A colour photograph of Uranus, taken by Voyager 2 in 1986 as it headed towards the planet Neptune
The exploration of Uranus has, to date, been through telescopes and a lone probe by NASA's Voyager 2 spacecraft, which made its closest approach to Uranus on January 24, 1986. Voyager 2 discovered 10 moons, studied the planet's cold atmosphere, and examined its ring system, discovering two new rings. It also imaged Uranus' five large moons, revealing that their surfaces are covered with impact craters and canyons.
Voyager 2 made its closest approach to Uranus on January 24, 1986, coming within 81,500km (50,600 miles) of the planet's cloud tops. This was the probe's first solo planetary flyby, since Voyager 1 ended its tour of the outer planets at Saturn's moon Titan.
Uranus is the third-largest and fourth most massive planet in the Solar System. It orbits the Sun at a distance of about 2.8billion kilometers (1.7billion miles) and completes one orbit every 84 years. The length of a day on Uranus as measured by Voyager 2 is 17 hours and 14 minutes. Uranus is distinguished by the fact that it is tipped on its side. Its unusual position is thought to be the result of a collision with a planet-sized body early in the Solar System's history. Given its odd orientation, with its polar regions exposed to sunlight or darkness for long periods and Voyager 2 set to arrive around the time of Uranus's solstice, scientists were not sure what to expect at Uranus.
The presence of a magnetic field at Uranus was not known until Voyager 2's arrival. The intensity of the field is roughly comparable to that of Earth's, though it varies much more from point to point because of its large offset from the center of Uranus. The peculiar orientation of the magnetic field suggests that the field is generated at an intermediate depth in the interior where the pressure is high enough for water to become electrically conductive. Voyager 2 found that one of the most striking influences of the sideways position of the planet is its effect on the tail of the magnetic field, which is itself tilted 60 degrees from the planet's axis of rotation. The magnetotail was shown to be twisted by the planet's rotation into a long corkscrew shape behind the planet.
Radiation belts at Uranus were found to be of an intensity similar to those at Saturn. The intensity of radiation within the belts is such that irradiation would quickly darken (within 100,000 years) any methane trapped in the icy surfaces of the inner moons and ring particles. This may have contributed to the darkened surfaces of the moons and ring particles, which are almost uniformly gray in color.
A Voyager 2 image of the Uranian dark rings
A high layer of haze was detected around the sunlit pole, which also was found to radiate large amounts of ultraviolet light, a phenomenon dubbed "electroglow". The average temperature of the atmosphere of the planet is about 59K (−214.2°C). Surprisingly, the illuminated and dark poles, and most of the planet, show nearly the same temperature at the cloud tops.
Voyager 2 found 10 new moons, bringing the total number to 15 at the time. Most of the new moons are small, with the largest measuring about 150km (93mi) in diameter.
The moon Miranda, innermost of the five large moons, was revealed to be one of the strangest bodies yet seen in the Solar System. Detailed images from Voyager 2's flyby of the moon showed huge oval structures termed coronae flanked by faults as deep as 20km (12mi), terraced layers, and a mixture of old and young surfaces. One theory holds that Miranda may be a reaggregation of material from an earlier time when the moon was fractured by a violent impact.
The five large moons appear to be ice–rock conglomerates like the satellites of Saturn. Titania is marked by huge fault systems and canyons indicating some degree of geologic, probably tectonic, activity in its history. Ariel has the brightest and possibly youngest surface of all the Uranian moons and also appears to have undergone geologic activity that led to many fault valleys and what seem to be extensive flows of icy material. Little geologic activity has occurred on Umbriel or Oberon, judging by their old and dark surfaces.
All nine previously known rings were studied by the spacecraft and showed the Uranian rings to be distinctly different from those at Jupiter and Saturn. The ring system may be relatively young and did not form at the same time as Uranus. Particles that make up the rings may be remnants of a moon that was broken by a high-velocity impact or torn up by gravitational effects. Voyager 2 also discovered two new rings.
