure on the
left, Bahet Corona, is about 230 kilometers (138 miles) long and
150 kilometers (90 miles) across.  A portion of Onatah Corona,
over 350 kilometers (210 miles) in diameter, can be seen on the
right of the mosaic.  Both features are surrounded by a ring of
ridges and troughs, which in places cut more radially-oriented
fractures.  The centers of the features also contain radial
fractures as well as volcanic domes and flows.  Coronae are
thought to form due to the upwelling of hot material from deep in
the interior of Venus.  The two coronae may have formed at the
same time over a single upwelling, or may indicate movement of
the upwelling or the upper layers of the planet to the west over
time.  A 'pancake' dome, similar to low-relief domes see in the
southern hemisphere, is located just to the southwest of Bahet.
Resolution of the Magellan data is about 120 meters (400 feet).
      ___    _____     ___
     /_ /|  /____/ \  /_ /|      Ron Baalke         | baalke@mars.jpl.nasa.gov
     | | | |  __ \ /| | | |      Jet Propulsion Lab | 
  ___| | | | |__) |/  | | |___   M/S 301-355        | Change is constant. 
 /___| | | |  ___/    | |/__ /|  Pasadena, CA 91109 | 
 |_____|/  |_|/       |_____|/                      | 

