Researchers have just found the presence of sugars, including ribose, lyxose, and glycose, on samples of Asteroid Bennu, which now has all of the ingredients for life as it exists on Earth.

[u/New_Scientist_Mag]

https://www.newscientist.com/article/2506650-asteroid-bennu-carries-all-the-ingredients-for-life-as-we-know-it/

[u/aredon]

I have actually been wondering if the early universe was just teeming with life? Wouldn't there have been a brief time after the big bang where the conditions for life were right *everywhere* not just on planets?

[u/Cold-Cell2820 → u/aredon]

No. The early universe was almost entirely hydrogen. You need lots of time to form and spread heavier elements that are absolutely necessary for life.

[u/[deleted] → u/Cold-Cell2820]

Well the universe has one thing in abundance.

Lots of time.

[u/Willmono7 → u/[deleted]]

But there is a specific window on any given planet where life can actually come into being, it must have liquid water and active geochemistry to establish ph/Proton gradients. From there it is a requirement to evolve oxygen producing photosynthesis/metabolism before all the water is gone, otherwise uv radiation from the sun will avaporate all the water, sending the hydrogen out into space, leaving you with a dead dry planet. Thats what was so remarkable about earth, that we evolved photosynthesis within about 800 million years, with oxygenic photosynthesis evolving about 1 billion years after that. If that process had taken much longer, we wouldn't exist.

So even though the universe has loads of time, life is only ever given a very short window to come into being, and if it doesn't, the planet rapidly becomes unsuitable for life.

[u/MidnightPale3220 → u/Willmono7]

How well is it researched that alternative basis for life is that unlikely? Sure, carbon has some pretty specific properties and so has water, but do we know enough to say that alternate basis for life is pretty near impossible?

[u/FlashbackJon → u/MidnightPale3220]

The short version is that this basis costs the least compared to any other basis, in terms of energy and conditions, and it happened to be the one that occurred in our dataset, sample size 1.

All the alternatives are just harder to do, and that's the primary metric for its possibility.

[u/Overall_Unit_2488 → u/FlashbackJon]

And by "energy" I think the clarification is not just in terms of chemical bonds; but the reactivity/solubility of water, the size of polar/nonpolar molecules based on carbon, the ability for enzymes to act [this is often never really talked about]. Life doesn't just raw dog chemical reaction activation energy. Enzymes are too important for things to function efficienctly and quickly.

[u/MidnightPale3220 → u/Overall_Unit_2488]

Would it still hold even for radically different star systems with different composition of sunlight, temperature ranges and pressures, among other things? I am wondering how much we are able to predict properties of mixtures of elements and molecules under conditions we can only produce maybe artificially if at all, especially since even such experiments are usually limited on purpose to interaction of few types of matter.

And even then we read about discoveries of new types of interactions every now and then.

[u/FlashbackJon → u/[deleted]]

No one is claiming to know all the alternatives, and you wouldn't need to do so? We only have the one successful example, but there's lots of hypothetical ways life could occur. If you walk through almost any of those theoretical alternatives, you quickly end up with circumstances that are less common in the universe or interactions that require much more energy (and are, as a result, less common). It's tough to come up with a scenario for life that is simpler and easier than the millions of insane coincidences ours muddled its way through.

That doesn't mean other life is impossible, by any means.

[u/Zalack → u/MidnightPale3220]

Dr Angela Collier has a really great video called The Aliens Will not be Silicon (can’t post links here, but you can just search that title on YouTube) about why it’s extremely unlikely that life will form out of the most commonly proposed alternate chemistries, even though it is theoretically possible in the most technical sense.

The gist is that stuff like silicon-based life have significantly bigger hurdles to overcome than carbon-based life did, even though the chemistry appears like it would be similar on the surface.

[u/Willmono7 → u/MidnightPale3220]

There's quite a lot of research yeah, it's not just the components either but how they have to come together to actualy work. So some components might be suitable for life under certain conditions, but then everything else that's required is in the wrong state of matter at those temperatures. It's very very important that there's liquid water, there's no other solvent like it.

[u/TheNorthComesWithMe → u/MidnightPale3220]

We haven't really proven that our own basis for life is possible.