I'm sure there's life some hundred light years away.
I'm not saying that we should just ignore the search for life, in whatever form it is in (A lot of us seem to be getting confused. Most professional research into the existence for life is not searching for advanced life-forms like us, but rather looking for single-celled organisms and such), but we should be reasonable and acknowledge that we're not likely to find life quite like we know it, anytime soon.
There's a possibility that life is out there, but that isn't 100% at all. And just because there is a possibility, a probability, it does not mean that there is life out there.
Statistics work that way. There may be a 99% chance that there is life out there, but that could still mean that despite the odds there is none.
And if we do find life, it's more likely to be microscopic. Which isn't a bad thing. It's still good news for us, and an exciting prospect to research.
If there were advanced life out there (like us), then they are some incredible distance away.
If they were in our solar-system, we'd very likely know about them.
If they're not in our solar system, then they are an incredible distance away.
Light-years away, at least. And while that might seem like not much, it is. It might take light just 1 year to travel a light-year (not very long in universal scales) it would take us a lot longer, because we just can not go that fast.
That isnt how radiation works.
Radiation isnt a gas that glumps up into layers. Its energy.
Of course you could have maybe radioactive gas, although im not sure.
Clouds of Radioactive Isotopes is entirely possible (and is exceedingly common in space, where they make up the large proportion of things like Nebulae), but if that was on Mars in any good quantity, we'd definitely know about it.