Earth Science is only 10% of NASA's budget.

From NASA's 2014 budget request (in millions of dollars):

http://www.nasa.gov/pdf/750614main_NASA_FY_2014_Budget_Estim...

   Science               5,017.8
   Aeronautics             565.7
   Space Technology        742.6
   Exploration           3,915.5
   Space Operations      3,882.9
   Education                94.2
   Cross Agency Support  2,850.3
  ===============================
   Total Request        17,715.4

To break down "Science":

  Earth Science              1,846.1
  Planetary Science          1,217.5
  Astrophysics                 642.3
  James Webb Space Telescope   658.2
  Heliophysics                 653.7

By comparison, most of the "Exploration" budget is spent on the development of the Space Launch System -- which some sarcastically refer to as the "Senate" Launch System, because it is designed to spread money among the states. Just the SLS alone is bigger than the Earth Science budget.