They have never had the intention of interfering with the free will of the individuals living on Earth, so they had a particular concern regarding being observed from Earth. They could never permit that a single observation could generate a chain reaction that would spread the news about the existence of life on Mars and that would cause profound changes in the terrestrial society.
The terrestrial mentality of "conquering", "taking", "exploring" new "territories" and using them in their own "benefit" to generate "profits" for a few individuals certainly would prevail above any other point of view.
So since the beginning a Martian military operation has been activated on Earth : all the telescopes precise enough to detect undoubtable signs of intelligent life on Mars (no more than twenty supertelescopes around the world - or in orbit) have been manipulated. Their lenses and instruments, at least when pointing to Mars, have been provided with holographic images of rocks, craters, sand and desert.
On the night of Tuesday, November 15, 1988, however, there was a flaw in this system of control. A couple of terrestrial scientists working in the Green Bank Observatory in West Virginia had inadvertently pointed the telescope to Mars and made intriguing discoveries about cities, something resembling "buildings", flying transportation systems, and so on. The flaw was detected and the next day all the area of the Observatory - an entire complex gathering scientists from several universities, including one of the ten biggest and most powerful radiotelescopes operating on Earth - was misteriously "smashed" by unknown forces. The metals of the equipments were twisted, and the wreckage of the main telescope looked like if it has been trampled on by a giant's foot. In a question of days, all the news about the happening have played down the facts. U.S. military forces investigating the incident found nothing but twisted metals, but anyway the case has been covered up, as always.
Martian society has a very advanced technology for terrestrial patterns. Their science has developed the capacity of travelling beyond light speed. They use "worm-holes" as windows in space to jump to another space quadrant. They dominate the anti-gravitational technology whithin the atmosphere of a planet, which is used by their flying saucers (mostly triangle-shaped ones) and mother-ships while on Earth. And they use the teleportation technology as well, among several other technologies.
Regarding terrestrial religions, they also separate the subject from the object. Religious men, faithful ones and churchgoers in general believe that God is an external superior entity to be adored and worshipped, and that they are the sinners. This external entity, some believe, would be capable of judging them, punishing or rewarding them, and of controlling their destinies, and would need intermediaries - the churches and their priests or clergymen - in order to transmit to them the words or the wisdom of God, of His representatives on Earth (the Messiah or founder of each religion), or of the so-called "prophets". Some religions have several Gods, demi-Gods or deities, but they are also idolized or venerated by their followers.
For Martians, God is inside every one of us. It is not something separated from us, or something that needs intermediaries, Messiahs or "prophets" to be manifested. For them, God - or Unab, as they like to call - is also in the Universe itself, and within the atoms and molecules. It is the force that permeates all that exists - matter and anti-matter, visible and invisible - and that you feel right in the bottom of your heart.
For Martians, there is not a "Table of Commandments" or something like that. Martians don't think in terms of "right" or "wrong". What are "sins" but unresolved dualities on one's mind?
Martians have developed practically all the areas of their brains - all the paranormal faculties - that are still latent for part of the earthlings. They can levitate, move objects, communicate to each other by telepathy, and perform actions that defy the laws of terrestrial physics, like the interpenetration of the matter for instance.
They don't consider these actions as "miracles", but only as the result of a natural development of their spirits and of their minds. They just command the atoms and molecules of the objects with the appropriate will and wisdom necessary to move them the way they want. It's a joint effort between their scientific knowledge and their spirits.
If there would be a sentence that could define Martian feelings toward "God", it probably would be : "Know thyself, and you'll know the Universe".
So as long as mankind project its greed and its mentality of "conquering" or "taking advantage or profits" over other planets, instead of sharing and learning, all probes and ships sent to Mars will "find" only rocks, craters and sand.
In other words, the object that is seen depends on the mentality of the subject. The phenomenon depends on the mentality of the observer. Martians know quantum physics.
Over forty million Martians operate as characters on the Earth stage nowadays, besides ten more million of their allies from other planets. Terrestrial society is organized in such a way that any observer that had the opportunity to "prove" the existence of the phenomenon would probably be tempted to make use of this evidence to take personal advantage and attain fame, money and success. The phenomenon would be transformed into a circus. Martians are spiritually developed and don't like this. Would you like this?
So an Earth-based corollary of the sentence above could be: "Know thyself, and you'll know the Martians around you", or perhaps "Know thyself, and you'll know the Martian behind the mask".