Sentence:  Space elevators proposed for the Earth require novel high-strength materials and a substantial counterweight for their implementation.  The problem becomes easier for Mars.  There is no available "counterweight" for a synchronous "<WSD>beanstalk</WSD>" but Phobos proves a substantial anchor in non-synchronous orbit.  A tether extending 1456 km from Phobos could release objects into an orbit just entering the Martian atmosphere, providing a launch and recovery device for Mars Excursion Modules. Extending the "<WSD>beanstalk</WSD>" to a length of 5832 km would place the end at the fringes of the Martian atmosphere. 
Meaning of the word marked with <WSD> tags:  A space elevator.