Reminder: Europe's Rosetta probe will fly past asteroid 21 Lutetia in July

Remember the flyby of asteroid 2867 Šteins by the Rosetta probe in 2008? That produced some nice imagery of the asteroid, which turned out to have a diamond-like shape.

It's now almost two years later and Rosetta will fly by another asteroid very soon. This encounter will be a bit farther away and at a higher velocity, but the asteroid it will be flying by (21 Lutetia) is much, much larger. The lower the number for an asteroid generally the larger (or more visible) it is, and 21 Lutetia has been a target of interest for quite some time. Here's how the two encounters compare.

Flyby distance: 800 km for 2867 Šteins, 3160 km for 21 Lutetia
Relative velocity: 8.6 km/s for 2867 Šteins, 15 km/s for 21 Lutetia

The average diameter for 2867 Šteins is about 6 km, but 21 Lutetia is about 95 km, so here's what they would look like next to each other.


For more information on the asteroid and the flyby, see here.