The Great Galactic Ghoul
is a fictional space monster that consumes Mars probess
. It was coined as a humorous attempt to explain the high failure rate of probes sent to that planet; of approximately thirty probes, two thirds have failed - sometimes for unclear reasons. The Galactic Ghoul seems to particularly enjoy the taste of Soviet
In reality, the failure of so many probes is not particularly unexpected; space is a very harsh environment, and probes must function unmaintained for years to reach their destinations.
Some people believe that the ghoul is actually a group of intermediary aliens who are trying to protect Mars from Earth probes that have unfriendly motives.