Small bodies in the early solar system were likely heated by short lived radionuclides, which were injected into the gas cloud that formed the solar system by a nearby supernova explosion. Remnants of the decay of such isotopes have been found in primitive grains in meteorites.
This heating would have kept the bodies warm enough for liquid water to exist in their interiors for a periods of perhaps some millions of years. The total volume of these could have been quite large, and offers the interesting possibility that life originated in our Solar System in one of these bodies, not on Earth itself. If so, this could explain why life appeared on Earth so early: if OoL tends to occur in such bodies, it either happens early (before they freeze up) or it doesn't occur at all. This would counter the inference that because life originated early on Earth, OoL must be a high probability event.
The presence of phosphate minerals is mildly promising as phosphate is somewhat rare and is biologically essential in nucleic acids, ATP, and some cell membranes.
It's still a heck of a coincidence that one of these life-bearing asteroids hit Earth at exactly the time life could survive here. This becomes more likely if a lot of asteroids develop life, pushing it back into high-probability. Though it's still more susceptible to view bias, since you could have lots of stellar systems where life freezes before it makes it to a planet.
Either way, the notion of asteroids being more hospitable to OoL than planets, with their complex and varied environments and chemistry, would require quite the extraordinary evidence in my book.
Since we don't have a great idea how life originated, preferring Earth to these small bodies seems to me to be mere prejudice. This is especially the case when early Venus and Mars were likely more habitable than early Earth.
It wouldn't be necessary for a life bearing asteroid to hit Earth in order to seed Earth. Rather, a collision of a life-bearing asteroid (perhaps since frozen) in space would create a large number of fragments, any one of which could seed Earth. This strikes me as the most certain part of the scenario. After all, this is how meteorites are created.
> preferring Earth to these small bodies seems to me to be mere prejudice.
I really don't think it is. For any favorable condition you might find in asteroids, early planets can probably match it, and a bunch of other possible conditions besides, with the additional benefit of not requiring a stage where the nascent life has to survive an impact at orbital speeds, subsequent flight through cold irradiated vacuum, and then re-entry through a dense planetary atmosphere. I'm not saying it's impossible, but I'm saying it needs a lot more evidence to take it seriously.
For life to emerge in the span of a few million years within liquid interiors of early solar system bodies, life would need to be a relatively high probability event. I don't think this changes the probability of life calculus vs the traditional life emerging on Earth story.
No, that's wrong. You're ignoring that if it didn't happen, we wouldn't be here to see the result. Observer selection bias. The less common OoL is, the more biased our observation is.
Yes, it also demolishes the naïve Copernican argument that because life is on Earth, it must be common.
The more subtle argument was that because life originated early on Earth, OoL must be a high probability event. But that argument implicitly assumes the probability of OoL is relatively constant with time, so it wouldn't be biased to occur early. OoL on small planetesimals is naturally biased to occur early, due to decay of those short lived radioisotopes. After the planetesimals freeze OoL there doesn't seem possible.
I would suggest replacing 'Ool' by 'origin of life' or even better just 'life' then. Is much easier to understand and it just adds one character to the term
I would think this point would be obvious, but apparently not given the many frustrating discussions I’ve had with smart people on the topic. (Maybe there is a subtlety I’m not appreciating?) It’s a relief to see the good solid sense in all your comments on this thread.
Especially if the "enough" is "enough around any star, anywhere". The a priori probability of it happening around any particular star need not be high. And "anywhere" can be something extremely broad, as in "on any branch of a universal Many Worlds wave function".
Yes but the window of time during which these bodies could have contained liquid water was very narrow, so there would have needed to be a very high number of such bodies to support the low probability of life hypothesis
Tons of assumptions, we can go hyperbolic onto almost anything if you lean into it hard enough.
Unless there is some solid proof that life happened on Earth well before larger bodies of water formed, I'd go for the most obvious theory - biggest stable body of water around and that is our pretty unique planet.
The current mass of asteroids is estimated to be about the same as the current mass of Earth's oceans. The mass of asteroids early in the solar system was likely much larger. So I don't see why one would necessarily prefer Earth to be the OoL location.
Maybe i lack imagination but i don't see how rock formed in a deep ocean could survive relatively unchanged by the kind of impact that would launch it out into space.
