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.
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.
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.
I mean, anything? That's got to be close enough to 100% to make no difference. Rocks in space hit planets, pieces break off at escape velocity, they become the space rocks that hit other planets. I doubt there's a solid body in the inner solar system that doesn't have at least a little bit of Mars on it.
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
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.
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.