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New Horizons - In January 2019, NASA's New Horizons spacecraft photographed a 32-km-long (20-mi-long) space rock located in the Kuiper belt—a collection of debris and dwarf planets. Nicknamed "Ultima Thule," this is currently the farthest object in the solar system visited by a spacecraft.

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New Horizons - The interplanetary space probe New Horizons, launched in 2006, reached Pluto in 2015.

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New Horizons - The remote dwarf planet was captured by New Horizons' Long Range Reconnaissance Imager during a flyby. It then continued towards the Kuiper belt.

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Messenger - Messenger was the first spacecraft to orbit Mercury, doing so between 2011 and 2015.

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Voyager 2 - A photograph of Uranus, taken by Voyager 2 in 1986 as it headed towards the planet Neptune.

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Voyager 2 - The Great Red Spot photographed during the Voyager 2 flyby of Jupiter.

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OSIRIS-REx - Launched in September 2016, OSIRIS-REx reached the proximity of the near-Earth asteroid 101955 Bennu in December 2018.

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OSIRIS-REx - Asteroid 101955 Bennu photographed by OSIRIS-REx from a range of 24 km (15 mi).

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Cassini - Sent in 1997 to study Saturn and its system, Cassini's trajectory allowed flybys of Venus, the Masursky asteroid, and Jupiter.

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Cassini - Titan, one of Jupiter's moons, reveals its true colors in this view from the Cassini spacecraft.

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Pioneer space probes - Pioneer 6, 7, 8, and 9 were a series of solar orbiting probes launched between 1965 and 1968. Designed to measure the first detailed measurements of solar wind, the solar magnetic field, and cosmic rays, two of the spacecraft were still contactable as late as 2000.

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Pioneer 10 - An artist's rendition of a Pioneer spacecraft on its way to interstellar space. The American space probe was launched in 1972 and completed the first mission to the planet Jupiter.

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Pioneer 10 - A Pioneer 10 image of Jupiter showing the characteristic Great Red Spot.

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Pioneer Venus project - Launched to Venus in 1978, the Pioneer Venus Orbiter and the Pioneer Venus multiprobe transmitted data until October 1992.

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Pioneer - Cloud structure in the Venusian atmosphere in 1979, revealed in ultraviolet observations by Pioneer Venus Orbiter.

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Mariner 4 - Launched in November 1964, Mariner 4 was designed to conduct planetary investigation in flyby mode.

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Mariner 4 - Mariner 4 sent back the first close-up images ever taken of Mars, a remarkable achievement at the time.

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Curiosity - The Mars rover Curiosity landed on the planet in August 2012, and is still operational. This image shows a self-portrait of the vehicle at the Big Sky site.

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Curiosity - The Mars rover Curiosity's stunning view of Mount Sharp, taken on the Martian surface in September 2015.

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Galileo - The Galileo probe entered Jupiter's hot spot in December 1995 and was able to function for nearly one hour before contact was lost. NASA scientists gained significant insight into the planet's atmosphere.

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Galileo - This image of Europa was produced from the Galileo images of the moon, one of dozens of moons orbiting the giant planet.

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International Cometary Explorer - The ISEE-3 International Cometary Explorer was the first spacecraft to visit a comet, Giacobini-Zinner, in 1985.

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Mariner 2 - Mariner 2 was the first space probe to conduct a successful planetary encounter by achieving a Venus flyby in December 1962.

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PDInSight - Successfully having landed on Mars in November 2018, InSight was designed to study the deep interior of the red planet.

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Interstellar space - Voyager 1 and Voyager 2, both launched in 1977, have now reached interstellar space. Voyager 1 is currently 18.8 billion km (11.7 billion mi) away from Earth, while Voyager 2 is 15.3 billion km (9.5 billion mi) away from Earth.

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Voyager Golden Record - Flying aboard Voyagers 1 and 2 are identical "golden" records, carrying the story of Earth towards the outermost border of our solar system.

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