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New Mars Global Surveyor Images - March 18, 1999


NEW MARS GLOBAL SURVEYOR IMAGES
March 18, 1999

The following new images from the Mars Global Surveyor spacecraft have been
added to the MGS website: 

http://mars.jpl.nasa.gov/mgs/msss/camera/images/index.html

  o Small Impact Craters with Dark Ejecta Deposits
  o Hot Dog and Butterfly, Nereidum Montes
  o Mariner 4 Meets Mars Global Surveyor--Mariner Crater 1965 and 1999

Image captions are appended below.

Ron Baalke

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                            Mars Global Surveyor
                             Mars Orbiter Camera

               Small Impact Craters with Dark Ejecta Deposits

                 MGS MOC Release No. MOC2-96, 18 March 1999

When a meteor impacts a planetary surface, it creates a blast very much like
a bomb explosion. Shown here are two excellent examples of small impact
craters on the martian surface. Each has a dark-toned deposit of material
that was blown out of the crater (that is, ejected) during the impact.
Materials comprising these deposits are called ejecta. The ejecta here is
darker than the surrounding substrate because each crater-forming blast
broke through the upper, brighter surface material and penetrated to a layer
of darker material beneath. This darker material was then blown out onto the
surface in the radial pattern seen here.

The fact that impact craters can penetrate and expose material from beneath
the upper surface of a planet is very useful for geologists trying to
determine the nature and composition of the martian subsurface. The scene
shown here is illuminated from the upper left and covers an area 1.1 km (0.7
mi) wide by 1.4 km (0.9 mi). The larger crater has a diameter of about 89
meters (97 yards), the smaller crater is about 36 meters (39 yards) across.
The picture is located in Terra Meridiani and was taken by the Mars Global
Surveyor Mars Orbiter Camera.

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                            Mars Global Surveyor
                             Mars Orbiter Camera

                   Hot Dog and Butterfly, Nereidum Montes

                 MGS MOC Release No. MOC2-97, 18 March 1999

Some of the pictures returned from Mars by the Mars Orbiter Camera (MOC)
onboard the Mars Global Surveyor (MGS) spacecraft show features that--at a
glance--resemble familiar, non-geological objects on Earth. For example, the
picture above at the left shows several low, relatively flat-topped hills
(mesas) on the floor of a broad valley among the mountains of the Nereidum
Montes region, northeast of Argyre Planitia. One of the mesas seen here
looks like half of a butterfly (upper subframe on right). Another hill looks
something like a snail or a hot dog wrapped and baked in a croissant roll
(lower subframe on right). These mesas were formed by natural processes and
are most likely the eroded remnants of a formerly more extensive layer of
bedrock. In the frame on the left, illumination is from the upper left and
the scene covers an area 2.7 km (1.7 miles) wide by 6.8 km (4.2 miles) high.
The "butterfly" is about 800 meters (875 yards) in length and the "hot dog"
is about 1 km (0.62 miles) long.

  ------------------------------------------------------------------------

                            Mars Global Surveyor
                             Mars Orbiter Camera

     Mariner 4 Meets Mars Global Surveyor--Mariner Crater 1965 and 1999

                 MGS MOC Release No. MOC2-98, 18 March 1999

Mars exploration in the last half of the 20th Century comes full circle with
a modern view of Mariner Crater obtained by the Mars Global Surveyor (MGS)
Mars Orbiter Camera (MOC) in early March 1999.

Mariner 4 was the first spacecraft to reach the red planet and take close-up
pictures that revealed its ancient, cratered surface. The picture on the
left, above, is the 11th image taken by Mariner 4 during its July 1965
flyby. The center of the Mariner 4 image is dominated by a crater that is
about 155 kilometers (96 miles) in diameter and located at 32°S latitude and
164°W longitude. The crater was named "Mariner" in 1967 by the International
Astronomical Union in honor of its discovery by Mariner 4. The white arrow
indicates the location of the new MGS MOC image.

The picture on the right represents an improvement in resolution of almost a
factor of 400. It shows a view of a tiny portion of the southeastern floor
of Mariner Crater, as it appeared to the MGS MOC in 1999. In 1965, it was a
surprise to find that the martian surface is pocked with craters. In 1999,
using the MGS MOC, we now have the ability to see objects the size of
automobiles on the martian surface. This view of the Mariner Crater floor
has a spatial resolution of 1.5 meters (5 feet) per pixel and covers an area
only 1.5 km (0.9 mi) wide by 2.2 km (1.4 mi) long. Illumination is from the
upper left in both the Mariner and MGS images. For a mercator-projected
Viking 1 Orbiter view of this crater (obtained in 1978), click here
[Image].

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