To see an asteroid in your dream indicates that you will receive some sort of inspiration or revelation from an outer source. It may also represent your ability to be imaginative and innovative.
If the asteroid hits the earth then it may mean that these initiatives are not taking root and you must think of new ideas.
[1]1. + Message from Heaven; Christ’s return Rev. 8:10
2. – Judgment; Matt. 24:29.
[2]Potential destruction, Rev. 8:10 NLT
[3]