At https://spaceweather.com (October 14th 2019) … we have been told that Comet Borisov is an interloper – from another solar system. However, it is behaving in much the same way as any ordinary run of the mill comet. It sports a tail for example and the tail is rich in cyanide (much like most of the comets in our solar system). The comet is fairly bright, and dusty – also much like any other comet. Is it really an interloper? Prior to the advent of last year's interloper it would have been described as a comet with an origin in the Kuiper Belt.
At www.dailymail.co.uk/sciencetech/article-7563375/ … in a link provided by Gary we learn that ice formed on the Moon is fairly recent in date it is being conjectured. Where then did it originate? We are provided with a few explanations such as meteorite impacts – or even an avalanche of tiny meteors (dust grains in other words). Then we have tectonic activity releasing water from an underground source – but most scientists believe the Moon has been tectonically inactive for many thousands upon thousands of years. At the moment they appear to be stumped. Ice craters are scattered across the Moon's south polar region but does that infer the interior of the Moon holds a deep reservoir of water (useful for astronauts if it can be accessed). This may be somewhat like water vapour spewing forth from comets as most comet surfaces so far explored appear to be rocky and strewn with debris (but no water).