Question about MAD

I’ve had a thought and was wondering if it is a viable option.

I know roughly that MAD (magnetic Annomally Detection) is good for finding subs in the ocean and is carried on such a/c as Nimrod, P-3’s and S-3’s

Would it work over land, and if so would it be viable to use it in Iraq to find out once and for all if there are any WMD burried in the desert? Or at least find and and all arms caches or any other military equipment.

Failing this why don’t the US send up one of those satelites that are able to penetrate the surface of mars but have it go over the surface of suspected areas, this would also find any Terrorist tunnels that cross borders and save innocent people getting killed or Governments falsly accusing other governments? Is this common sence thinking?