Solve the crossword using the clues.

Across

1. The protective layer of the Earth's atmosphere

2. The constellation which appears like a distorted letter W or M

3. The objects that revolve around the Sun and are majorly present between Mars and Jupiter

4. The least dense planet in our solar system

Down

5. The mass of this planet is about 318 times that of the Earth

6. The fixed elliptical path on which planets revolve

7. The first Indian satellite