PRODUCTS

Map of Phobos Surface Slopes, Elevations, and Gravitational Acceleration

Phobos is a moon of Mars with a size of 26.06 by 22.80 by 18.28 km in diameter. Mars also has another moon called Deimos, and Phobos is closer to Mars. We plan to extract samples from Phobos in the Martian moons exploration program (MMX: Martian Moons eXploration) currently being carried out by the Japan Aerospace Exploration Agency (JAXA). Phobos’s gravitational force and the contours and terrain on its surface must be extensively known beforehand for a probe to be able to safely operate in its vicinity and land on it.

Since Phobos is closer to its planet than any other moon in our solar system, it is greatly influenced by Mars. Like Earth’s moon, Phobos always keeps the same face towards Mars. Thus, if a person were to stand still on the surface of Phobos, that person would feel centrifugal force from gravity of Phobos, the gravity of Mars, and the revolutions of Phobos around Mars. The internal composition of Phobos is not known, but the slopes (Illustration 1), elevations (Illustration 2), and gravitational acceleration (Illustration 3) of its surface can be calculated assuming that it has a body of uniform density. These calculation results that we produce along with other products such as exploration images (Illustration 4) are used for considerations when choosing landing sites.

Illustration 1: Slopes on the surface of Phobos. Vertical axis is latitude [°], vertical axis is west longitude [°]. West longitude 0° shows the progression side of Phobos at 90° of the Mars side.（Large image）

Illustration 2: Elevations on the surface of Phobos. We set the average gravitational acceleration on Phobos’s surface to a reference point of 0 meters, in relation to which we display relative height.（Large image）

Illustration 3: Gravitational acceleration on Phobos’s surface. It has roughly 1/2,000 the gravitational acceleration of Earth’s surface. （Large image）

Illustration 4: Mosaic image of Phobos’s entire surface（Stooke. P., 2015）．（High-resolution image 35 MiB）

Reference:

Thomas, P. C., 1993. Gravity, Tides, and Topography on Small Satellites and Asteroids: Application to Surface Features of the Martian Satellites. Icarus. 105, 326-344.
Gaskell, R., 2011. Gaskell Phobos Shape Model V1.0. VO1-SA-VISA/VISB-5-PHOBOSSHAPE-V1.0. NASA Planetary Data System.
Willner, K., Shi, X., Oberst, J., 2014. Phobos' shape and topography models. Planet Space Sci. 102, 51-59.
Stooke. P., Stooke Small Bodies Maps V3.0. MULTI-SA-MULTI-6-STOOKEMAPS-V3.0. NASA Planetary Data System, 2015.

Downloads