In March 2020, after reevaluating old data recorded by Voyager 2, NASA astronomers reported the detection of a large magnetic bubble known as a plasmoid, which may be leaking Uranus's atmosphere into space.[5][6]
A number of missions to Uranus have been proposed. Scientists from the Mullard Space Science Laboratory in the United Kingdom have proposed the joint NASA–ESAUranus Pathfinder mission to Uranus. A call for a medium-class (M-class) mission to the planet to be launched in 2022 was submitted to the ESA in December 2010 with the signatures of 120 scientists from across the globe. The ESA caps the cost of M-class missions at €470 million.[7][3][8]
In 2009, a team of planetary scientists from NASA's Jet Propulsion Laboratory advanced possible designs for a solar-powered Uranus orbiter. The most favorable launch window for such a probe would have been in August 2018, with arrival at Uranus in September 2030. The science package would have included magnetometers, particle detectors and, possibly, an imaging camera.[9]
In 2010, scientists at the Applied Physics Laboratory proposed the Herschel Orbital Reconnaissance of the Uranian System probe, heavily influenced by the New Horizons probe, and set for launch in April 2021.[10][11]
A mission to Uranus is one of several proposed uses under consideration for the unmanned variant of NASA's heavy-lift Space Launch System (SLS) currently in development. The SLS would reportedly be capable of launching up to 1.7 metric tons to Uranus.[14]
In 2013, it was proposed to use an electric sail (E-Sail) to send an atmospheric entry probe to Uranus.[15]
In 2015, NASA announced it had begun a feasibility study into the possibility of orbital missions to Uranus and Neptune, within a budget of $2 billion in 2015 dollars. According to NASA's planetary science director Jim Green, who initiated the study, such missions would launch in the late 2020s at the earliest, and would be contingent upon their endorsement by the planetary science community, as well as NASA's ability to provide nuclear power sources for the spacecraft.[16] Conceptual designs for such a mission are currently[when?] being analyzed.[17]
MUSE, conceived in 2012 and proposed in 2015, is a European concept for a dedicated mission to the planet Uranus to study its atmosphere, interior, moons, rings, and magnetosphere.[18] It is suggested to be launched with an Ariane 5 rocket in 2026, arriving at Uranus in 2044, and operating until 2050.[18]
In 2016, another mission concept was conceived, called Origins and Composition of the Exoplanet Analog Uranus System (OCEANUS), and it was presented in 2017 as a potential contestant for a future New Frontiers program mission.[19] Students at Purdue University released their Flagship-class version of OCEANUS around that time; it featured more than twice as many instruments in a more compact design with a larger high-gain antenna, as well as two atmospheric probes for Saturn and Uranus rather than the previous concept's sole Uranian one.[20]
Another mission concept of a New Frontiers class mission was presented in 2020. It is called QUEST (Quest to Uranus to Explore Solar System Theories) and as its authors claim is more realistic than previous such proposals. It envisions launch in 2032 with Jupiter gravity assist in 2036 and arrival to Uranus in 2045. The spacecraft then enters an elliptical polar orbit around the planet with a periapsis of about 1.1 of the Uranus' radius. The spacecraft's dry mass is 1210 kg and it carries four scientific instruments: magnetometer, microwave radiometer, wide angle camera and plasma wave detector.[21]
In October 2021, a team of mostly JPL and Ames Research Center staffers suggested another New Frontiers class mission be undertaken preferably in the late 2040s, called the Uranian Magnetosphere and Moons Investigator.[22]
In response, in July 2023, a team of scientists at Johns Hopkins University proposed a Uranus orbiter called Plasma Environment, Radiation, Structure, and Evolution of the Uranian System (PERSEUS), focusing mostly on the plasma, magnetic, and heliophysics environment of Uranus. Launch is envisioned for February 2031, and arrival set for mid-2043, with the dry mass estimated at 913.1 kg.[24]
Future launch windows are available between 2030 and 2034.[25]
China plans to send its first exploration mission to Uranus in 2045 as part of Tianwen-4.[26][27][28]
Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is currently carried out mainly by astronomers with telescopes, its physical exploration is conducted both by uncrewed robotic space probes and human spaceflight. Space exploration, like its classical form astronomy, is one of the main sources for space science.
Voyager 2 is a space probe launched by NASA on August 20, 1977, as a part of the Voyager program. It was launched on a trajectory toward the gas giants Jupiter and Saturn and enabled further encounters with the ice giants Uranus and Neptune. It remains the only spacecraft to have visited either of the ice giant planets, and was the third of five spacecraft to achieve Solar escape velocity, which will allow it to leave the Solar System. It has been sending scientific data to Earth for 46 years, 8 months, 15 days, making it the oldest active space probe. Launched 16 days before its twin Voyager 1, the primary mission of the spacecraft was to study the outer planets and its extended mission is to study interstellar space beyond the Sun's heliosphere.
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine-and-a-half times that of Earth. It has only one-eighth the average density of Earth, but is over 95 times more massive. Even though Saturn is nearly the size of Jupiter, Saturn has less than one-third of Jupiter's mass. Saturn orbits the Sun at a distance of 9.59 AU (1,434 million km) with an orbital period of 29.45 years.
Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a supercritical phase of matter, which in astronomy is called 'ice' or volatiles. The planet's atmosphere has a complex layered cloud structure and has the lowest minimum temperature of 49 K out of all the Solar System's planets. It has a marked axial tilt of 82.23° with a retrograde rotation period of 17 hours and 14 minutes. This means that in an 84-Earth-year orbital period around the Sun, its poles get around 42 years of continuous sunlight, followed by 42 years of continuous darkness.
The Voyager program is an American scientific program that employs two interstellar probes, Voyager 1 and Voyager 2. They were launched in 1977 to take advantage of a favorable alignment of the two gas giants Jupiter and Saturn and the ice giants, Uranus and Neptune, to fly near them while collecting data for transmission back to Earth. After launch, the decision was made to send Voyager 2 near Uranus and Neptune to collect data for transmission back to Earth.
