Exploration of Neptune
Encyclopedia
The exploration of Neptune
has only begun with one explorer, Voyager 2
, which visited on August 25, 1989. The possibility of a Neptune Orbiter
was discussed, yet other than that, no other missions have been given serious thought. As Neptune
is a gas giant
and has no solid surface, a surface mission such as a lander
or rover
is impossible.
. Voyager 2 studied Neptune's atmosphere, Neptune's rings, its magnetosphere
, and Neptune's moons. Several discoveries were made, including the discovery of the Great Dark Spot
and Triton
's geysers.
Voyager 2 revealed that Neptune's atmosphere was very dynamic, even though it receives only 3% of the sunlight Jupiter
receives. Voyager 2 discovered an anticyclone
called the Great Dark Spot
, similar to Jupiter's Great Red Spot and Little Red Spot. However, images taken by the Hubble Space Telescope
revealed that the Great Dark Spot had disappeared. Also seen in Neptune's atmosphere at that time was an almond
-shaped spot designated D2, and a bright, quickly moving cloud high above the cloud decks dubbed "Scooter".
Voyager 2 found four rings and evidence for ring arcs, or incomplete rings above Neptune. Neptune's magnetosphere was also studied by Voyager 2. The planetary radio astronomy instrument found that Neptune's day lasts sixteen hours, seven minutes. Voyager 2 also discovered auroras, like on Earth
, but much more complex.
Voyager 2 discovered six moons orbiting Neptune, but only three were photographed in detail: Proteus
, Nereid
, and Triton
. Proteus turned out to be an ellipsoid, as large as an ellipsoid could become without rounding in a sphere
. Proteus is very dark in color, almost like soot
.
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Nereid, though discovered in 1949, still has very little known about it. Triton was flown by at about 25,000 miles away, and became the last solid world Voyager 2 would explore within the Solar System. Triton was revealed to have remarkable active geysers and polar caps. A very thin atmosphere was found, as well as thin clouds.
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has researched several mission possibilities for Cassini–Huygens-like missions to this planet, but budgetary and other constraints have so far yet to yield any success.
It is known that any future mission will have RTGs
and similar instrumentation to Voyager craft, but with more cameras and storage capacity; and will need better error correction than Voyager.
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
has only begun with one explorer, 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...
, which visited on August 25, 1989. The possibility of a Neptune Orbiter
Neptune Orbiter
Neptune Orbiter was a proposed NASA unmanned planetary spacecraft to explore the planet Neptune. It was envisioned that it would be launched sometime around 2016 and take 8 to 12 years to reach the planet; however, no longer lists any possible launch date. The Neptune Orbiter was designed to...
was discussed, yet other than that, no other missions have been given serious thought. As Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
is a gas giant
Gas giant
A gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune...
and has no solid surface, a surface mission such as a lander
Lander (spacecraft)
A lander is a spacecraft which descends toward and comes to rest on the surface of an astronomical body. For bodies with atmospheres, the landing is called atmospheric reentry and the lander descends as a re-entry vehicle...
or rover
Rover (space exploration)
A rover is a space exploration vehicle designed to move across the surface of a planet or other astronomical body. Some rovers have been designed to transport members of a human spaceflight crew; others have been partially or fully autonomous robots...
is impossible.
Voyager 2
In Voyager 2's last planetary encounter, the spacecraft swooped only 3,000 miles above Neptune's north pole, the closest approach it made to any body since it left EarthEarth
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...
. Voyager 2 studied Neptune's atmosphere, Neptune's rings, its magnetosphere
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...
, and Neptune's moons. Several discoveries were made, including the discovery of the Great Dark Spot
Great Dark Spot
The Great Dark Spot is the name given to a series of dark spots on Neptune similar in appearance to Jupiter's Great Red Spot. The first one was observed in 1989 by NASA's Voyager 2 probe. Like Jupiter's spot, they are anticyclonic storms...
and Triton
Triton (moon)
Triton is the largest moon of the planet Neptune, discovered on October 10, 1846, by English astronomer William Lassell. It is the only large moon in the Solar System with a retrograde orbit, which is an orbit in the opposite direction to its planet's rotation. At 2,700 km in diameter, it is...
's geysers.
Voyager 2 revealed that Neptune's atmosphere was very dynamic, even though it receives only 3% of the sunlight Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
receives. Voyager 2 discovered an anticyclone
Anticyclone
An anticyclone is a weather phenomenon defined by the United States' National Weather Service's glossary as "[a] large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere"...
called the Great Dark Spot
Great Dark Spot
The Great Dark Spot is the name given to a series of dark spots on Neptune similar in appearance to Jupiter's Great Red Spot. The first one was observed in 1989 by NASA's Voyager 2 probe. Like Jupiter's spot, they are anticyclonic storms...
, similar to Jupiter's Great Red Spot and Little Red Spot. However, images taken by the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
revealed that the Great Dark Spot had disappeared. Also seen in Neptune's atmosphere at that time was an almond
Almond
The almond , is a species of tree native to the Middle East and South Asia. Almond is also the name of the edible and widely cultivated seed of this tree...
-shaped spot designated D2, and a bright, quickly moving cloud high above the cloud decks dubbed "Scooter".
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...
, but much more complex.
Voyager 2 discovered six moons orbiting Neptune, but only three were photographed in detail: Proteus
Proteus (moon)
Proteus , also known as Neptune VIII, is the second largest Neptunian moon, and Neptune's largest inner satellite. Discovered by Voyager 2 spacecraft in 1989, it is named after Proteus, the shape-changing sea god of Greek mythology...
, Nereid
Nereid (moon)
Nereid , also known as Neptune II, is the third-largest moon of Neptune. It has a highly eccentric orbit. Nereid was discovered by Gerard Kuiper in 1949 and was the second moon of Neptune to be discovered.- Discovery and naming :...
, and Triton
Triton (moon)
Triton is the largest moon of the planet Neptune, discovered on October 10, 1846, by English astronomer William Lassell. It is the only large moon in the Solar System with a retrograde orbit, which is an orbit in the opposite direction to its planet's rotation. At 2,700 km in diameter, it is...
. Proteus turned out to be an ellipsoid, as large as an ellipsoid could become without rounding in a sphere
Sphere
A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...
. Proteus is very dark in color, almost like soot
Soot
Soot is a general term that refers to impure carbon particles resulting from the incomplete combustion of a hydrocarbon. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolyzed fuel particles such as cenospheres,...
.
Planned future missions
NASANASA
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...
has researched several mission possibilities for Cassini–Huygens-like missions to this planet, but budgetary and other constraints have so far yet to yield any success.
It is known that any future mission will have RTGs
Radioisotope thermoelectric generator
A radioisotope thermoelectric generator is an electrical generator that obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect using an array of thermocouples.RTGs can be...
and similar instrumentation to Voyager craft, but with more cameras and storage capacity; and will need better error correction than Voyager.