Vesta Comes into View

Well, this may not look like much, but it’s a big deal in the asteroid-study game. It’s an image of asteroid Vesta, taken with the Dawn spacecraft. If you visit the the mission’s web pages at NASA, you can watch a multi-still “movie” made from frames taken by the spacecraft’s framing cameras on June 1.  The video presents 20 frames, looped five times, that span a 30-minute period. During that time, Vesta rotates about 30 degrees. The images included here are used by navigators to fine-tune Dawn’s trajectory during its approach to Vesta, with arrival expected on July 16, 2011.

Why a mission to Vesta?   It is the only large asteroid with a basaltic surface that formed due to volcanic processes early in the solar system’s history. Asteroids, like comets, are treasure troves of information about what was going 0n in the infant solar system — some 4.5 billion years ago. Here’s how that works. During the earliest history of our solar system, the elements, minerals, and chemical compounds in the solar nebula were distributed throughout the nebula, with their exact locations varying due with their distance from the Sun (and its heat). As distance from the Sun increases, the temperature drops. The young Sun, hot and active, drove away or consumed gases and icy bodies, leaving behind rocky materials to form the inner (so-called “terrestrial” bodies) close by. The icy worlds and gas giants formed farther away.

So, the division of the solar system into terrestrial and gas/ice giant worlds is a large-scale division.  Our planets have changed over time, particularly the Earth, with its atmospheric change, its geological change, and the evolution of life (which has affected conditions on the planet as well). To learn more about the “pure” or what planetary scientists call, the “pristine” materials that made up the big parts of the solar system, we need to look at the smaller-scale objects: asteroids and comets. Studying asteroids (and comets) and studying their compositions are a way of peering into the distant past and learning what it was like, sort of like looking at your baby pictures and seeing what you were then and comparing it to what you are now.

You probably didn’t know this, but Vesta is considered a protoplanet because it is a large body that almost formed into a planet.  It is 330 miles (530 kilometers) across, and is the second most massive object in the Asteroid Belt — that region of space between Mars and Jupiter that is populated with asteroids.  In a few days, we’ll have even better images of this distant “almost-a-planet” world, so keep your eyes peeled for more news.

Speaking of news, this week’s Carnival of Space is up, posted over at John Williams’s Starry Critters web site. Check it out for some unique looks at places and spaces throughout the cosmos.