This is fascinating, especially whether the hole was created from a top impact or from the bottom such as volcanic eruption.
On another note, why are we discovering this just now? I was under the amateur impression that the entire surface of Mars was scanned and imaged by NASA at some point. But again, I may have interpreted that incorrectly.
On another note, why are we discovering this just now? I was under the amateur impression that the entire surface of Mars was scanned and imaged by NASA at some point. But again, I may have interpreted that incorrectly.