[cthalupa]

It's a (mildly) scientific discussion. Lots of medical discussion happens on HN due to their scientific nature.

Kobe's death, while tragic, is more along the lines of current event discussion.

[TrickyRick]

It's related to aviation which always tends to make the front page. While this particular thread I think very much belongs here, there have been a bunch of links to nothing more than news articles over the last few days which are of little interest from a HN perspective.