When placing a greenery tile in Terraforming Mars, you have to place it next to a tile you own. Let's say all you own is the "Mining Rights" tile and you are now playing a greenery tile. Do you have to play your greenery tile next to it?
Special tiles have your player marker on them, so they are your tiles, just like greenery or city tiles.
From the rules, page 5:
Special tiles: Some cards allow you to place special tiles. Any function or placement restriction is described on the card. Place the tile, and place a player marker on it.
Player markers: Each player uses his own color to mark TR, ownership of tiles, production (see page 6), and to indicate used blue card actions (see page 11).