Earth Was Born Dry Until a Cosmic Collision Made It a Blue Planet
Posted3 months agoActive3 months ago
sciencedaily.comResearchstoryHigh profile
skepticalmixed
Debate
80/100
Planetary FormationWater OriginAstrobiology
Key topics
Planetary Formation
Water Origin
Astrobiology
A new study suggests that Earth was initially dry and received its water through a cosmic collision, sparking debate among commenters about the theory's validity and implications for the search for life elsewhere.
Snapshot generated from the HN discussion
Discussion Activity
Very active discussionFirst comment
4d
Peak period
102
Day 5
Avg / period
40
Comment distribution160 data points
Loading chart...
Based on 160 loaded comments
Key moments
- 01Story posted
Sep 30, 2025 at 12:54 PM EDT
3 months ago
Step 01 - 02First comment
Oct 4, 2025 at 6:58 AM EDT
4d after posting
Step 02 - 03Peak activity
102 comments in Day 5
Hottest window of the conversation
Step 03 - 04Latest activity
Oct 15, 2025 at 7:29 AM EDT
3 months ago
Step 04
Generating AI Summary...
Analyzing up to 500 comments to identify key contributors and discussion patterns
ID: 45427972Type: storyLast synced: 11/20/2025, 8:23:06 PM
Want the full context?
Jump to the original sources
Read the primary article or dive into the live Hacker News thread when you're ready.
But, yeah, political implications nowadays are a slippery slope.
It's a pretty safe assumption that all life requires water.
Right. Silicon dioxide is quartz.
Longer analysis.[1]
[1] https://www.the-ies.org/analysis/does-silicon-based-life-exi...
Well, the thing is that all of those are environment-dependent.
We do have data on a somewhat diverse set of environments, and it's enough to confirm what we knew about the flexibility of carbon. But it's not enough to disprove the alternatives.
I for one remember reading about possible silicon/methane based life, etc. Actually, here’s a whole wikipedia article on what you’re talking about.
https://en.m.wikipedia.org/wiki/Hypothetical_types_of_bioche...
Perhaps HN folks will lose your scent now and direct their snark there
https://en.wikipedia.org/wiki/The_Devil_in_the_Dark
https://lweb.cfa.harvard.edu/~ejchaisson/cosmic_evolution/do...
So while it may be possible for life to exist without water, any alternatives should be reasonably expected to be even more rare than water-based life
2. joshuahedlund’s reply: Grounds the argument in chemistry and probability.
There are only ~90 stable elements → a finite combinatorial chemistry space.
Among possible solvents, water is the most abundant and chemically versatile (dipolar, wide liquid range, high heat capacity, good at dissolving ions and organics). → So even if other solvents can work (like ammonia, methane, formamide), the odds heavily favor water-based life.
3. caymanjim’s addition: Brings in carbon’s unique valence behavior:
4 valence electrons → can form stable, complex chains and rings.
Bonds are strong but not too strong → dynamic yet stable biochemistry.
Silicon (next best candidate) forms brittle, static lattices and poorly soluble oxides → bad for metabolism. → Therefore: if life is carbon-based, water is the only sensible solvent.
A major reason we are interested in Europa is because it might have underground oceans. Hypothetically, through tidal forces with Jupiter, the moon's core is hot enough to create oceans under the ice crust. Combined with hydrothermal vents you have the possibility for deep sea life similar to our own deep oceans. The Drake Equation does not predict this possibility.
As a reminder, this is the equation: https://en.wikipedia.org/wiki/Drake_equation#Equation
It makes very few assumptions.
> n_e = the average number of planets that can potentially support life per star that has planets.
The fact that the planet is neither too hot nor too cold would seem to be a major component of this term:
https://en.wikipedia.org/wiki/Habitable_zone
The last five factors in the equation will be filled in by assumptions based entirely on one data point, life on Earth. From your link:
Can you define any one of those without assumptions, in a scientifically proven way?Edit: the parent post has been edited substantially after I replied.
They are "defined" conceptually, in words, not in physical quantities. It assumes we can assign a known value to any of that when we don't and likely never will. It's like saying "Let X answer the unanswerable question. X is the answer".
> at no point does it assume a planet must be in the Goldilocks zone
You could say it implies it with fl.
> Edit: the parent post has been edited substantially after I replied.
Only for legibility.
