Our sense of scale tends to adjust to circumstances. So when we think about comets it is easy to compare them with other astronomical objects. In which case, comet 67P/Churyumov-Gerasimenko –just three kilometers wide –sounds tiny.
However, as you can see in the image above, things look rather different when you compare the comet to something we are really familiar with - such as tall buildings.
While Churyumov-Gerasimenko is small enough that one could walk from one end to the other in less than an hour, it’s easy to forget the three dimensional nature of something like this – three kilometers across is no big deal, but two kilometers helps make sense of what happened to the dinosaurs.
The image is by Matt Wang, who combined a photograph of Los Angeles with an image from the Rosetta spacecraft rendezvousing with Churyumov-Gerasimenko, prior to going into orbit and eventually landing.
While Rosetta will be doing its best to touch down very gently on the comet’s surface, we can’t count on Churyumov-Gerasimenko doing the same if it ever paid LA a visit. You can get some idea of what would happen in such a collision here, although the scale of the damage depends greatly on the impact speed you choose to enter.
Since Churyumov-Gerasimenko never crosses the Earth's orbit there is no danger of a collision, at least until a close encounter with some other planet shifts its orbit. Unfortunately the same cannot be said for other, even larger, asteroids and comets.
Note: An update to the image credit has been made. Credit: Matt Wang, Flickr: anosmicovni. European Space Agency.