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Dynamical origin of Theia, the last giant impactor on Earth

(arxiv.org)
92 points bikenaga | 7 comments | 08 Jul 25 18:10 UTC | HN request time: 0.424s | source | bottom
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echelon ◴[08 Jul 25 19:36 UTC] No.44503282[source]▶
Imagine if life had evolved on Earth or Theia prior to impact. Imagine if it was intelligent and played witness to the giant cataclysm.

Given that intelligence took an awfully long time to emerge from LUCA, that seems implausible. But it's fun to imagine pre-Theia "Silurians". That sort of impact would have scorched earth of any trace or remnant of their existence. It feels as though there must be sufficiently advanced civilizations out there witnessing this exact scenario play out without the necessary technology to stop it. Though that fate would be horrifying.

Another thing to think about is that shortly after the Big Bang (if there was one, Lamda-CDM or similar models holding up), was that shortly after the Big Bang the temperature of the early universe was uniformly 0-100 degrees Celsius. It may have been possible for life to originated in this primordial interstellar medium without even so much as needing a host planet or star! Just life coalescing in space itself.

That early primordial soup, if it existed, could have seeded the whole universe. Most aliens might have matching molecules and chirality if those decisions predate our galaxy.

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1. MarkusQ ◴[08 Jul 25 20:39 UTC] No.44503871[source]▶
That early warm interval would have been a soup of 75% H, 25% He, and 0.0000000% or so Li, with nothing heavier.

Not much to start life with.

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2. echelon ◴[08 Jul 25 23:22 UTC] No.44504908[source]▶
No metals whatsoever. That's unfortunate.
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3. GuB-42 ◴[08 Jul 25 23:44 UTC] No.44505027[source]▶
Metal and hard rock are essential for life.
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4. labster ◴[09 Jul 25 00:14 UTC] No.44505172{3}[source]▶
I think they were referring to metals like carbon and oxygen, but I’m sure Led Zeppelin is important too.
5. Towaway69 ◴[09 Jul 25 04:16 UTC] No.44506301{3}[source]▶
As Douglas Adams wrote, life is about banging the rocks together.
6. eru ◴[09 Jul 25 09:36 UTC] No.44507945[source]▶
Also more importantly: it was uniformly warm. No gradients.

Life on earth doesn't work because we get energy from the sun. It works because we get low entropy energy from the sun and can radiate high entropy energy into cold space.

(There's approximately no net energy inflow.)

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7. adrian_b ◴[09 Jul 25 14:21 UTC] No.44510403[source]▶
You are right about gradients, but while the energy from the Sun is what sustains most of the life today, it played no role in the appearance of life (because capturing solar energy requires exceedingly complex structures).

For the appearance of life it is necessary for the planet to have a much warmer interior than its surface (i.e. a radial gradient of temperature). In that case, volcanism and related phenomena bring to the surface chemical substances that have formed at higher temperatures and which are no longer in chemical equilibrium at the cooler planet surface, providing the chemical energy for the synthesis of the complex organic substances.

Some bacteria and archaea (belonging to the so-called acetogens and methanogens) still exploit the inner heat source of the Earth, living completely independently of the solar energy, in the same way like the first living beings. (However, in many popular science publications one can see frequently wrong claims about various organisms, including some animals, that they do not depend on solar energy, but those claims are false, because those living beings depend on using free oxygen for the oxidation of various substances, like hydrogen sulfide from oceanic vents, and the free oxygen comes from algae and plants that have used solar energy to separate it from water.)