parallelism

''...For Nasa, the medical questions are reaching crisis point as they plan to send a group of astronauts on a three-year mission to Mars, taking 12 months to fly each way. It is planned for 2020, and in spite of masses of technical problems, Nasa seems reasonably confident of building the rockets and the space capsule.''

There is a lack of grammatical parallelism between the first and the second sentences. I tried to find it but I couldn't. Maybe I wasn't able to find it because of my lack of information on this ''grammatical parallesim'' issue. Can you either share the answer of the question or the detailed explanation of this parallesim thing?