For all we know civilization exists inside our car battery. Why assume it only exists on planets.
It's not explicit in it's assumption but implicit assumption the equation is meaningful.
Rick Sanchez uses a microverse battery
https://annas-archive.org/md5/4c381ac344506d10037fc8e7747098...
The cheela lived on the surface of a neutron star, and they lived faster because the nuclear physics that powered their metabolism are far faster than the chemical and mechanical physics that power our own.
Anyway, sounds interesting, gunna add that to my list
Also Macbeth was written 400 years ago. Let's not pretend this is a fair comparison. This author has been dead only 20 years - it might be that their partner is still alive and needs that money, or their children.
We need more discussion about copyright in our society, and we need it most in front of those who are unaware, inattentive, or would otherwise shirk that discussion. Posting a relevant link in a relevant discussion appears as good an avenue as any to get people talking.
https://en.wikipedia.org/wiki/The_World_at_the_End_of_Time
Drexler and colleagues did that, and found "a substantial probability that we are alone in our galaxy, and perhaps even in our observable universe (53%–99.6% and 39%–85% respectively). ’Where are they?’ — probably extremely far away, and quite possibly beyond the cosmological horizon and forever unreachable."
https://arxiv.org/abs/1806.02404
It's nowhere near a precise estimate of the probability of life. What it mainly shows is that the Fermi "paradox" is no such thing. It can look that way if we guess specific parameter values, but if we fully account for our uncertainty on the various parameters, then the result is a decent chance that we are alone, given the knowledge we have so far.
You can’t have a distribution with one data point.
It’s similar to the arguments about 3I/Atlas being an alien spacecraft because it’s so ‘weird’.
With so few data points, everything is fundamentally ‘weird’ - or normal - we have no way to tell, so making any sort of statistical argument about it is fundamentally useless and misleading, as statistics is based on groups. And we don’t have a group yet.
One of the most uncertain parameters is the rate of abiogenesis events per planet. For that one they used a log-normal with a standard deviation of 50 orders of magnitude. They discuss specific theoretical limits from biology for both ends of the range.
Compared to this approach, the usual method is to just pick particular values out of a hat. This paper at least improves that by directly representing our vast uncertainty for some of the values.
It doesn't tell us how many alien civilizations there are. But it does tell us the range of possibilities, given what we know and don't know.
The underlying model is just:
N*f
How many planets are there, and what proportion of them have detectable life?
The f does not have to be structured as fl->fi->fc, although we can see why you'd assume that kind of structure. It's simple to calculate the PI(series) when the model is just a funnel. Like the Million Dollar Money Drop gameshow.
But you could imagine a more complex model of probabilities that branches and merges. There could be events on the bayesian tree that amplify downstream events. For instance, suppose there is some pathway that if reached will leave certain minerals that future civilizations could use. This has happened already on earth at least once: lignin bearing plants could not be easily digested for a long time, and that led to coal formation during the carboniferous period.
You could imagine many such potential trees, but we only have one iteration.
With sublight velocities achievable today, I recall it would only take around a million years for a Von Newmann probe to cover the entire galaxy. Such a probe is quite conceivable, so why isn't there more evidence of such probes everywhere?
Another point I feel is that proliferation of life should be an self-reinforcing affair, for intelligent life even more so. A spacefaring nation may terraform or just seed planets, and these in time will replicate similar behaviors. At a certain point, a galaxy teeming with life should be very hard to reverse given all the activity. A life itself isn't necessarily evolved from biology, AI machine lifeforms should also well suited to proliferate, yet we don't see them anyways.
What are the incentives to build and deploy such a thing though? We as a civilization fail to fund things that have a ROI of more than a few years, how are you going to fund something that pays off after a million year?
Consider that in some countries on Earth, we can't even get consensus that obtaining energy directly from the Sun via solar panels is a good idea.
"Extremely improbable" would be a better assessment.
Even ignoring the project complexity, difficulty, and energy budget, which can't simply be handwaved away by "robotic automation", one reason is simply that such colonies don't solve any problem that we're likely to have, that can't be solved much more cheaply, safely, and effectively.
But even the idea that we'll eventually have the technology to build such structures is debatable. Will this be before or after we solve climate change, for example? Because that issue is likely to severely impact our technological capabilities over the timescales involved. And as of today, the most technologically advanced nation is doubling down on atmospheric carbon production.
