On the latest episode of 'The Big Bang Theory' ("The Lizard-Spock Expansion"), Howard Wolowitz crashed the Mars Rover into a crevice while trying to impress a girl he picked up in a bar. Unable to extricate the vehicle with the help of Sheldon and Koothrapalli, they wiped the control room clean of the data and their fingerprints so that no one could ever figure out who did it.
Unfortunately for Wolowitz, that meant he couldn't claim credit later when it turned out that the crash led to the confirmed discovery of life on Mars (but having nothing to do with the song or the two TV series).
The reptilian "Ice Warriors" were probably the oldest sentient species on Mars, but they had to abandon the planet when the temperature changed. This gave the other two species the chance to evolve to their civilizations' heights. So although they would claim to be from Mars, they no longer lived there when they clashed with various incarnations of the Time Lord known as the Doctor.
In the TV Universe, even if most of the residents of Earth Prime-Time were not aware of it, there has always been life on Mars. In fact, at least two intelligent species co-existed there at the same time, until the early 1960's. (That's when the more avian species abandoned the planet and took human form in an attempt to take over Earth.)
The humanoid aliens with three arms could be the fourth sentient species, but they could also have just claimed to be from Mars to simply avoid lengthy explanations for the humans. (Those aliens who claimed to be Venusians, but had a third eye, were in fact Traskians. At best, they used the Red Planet as a launching base for their own aborted attempt to invade Earth.)
The other true Martian species was more human-like in appearance, and several of their citizenry would visit Earth where they could walk among humankind without notice. (One of whom, Exigius 12½, was stuck on Earth far longer than he would have liked. It's the contention of Toobworld Central that he lied to his human benefactor, Tim O'Hara, as to why he was there in the first place. Instead of being on some sort of anthropological expedition, it's conjectured that he was eradicating the last remnants of that other Martian race before they could take over the planet. In this mission, he was probably working with other undercover Martians like Phobos and Deimos.)
After the arrival of astronaut Sam Conrad on the surface of the Red Planet, the Martians realized that it was only a matter of time before humans arrived... and in greater numbers. Thus began their mass exodus project which has been taking place over the last several decades, unseen by even the most sophisticated telescopes in Toobworld (especially at the Royal Australian Observatory).
For the most part, those Martians still living on Mars have been able to dodge notice from the Earthlings even when the Rovers first started exploring in the late 1990's. With their advanced intellects, the Martians were able to successfully evade detection by the unmanned vehicles by anticipating their destinations and even guiding the Rovers as to what they were allowed to "see".
However, not even the most brilliant of Martian minds could have foreseen that one horny geek would gum up the works and send the Rover crashing into a ditch. Unprepared for that contingency, the Martians failed to remove the evidence of their presence from that ditch (which for alls I know, was used as a land-fill by the Martians).
This has been all speculation, of course. But if I could have proven it, it would have taken all the fun out of it. And where's the sport in that?
'The Big Bang Theory'
"The Lizard-Spock Strategem"
'My Favorite Martian'
'The Twilight Zone'
"People Are Alike All Over"
"Will The Real Martian Please Stand Up?"
"The Ice Warriors"
"The Seeds Of Death"
'Alfred Hitchcock Presents'
"Human Interest Story"
'The Outer Limits'