There are billions of comets available https://en.wikipedia.org/wiki/Kuiper_belt https://en.wikipedia.org/wiki/Kuiper_belt Then there is also https://en.wikipe

There are billions of comets available https://en.wikipedia.org/wiki/Kuiper_belt https://en.wikipedia.org/wiki/Kuiper_belt Then there is also https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud Don't worry - there is more than enough comets to bomb the Mars with all the future settlements. Muhaha