First of all it's going to be massively more expensive than any housing we've ever built on earth so only a very small elite could afford living there.
But then again, space is a very hostile environment: it's super dangerous (any incident will almost certainly snowball into a dramatic accident), very unhealthy (billionaires are currently funding longevity research, so I don't think they'd like to go in a place where they would age up significantly faster than on earth…), and life is just worse up there on all respect…
Time, not space, is your answer here.
Two reasons -
(1) civilizations might not survive long enough to do this.
(2) 13 billion years is a long time. So you have the reciprocal of that as the chances to be in the right year to see such a probe. And with results from the new telescope we now have hints that the 13 billion number is bogus, the universe is likely far older.
The fundamental problem with the Drake equation is that it's frequentist, not Bayesian
Hence why you get too high sensitivity to parameters you have no way of having an estimate with a small margin of error
We "don't care" about how many civilisations are out there, we care to the point where we can interact with them.
As mentioned, it has several assumptions. "Rate of birth of sun like stars" means nothing. You can "always" have an exception for life that will throw the data off: "star too bright but with a hot Jupiter tidally locked in front of your moon, shielding it" etc
It seems unlikely that such exceptions would amount to more than part of a reasonable margin of error.
e.g. Say chance of a random planet ever being hit by a water-carrying comet is one in a billion, then with 100B - 1T planets in the milky way it'd happen here 100-1000 times. If chances are only one in a trillion, and we're the one in the milky way, then there are still another 100B - 1T galaxies out there and therefore a similar number of such events.
Enough AI and robotics for an autonomous factory may be a mirage (such mirages have (metaphorically) happened before), but it seems like it's on the horizon.
Even with relatively mundane growth assumptions, that can go from "species inventing writing" to "Dyson sphere completed, is now sending out seeds to every accessible galaxy" on significantly less than the timescale of light crossing a spiral galaxy's disk.
But contrawise, I do have data, they're broadly categorised as "history", "biology", and "all the stuff cited by Stuart Armstrong that time".
Any given colony has to create only slightly more than 1 additional colony in order to drive exponential growth. There doesn't have to be any coordinated action by a central authority for it to happen. For it not to happen (if it is physically feasible), in contrast, every species has to refrain from doing it at all points in their history, almost without exception. And those that do the colonization will seed additional colonies with a mindset that led to colonization; such mindsets will be selected for for further expansion.
We have no reason to believe alien (or even human) civilization will continue to grow and expand forever. Heck even the human population curve has started to slow down and is now revealing it self to be a logistical curve.
But regardless of this, space is very very very big. And there are a lot of extremely hostile worlds out there. Any civilization will experience biological limitation to which worlds they can (and will want to) colonize. Likewise they will experience both economical and physical limitations to how far they will send their machines. Lets say an alien species is lucky and has a habitable world inside their solar system which they will colonize. I think this is likely. They also spot another world in a nearby solar system which takes them 200 years to travel to, eager colonists travel in a generational ship, and 600 years later the colony is thriving. Now they run out of nearby habitable worlds. There is a world of questionable quality 500 years away and they are unable to persuade enough people to fill a generational ship. Also they learned the stories of the passengers in the generational ship, their lives kind of sucked, we have it much better on this world. So it is better to just stay here. This might happen after 1 or 100 successful colonizations, but I think space is so freaking large, it will happen to all civilizations. At some point they will run out of worlds to colonize, and they will never expand far outside of some local area near their home world.
But you're saying galactic colonization would terminate without running out of new systems to colonize.
There would be a slowdown due to geometric constraints -- only so many new systems adjacent the boundary of the colonized zone -- but that hardly solves your problem.
If we look at humans, we have both the space, technology, and the resources to expand even further on earth, yet our span only marginally larger then it was 10 000 years ago. We can have permanent settlements on Antarctica, floating on the ocean, etc. but we don’t. We can increase our population by another order of magnitude, but again, it looks like we won’t. This follows the same population dynamics as most other species on earth. I think aliens will be no different.
Even if 99% stop and fail, the 1% will continue and continue expanding.
The only way to stop would be to run out of planets, which would mean every habitable planet and star system has been populated. There wouldn’t be a biological urge to stop, as the successful colonies are ones which have the urge to expand. An environmental need wouldn’t affect every colony and ship short of a galaxy spanning event of some sort which we can’t even conceive.