What if the origin of Osiris-Rex (Asteroid) is higher energy debris from a major impact to Earth during the early stages of organic life on the planet. Wasn't one theory (?) for our moon's creation such an impact and then a large mass splitting off to form the moon? I could easily imagine smaller bodies with higher local concentrations of energy being ejected from such an event.
Rocks on Earth (and the Moon) are distinguished by being on a specific line on the oxygen isotope plot, the SMOW (Standard Mean Ocean Water) line. This may reflect a large, homogenizing event in the early history of the Earth (like a giant impact that formed the Moon).
The realization that meteorites come from multiple different parent bodies is that they are distributed widely, not all on one line on this plot. Bennu, like primitive meteorites, appears to be off the terrestrial line.
> Bennu's basic mineralogy and chemical nature would have been established during the first 10 million years of the Solar System's formation [...]
> Bennu probably began in the inner asteroid belt as a fragment from a larger body with a diameter of 100 km. Simulations suggest a 70% chance it came from the Polana family and a 30% chance it derived from the Eulalia family. Impactors on boulders of Bennu indicate that Bennu has been in near Earth orbit (separated from the main asteroid belt) for 1–2.5 million years.
Perhaps it came from Earth when the Chuxhulub asteroid struck?
It's really too bad we weren't able to get a sample from the ['Oumuamua](https://en.wikipedia.org/wiki/%CA%BBOumuamua) asteroid when it flew through the system. It was definitely an extra-solar asteroid, so it would have had material completely unrelated to our own system's formation and history.
Not just identifying them, but also being able to catch them in time. They're coming in at solar escape velocities, and going out with same - and the odds of everything being aligned in such a way that we can take several years to do gravity assists are incredibly low.
> odds of everything being aligned in such a way that we can take several years to do gravity assists are incredibly low.
Project Lyra develops concepts for reaching interstellar objects such as 1I / 'Oumuamua and 2I / Borisov with a spacecraft, based on near-term technologies. [0]
Several technology options are outlined, ranging from a close solar Oberth Maneuver using chemical propulsion, and the more advanced options of solar and laser sails. [1]
It occurs to me since survivability isn't a problem for an unmanned probe, that a "cold" nuclear thermal engine vehicle could be used as a loitering interceptor: get it a solar orbit, and leave it till you see a target, then accelerate up to extra-solar escape velocity.
It solves the disposal problem neatly, since the probe and reactor are both leaving the solar system forever afterwards.
Oh yeah, I don't think we're anywhere near "sample return" capability for an extra-solar object.
I doubt we're even near "impactor" capability, tbh. I think our best bet might be "catch up with something in the Oort somewhere around 2070, if we see something coming a decade ahead of time".
Never underestimate the ability of humans to throw something really hard ;)
I actually think if the object was on the right trajectory and we had enough time, that you could pretty much park an impactor in its path. You could probably do a lot of science based on the spectra of the resulting cloud.
I agree that gently landing and return a sample with that much delta V is out of our reach at this point. Maybe with enough shielding, you could park a second sample return vehicle in the path of debris.
The Moon forming impact (4.5 Gyr) occurred ~100 million years after Earth's formation. The earliest solid grain comes from another ~100 million years after that (4.4 Gyr). The earliest signs of life (4.1 Gyr) are from ~300 million years after the earliest grain. Does not seem implausible that life could have arisen during the first 100 million years as well. We know very little about that era since the impact liquified the whole surface.
There's been some research from my alma mater that it might have had water even that early [1]. I haven't seen good data on the estimated temperature during this time (it was hot certainly, the question would be how frequently were there pockets where hyperthermophiles would be able survive). I like this paper's approach [2] - they end up with a small chance of life before the impact.
The only way a widmanst pattern forms is by slow cooling of the iron over millions of years. Check out the wiki section on why it can't be reproduced in a lab
This heating would have kept the bodies warm enough for liquid water to exist in their interiors for a periods of perhaps some millions of years. The total volume of these could have been quite large, and offers the interesting possibility that life originated in our Solar System in one of these bodies, not on Earth itself. If so, this could explain why life appeared on Earth so early: if OoL tends to occur in such bodies, it either happens early (before they freeze up) or it doesn't occur at all. This would counter the inference that because life originated early on Earth, OoL must be a high probability event.
The presence of phosphate minerals is mildly promising as phosphate is somewhat rare and is biologically essential in nucleic acids, ATP, and some cell membranes.