Apparently a 1.5mm puncture due to a meteor/debris strike in the Russian Soyuz MS-09 module.
More information:
http://blogs.esa.int/alexander-gerst/2018/08/30/slow-leak-de...
https://twitter.com/RussianSpaceWeb?ref_src=twsrc%5Egoogle%7...
More information:
http://blogs.esa.int/alexander-gerst/2018/08/30/slow-leak-de...
https://twitter.com/RussianSpaceWeb?ref_src=twsrc%5Egoogle%7...
The ISS is also designed to take a hit and can generally survive similar impacts without issue.
But as that incident shows, such impacts are often relatively benign - in that case, they didn't even need to replace the outer layer window.
The hull is reinforced with four or five layers of shielding - the above article has a nice diagram: https://i2.wp.com/www.spacesafetymagazine.com/wp-content/upl...
This means the usual consequence of a micrometeroid impact is pitting of the outer layers that may not even be noticed.
For larger objects that present a serious danger, the US Space Surveillance Network attempts to track them and predict "conjunctions" with a zone around the ISS which extends 2km above and below it, and 25 km in each direction on the orbital path. Anything that's expected to intersect with this zone is analyzed and may result in the station being moved to get out of the way. These are mostly due to space junk of human origin. In 2013, there were at least ~70 of these "conjunction notifications", although this results in only about one move of the station per year, on average.
There's a description of how these cases are handled at https://arstechnica.com/science/2013/07/how-nasa-steers-the-... :
> "Any object with between a 1-in-10,000 and 1-in-100,000 chance of colliding with the station meets the "yellow" threshold. Flight rules say that the station must be moved out of the way in response to a yellow threshold object unless such a move results in a mission impact—"Like, if we do the burn, we're going to miss an opportunity to launch a Soyuz, for instance," explains Parris. "Do we delay the Soyuz, or do we do the maneuver?" A "red" threshold is assigned to any collision with a likelihood of between 1 (in other words, absolutely certain) and 1-in-10,000. Flight rules are more strict for maneuvers in response to red threshold objects: the station is always moved for a red threshold object, regardless of mission impact, unless a maneuver represents more risk than not maneuvering (for example, if there's a piece of equipment that's damaged on the ISS and a maneuver would exacerbate that damage)."
This doesn't help in the case of meteor showers, where the Earth is travelling through a zone full of small debris, typically caused by the trail of a comet. In those cases, the station has to rely on its shielding, but the debris sizes in those cases are almost all within the limits that the shielding can handle.
Most likely, there would be fragments of the impactor and the hull, mixed together with each other and oxidized with the station air, floating about. I won't risk speculating about the fragment size, other than to say it would be pretty dang small. (I'm leaning toward "powder," but personally wouldn't rule out either "grit" or whatever "finer than powder" is.)
silt.
if its even smaller its clay.
https://www.livescience.com/32337-is-house-dust-mostly-dead-...
If you're hit by a speck of dust or a grain of sand you're probably good for most impact sites. If you're hit by a marble you're going to be in real trouble (same is true of the ISS itself in this case).
In any case, it's pretty unlikely.
MMOD protection for visiting vehicles is actually a bit tough; they are on orbit for quite a while but have constraints around shielding. Both the new Boeing and SpaceX vehicles have had problems achieving high enough statistical survivability rates, mostly due to MMOD strikes. (Soyuz probably wouldn't pass those criteria either, but it's not asked to.)