Data from the Sharad (SHAllow RADar) instrument (on Mars Reconnaissance Orbiter), document that some of these glacial-like features, which you find at Mars' mid-latitudes, have a significant volume of ice left below a surface of rock debris.
Unless it somehow managed to burrow a very long way down before exploding, such a weapon detonated beneath the earth's surface would throw up huge amounts of radioactive debris, a danger to all.