A gravity assist, gravity assist maneuver, swing-by, or generally a gravitational slingshot in orbital mechanics, is a type of spaceflight flyby which makes use of the relative movement and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft, typically to save propellant and reduce expense.
Titania, also designated Uranus III, is the largest of the moons of Uranus. At a diameter of 1,578 kilometres (981 mi) it is the eighth largest moon in the Solar System, with a surface area comparable to that of Australia. Discovered by William Herschel in 1787, it is named after the queen of the fairies in Shakespeare's A Midsummer Night's Dream. Its orbit lies inside Uranus's magnetosphere.
The Grand Tour is a NASA program that would have sent two groups of robotic probes to all the planets of the outer Solar System. It called for four spacecraft, two of which would visit Jupiter, Saturn, and Pluto, while the other two would visit Jupiter, Uranus, and Neptune. The enormous cost of the project, around $1billion, led to its cancellation and replacement with Mariner Jupiter-Saturn, which became the Voyager program.
The exploration of Jupiter has been conducted via close observations by automated spacecraft. It began with the arrival of Pioneer 10 into the Jovian system in 1973, and, as of 2023, has continued with eight further spacecraft missions in the vicinity of Jupiter. All of these missions were undertaken by the National Aeronautics and Space Administration (NASA), and all but two were flybys taking detailed observations without landing or entering orbit. These probes make Jupiter the most visited of the Solar System's outer planets as all missions to the outer Solar System have used Jupiter flybys. On 5 July 2016, spacecraft Juno arrived and entered the planet's orbit—the second craft ever to do so. Sending a craft to Jupiter is difficult, mostly due to large fuel requirements and the effects of the planet's harsh radiation environment.
The exploration of Saturn has been solely performed by crewless probes. Three missions were flybys, which formed an extended foundation of knowledge about the system. The Cassini–Huygens spacecraft, launched in 1997, was in orbit from 2004 to 2017.
Neptune has been directly explored by one space probe, Voyager 2, in 1989. As of 2024, there are no confirmed future missions to visit the Neptunian system, although a tentative Chinese mission has been planned for launch in 2024. NASA, ESA, and independent academic groups have proposed future scientific missions to visit Neptune. Some mission plans are still active, while others have been abandoned or put on hold.
Neptune is the eighth and farthest known planet from the Sun. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, and slightly more massive than fellow ice giant Uranus. Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. Being composed primarily of gases and liquids, it has no well-defined solid surface. The planet orbits the Sun once every 164.8 years at an orbital distance of 30.1 astronomical units. It is named after the Roman god of the sea and has the astronomical symbol , representing Neptune's trident.
The Uranus Orbiter and Probe is an orbiter mission concept to study Uranus and its moons. The orbiter would also deploy an atmospheric probe to characterize Uranus's atmosphere. The concept is being developed as a potential large strategic science mission for NASA. The science phase would last 4.5 years and include multiple flybys of each of the major moons.
A subsatellite, also known as a submoon or a moonmoon, is a "moon of a moon" or a hypothetical natural satellite that orbits the moon of a planet.
The following outline is provided as an overview of and topical guide to the Solar System:
Argo was a 2009 spacecraft mission concept by NASA to the outer planets and beyond. The concept included flybys of Jupiter, Saturn, Neptune, and a Kuiper belt object. A focus on Neptune and its largest moon Triton would have helped answer some of the questions generated by Voyager 2's flyby in 1989, and would have provided clues to ice giant formation and evolution.
The following outline is provided as an overview of and topical guide to Uranus:
OCEANUS is a mission concept conceived in 2016 and presented in 2017 as a potential future contestant as a New Frontiers program mission to the planet Uranus. The concept was developed by the Astronautical engineering students of Purdue University during the 2017 NASA/JPL Planetary Science Summer School. OCEANUS is an orbiter, which would enable a detailed study of the structure of the planet's magnetosphere and interior structure that would not be possible with a flyby mission.
Neptune Odyssey is an orbiter mission concept to study Neptune and its moons, particularly Triton. The orbiter would enter into a retrograde orbit of Neptune to facilitate simultaneous study of Triton and would launch an atmospheric probe to characterize Neptune's atmosphere. The concept is being developed as a potential large strategic science mission for NASA by a team led by the Applied Physics Laboratory at Johns Hopkins University. The current proposal targets a launch in 2033 using the Space Launch System with arrival at Neptune in 2049, although trajectories using gravity assists at Jupiter have also been considered with launch dates in 2031.
↑ New Frontiers-Class Missions to the Ice Giants. C. M. Elder, A. M. Bramson, L. W. Blum, H. T. Chilton, A. Chopra, C. Chu6, A. Das, A. Davis, A. Delgado, J. Fulton, L. Jozwiak, A. Khayat, M. E. Landis, J. L. Molaro, M. Slipski, S. Valencia11, J. Watkins, C. L. Young, C. J. Budney, K. L. Mitchell. Planetary Science Vision 2050 Workshop 2017 (LPI Contrib. No. 1989).
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
