Hubble Space Telescope images of Vesta, as fuzzy as they are, still point to an object with variations in minerals across the surface and hint at interesting features on its surface, notes Carol Raymond, the deputy lead scientist for the Dawn mission.
As the research team pored over images the craft has taken since it arrived, it was clear Vesta's variety has been generated by more than material ejected and spread over the surface by periodic collisions with other objects.
"We have strong structural features that have been preserved over billions of years. We have apparent layering of the surface. The degree to which Vesta appears to have preserved a geologic record is something that's very thrilling," Dr. Raymond says. "It's a small world that's quite unique."
The northern half of Vesta is relatively old and heavily cratered, she explains. But the southern half? It's looking like a planetary geologist's dream, members of the science team suggest.
Perhaps Vesta's most striking feature is an enormous impact basin at its south pole, notes Paul Schenk, a researcher at the Lunar and Planetary Institute in Houston and a member of Dawn's science team.
Hints of something unusual there appear in Hubble images taken in the late 1990s.
Now it appears the feature might qualify as one of the Seven Wonders of the Solar System. The basin is nearly 300 miles across and between 12 and 15 miles deep. In its center sits the asteroid belt's version of Mt. Everest – a mountain whose base spans just over 100 miles and whose summit soars an average of about 13 miles above the surrounding terrain.
"It's one of the deepest impact craters we've seen in the solar system," he says, adding that it hosts one of the biggest mountains yet found in the solar system.
As if that wasn't enough to suggest Vesta had a rough childhood, the impact basin, dubbed Rhea Silvia, sits atop an older basin of somewhat smaller diameter. "We didn't expect this," Dr. Schenk says, noting that the team has also identified several other, older impact basis north of Rhea Silvia.