Could Phobos’ Moon be Hollow?

It’s been speculated for some time that the Martian moon of Phobos may be exhibiting the unusual orbital pattern that it does because it is actually hollow.  Or rather than completely shelled like an egg with a hollow center, it may rather be largely porous rock with massive caverns reaching all the way into its core.  If this were the case, there are several possible applications and advantages to exploring a moon or planetoid that has caverns reaching to the center.

The Mars Express Spacecraft on Wednesday made an ultra-close flyby to the Martian moon last Wednesday to help scientists get a clearer picture on the object’s interior.  With a distance of merely 67 kilometers, the Mars Express is the closest manmade object to ever explore the surface of Phobos.  And from the cheers heard from NASA after the mission, it turned out to be an apparent success.  The mission was not documented by any visual surveillance equipment such as cameras, and in fact all scanners were turned off so the gravitational pull of the planet itself could be detected with the greatest amount of accuracy possible.  

Previous missions indicated that the Martian moon was likely at the very least 25% porous, and possibly more than a likely 35% porous.  The official story on Phobos’ formation is that it is little more than a rubble pile that is still forming together.  In certain places, so many scientists think, it will likely be compacting as time progresses, but in the mean time there are large tunnels where the pieces do not quite fit together perfectly yet.  

The radio waves used to detect the porous nature of the planet were sent from Earth to Phobos, and as it was received, its gravitational perturbations were analyzed and as a result they were able to calculate the potential effect the gravity of Phobos was having on the radio waves.  It took six minutes and thirty four seconds for a radio signal to travel from Earth to Phobos.  With any luck, as this data is analyzed, scientists will be able to get a clearer estimation of how much of Phobos is made up of holes.  This latest inventive experiment is thought to have been a huge success.  Previously the Mars Express had made two flybys to the planet, including one where radar was used in an attempt to seriously investigate potential structures hidden within the caverns.  The next experiment slated for the Mars Express is to take several extremely high resolution photographs of the surface so scientists can examine the surface and the potential benefits of exploring it more thoroughly.  The experiments will continue throughout March, ultimately hopefully finding some evidence of a porous surface complete with caverns that could potentially be used in a similar way Luna’s surface is being considered for potential operational bases and future launch sites.  Altogether there is expected to be somewhere around 12 experiments run by the end of the month exploring the red planet’s moon.  And along with it, perhaps we’ll be able to find out why so many probes mysteriously vanished while approaching it in the past.