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After the Voyager flyby, NASA's next step in scientific exploration of the Neptune system was considered to be a flagship orbiter mission. [11] Such a hypothetical mission was envisioned to be possible in the late 2020s or early 2030s. [11] Another concept mission proposed for the 2040s is called the Neptune-Triton Explorer (NTE). [12]
Planetary habitability in the Solar System is the study that searches the possible existence of past or present extraterrestrial life in those celestial bodies. As exoplanets are too far away and can only be studied by indirect means, the celestial bodies in the Solar System allow for a much more detailed study: direct telescope observation, space probes, rovers and even human spaceflight.
Neptune's mass of 1.0243 × 10 26 kg [8] is intermediate between Earth and the larger gas giants: it is 17 times that of Earth but just 1/19th that of Jupiter. [g] Its gravity at 1 bar is 11.15 m/s 2, 1.14 times the surface gravity of Earth, [71] and surpassed only by Jupiter. [72] Neptune's equatorial radius of 24,764 km [11] is nearly four ...
Therefore, the first observations of Neptune were only possible after the invention of the telescope. There is evidence that Neptune was seen and recorded by Galileo Galilei in 1613, Jérôme Lalande in 1795, and John Herschel in 1830, but none are known to have recognized it as a planet at the time. [ 6 ]
Four years ago, astronomers noticed the abundant clouds on Neptune had largely disappeared. Telescope data may have helped researchers figure out why. Neptune’s clouds have disappeared, and ...
The discovery of exoplanets, beginning in the early 1990s [8] [9] and accelerating thereafter, has provided further information for the study of possible extraterrestrial life. These findings confirm that the Sun is not unique among stars in hosting planets and expands the habitability research horizon beyond the Solar System.
The following list includes some of the potentially habitable exoplanets discovered so far. It is mostly based on estimates of habitability by the Habitable Worlds Catalog (HWC), and data from the NASA Exoplanet Archive.
Voyager 2 is the only space probe to have visited the Neptune system, completing a flyby on August 25, 1989. An orbiter to Neptune was considered as part of the aborted Mariner Mark II program in the 1990s, and several mission concepts for an orbiter were developed in the 2000s, including a concept by the California Institute of Technology [4] and a version by the University of Idaho and ...