Was Mars the Earth of the past and Venus the Earth of the future?

[PiRsq]

I am not a student of astronomy or physics, or any sciences for that matter. But I do have some things I wish to ask the scientific community here in the hopes of better understanding all of your viewpoints as to the title of this topic. First question:

a. Assume that Earth is about to face a mass extinction (either through asteroids or human causes), one in which there will not remain any form of life as we know it (so far). What will we as a human race (collectively, leaving aside differences) do in the hopes that one day a future civilization, either evolving on Earth or from a location outside of the Earth, be able to acknowledge that previously there was intelligent life on this planet?

[berkeman]

Thread moved to General Discussion.

[Mallignamius]

"to acknowledge that previously there was intelligent life on this planet"?

Footprints and a flag on the moon should be a good first indicator. And then we have our Mars Rovers...

[PiRsq]

I guess what I am trying to get at is that we see landmarks in Mars that conspiracy theorists would argue are man-made structures (ie: the face on Mars). So, there could've been life on Mars previously, intelligent life. Now what are the arguments that non-conspiracy theorists have for that statement?

[Mallignamius]

The face on Mars is Cydonia Mensae.

However, today it is generally accepted to be an optical illusion, an example of pareidolia. After analysis of the higher resolution Mars Global Surveyor data NASA stated that "a detailed analysis of multiple images of this feature reveals a natural looking Martian hill whose illusory face-like appearance depends on the viewing angle and angle of illumination"[4]. Similar optical illusions can be found in the geology of Earth; an example is the Badlands Guardian, which resembles a human head wearing a Native American headress[5].
http://en.wikipedia.org/wiki/Cydonia_Mensae

[kach22i]

Our radio (and TV) waves will continue forever traveling the universe.

Yes, the humans were crazy.

[Astronuc]

Was Mars the Earth of the past and Venus the Earth of the future? All three are vastly different. The mass of Mars is much less than that of Earth or Venus, and Venus is much closer to the Sun, so there is not good comparison.

The only immediate threat to humanity is us.