Scientists estimate that every few hundred thousand years an asteroid capable of causing global catastrophe careens dangerously close to Earth. Science-fiction writers and movie directors have capitalized on this statistic so much that many people connote “asteroid” with apocalypse. Yet asteroids are, in fact, incredibly useful objects by which to study the very beginnings of the Solar System.
Asteroids are astronomical leftovers—ancient rubble that failed to accrete into planets as the Solar System formed more than four billion years ago. Many asteroids retain chemical components that are virtually unchanged from this formative period, whereas on the planets, the Moon, and some large asteroids, these components have melted and undergone other geologic alterations. Asteroids range in size from about one-third the size of the Moon to little more than gravel. Astronomers estimate that there are billions of asteroids in the Solar System, and most of them reside in the asteroid belt between the orbits of Mars and Jupiter.
Scientists from around the world are currently experimenting with new ways to study these treasure troves of data, including three missions designed to collect asteroid images, samples, and other data.
Japan’s Hayabusa spacecraft, which launched on May 9, 2003, was the first mission specifically designed to return asteroid samples to Earth. Hayabusa began orbiting the near-Earth asteroid Itokawa in September 2005. After remotely collecting data about the asteroid’s composition, density, topography, and more, the spacecraft made a successful landing on Itokawa in November of that year. Unfortunately, the sampling equipment malfunctioned. While Hayabusa’s capsule successfully returned to Earth on June 13, 2010, the technical glitches may mean that very little useful material from the asteroid was captured. Scientists are now investigating the few particles discovered in the capsule to know for certain.
The Rosetta robotic spacecraft, which was launched by the European Space Agency (ESA) on March 2, 2004, is currently en route to reach comet 67P/Churyumov-Gerasimenko in 2014. Along the way, it aims to fly by a handful of main-belt asteroids for data collection. The first fly-by, of asteroid 21 Lutetia, was successfully completed on July 10, 2010, yielding some of the most detailed asteroid images ever collected.
Another asteroid-bound spacecraft, NASA’s Dawn, will reach 4 Vesta, the first of two large main-belt asteroids it will visit, by autumn 2011. After nearly a year in orbit around Vesta, Dawn will depart for its three-year trip to the most massive known asteroid, 1 Ceres. Dawn is not only the first spacecraft to visit either of these space rocks, but also is taking the first attempt to orbit a space body and then proceed to orbit a second target.
For more recent space news, visit the Science Bulletins website.