Exploring Asteroid Belt

The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars, that is occupied by a great many solid, irregularly shaped bodies. These are called asteroids or minor planets, are of many sizes but much smaller than planets.

This asteroid belt is also called the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such as near-Earth asteroids and trojan asteroids.

About half the mass of the belt is contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea. The total mass of the asteroid belt is approximately 4% that of the Moon

Ceres is the only object in the asteroid belt large enough to be called a dwarf planet. It is about 950 km in diameter, whereas Vesta, Pallas, and Hygiea have mean diameters of less than 600 km. The other bodies range down to the size of a dust particle.

Individual asteroids within the belt are categorized by their spectra, with most falling into three basic groups: carbonaceous (C-type), silicate (S-type), and metal-rich (M-type).

The asteroid material is so thinly distributed that numerous unmanned spacecraft have traversed it without incident.

The asteroid belt formed from the primordial solar nebula as a group of planetesimals, the smaller precursors of the protoplanets.

Between Mars and Jupiter, however, gravitational perturbations from Jupiter gave the protoplanets too much orbital energy for them to accrete into a planet. Collisions became too violent, and instead of fusing together, the planetesimals and most of the protoplanets shattered.

As a result, 99.9% of the asteroid belt's original mass was lost in the first 100 million years of the Solar System's history. Some fragments eventually found their way into the inner Solar System, leading to meteorite impacts with the inner planets.

Classes of small Solar System bodies in other regions are the near-Earth objects, the centaurs, the Kuiper belt objects, the scattered disc objects, the sednoids, and the Oort cloud objects.

Reference: Wikipedia - Asteroid belt

Spacecraft Missions

A spacecraft mission to explore our Solar System starts with its launch from earth using a rocket launcher. The spacecraft then uses its own engines to reach its objective and carry out its mission. Some missions have multiple objectives.

The duration of a mission varies, depending on the craft used and purpose of the mission.

The table below is an overview or all the successful spacecraft missions, to date, used to study asteroid belt objects. It only includes spacecraft that left Earth orbit to perform their mission.

Point to ℹ for table information. (Table head remains visible while scrolling)
Select the Spacecraft name or Target for more information.

Img ℹ Reference number for image gallery below.	Spacecraft ℹ Used to perform the mission.	Launcher ℹ Used to carry the spacecraft out of the Earth's atmosphere.	Country ℹ Main country which developed the mission.	Year ℹ Year the spacecraft was launched and when the mission came to an end.		Target ℹ Main mission objectives or events.	Notes ℹ Additional information.
				Launch	End

1	Dawn	Delta II 7925H	U.S.	2007	2018	4 Vesta, 1 Ceres	Studied two of the three known dwarf planets of the asteroid belt, Vesta and Ceres. First spacecraft to orbit two extraterrestrial bodies,the first spacecraft to visit either Vesta or Ceres, and the first to orbit a dwarf planet.
2	Galileo	Space Shuttle STS-34 / IUS	U.S.	1989	2003	951 Gaspra, 243 Ida	Destined for Jupiter, flew past 951 Gaspra which is an S-type asteroid that orbits very close to the inner edge of the asteroid belt. Also flew past 243 Ida which is an S-type asteroid in the Koronis family of the asteroid belt.
3	NEAR Shoemaker	Delta II 7925-8	U.S.	1996	2001	253 Mathilde, 433 Eros	Near Earth Asteroid Rendezvous – Shoemaker (NEAR Shoemaker) flew within 1200 km of 253 Mathilde en route to 433 Eros. It flew past Eros in 1998 and then orbited it in 2000 and photographed its surface. In 2001 it landed on Eros' surface. This was the first time a Near Earth asteroid was closely visited by a spacecraft.
4	Deep Space 1	Delta II 7326	U.S.	1998	2001	9969 Braille	NASA technology demonstration spacecraft part of the New Millennium Program. Carried out a flyby of asteroid 9969 Braille and extended twice to include an encounter with comet 19P/Borrelly.
5	Stardust	Delta II 7426-9	U.S.	1999	2011	5535 Annefrank	Flew by and studied the asteroid 5535 Annefrank en route to its primary mission to collect dust samples from the coma of comet Wild 2.
6	Hayabusa	M-V	Japan	2003	2010	25143 Itokawa	Formerly known as MUSES-C, studied the asteroid in 2005 then landed on it and collected samples. These were returned to Earth aboard the spacecraft in 2010. Also carried a detachable minilander which failed.
7	New Horizons	Atlas V (551) Star 48B 3rd stage	U.S.	2006	2019	132524 APL	Part of NASA's New Frontiers program. Its primary mission to perform a flyby study of the Pluto system in 2015, and a secondary mission to fly by and study one or more other Kuiper belt objects. It is the fifth space probe to achieve the escape velocity needed to leave the Solar System.
8	Rosetta	Ariane 5G, V-158	Europe	2004	2016	2867 Šteins, 21 Lutetia	Part of ESA's Horizon 2000 programme. Flew past asteroids 2867 Šteins and 21 Lutetia on its way to study of comet 67P/Churyumov–Gerasimenko.
9	Chang'e 2	Long March 3C	China	2010	2014	4179 Toutatis	Luna observation from orbit for 6 months. Left orbit to flyby asteroid 4179 Toutatis.
10	Hayabusa2	H-IIA 202	Japan	2014	2031	162173 Ryugu	Carried multiple science payloads for remote sensing, sampling, and four small rovers that investigated the asteroid surface and collected samples. It left the asteroid in 2019 and is expected to return to Earth in 2020.
11	OSIRIS-REx	Atlas V (411), AV-067	U.S.	2016	2023	101955 Bennu	Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer is to obtain a sample from 101955 Bennu. It is currently in orbit around Bennu and is expected to return with its sample to Earth in 2023.
12	DART (LICIACube)	Falcon 9, Block 5, B1063.3	U.S.	2021	2022	Dimorphos, 65803 Didymos	NASA mission to test planetary defense against near-Earth objects (NEOs). In 2022 will deliberately crash into moon Dimorphos of double asteroid Didymos to assess impact to deflect an asteroid on a collision course with Earth. A small CubeSat, Italian LICIACube, sent with DART will separate and observe impact.
13	Lucy	Atlas V (401), AV-096	U.S.	2021	2033	52246 - Donaldjohanson, 3548 Eurybates, 15094 Polymele, 11351 Leucus, 21900 Orus, 617 Patroclus	NASA's Discovery Program missions 14. A probe on a 12 year mission to 8 asteroids, 1 main belt and 7 Jupiter trojans including 2 binary asteroids. It will gain two gravity assists from Earth; one in 2022, and one in 2024. In 2025, it will fly by the inner main-belt asteroid 52246 Donaldjohanson. In 2027, it will arrive at the L4 Trojan cloud of asteroids that orbits 60° ahead of Jupiter, where it will fly by 3548 Eurybates (and satellite Queta), 15094 Polymele, 11351 Leucus, and 21900 Orus.Another Earth gravity assist in 2031 will send Lucy to the L5 Trojan cloud which trails 60° behind Jupiter, where it will visit the binary Trojan 617 Patroclus (and binary asteroid Menoetius) in 2033. Lucy will then be in a 6-year orbit between the L4 and L5 clouds, and a mission extension will be possible.

Spacecraft and Launcher Gallery

This gallery contains images of spacecraft and their launch vehicles (rockets) used on the above missions. (Numbers relate to the table above)

Thumbnails: Click on a thumbnail image to enlarge it. | Enlarged image: Click on right side of image for next image or on left side for previous image. Click outside image to close.