This is similar to my previous Destiny question but I’ve done all the moon and earth story missions, scouting missions, and strikes that I can do and I can’t move on to Venus or Mars. Are they part of a DLC or am I doing something wrong?
No, Venus is not part of a DLC in Destiny.
In order to access the first mission on Venus (A Stranger's Call), you need to have completed the requisite story missions on the Moon, as well as meeting a level requirement (I believe it's 12 or 13).
The only destinations that are locked behind DLC are the Reef (House of Wolves), the Dreadnaught (The Taken King) and the Plaguelands (Rise of Iron).