As we've all seen from the videos of NASA with their robots exploring in a desert like surface of Mars. But is it real? since there's no actual footage that came out the landing of the certain robots or satellite or whatever they sent there.
If you're implying that the photos from the various Mars rovers were taken in an Earth desert (say Australia) this isn't possible as the coloration of the sky is different and most importantly the apparent magnitude, size, and coloration of the sun is different than it is on Earth (because Mars is further away). Also, there's pictures of sunsets on Mars which are different than Earth sunsets due to the thin and different composition of Mars' atmosphere. Also, some pictures from the surface of Mars showcase the moons of Mars: Phobos and Deimos. Earth doesn't have these so they wouldn't show up.
If you're asking why no footage is taken during the descent, it actually is! On the curiosity Rover, the MARDI camera, or MARs Descent Imager photos are taken and analyzed during the descent to avoid landing on rocks and boulders.The video can be watched here!
Attaching HD landing cameras to Mars rovers and Landers isn't really a priority as the main goal of the mission is science, not PR. Having a camera record multiple hours of footage, store that footage, and then transmit it back is very expensive in dollars but also in engineering work. You need large amounts of storage, a radiation hardened camera, and a computer capable of handling it. All this extra added cost and weight can't be justified by the scientists because it gives them very little scientific data. However, this is probably going to change on upcoming Mars missions as technology has progressed quite a bit since Curiosity landed. Remember, Curiosity was launched in 2011 and constructed in the mid 2000's and since then camera, storage, and computer technology in general has increased at an incredible speed.
Mars has been visited by missions from NASA, ESA and the Soviet Union/Russia. The first missions by NASA were in the middle of the Cold War. If the Russians had noticed anything wrong (like transmissions from Viking not coming from Mars) they'd have published that as it'd have been a propaganda coup. Science return from all these missions has been consistent with each other.
More recently, ESA's Mars Express orbiter was used to relay data from NASA's Mars Exploration Rovers and Phoenix.
To pull this all off would require a giant, worldwide conspiracy that managed to remain secret for 50 years. That is very unlikely, it'd be easier to run a real Mars program.