More Like Asteroids Than Expected

When scientists began analyzing dust samples from Comet Wild-2, they discovered unexpected things under the microscope.

The team of analysts at Lawrence Livermore National Laboratory found that thousands of the comet's grains are actually bits of the same silicate rocks found in meteorites that fall to Earth from the asteroid belt between Earth and Mars.

Simply put, Wild-2 may orbit like a comet, but it's built like an asteroid.

Conventional scientific theory has long held asteroids were formed from rock in the inner, warmer regions of the solar system, while comets come from the colder, more distant regions. They were thought to contain dust from other stars, along with the ice and gas that give comets their tails when close to the sun.

This assumption was supported by decades of studies of comet dust captured by high-altitude balloons and aircraft in our stratosphere.

But Wild-2 contains far less of those primitive materials than anticipated. "We all expected the picture that emerged to be simple, but it's not," said Donald Brownlee, University of Washington astronomer and principal investigator for NASA's Stardust program, which collected and returned the comet samples in 2006.

There is no doubt that Wild-2 is a comet, and a newcomer to the inner solar system. Scientists think it was bumped from its probable birthplace in the Kuiper Belt beyond Neptune by a chance encounter with Jupiter in 1974.

Physicist Hope Ishii says, "It's a wake-up all that small bodies in the solar system don't necessarily come in two flavors. Instead it's more of a continuum."

The new research, published in the journal Science, contains the latest findings from the Stardust mission, which flew through the tail of the comet to collect dust samples. As ANN reported, the probe's collector device returned safely to the Utah desert in 2006... and since then, over 200 scientists have been analyzing the materials.

All of this interesting and unexpected information has led to a call for... you guessed it! Another mission to collect comet material.

A spacecraft named Rosetta from the European Space Agency is now on a ten-year journey to an even-more distant comet. In 2014, Rosetta will fly alongside the comet Churyumov-Gerasimenko for a full year as it orbits the sun. It will then release a lander to the comet's surface and bake samples in an oven for analysis right there.

FMI: www.nasa.gov; www.esa.int