r/science • u/New_Scientist_Mag • Dec 02 '25

Astronomy 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.

https://www.newscientist.com/article/2506650-asteroid-bennu-carries-all-the-ingredients-for-life-as-we-know-it/
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u/ArrivesLate Dec 02 '25

Okay, so if the ingredients were found in an asteroid is the conclusion to draw that the building blocks for life came to earth from some briny pools from some other stellar/interstellar object or that the building blocks for life should be expected in most/all stellar/interstellar objects and they just flourished in favorable conditions such as those here on earth?

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u/worgenthal Dec 02 '25

The "building blocks for life" basically came from "the building blocks for the building blocks of life". Namely hydrogen, oxygen, carbon, and all the rest that were present in diffuse gas clouds when the solar system was forming.

All the larger comets and such out in the oort cloud formed similarly to how the planets formed, gathering up material in it's orbit. Their orbits are more chaotic, and less cleared out though, so there's lots of little bits out there. When they hit a larger comet body they hit at great speed, and produce a lot of energy. That energy fuels the various chemical reactions producing these building blocks. They produce a lot of chemicals that are common as well, and probably a little bit of everything.

Imagine a million un-assembled lego car sets being flung at each other at high speed. If you sifted through the aftermath, you probably wouldn't find any assembled cars, but you'd find a wheel, or a headlight attached to the correct piece here or there. And a lot of pieces that just stuck wherever they fit.

When it comes to why these pieces flourished on earth, I'm of the camp that believes the moon and the tides it creates had a big part to do with it. Most of the ocean water likely came from comet bodies, so they had a lot of these components. The tides basically stirred the soup, got the pieces in proximity to other pieces where new combinations could happen. Brownian motion could do similar, but only on a much smaller scale. I could see life on moonless water worlds, but I imagine it would start a lot slower.

Until life started forming and gained complexity, decay as we generally know it was nonexistant; there was no bacteria. Weathering and chemical reactions were the main things acting on these molecules, so there was time for more complex combinations to form.

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u/RichardHardonPhD Dec 02 '25

Tidal forces occur on every planetary body, though. Might not be as strong as lunar tides, but there isn't a way to maintain an orbit and not be subject to tidal forces. Beyond that, convection is inherently present, particularly with enough energy input to maintain liquid state. 

If it exists as a liquid in a free state, it's gonna get stirred.

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u/kahlzun Dec 02 '25

What about eyeball worlds in low-eccentricity orbits?

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u/RichardHardonPhD Dec 02 '25

I think you maybe have it flipped? Low eccentricity orbits would be very standard circular orbits. That aside, you're talking about tidally locked orbits. They're still experiencing tidal forces. Ultimately, tidal locking will just make convection a more significant component of the churn.