In general, are carbonaceous chondrites (CC) or comets more water rich?

I know that evidence has suggested that both CC and comets are partly composed of water, but which body is generally more water rich?


I compared C type asteroids and comets for this question. C type asteroids have around 30% of empty space, meaning that that much space can be for water.

Comets have around 40% of empty space.

Obviously, just because they have more empty space does not mean they have more water. However, evidence for water on Earth originally comes from comets. Not only that, but comets are occasionally balls of ice with some rock. Asteroids are known for being just rocks, and only have a limited amount of water.

In conclusion, comets are more water rich.

Hope that helps...?

  • $\begingroup$ Not sure how "empty space" corresponds to water at all. $\endgroup$ – antlersoft Aug 24 '18 at 16:29
  • $\begingroup$ The more empty space, they have more space that can contain ice. For instance, if you don't have space, then how do you put water in? So having more space shows that there is a possibility of containing more water. Obviously, every asteroid is different in terms of their water quantity, so seeing the space of an asteroid can help us determine how much approximate water it can fit. $\endgroup$ – MystaryPi Aug 24 '18 at 20:21

Well, in response to the response of @MystaryPi.

"..However, evidence for water on Earth originally comes from comets.." The above statement is not 100% true, despite that fact that was the common belief how the Earth got its water until the recent Rosetta mission. This question can be partially answered by the ratio between the Deuterium and Hydrogen atoms of observed comets. The D/H isotope ratios of water measured on comet 67P/Churyumov-Gerasimenko by Rosetta and on other comets by other in-situ spacecraft have obtained accurate values, bringing up the prelude to the idea that water on terrestrial oceans may emanate from objects that were of non-cometary nature, simply because those D/H values do not correspond to the D/H values measured on terrestrial oceans. As such, it is thought now that the origin of water-brining objects to Earth to be more asteroid-like, which likely formed much closer to the Sun than the comets.

For more information please refer to Altwegg et al., 2014 (DOI: 10.1126/science.1261952)

D/H ratio of Solar bodies relative to Earth

  • $\begingroup$ Wow! Great work! I think what you wrote clarifies a lot. Just a question - what exactly is D/H ratio? $\endgroup$ – MystaryPi Aug 27 '18 at 1:08
  • $\begingroup$ D/H ratio is the isotopic ratio between the Deuterium and Hydrogen atoms. An easy way to describe Deuterium is that it is a Hydrogen atom plus one more neutron inside the nucleus of the Hydrogen. For example if there are two neutrons inside the Hydrogen atom it is called Tritium, as the mass number (total number of protons and neutrons inside the nucleus) is 3. For neutral Hydrogen it is 1, for there is only one proton makes up its nucleus. I hope this is clear. As more neutrons get added to the nucleus, they are called isotope of the atom in question. I hope this explains it. $\endgroup$ – mysterium Aug 27 '18 at 9:12

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