Those of you hoping to relocate to the Moon may be out of luck: it appears that although there’s ice on the surface, that might be it as far as water goes.

Geochemist Zachary Sharp of the University of New Mexico believes his studies of lunar rock suggest that not only is the inside of the moon completely dry, but that it’s always been that way.

Sharp came to the conclusion after studying chlorine in the rock. He looked at the relationship between the two stable isotopes, chlorine 37 and chlorine 35. On Earth the ratio between the two is virtually constant, but the samples on the moon showed the ratio varying by a factor of 25 — a finding so unusual that his team rechecked everything to make sure.

According to Sharp, who writes in the latest edition of Science (PDF), the hydrogen levels in rocks on Earth would make such variation impossible. He believes the most likely explanation is that when the lunar rocks were formed, the lava which created them was completely free of water.

That implies that while the Earth has oceans formed from steam from the gases in volcanic eruptions, the same didn’t happen with the Moon. Instead whatever water was inside the Moon and released in such a way may have been lost to space because the Moon’s gravity was too weak to hold on to it.

If that’s correct, it would bring us back to the beliefs of earlier lunar rock geologists that the Moon is completely dry. While that has been questioned because of the discovery of ice, Sharp suggests that this ice may not have originated on the Moon and instead come from comets which collided with it.