I also think fast space travel (like 0.1c) is rare among civilizations, and may only happen in the order of hundreds of time in the history of some civilizations. And most of these fast space travel will scientific instruments for curiosity and exploration, not for colonization. And that a technologically advanced civilization would favor doing their explorations with telescopes, not probes. So probes would only be sent long distance for rare occasions.
This would mean that almost no civilizations will be expand beyond their solar system, and those that do, will only do it a handful of times, and the expansion will finally stop.
Especially once you reach the “hundreds” level then given the technology exists and the people exist why would it stop, until there’s nowhere else to go.
There is the light cage issue where a civilisation can only spread so far with exponential growth before internal pressures overwhelm it (the leading edge never gets a chance to continue as it is overwhelmed by trailing edges)
Even in that situation though you’d still have self replicating probes - likely at a far lower tech level than biological. Once you reach the tech to send one probe which can duplicate itself more than once using resources in a new system then its game over.
Send 50 probes to each of the 50 stars within 15 light years at 0.01c. If 10% make it they then use local materials and send 50 more, that’s 250 out in 1500 years. Then it’s 1250 out in 3000 years. Within a few millennia years you’ve got millions of probes spreading in an unstoppable way. The ones heading back “inwards” will fail, but those heading outwards will reach each new star dozens of times, only one will need to get there. Within 10 million years you’ve reached the entire galaxy.
To stop it you’d have to make a self replicating probe which was faster and did exactly the same thing and caught the earlier probe, but then when would that probe itself stop, it would have no way of knowing if there were any other “bad” probes to find without becoming the bad probe itself.
Living beings are the same. Once a few dozen have made it and passed on, it’s inevitable it will continue. It may leave out a hollowed husk in the origin point with all resources having being consumed in the centre, but that doesn’t matter as the centre has no way of affecting what happens on the edge, and one edge has no way of affecting another edge.
What’s the probability that a radio-capable civilization becomes a galactic type 3 one? Looking at the only example we have, it appears very unlikely. It seems much more probable that we’ll destroy ourselves within the next centuries.
In either case it's a statistical question of how common is life, and intelligent life, but of course there's the human interest in potential contact with another intelligent life form.
But numbers can go arbitrarily low.
We had a good start. A Jupiter to clear the debris, a Theia impact to create tides and contribute to tectonics, a magnetic core, a shielded atmosphere. We had water delivered to us. Maybe even panspermia.
Maybe cell walls and mitochondria are hard. Maybe multicellular is hard. Maybe life on land is hard. Building lungs, rebuilding eyes, having actual energetic gasses on land...
Maybe life is easy, but intelligence is hard. Maybe civilization is hard.
Maybe technology development can only happen on dry land, because aqueous chemistry is hard in water. Sorry mollusks and cetaceans: you'll probably never be able to do chemistry or materials science.
Maybe you need water and carbon and other chemistries aren't robust enough.
Maybe you need lots of fossil fuel deposits to develop industry. And that requires growth without bacteria and decomposers for millions of years, implying a certain order to evolution.
Maybe you need a certain sized gravity well to escape.
Maybe surviving the great filter is hard and still ahead of us. Maybe every species can build tech where a kid in their garage can extinct the entire species by 3d printing grey goo.
There's just so much we don't know about how life could happen. Let alone intelligent life. We don't even know where we're headed.
I suspect that any evolutionary environment will eventually create enough variety and instability that some generalists emerge, creating a reward for intelligence. The rise in intelligence from early water-bound life to later forms was likely all driven by more complex and diverse environments.
This forced some apes to climb down the trees and depend on a diet of scavenging for meat, which happened to both increase brain size AND require improved intellect to survive, forcing the evolution of our hypertrophied symbolic brain.
Had this not happened however, other intelligent species could have filled the niche. There's no shortage of other intelligent species in our planet, not just other mammals but octopus and some birds. And then you get hive intelligence, which could equally be forced to evolve into a high problem-solving organism.
[0] Unless that episode of Voyager was right on the mark https://memory-alpha.fandom.com/wiki/Distant_Origin_(episode...
Basically I fear we’re the universe’s only shot of appreciating and populating the galaxy (or beyond) and we’re on the brink of throwing that away.
Having coal/oil is pretty irrelevant in terms of whether a civilization can build spacecraft.
Successor. Whoever comes along after we've done ourselves in.
