|Asteroids of the Solar System
Exploring the Asteroid Belt:
Spacecraft Navigating the Ancient Rocks
Gaspra | Ida | Dawn | NEAR | Falcon
Astronomers have looked at a number of asteroids through the use of telescopes and radar antennas on Earth -- notably the asteroids Toutatis, Castalia, Geographos and Vesta. As each approached close to Earth, asteroids Toutatis, Geographos and Castalia were studied using radar signals transmitted from Earth. Vesta was observed by the Hubble Space Telescope, which is in orbit above Earth.
Taking A Closer Look. Before 1991, the only way we could learn about asteroids was though observations from Earth. Then, we started sending probes:
Spacecraft from Earth that have flown through the Asteroid Belt have found it mostly empty because, after all, the individual asteroids are separated by great distances. The blizzard of rocks depicted in science fiction movies seems not to be accurate.
- in October 1991, asteroid 951 Gaspra was visited by the Galileo spacecraft from Earth on its way to the major planet Jupiter. The first asteroid recorded in hi-resolution images, Gaspra is a big stone, classified as an S-type asteroid composed of metal-rich silicates.
- in August 1993, the asteroid 243 Ida became the second asteroid to be visited by spacecraft from Earth when Galileo undertook a close encounter. Ida also is a big stone, classified as an S-type asteroid composed of metal-rich silicates.
- in June 1997, the NEAR spacecraft from Earth took a high-speed close-up look at asteroid 253 Mathilde. The encounter was the first close look at a carbon rich C-type asteroid. NEAR later landed went into orbit around the asteroid 433 Eros in February 2000. Then it landed on Eros in February 2001. NEAR was the first spacecraft to orbit an asteroid and to land on an asteroid. [Story of NEAR and Eros »»]
Exploring the two largest asteroids
A NASA deep space probe named Dawn was to have been launched in 2006 on a path that would have carried it into orbit around the two largest asteroids in the Solar System.
Unfortunately, after years of preparing for a June 2006 launch, NASA cancelled the Dawn mission in March 2006.
Dawn would have flown for nine years on its journey to orbit the two most massive asteroids known, Vesta and Ceres. Those two "baby planets," located in the main Asteroid Belt between Mars and Jupiter, are very different from each other, yet both contain tantalizing clues about the formation of the Solar System. Using the same set of instruments to observe these two bodies, Dawn would have improved human understanding of how planets formed during the earliest epoch of the Solar System.
Dawn was a NASA Discovery-program flight. That program uses small inexpensive spacecraft to explore the Solar System. Dawn was managed by NASA's Jet Propulsion Laboratory (JPL) at Pasadena, California. The Discovery program included the Stardust mission, which returned to Earth in January 2006 with samples of comet dust.
Dawn would have visited Vesta and Ceres »»
NASA JPL Dawn website »»
Exploring asteroids NEAR Earth
Near-Earth asteroids seem to have broken away from the main Asteroid Belt which orbits the Sun at a distance between Mars and Jupiter. They fly into the inner Solar System, within 121 million miles of the Sun. Aside from the Moon. they're our closest neighbors in the Solar System.
The NEAR-Shoemaker spacecraft was launched on Feb. 17, 1996, as the first in NASA's Discovery series of low-cost science missions. It became the first spacecraft to orbit an asteroid in February 2000 and then the first to land on an asteroid in February 2001. NEAR is short for Near Earth Asteroid Rendezvous.
The car-sized spacecraft snapped 160,000 pictures while orbiting asteroid 433 Eros. After a year in orbit around 433 Eros, NEAR-Shoemaker made an historic controlled descent and touch down on the surface of the asteroid Eros in February 2001. As the first human probe to land on an asteroid, it transmitted 69 close-up images of the surface during its final approach. [All about NEAR's landing on Eros »»]
Japanese probe to return asteroid dust
A Japanese interplanetary probe named Falcon arrived September 12, 2005, at the small near-Earth asteroid known as 1998 SF36 some 186 million miles across the Solar System to pick up a sample of the dust from that small body and return it to Earth for analysis.
Learn more about Falcon »
Originally, Falcon was known as MUSES-C, short for Mu Space Engineering Spacecraft - C. The spacecraft was a project of Japan's Institute of Space and Astronautical Science (ISAS). After it was launched, the spacecraft was renamed Hayabusa, which means Falcon in Japanese.
JAXA renamed the asteroid Itokawa after Hideo Itokawa, an early leader of the Japanese space program. The asteroid is 2,300 feet long, 1,000 ft. wide, and oval shaped somewhat like a football.
As Falcon loitered near the asteroid, it observed the rocky surface with visible-light and infrared-light cameras.
The probe is to leave the asteroid for a return trip to Earth with the dust sample carried in a capsule inside Falcon. When the spacecraft arrives back in Earth orbit, the sample capsule will be ejected to re-enter the atmosphere. It will parachute to land in the desert near the southern Australia town of Woomera in July 2007.
If successful, Falcon will be the first probe to make a round trip to an asteroid. NASA's Eros probe collected data for two weeks from the surface of the asteroid Eros in 2001, but did not return to Earth with samples. NASA's Stardust probe is on its way to visit Comet Wild-2 in January 2004 and return samples to Earth. That package will parachute into Utah in January 2006.
No probe has brought back extraterrestrial samples since the American and Russian Moon programs of the late 1960s and early 1970s.
MORE ON FALCON AND ASTEROID ITOKAWA »
Learn more about asteroids
- NASA JPL Dawn website
- Dawn's visit to Vesta and Ceres
- UCLA Info on Dawn and Images
- A Texas-Sized Space Rock
- NASA's Near-Earth Asteroid Tracking Program
- Alphabetical list of minor planet names
- Asteroid Orbit Diagrams
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