Here's a breakdown of the discovery dates for the planets in our solar system:

* Mercury: Known since ancient times (prehistoric)

* Venus: Known since ancient times (prehistoric)

* Earth: Not "discovered" as it's our home planet.

* Mars: Known since ancient times (prehistoric)

* Jupiter: Known since ancient times (prehistoric)

* Saturn: Known since ancient times (prehistoric)

* Uranus: Discovered by William Herschel in 1781

* Neptune: Discovered by Urbain Le Verrier and John Couch Adams (mathematically predicted) and then observed by Johann Galle in 1846

Let me know if you have any other questions!