It is very long — 31 miles, according to Japan’s Institute of Space and Astronautical Science.

It is very long — 31 miles, according to Japan’s Institute of Space and Astronautical Science.

It must be ancient, and may be buried more than 300 feet below the surface. It might even contain ice or water.

If the researchers are correct, it sounds just like what the old Apollo scientists and would-be colonists were looking for.

http://wapo.st/2xWBKsu