Is Mars Hollow? We are pretty sure it is not, but no one can be certain however we might soon know. The reason such a question is asked is because of questions about the Earth and the time it takes for sound waves to travel through it. And the speed of the spin rate of Mars, the question of moons is interesting and a few other interesting a recent discoveries. Here is one of the thoughts on the matter. By bouncing waves off the polar ice caps this can be proven or disproven;

http://www.ourhollowearth.com/MarsIsHollow.htm

http://www.goddardmultimedia.fsnet.co.uk/atpai/canals.htm

Most scientists to do not buy into the hollow planet theories, yet others admit we just do not know. The most interesting of all is the straight-line canals, which is hard to fathom considering using our own knowledge about our planet here. But Mars is a different planet or satellite and therefore has different characteristics completely.

http://www.spacedaily.com/news/life-00v1.html .

http://www.lpi.usra.edu/meetings/largeimpacts2003/pdf/4102.pdf

And what is underneath our surface? Well we know certainly more than we did before. CalTech which runs JPL is getting to the under bottom of this. After all with all the seismic knowledge we have from there they ought to know. We are not the only ones studying this; the UK has ideas and so does Japan.

http://basic1.easily.co.uk/057044/04D005/NAW2003p2.pdf

So the question is not as far fetched as you might think. We will soon find the truth? We do not seem to be finding much complex life on the surface of Mars, although we have a lot more area to look at. We know of water on Mars and expect to find underground water too. Is this where life might be? Could it be in the polar ice caps and in the ground water in cavities under the surface? If there is anything such as the complex life forms we find on Earth, then they are probably underground, where we have not looked yet. Or perhaps the biblical scholars can rejoice and say; see we told you so? Think about it.