There will be no successor civilization to humans. Earth won't be able to support multicellular life in a few hundred million years due to the sun becoming gradually more luminous over time, resulting in higher surface temperatures that will eventually culminate in a runaway greenhouse happening, as it already has on Venus. Due to human-driven climate change effects this event will certainly happen much sooner (<100m years) as well, which is simply not enough time for another intelligent species to evolve after a large-scale extinction event.
Even if life evolving on earth was an incredibly rare event the chance of such circumstances not happening elsewhere even in our own galaxy is infinitely small - there are trillions of planets and 100b+ stars. On top of that there are 100s of billions of galaxies within the observable universe as well.
Modern humans have only been around for < 1 millions years, and all the technology we have invented is incredibly recent. 200 years ago we had neither electric light or bicycles.
Over the course of 100s of millions of years, as the sun's increasing luminosity becomes an issue, I'd have to assume we could create some sort of atmospheric solar shield to reflect or absorb a lot of the energy. Of course you can only postpone the inevitable (red giant).
Assuming the evolutionary lineage of our species survives a few hundred more million years (which seems rather doubtful), then it's not going to be homo sapiens any more - we'll have evolved into successor species that may be barely recognizable. If you go BACK in time 100M years, our ancestor was some mouse-like animal.
No, it will not. Human driven climate change is drastic, but the Earth has seen far worse events than our anthropogenic carbon emissions. For instance, the Chicxulub impactor at the end of the Cretaceous changed atmospheric conditions overnight, and to a much greater degree than whatever we have cooked up. It was the equivalent of detonating the world's entire nuclear arsenal about a million times over.
Sure, it finished off the dinosaurs. But 66 million years later, we, the descendants of tiny rodent-like mammals, are still here, as are the dinosaur's own descendants, the birds.
Additionally, during the Carboniferous about 300 Mya, both carbon dioxide and oxygen levels were considerably higher than they are today, and life actually thrived. I would say that with the increasing luminosity, there will be at least a decent period on Earth where life returns to that sort of diversity. We are actually still only in an interglacial of an ice age—this has effectively sterilised large tracts of our planet by covering them with ice sheets, or locking permafrost into the soil and making them unavailable for large trees.
Let me be very clear: our emissions—if unchecked—will make life very difficult for us as the rising seas and temperatures scatter millions of people out of coastal cities in the tropics further north and south and cause war, division, strife, and discord like we have never yet seen. But actually bring forward the planet's overall demise? Nearly impossible.
Let's not have the hubris to think we puny humans could remotely affect the planet's geological timeline. If we somehow all disappear simultaneously, most direct evidence that we ever lived will disappear with us–perhaps within a hundred thousand to a million years of erosion and weathering. Our emissions will similarly lurch to a halt and will reach equilibrium within a similar time span. That's all it takes to remove our direct creations from the geological record.
On the flip side, that could also be plausibly a blessing, avoiding them to fall into the same trap of becoming too powerful before they get wise. These comics illustrate it: https://www.badspacecomics.com/post/grounded
Intelligence has evolved three times independently on earth - dinosaurs/birds (raptors, covids), mammals, and cephalopods (Octopus)
> Maybe you need water and carbon
Maybe so, but Oxygen and Carbon are only behind (albeit far behind) Hydrogen and Helium as the most abundant elements in the universe
Which begs the question, why 1, and not zero? I can buy zero, or a very large number. But 1 exactly? Nature doesn’t do that.
But in seriousness, I agree.
I doubt water (H2O) is actually that rare. The most common elements by far, both in our own galaxy and the universe as a whole, are Hydrogen and Helium, but the next two most common are Oxygen and Carbon.
Keep in mind, the solar system formed from a relatively homogenous nebula. It was the formation of the sun that forced lighter elements to migrate outwards, and that only happens if the lighter elements aren't already part of a larger object. There isn't much of a difference between a 10 km chunk of ice and a 10 km chunk of iron gravitationally speaking. Bouancy doesn't play a role here, so density doesn't matter. Outgassing does matter, but that is a slow process for large object, like the Earth, or for smaller objects on Earth crossing orbits that don't get too close to the sun.
It's also worth considering that each planet's situation is unique. There is much more water ice on the moons of the outer solar system because there was more water at the time of formation and the lower temperatures mean the water that was there stayed there. As for Mars, even though it is colder than the Earth, it is much less massive. As such, its atmosphere bleeds away lighter molecules (never mind lighter elements).
