In 1989, NASA’s Voyager 2 zipped past Neptune—its final planetary target before speeding to the outer limits of the solar system. It was the first time a spacecraft had visited the remote world. As the craft zoomed by, it snapped pictures of two giant storms brewing in Neptune’s southern hemisphere. Scientists dubbed the storms “The Great Dark Spot” and “Dark Spot 2.”
The outer region of the solar system may be the least explored, but scientists have managed to unravel several of its mysteries in recent weeks. On New Year’s Day, the NASA spacecraft New Horizons encountered the icy object Ultima Thule for the first time, shedding light on how it formed. Astronomers have also just discovered a previously unknown moon orbiting Neptune, which has been dubbed “Hippocamp”.
The study of the Solar System’s many moons has revealed a wealth of information over the past few decades. These include the moons of Jupiter – 69 of which have been identified and named – Saturn (which has 62) and Uranus (27). In all three cases, the satellites that orbit these gas giants have prograde, low-inclination orbits. However, within the Neptunian system, astronomers noted that the situation was quite different.
A NASA-led and NASA-sponsored study of potential future missions to the mysterious “ice giant” planets Uranus and Neptune has been released—the first in a series of mission studies NASA will conduct in support of the next Planetary Science Decadal Survey. The results of this and future studies will be used as the Decadal Survey deliberates on NASA’s planetary science priorities from 2022-2032. The study identifies the scientific questions an ice giant mission should address, and discusses various instruments, spacecraft, flight-paths and technologies that could be used.
The Solar System is filled with what are known as Trojan Asteroids – objects that share the orbit of a planet or larger moon. Whereas the best-known Trojans orbit with Jupiter (over 6000), there are also well-known Trojans orbiting within Saturn’s systems of moons, around Earth, Mars, Uranus, and even Neptune.
New images obtained on May 16, 2016, by NASA's Hubble Space Telescope confirm the presence of a dark vortex in the atmosphere of Neptune. Though similar features were seen during the Voyager 2 flyby of Neptune in 1989 and by the Hubble Space Telescope in 1994, this vortex is the first one observed on Neptune in the 21st century.