There are a number of navigational buttons on each map-location page. You may need to scroll down to see some of them, depending on the size of your window. (Also, be sure that Auto-Load Images is turned on in your browser.)
The eight buttons around the compass will move you 5 degrees north or south, and/or 5 degrees east or west. The button in the very center will "zoom out" to a global map that you can click on to choose a completely different location.
The map displayed in the Mosaic window is scaled down to 16 pixels per degree
and is made up of several squares, reprojected so that they fit together as
seamlessly as possible. Links are provided to the original USGS map segment
for the center of whichever part of the map you are looking at.
These are in PDS format and can be read by an external viewer,
with a little work.
The scrollable map is low resolution, and even the original USGS
map segments it was scaled down from
are only 256 pixels/degree, or 230 meters/pixel at the equator. Many parts
of Mars were imaged at 80 meters/pixel or better during the Viking Orbiter
mission's Survey phase,
(long after VO1 had outlasted its projected lifetime).
Many of those images are on the Web and are reachable through this atlas.
A few spots were imaged at better than 10 meters/pixel. If you need the
highest resolution images available, don't settle for the scaled down, cartographically
registered maps! One of the main purposes of this tool is to help scientists and others
to find raw images of the area of interest. (If you need higher than the highest
resolution available, we may be able to help you with that, too. See the
description of our
image super-resolution project.)
Several color composites are available for most parts of Mars.
Currently, one icon for each will appear, but only when the
bounds of the grayscale map you are viewing corresponds
to the bounds of a color image, so you will have to hunt for them.
(Soon, I plan to provide a global map pointing to the color images.)