# How much ice is there in the inner asteroid belt?

After asking this question (How long would it take before we use up all the ice in the asteroid belt?)I did some research to find out how much ice there is in the inner asteroid belt (Not the Kuiper Belt), but couldn’t find any results. In my answer I calculate how long before all the ice would be used up in a big range of possibilities. Are there any estimations or studies about the amount of ice in the asteroid belt?

• Either you answered it as you claimed in the comments there and this is useless, or your answer is useless as it is based of a false number. Chose one Mar 23, 2023 at 14:01
• I said in my answer I couldn’t find a number. That is why I asked this question. Mar 23, 2023 at 14:02
• Then the answer is based of a guess and shouldn't be there Mar 23, 2023 at 14:03
• @Starshipisgoforlaunch No, I am wanting to know if any studies have been done. Mar 23, 2023 at 14:04
• Note that the "inner main belt" is a subsection of the asteroid belt that is <2.5 AU from the Sun. This is inside of the primordial frost line for the solar system of about 2.7 AU, and excludes Ceres which orbits at 2.77 AU. The strict answer to "How much water is in the inner asteroid belt? " is: None. - But I get from the question body that you're trying to differentiate between the Kuiper Belt and the Asteroid belt. Mar 24, 2023 at 17:48

## About 250 Trillion Metric Tonnes

At first glance, this is a tough question. There's a lot we don't know about the composition of asteroids in the asteroid belt.

Additionally, the frost line is very relevant to the amount of water in the asteroid belt, and over time is has moved from about 2.7 AU (inside the belt!) to about 5 AU (well outside the belt!).

So theoretically, there should be no ice in the inner portions of the asteroid belt, and in the outer portions ice should only exist in regions of permanent shadow.

## Ceres

But then there's Ceres. Ceres represents almost half (!) of the mass of the asteroid belt, and it is thought that water ice is about a quarter of Ceres' mass. This puts a lower limit on the mass of water in the asteroid belt of about 2.25x10^20 kg, or about 110 Trillion metric tonnes.

A naive assumption that Ceres is perfectly representative of the composition of the rest of the asteroid belt gives a mass of water in the belt of 281.25 Trillion Metric Tonnes.

I rounded this down to 250 T tonnes in my headline to be conservative.

• I doubted the water mass%, but slide 3 from Dawn at Ceres: What have we Learned? supports that figure. I don't condone destroying Ceres to get to all of it, but it seems like you could! Mar 24, 2023 at 21:48
• @ErinAnne I also agree that it wouldn't be a good idea to destroy Ceres. If you look at the answer in the question I linked, you will see that even if we left the ice on Ceres untouched, we would still have enough ice in the asteroid belt to support a society for over a million years. Mar 25, 2023 at 9:09
• The conditions in the society I mentioned were very futuristic compared to our current society, but who knows! We probably will reach that stage. In any case, with our current needs we will have enough ice for millions of years. Mar 25, 2023 at 9:11
• It isn't necessary to use up all the ice on Ceres. Mar 25, 2023 at 9:11