For a site whose UX relies on scrolling, that's a horribly done scroll
The downside is that you'll be waiting 4:47:50.88 to reach Pluto.
Alternatively, there's a planet browser on the top, but that kind of "cheating" kind of diminishes the point of the website.
Personally, I would've liked the website to scroll vertically instead. Shift+scroll isn't difficult, but it's a trick many people don't know about so relying on it (or on a touch screen, or a scroll bar at the bottom that completely defeats the sense of scale that scrolling leaves behind) is a bit annoying.
You can clear the entire screen in around 15 seconds if you go max speed!
Also, my OS usually allows me to change line skips per mouse wheel increment to three quarters of a page. That does not seem to work here.
Agreed, my other mouse is free-scrolling, it would be fun to scroll huge distances (IN SPACE!) there.
I initially found none of the helpers that scroll somewhere, but thanks for all the tips here and in other replies.