Dawn Approaches the Asteroid Belt
Jun 03, 2010

On September 27, 2007, NASA launched the Dawn spacecraft on a mission that will take it into the asteroid belt, where it will study two of the largest planetesimals in orbit between Mars and Jupiter, Ceres and Vesta. Dawn is so named because it will be observing objects thought to have existed since the dawn of the Solar System.

"Asteroid" was first coined by William Herschel and means "star-like." Ceres was the first asteroid discovered in 1801 by Guiseppe Piazzi and the largest known, with a diameter of approximately 950 kilometers. Since no spacecraft has visited Ceres, its size estimate is determined by combining data from various telescope observations. Ceres compares in size to Saturn's moons Tethys and Dione and might look similar to Dione, with craters and ridges, although Ceres is about 15% smaller.

Ceres has recently been added to the roster of "dwarf planets" along with Pluto—Ceres being the only one within the asteroid belt. Vesta, the first one of the Dawn mission's targets, could also be added, something that data from the space probe will help to determine.

Vesta is the second largest asteroid, with a diameter of approximately 530 kilometers. It was found in 1807 by Heinrich Wilhelm Olbers. Using Saturn's moons for scale again, Vesta compares to Enceladus or Mimas in size.

There are indications that Vesta has experienced some powerful collisions in the past, since more than one large crater marks its surface. One of the craters near Vesta's south pole is 460 kilometers in diameter, more than 80% of the asteroid's size. The crater is close to 13 kilometers below the mean elevation of the terrain, with a rim about 6 kilometers above. There is an 18 kilometer high central peak, as well. Why did an impact that removed more than 1% of the asteroid's mass not blast it into pieces?

The "rubble pile" theory of asteroid composition was created to help explain the mass anomalies that have been seen in asteroid crater studies. Other asteroids, as well as small moons, exhibit craters that should have exploded them into fragments when they were hit. The only suitable explanation, according to gravity-based models, is that they are loosely compacted. It is presumed that they act like big sand piles and absorb the impacts without shattering. They have no hard crust to begin with so they haven't fractured despite repeated pounding.

The Electric Universe theory of asteroid formation does not require that one object smash into another one for there to be craters. Electric arcs can gouge surfaces and scoop out material, accelerating it into space, leaving clean, deep pits. Comets also exhibit surface features that are the same as those observed on asteroids, so the conclusion is that the two are really one thing and not "dirty snowballs" versus rocky bodies.

Plasma arcs do not disturb the surrounding surfaces when they are used in industrial applications. Based on laboratory analysis, that is what has occurred on Vesta and on all the asteroids, moons, and planets of the solar system: plasma discharge erosion. Planetary scientists ignore electrical explanations, which rectify the anomalies in other theories, because they know almost nothing about plasma and electric currents in space. Electricity can create the very things they are sending out probes to study

Stephen Smith