How are those tied together? Glad you asked. In the last
paragraph of the Vesta post, I said we have samples of Vesta
that fell as meteorites. As it happens, they had a sample of one
of those rocks at the show! Here it is: Other such meteorites
have been found on Earth as well, and are generally referred to
as HEDs, short for Howardite/Eucrite/Diogenite — the three main
types of these rocks. So how do we know these meteorites were
once part of Vesta? A couple of ways, actually, but they rely on
spectroscopy. That’s the process of taking the light from an
object and breaking it up into individual wavelengths (using a
prism or a finely etched grating, for example), essentially
creating a rainbow with as many as hundreds of thousands of
colors. The spectrum of an object can be affected by its
composition, how fast it’s spinning, whether it’s moving toward
us or away from us, and much more. Reading its spectrum is like
reading its DNA. In the 1970s, studies of HED meteorites (PDF)
indicated their spectra were muc