Hi,
NET exam is a really prestigious exam and if you qualify that you will really get into good places. Speaking of your eligibility for earth sciences, YES you can answer in that subject. There is no restriction of the subjects. You can choose any.
Good luck and answer well

Hii Sadhna ,

Coming to your question I would like to tell you that as you have done your msc in zoology you  can apply for CSIR NET life science or the earth science subjects.

Coming to the question paper so it will be printed in hindi and English both.

Hope this helps you , feel free to ask if you had any doubt.

Good luck.