Here are the sentences changed into reported speech:

1. Susan asked her teacher why there was no gravity in space.
2. Paul asked Helen how far it was from the Earth to the sun.
3. Natalie asked Alexander if black holes could get smaller.
4. Johnson asked Melinda if she was reading about UFO sightings.
5. Penelope asked Nicholas if there could be life on Mars.
6. Bella asked Nolan if there was actually life somewhere in the Solar System outside Earth.
7. Stella asked Alice if intelligent life had existed on that planet billions of years ago.
8. Chloe asked Grace if they were alone in the Milky Way galaxy.
9. Adam asked his little brother what he would do with those alien toys.
10. Eleanor asked me which stars I liked to point the telescope at.