An interplanetary mission is a voyage or trip through space involving more than one planet

Planet

A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

. This is an important distinction because it requires significantly more ΔV

Delta-v

In astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....

 (change in velocity) than do missions within a single planetary system.

As of 2011, there have been no manned interplanetary missions, although the Apollo Applications Program planned a three month interplanetary mission to Venus using Apollo hardware in the 1970s. So far, all manned missions have been within the Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

's planetary system (i.e. to the moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 or closer). The American space agency NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 intends to be able to launch a manned interplanetary mission to Mars

Mars

Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 by some time after 2015 under the Vision for Space Exploration

Vision for Space Exploration

The Vision for Space Exploration is the United States space policy which was announced on January 14, 2004 by President George W. Bush. It is seen as a response to the Space Shuttle Columbia disaster, the state of human spaceflight at NASA, and a way to regain public enthusiasm for space...

. The European Space Agency

European Space Agency

The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...

 has the long-term vision of sending a human mission to Mars by 2030 under the Aurora Programme

Aurora Programme

The Aurora programme is a human spaceflight programme of the European Space Agency established in 2001 with the primary objectives of creating, and then implementing, a European long-term plan for exploration of the Solar System using robotic spacecraft and human spaceflight...

.

A large number of robotic interplanetary missions have been performed by the USA, the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 (and later by Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

), Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 and the European Union

European Union

The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

.

The first interplanetary mission to fly past another planet was the Soviet Union's Venera 1

Venera 1

On February 12, 1961, 00:34:36 UTC, was the first planetary probe launched to Venus by the Soviet Union. The Venus-1 Automatic Interplanetary Station, or Venera 1, was a 643.5 kg probe consisting of a cylindrical body 1.05 metres in diameter topped by a dome, totalling 2.035 metres...

. The robotic spacecraft

Robotic spacecraft

A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 was intended to enter into orbit around Venus

Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

, but suffered a malfunction and radio

Radio

Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

 contact with the spacecraft was lost. The defunct Venera 1 passed within 100000 km (62,137.3 mi) of Venus before entering a heliocentric orbit

Heliocentric orbit

A heliocentric orbit is an orbit around the Sun. All planets, comets, and asteroids in our Solar System are in such orbits, as are many artificial probes and pieces of debris. The moons of planets in the Solar System, by contrast, are not in heliocentric orbits as they orbit their respective planet...

. The United States' Mariner 2

Mariner 2

Mariner 2 , an American space probe to Venus, was the first space probe to conduct a successful planetary encounter . The first successful spacecraft in the NASA Mariner program, it was a simplified version of the Block I spacecraft of the Ranger program and an exact copy of Mariner 1...

 became the first successful interplanetary mission in December 1962 when it collected data within 35000 km (21,748 mi) of Venus.

The Soviet Union's Venera 3

Venera 3

Venera 3 was a Venera program space probe that was built and launched by the Soviet Union to explore the surface of Venus. It was launched on November 16, 1965 at 04:19 UTC from Baikonur, Kazakhstan....

 crashlanded on Venus in March 1966 without returning any data on the planet, although technically becoming the first manmade object to land on another planet. In October 1967, the Soviet Union's Venera 4

Venera 4

Venera 4 ) was a probe in the Soviet Venera program for the exploration of Venus. Venera-4 was the first successful probe to perform in-place analysis of the environment of another planet. It was also the first probe to land on another planet...

 became the first successful interplanetary mission to land on another planet.

The United States' Mariner 10

Mariner 10

Mariner 10 was an American robotic space probe launched by NASA on November 3, 1973, to fly by the planets Mercury and Venus. It was launched approximately two years after Mariner 9 and was the last spacecraft in the Mariner program...

 became the first successful interplanetary mission to visit more than one planet outside Earth's planetary system. Mariner 10 flew by Venus once, in February 1974, and flew by Mercury three times, in March and September 1974, and March 1975.

There are currently five spacecraft on trajectories which either will or have already taken them out of the solar system

Solar System

The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

, depending on the definition used to determine the solar system's boundary. These probes are Voyager 1

Voyager 1

The Voyager 1 spacecraft is a 722-kilogram space probe launched by NASA in 1977, to study the outer Solar System and eventually interstellar space. Operating for as of today , the spacecraft receives routine commands and transmits data back to the Deep Space Network. At a distance of as of...

, Voyager 2

Voyager 2

The Voyager 2 spacecraft is a 722-kilogram space probe launched by NASA on August 20, 1977 to study the outer Solar System and eventually interstellar space...

, Pioneer 10

Pioneer 10

Pioneer 10 is a 258-kilogram robotic space probe that completed the first interplanetary mission to Jupiter, and became the first spacecraft to achieve escape velocity from the Solar System. The project was managed by the NASA Ames Research Center and the contract for the construction of the...

, Pioneer 11

Pioneer 11

Pioneer 11 is a 259-kilogram robotic space probe launched by NASA on April 6, 1973 to study the asteroid belt, the environment around Jupiter and Saturn, solar wind, cosmic rays, and eventually the far reaches of the solar system and heliosphere...

 and New Horizons

New Horizons

New Horizons is a NASA robotic spacecraft mission currently en route to the dwarf planet Pluto. It is expected to be the first spacecraft to fly by and study Pluto and its moons, Charon, Nix, Hydra and S/2011 P 1. Its estimated arrival date at the Pluto-Charon system is July 14th, 2015...

, all launched by the United States.

See also:

• Timeline of planetary exploration.
• NASA Exploration Systems Mission Directorate