(Never is an an acceptable answer for all 3, but please state why you hold your position)
Intelligent life, though...that's tricky. Given the size of the universe, it is almost certain that there is other intelligent life but who knows whether or not it survives long enough to come into contact? Discovering another civilization would be one of the most incredible experiences I can imagine, so I certainly hope it happens (peacefully) within my lifetime.
To be clear, microbial life in no way entails higher life. It's only by the insanely chance event of the eurkaryotic cell emerging that sophisticated multicellular life became possible on earth. Even if life is common in the universe, sophisticated multicellular life is extremely rare.
The selective pressures on bacterial life favors small size and rapid reproduction, jettisoning any unnecessary genetic material.
Mitochondrial ancestors relieved those pressures in a couple ways. Once the eukaryotic cell developed, multicellularity has evolved several times. All the cool things (multicellularity, eyes, flight) have evolved independently a bunch of times, and the eukaryote has happened only fucking once. Here's a deeper explanation of why it's so rare: http://rstb.royalsocietypublishing.org/content/368/1622/2012...
Even if life is common in the universe, multicellular life is extremely rare because the evolution of eukaryote-esque organisms is extraordinarily rare and chance.
Edit: That is to say, there's a strong case that step 4 is the Great Filter: http://en.wikipedia.org/wiki/Great_Filter#The_Great_Filter
Honestly, me neither. I'm just a software engineer who is excited about space and hopes for the best. =)
> but it would be fucking awesome.
Wouldn't it? Holy hell, that would be wonderful. I hope it happens soon. Discovering life on Europa would be our generation's moon landing.
Thanks for the clarification. My knowledge of biology is limited, so I imagined each step (crude self-replicating molecules -> sophisticated DNA -> the cell -> etc.) being roughly as unlikely as the next. I had no idea eukaryotic cells were such a massive jump.
Earlier today I was watching a documentary about the Kepler telescope's search for exoplanets[0] that estimated the number of planets in our galaxy at 10^19. So many of those planets are unsuitable for any life, microbial or otherwise, but such a large number fills me with hope that the unlikely miracle of eukaryotic evolution could happen more than once. Then again, there are very plausible interpretations of the Drake equation[1] that pin the number of intelligent civilizations in our galaxy to less than 5...maybe even 1...so who knows?
[0]: https://www.youtube.com/watch?v=DD6QHP9ouuU [1]: http://en.wikipedia.org/wiki/Drake_equation
http://ronbarak.tumblr.com/post/25996121029/life-is-it-inevi...
http://news.nationalgeographic.com/news/2012/04/120413-nasa-...
http://en.wikipedia.org/wiki/Viking_lander_biological_experi...
A future mission should definitely include a biologically-useful microscope, as suggested by USC neurobiologist Joseph Miller in the National Geograhic article linked above. Miller, also a former NASA space shuttle program director, is one of the proponents of the idea that the 1976 Viking results already demonstrated life.
http://www.sciencedaily.com/releases/2010/09/100904081050.ht...
That article is currently footnote #28 of the Wikipedia article, describing the 2010 paper referenced as footnote #25. Another footnoted reference from 2011 (#29) disagrees. But presumably, all that perchlorate-related reasoning was available to the authors of the 2012 paper defending the positive result.
The chlorometane results were a true result after all.
However, I have the impression that, organics, in contact with perchlorates (or any strong oxidant) will result in CO2
Also, it was repeated one week later, with no results
http://en.wikipedia.org/wiki/Viking_lander_biological_experi...
With enough perchlorate, it will. But with smaller amounts of it, there's a huge number of possibilities, including products that are more complex than the reactants.
I think it's unlikely that we will find life anywhere else in our solar system. It's possible that we'll evidence of past life on Mars, but not current. Basically, it's just way too cold or way too hot everywhere but Earth.
edit to add: I hope we do not discover intelligent life until we travel to distant star systems ourselves. If it discovers us here, the outcome will almost certainly be terrible for us, based on the long Earth history of species encountering species.
This isn't as big of a concern as it once might have been. See extremophiles.
> It's possible that we'll evidence of past life on Mars, but not current.
If life takes hold anywhere and has any amount of (geologic) time to spread, I'm guessing only an extremely powerful gamma ray burst or other high energy event could completely exterminate it. It might be impossible to sterilize the earth at this point without completely destroying it, and even then there'd probably be microbes in the resulting meteors, etc (until our sun dies at least).
That's not really true. Only a thin layer of Earth's crust and atmosphere are great for life. Such Goldilocks layers aren't that uncommon if we look at all boundary climates on each body (subsurface sea boundaries, polar boundaries, higher atmosphere boundaries, etc), and not just the boundary analog to Earth's.
Even Mercury has free standing water ice. Somewhere between that ice and the scorched plains there's going to be a somewhat comfy place.
I think the outlook for intelligent life in the solar system, other than us, is very bleak for them. If there are whales on Europa, Titan, or Enceladus then it would seem easier for us to damage their ecosystem than the other way around. Unless, of course, they've infiltrated our political systems and are steering us towards self destruction.
Or it finds us.
If they will find us and this only means more advanced intelligent life then this obviously can happen any time or might already happened and can be delayed by us not being considered ready/worthy for contact or according to many conspiracy theories our governments considers we are not ready.
I don't think we'll ever go beyond the solar system and that the only place with complex life in the solar system is the Earth.
Also, those rovers did a really wide range of things for their cost. From driving around 40km and taking pictures to analyzing chemistry and even testing for "wobbles" in the planet's rotation that would indicate a liquid core. Sure, they cost ~500 million a pop, but compare that to 100's of billion for a manned mission that might never reach Mars and things don't look so hot.