As you may or may not know, Vex have a great impact on time. Throughout the "story" missions in destiny we see the Vex utilizing time gates. And when we first enter The Black Garden it is the first Time Gate we use, and it takes us to some different dimension, as we all assumed when we first did that. Actually, this "other dimension" is probably the future of Mars. This future is a future where the Vex have taken control of Mars and remade the whole planet into a way they like it. In "The Echo Chamber" strike Ikora Rey states that they think of the way our solar system was made is an imperfection, and must be made anew. So, when you get to the Black Garden, you most likely enter a future where the Vex have rebuilt Mars from scratch. In the story mission, why else would it say "The Black Garden; Meridian Bay, Mars." This is just my theory and let me know what you think about this topic! Also, to get it out of the way, LAMBORGHINI IS LOVE, LAMBORGHINI IS LIFE