NASA Spacecraft New Horizons May Be In Peril As It Nears Pluto

The Kuiper belt is a is a region of the Solar System beyond the planets, extending from the orbit of Neptune at 30 Astronomical Units (AU) to approximately 50 AU from the Sun. 1 AU is exactly 149,597,870,700 meters (92,955,807.273 miles). This is the distance from the Earth to the Sun.

The Kuiper belt is similar to the asteroid belt although 20 times widers and twenty to two hundred times more massive. Within the belt are small bodies and left overs from when the Solar system was forming. Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water.

Within the belt lies the newly reclassified dwarf planet, Pluto. Pluto is composed primarily of rock and ice. It is about approximately one-sixth the mass of the Earth's Moon and one-third its volume. Five moons have been discovered orbiting the dwarf planet.

MIT News: Asteroid Vesta Once Had Dynamo That Generated Magnetic Field Like The Earth

On September 27, 2007, NASA launched its Dawn spacecraft. Its mission is to orbit the asteroid Vesta and then head over to another asteroid, Ceres.

Both Vesta and Ceres are situated in the asteroid field between Mars and Jupiter. Dawn's goal is to investigate in detail the two asteroids which are the largest protoplanets still intact. Protoplanets are small celestial bodies that show the beginning formation of a planet. These are differentiated objects which means, that these protoplanets underwent a process where their interior got hot enough to melt separating elements within into layers.

Vesta is a dry, differentiated object that has a rocky surface which resemble some features found on the Earth.

Last year, data from the Dawn mission revealed that Vesta may be the smallest terrestrial planet in the solar system. Meteorites found on Earth believed to have come from Vesta has shown extensive igneous processing not much different from the magma rocks found on Earth. This process makes them closely resemble terrestrial igneous rocks.

Meteorites From Asteroid Vesta May Give Clues To Origin of the Solar System

The giant asteroid Vesta is shown here as the smallest body among other similar bodies in the solar system - Mars, Mercury, Earth's moon and the dwarf planet Ceres
Image: NASA

A subgroup of achondrite meteorites are Howardite-Eucrite-Diogenite meteorites. Commonly reffered to as HED meteorites, these come from a differentiated parent body.

Differentiation is the process when the interior of an active planet gets hot enough to melt. As it melts, it separates its materials into layers. The light material floats to the top while the heavy elements, such as iron and nickel, sink to the center of the planet. They believe that this also happened to Vesta.

HED meteorites have experienced extensive igneous processing not much different from the magmatic rocks found on Earth. This process makes them closely resemble terrestrial igneous rocks

A subgroup of HED, diogenites are believed to originate from the asteroid Vesta. These are composed of igneous rocks of plutonic origin. A pluton is a body of igneous rock (called a plutonic rock) that has crystallized from slowly cooling magma.

Diogenites have solidified slowly enough deep within Vesta's crust to form crystals. These crystals are primarily magnesium-rich orthopyroxene, with small amounts of plagioclase and olivine.

New clues to the early Solar System from ancient meteorites

In order to understand Earth's earliest history--its formation from Solar System material into the present-day layering of metal core and mantle, and crust--scientists look to meteorites. New research from a team including Carnegie's Doug Rumble and Liping Qin focuses on one particularly old type of meteorite called diogenites. These samples were examined using an array of techniques, including precise analysis of certain elements for important clues to some of the Solar System's earliest chemical processing. Their work is published online July 22 by Nature Geoscience.

At some point after terrestrial planets or large bodies accreted from surrounding Solar System material, they differentiate into a metallic core, asilicate mantle, and a crust. This involved a great deal of heating. The sources of this heat are the decay of short-lived radioisotopes, the energy conversion that occurs when dense metals are physically separated from lighter silicate, and the impact of large objects. Studies indicate that the Earth's and Moon's mantles may have formed more than 4.4 billion years ago, and Mars's more than 4.5 billion years ago.

Theoretically, when a planet or large body differentiates enough to form a core, certain elements including osmium, iridium, ruthenium, platinum, palladium, and rhenium—known as highly siderophile elements—are segregated into the core. But studies show that mantles of the Earth, Moon and Mars contain more of these elements than they should. Scientists have several theories about why this is the case and the research team—which included lead author James Day of Scripps Institution of Oceanography and Richard Walker of the University of Maryland—set out to explore these theories by looking at diogenite meteorites.