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FluffyGarbage23 t1_j20gc4g wrote

Reply to comment by marketrent in Earth was brought to life by ancient water-rich asteroids from the outer Solar System by marketrent

What I dont get is how many (or big) asteroids would've had to cross its path with Earth, enough to create all the water that eventually enabled life to exist. Theyre not exactly water balloons filled to the brim with water.

How much water is in an asteroid, and how many did make it through the atmosphere? Earth must've been bombarded every second for however many years, and likely other planets like Mars as well.

Except Mars had a different fate than ours unfortunately.

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tarrox1992 t1_j20jlvl wrote

https://solarsystem.nasa.gov/planets/dwarf-planets/ceres/in-depth/

Ceres could be up to 25% water.

https://www.usgs.gov/media/images/all-earths-water-a-single-sphere

An asteroid (well, it'd be a dwarf planet) composed only of water-ice with the same mass of Earth's water would, presumably, be slightly larger than those spheres. Because water expands as it freezes and a dwarf planet would be at least partially frozen.

https://upload.wikimedia.org/wikipedia/commons/1/16/Ceres_Earth_Moon_Comparison.png

So, looking at the size of Ceres compared to Earth/Earth's water, I'd assume that we'd only need 5-6 bodies similar to Ceres to fill us up.

https://solarsystem.nasa.gov/moons/jupiter-moons/europa/in-depth/

They think there is more than twice the amount of water on Europa than on Earth. Not even mentioning the other very wet moons of the outer planets. The article here believes Earth water came from the outer solar system, and, looking at all the information here, it should be easy to see that some asteroids are basically water balloons. Even if they aren't, there are still plenty of water rich bodies the Earth could have amassed.

edit: typos

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citro-naut t1_j228qqb wrote

While we don’t know for sure, water probably makes up something like 0.05% of earths mass, which is not that much at all! And in fact, you can easily acquire this much water by only accreting the driest types of planetary building materials (eg enstatite chondrites) without needing any contribution from the water-rich bodies discussed in this article. Though, these water-rich bodies almost certainly did deliver some fraction of earths volatiles!

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