Right, which is why it's baffling to me that everyone in this thread seems to be losing their mind over this result, thinking it affects the Drake equation and rewrites solar system dynamics. The multiple impacts thing might not have actually happened to earth, but there's still no reason to believe it wouldn't work.
Whatever the great filter is, it's not planetary-scale collisions during the accretion phase of solar system formation.
The number of instances where this (something unreasonably unlikely) happened in our cosmological history is kinda surprisingly high. I’m absolutely convinced there’s no advanced life (and CERTAINLY no technological civilizations) outside of earth.
One other example: we gained most of our adaptability, curiosity, and problem solving skills as very tiny mammals while dinos ruled the earth. The only way we ever took over the planet was thanks to an asteroid wiping out all those huge creatures. Suddenly, high adaptability and intelligence and resilience was what mattered, and being big and strong suddenly was a massive disadvantage.
Our intelligence exploded largely because that extinction event removed almost all major predators, turning earth into a giant survival puzzle sandbox for mammals to grow in.
Edit: our brains only grew big because it was the best means of survival - they’re crazy expensive, so without this “sandbox puzzle” effect, we probably never would’ve grown them.
Maybe it was just being small, puny, and having a tendency to cower in burrows was what saved us. Our ancestors may not have been much smarter than squirrels, and squirrels aren’t very bright.
Hominids brains didn’t get big until long, long after the KT extinction. A Tigers brain is not that much smaller than that of an an Australopithecus.
It may be more correct to say that growing a larger brain (larger than a lizard’s, I mean) was only realistically possible because of the sudden loss of predators.
Look at the rest of the solar system. Mars - almost no water. Luna - almost no water. Venus, maybe water[1], but as steam. Too close to the sun and too hot.
[1] https://phys.org/news/2025-10-venus-clouds-reanalyzed.html
These channels helped me realize just how important all the planets in the solar system are to our continued existence. Its as if we have an entire family thats just perfect to make our existence possible. An entire family each one quietly doing their part without fanfare or credit.
What if we had 2 moons with half the mass?: Destruction [0]: https://www.youtube.com/shorts/v3xxaTkKGTQ
What if we moved Earth 5% further from the Sun?: Destruction [1]: https://www.youtube.com/shorts/g-na5x0Kldk
What if we dimmed the Sun by 1%: Destruction [2]: https://www.youtube.com/shorts/Cc3DRRJxhB8
What If We Delete the Biggest Planet from Our Solar System?: Destruction [3]: https://www.youtube.com/watch?v=kHJpIWoksKw
What If We Delete All Gas Giants Except Jupiter?: You guessed it...Destruction [4]: https://www.youtube.com/watch?v=Eg9fPNg00EE
No matter what the circumstances, live will evolve to perfectly match the conditions it is under. There are many species so perfectly adapted to their ecological niche, they are in great danger of extinction. Like peacocks, who are stuck in a local optimum with no way out.
Consider Mars. Endless probes for 50 years going to Mars looking for life. No clue of life has ever been found. At what point do we face the fact that Mars is a dead rock?
What we should be doing is collecting samples of extremophiles from the Earth, and attaching a few packets of them to every probe going to Mars, and see what happens. Probably nothing will happen, but it's worth a try.
Probably the strong magnetic activity of the Earth's core was key to maintaining the atmosphere, but also, the magmatic heat contributed to keeping the planet at a good temperature to support life when a young Sun provided significantly less radiation.
All these elements may suggest that the collision is needed to satisfy the very strict requirements about where the planet is located and about the size and composition of the colliding planet. This makes the probability for life-sustaining planets in the Drake equation extremely low.
As an indirect proof of the tightness of the condition is the fact that the Earth in its history had periods of climate extremes hostile to life, like the Snowball Earth when the planet was completely covered by ice and snow, or at the opposite extreme, the very hot periods when the greenhouse effect was dominating the climate.
"The hypothesis that life, in the form of “seeds” or spores, is distributed throughout the universe, traveling between planets, moons, and other bodies via space dust, asteroids, comets, and possibly even spacecraft."
I want to think that the water contained life and not the barren earth.
If you appreciate technical things, you'd be in for a treat.
(Also Mars could have been also hit.)
111 more comments available on Hacker News