Or at least getting more data to determine its likelihood.
If we examine dozens of planets within the “goldilocks zone” and none of them show any signs of life, that’s a datapoint in favor of life being rare. It doesn’t mean that it is, or that life may take on other forms, but it’s data in favor of that hypothesis.
OTOH, if we find signs of life on the first planet we look at, then that is certainly has a different effect on the hypothesis.
What signs of life are we going to be able to see at these distances?
Oxygen is a big one. There are processes that can create free oxygen that don’t involve life, but they are a bit rare and farfectched. It wouldn’t prove that there is life, but it would be a pretty good indicator.
Then we have all the way up to CFC’s, which would indicate technological life. There are no natural processes that we know of that would create them. If someone looked at our atmosphere, they’d know we were here.
The presence of oxygen and water vapour would be powerful indicators. Free oxygen tends to aggressively combine with other elements to create oxides, so its presence would tend to indicate some dynamic process creating it that may be life.
Probably limited to making inferences based on atmospheric compositions.
Of course, it’s also possible that life is common, but that most of it doesn’t produce atmospheric oxygen. To be honest, I’m still not sure how the Great Oxygenation Event was evolutionarially advantageous to any of the species involved at the time. I like to think that we’re the sort of species that other sophonts tell horror stories about, like the xenomorphs from Aliens: “And they breath oxygen!” “Gasp!”.
There are other compounds than oxygen that would suggest a biological source, that’s just an obvious one. Basically any substance that doesn’t come together naturally very often and tends to bind/decay/otherwise not accumulate would indicate some sort of life actively creating it.
Well, yes, fluorine or chlorine, for instance, would tell basically the same tale. But the point is, why would any living organism deliberately release any highly-reactive substance into the environment? Highly-reactive means there’s a lot of energy to be harvested there-- Wouldn’t it make more sense to actually harvest that energy, and produce only low-energy (and therefore incidentally non-distinctive) compounds as waste products?
I mean, obviously, in at least one case, life does do that, so clearly it’s possible. But it’s tough to generalize from a sample size of one, so we don’t know how common it is.
Well, plants produce oxygen because CO2 + water + energy => glucose necessarily releases oxygen. And glucose => cellulose + water doesn’t help. To use the O2, you need something to oxidize it with. Which plants of course do with their glucose stores, but the cellulose is what plants are made of, so they can’t exactly do that.
Of course, another life form can eat the cellulose and react with the oxygen. But that’s only going to evolve well after there’s plenty of free oxygen available.
Could an entirely different biochemical pathway have existed that didn’t release oxygen? Maybe somewhere else, but probably not on a planet where CO2 and water are the main feedstocks.
If they can announce life on other planets, I’m gonna say that exceeds expectations for the 12th.
BTW, since the launch was more than six months ago, should this topic be renamed to something like “James Web Space Telescope discussion thread”?
The oxygen wasn’t advantageous, it was the ability to generate and utilize energy from the combination of carbon dioxide and sunlight. The oxygen was just an exceptionally nasty waste product.
It’s not like the single-cell prototype chlorophyll-using microbes actually thought about any of this. They were just using one energy source and crapping out oxygen. But you’re right about energy sources, which is why other organisms rapidly evolved to take advantage of the energy-rich waste product. Rather like dung beetles taking care of cow patties.
As the OP, that’s what I intended it to be – an ongoing discussion thread. I probably should have titled it as such, but at the time the successful launch was the big news.
I flagged the thread so a moderator can retitle.
Brian
This image didn’t simply make me cry… it completely flabbergasted me! I fully expected the 183rd digit to be a “1”, but it isn’t! By god, it’s a “0”!!!
This turns our understanding of the universe upside down and requires a massive overhaul of both classical and quantum physics!
…oh, wait, I see the upside down image puts everything back in boring perspective. Never mind. 
Test image released:
https://blogs.nasa.gov/webb/2022/07/06/webbs-fine-guidance-sensor-provides-a-preview/
Brian
That’s a fantastic image when you realize that most of those objects – except for the ones with diffraction spikes – are distant galaxies, not stars. Also impressive is that the image comes from the Fine Guidance Sensor, which is primarily intended for telescope aiming and stability, not for imaging!
In one of his science essays Isaac Asimov hypothesized that we can’t smell oxygen only because our olfactory membranes are constantly bathed in it and further conjectured that if we could it would be something like ozone.
I have thought that if we don’t stop with the dumping CO2 into the atmosphere, it will be the second time the environment has been changed by the life in it to the point it couldn’t survive any more.
“Those images will include what will be – for a short time at least – the deepest image of the universe ever captured, as NASA Administrator Bill Nelson announced on June 29.”
I’m not certain this means we’re getting a new and improved Superduper Deep Field, but it does sound like that.
NASA names first 5 targets (WASP-96 b, The Carina Nebula, SMACS 0723, Stephan’s Quintet, Southern Ring Nebula). Descriptions in link
Brian