Bringing down Phobos
The moon Phobos will eventually break up into a planetary ring due to tidal stresses. However, Terraforming might increase the atmospheric resistance on phobos, causing it to crash down on Mars, potentially harming colonists. Thus, the Bringing down of Phobos could be a vital step in colonizing Mars.
Methods
With a small amount of fuel it might be possible to accelerate a small object from the asteroid belt toward Mars. The trajectory would be controlled by maneuvering rockets during the journey. It would end in a collision with Phobos in an appropriate angle in order to reduce orbital speed of Phobos, which would finally result in Phobos crashing onto the surface of Mars.
The idle velocity of the asteroid relative to the asteroid belt is 0. The journey of the asteroid is started with a small initial kick. Nearly all final velocity comes from the potential energy of the different solar orbits of Mars and asteroid belt, their orbital speed difference and the relative orbital speed of Phobos.
Results
The technology of crashing an asteroid into a potentially dangerous cosmic body may be useful for repelling threats from earth. The knowledge from this Phobos project could be valuable far beyond the Mars colonization.
The crash would have a global impact on Mars' atmosphere and climate. Dust that is evaporated into the atmosphere would temporarily reduce the sunlight on the surface. On the other hand, a huge amount of water steam would cause a greenhouse effect in medium-term, which will increase the planet's temperature in a couple of years.
Moreover, the impact would reveal lots of data about the geological structure of Mars. Seismic sensors can be used to analyze the Martian layer structure down to the core. With spectroscopic methods the chemical substances of the impact area can be analyzed.
Lifting Phobos into a higher orbit
Another less destructive method would be simply to lift Phobos into a higher orbit around Mars, possibly by using rockets.
Open issues
- What is the required mass of the asteroid used for the collision?
- What amount of energy can be brought to the asteroid belt for the initial kick with currently available technology?
- How long would the journey of the asteroid take?
- What is the final impact energy?
- How long would it take for Phobos to crash down on Mars after the collision?
