My tinfoil hat theory that is all in jest is that Mars was "First Earth" and it got real fucked up and anything that was there got wiped out and what we see now is all that's left of it.

“A million to one.” They said…

We've been there. For decades. You know that, right?

0%

What are the chances that this question came from Uranus?

Lol .... a probe or sample device gets picked up on Mars, sent back to earth carrying an exotic extra terrestrial virus that is indestructible. It infects our planet killing every biological organism on earth.

The Martians end up invading and conquering us ..... just not in the way we imagined.

Nothing cool, of course.

Zero.

One million to one

Even if an ice asteroid crashed and vaporized some semblance of an atmosphere onto the planet the solar wind would strip it off because there’s no magnetic field.

It’s a dead rock. Better to look to Jupiter’s moons than Mars.

A million to one of course.

edit: but still, they come!

I'd put the chances of Mars sample return going off in the next couple decades at about 70%.

https://wikipedia.org/wiki/Mars_sample-return_mission https://science.nasa.gov/mission/mars-sample-return

What do you mean by "coming from?" We get scientific knowledge from it. If you mean something physical, we are planning to do a sample return mission by the end of the decade. For something not from us, we very very occasionally get done ejects from it. The chances of anything being alive are basically nil.

Apart from a slim opportunity of one of the robots we put up there coming back in the future it currently stands at 0% we would know by now if something other than robots was on mars

I'm pretty sure we have quite a few meteorites that came from Mars.

John Carpenter did a documentary on it.

no

As for Allen life coming under it's own power from Mars, I'd put that extremely close to zero. More likely would be something from Europa or outside the solar system, but that's still pretty unlikely.

I would say 0% to >0%