Credit: USGS, The Viking Project, NASA
Yesterday, we showed part of the western hemisphere of Mars. The western hemisphere is dominated by several major geological features: Valles Marineris and the Tharsis bulge, upon which are four of the largest volcanos in the solar system: Olympus Mons (not visible in the picture) and the three Tharsis Montes (Ascraeus Mons (northern most), Pavonis Mons and Arsia Mons (southern most)). Alba Patera, an enormous shield volcano, is also in the western hemisphere, but is not visible in the picture.
Today, we show the Syrtis Major hemisphere; once again, this is a photo mosaic by the Viking 1 Orbiter in February 1980, when the season was early summer in the northern hemisphere. The viewer’s distance is 2,000 kilometers above the surface of the planet (for yesterday’s photo, the distance was 2,500 kilometers high).
The large bright colored area, located in the upper left area of the image is known as Arabia Terra. The dark area to the right of Arabia, called Syrtis Major Planus, is a low-relief volcanic shield of probable basaltic composition. Bright white areas to the south, including Hellas Planitia, an impact basin, at extreme lower right, are covered by carbon dioxide frost. Regions to the west and south of Syrtis Major are heavily cratered and relatively old. The dark feature coming around the western horizon is known as Sinus Sabaeus.