There is life on Mars -- JPL just doesn't want to tell us. Follow this logic: 1) two planets in habitable zone - both spontaneously cause life; 2) then many or most habitable zone planets have life; 3) Of the trillions of stars in our galaxy, there must be multitudes that have hosted intelligent life; 4) we don't hear SETI signals; 5) that means SETI must have snuffed themselves out with some super-technology; 6) ergo, cannot tell the masses, because they will freak out knowing that we are all doomed, including all our offspring.
It seems quite implausible that JPL would have sufficient confidence that things would play out as you say (everyone freaks out because everyone is convinced by this line of reasoning) to deny themselves a rather good opportunity to get people excited about space exploration.
The biological plausible explanation is that there simply has not been enough time for other civilizations to form up. It took us 4 billion years to reach civilization from primordial goo. Apparently not many planets remain habitable that long. It does not matter if you have a trillion planets if they don't remain stable long enough.
it's not even entirely a given that we are the first, as it's unlikely any evidence of a small tribe of sentient dino villagers for example would persist to the present day.
Suggested reading: Rare Earth: Why Complex Life is Uncommon in the Universe by Peter D. Ward and Donald E. Brownlee. The basic premise is that complex life is incredibly rare, because only through a series of effectively chance events, did complex life happen on Earth.
Even if each of those events were actually inevitable, planet size, radiation received from host star, exact chemical makeup of atmosphere/oceans and any number of other variables could affect the time scale for a planet to fruit.
But on the universes timescale, a slight variance could still be thousands of years or more. So maybe there is life in some distant reaches of the universe, who are +/- a thousand years from our level of development. Their signals simply haven't reached us yet, or ours them.
And the odds that it’s us are astronomically even longer than the odds that I’m going to win the next Powerball, and I’m probably not even buying a ticket.
It is also stupendously implausible that our civilization arrives at all in a mere 14 billion years, considered against the gazillions of years in the potentially infinite lifespan of the Universe. Yet here we are.
If it is difficult for civilizations to develop, then our existence is so implausible already that being the first is not such a leap.
I did not imply at any point that we were the first, or only. Perhaps in our galaxy. I don't know if we could ever find out about civilizations in other galaxies.
There are a 100 billion galaxies. I'm ready to guess each has at least a few planets theoretically capable to sustain life for long enough.
1. ET life formed and vanished so quickly that they didn't even get to the stage where they generate electromagnetic signals.
2. ET life formed and got to generate EM waves, but:
- they're either too far from us that we haven't detected those waves yet;
- they only recently got to this stage and the signals they produce have not reached us yet;
- or both.
3. ET life formed way sooner than we did; figured out how to generate EM waves, and then vanished entirely. So, any signals of their civilization they must have sent out there have already reached earth, but before we began listening for such signals.
4. Then again, since there are practically infinite number of planets with habitable conditions for ET life, statistically speaking, we must have already received a signal from at least one of them.
Which leads me to this:
5. ET life doesn't exist, because the universe as we know it is most probably a simulation inside a computer and the computational resources can only render so many different objects at a time. (This is serious stuff, researchers have already proposed methods for verifying this:
https://www.washington.edu/news/2012/12/10/do-we-live-in-a-c...).
Earth level EM waves are indistinguishable from background noise pretty quickly thanks to the inverse square law. And we've been reducing emissions, not increasing them, as we shift to cell networks rather than one to many broadcast networks of old.
I wonder if Type 3 civilizations might engulf their star in a Dyson Sphere to block out light and make it harder to find. A dark forest where the life-bearing trees aren’t even visible.
The thing about that is all the energy from a star is still being radiated, just in infared. So if this was true a IR telescope should see a star like object with no visible light but a large amount of infared emitted.
People have looked. There are some candidates that have not been ruled out, but are not particularly promising. Do a Google Scholar Search for "IRAS dyson spheres" and you'll get oodles of papers describing attempts, new places we might look (I recall one suggesting they might all be surrounding the galaxy's central blackhole), current theoretical limits of our ability to search, new methods we might use to find them, etc.
If genetic material did travel in either direction, it would be easily verified.