http://www.c3.lanl.gov/~cjhamil/SolarSystem/phobos.html (Einblicke ins Internet, 10/1995)Mars I
Phobos [FOH-bohs] (fear) is a moon of Mars and was named after an attendant of the Roman war god Mars. Phobos is a dark body appearing to be composed of C-type surface materials. It is similar to the C-type (blackish carbonaceous chondrite) asteroids that are formed in the outer asteroid belt. It is speculated that Phobos and Deimos are captured asteroids; however, there are also arguments that go against this theory. Phobos shows striated patterns which are probably cracks caused by the impact event of the largest crater on the moon.
Discovered by .................................... Asaph Hall Date of discovery ...................................... 1877 Mass (kg) .......................................... 1.08e+16 Mass (Earth = 1) ................................. 1.8072e-09 Radius (km) ................................... 13.5x10.8x9.4 Radius (Earth = 1) ............................... 2.1167e-03 Mean density (gm/cm^3) .................................. 2.0 Mean distance from Mars (km) .......................... 9,380 Rotational period (days) ............................ 0.31910 Orbital period (days) ............................... 0.31910 Mean orbital velocity (km/sec) ......................... 2.14 Orbital eccentricity ................................... 0.01 Orbital inclination ..................................... 1.0° Escape velocity (km/sec) ............................. 0.0103 Visual geometric albedo ................................ 0.06 Magnitude (Vo) ......................................... 11.3
Phobos
(GIF, 35K)
This image was taken by the
Viking Orbiter spacecraft in 1977.
Striated patterns can be seen in this image. These are
probably cracks caused by the impact event of the Stickney crater shown
below.
Stickney Crater
(GIF, 143K)
One of the most striking features of Phobos, aside from its irregular
shape, is its giant crater Stickney. Only 28 by 20 km (17 by 12 mi),
Phobos must nearly have shattered from the force of the impact that
caused the giant crater. Grooves that extend across the surface from
Stickney appear to be surface fractures caused by the impact. Near the
crater the grooves measure about 700 m (2300 ft) across and 90 m (295 ft)
deep. However, most of the grooves have widths and depths in the 100 to
200 m (328 to 655 ft) and 10 to 20 m (33 to 65 ft) ranges, respectively.
(Courtesy NASA/JPL).
Stickney Crater Another View
(GIF, 121K;
JPG, 16K)
This image shows a slightly different view of the Stickney crater.
A crater within the Stickney crater can be seen.
(Courtesy Calvin J. Hamilton, LANL/NSSDC/NASA).
Conformal Projection of Phobos
(GIF, 234K;
JPG, 38K;
caption)
This shows two different views of Phobos in a Morphographic
Conformal Projection. One view shows the
leading side and the
other the trailing side.
(Courtesy Phil Stooke/NSSDC/NASA).
Mars
Deimos
