Collision likely factor in creation of tiny Neptunian moon
An illustration of Hippocamp orbiting Neptune. Image Credit: NASA/ESA/J. Olmsted (STScI)
A moon orbiting Neptune that was discovered using the Hubble Space Telescope in 2013 finally has an origin theory, according to NASA.
The small moon, which was named Hippocamp (Greek for seahorse) in February 2019, is some 20 miles (34 kilometers across) and orbits Neptune at a distance of about 65,000 miles (105,000 kilometers). However, it is only 7,500 miles (12,000 kilometers) from another moon, the 260-mile (420-kilometer) wide Proteus, which NASA said is unusually close.
A team of scientists have now come up with a hypothesis on how Hippocamp was formed. They published their analysis in the Feb. 21, 2019, issue of the journal Nature.
A photo taken by the Voyager 2 spacecraft of Proteus. An impact on this moon likely created Hippocamp. Photo Credit: NASA
“The first thing we realized was that you wouldn’t expect to find such a tiny moon right next to Neptune’s biggest inner moon,” said Mark Showalter of the SETI Institute in Mountain View, California, said in a NASA news release. “In the distant past, given the slow migration outward of the larger moon, Proteus was once where Hippocamp is now.”
According to NASA, it is thought that Hippocamp was a small piece of Proteus that was blasted off its surface by an asteroid impact around a billion years ago.
Images of Proteus taken by NASA’s Voyager 2 spacecraft in 1989, the year the spacecraft flew by Neptune, show an impact crater that may have resulted in the creation of the much-smaller Hippocamp. The impact likely nearly destroyed the larger moon.
According to NASA, Neptune has had a violent history with its celestial neighbors as its moon Triton was actually pulled from the Kuiper belt by the ice giant’s very powerful gravity. Triton also orbits in a retrograde orbit, meaning clockwise, while the rest of the moons orbit counterclockwise.
The Kuiper belt is an area of the Solar System beyond Neptune and is being studied by NASA’s New Horizons spacecraft, which officially photographed and studied for the first time in high-resolution detail Pluto and, more recently, the small object Ultima Thule.
“Based on estimates of comet populations, we know that other moons in the outer solar system have been hit by comets, smashed apart, and re-accreted multiple times,” Jack Lissauer of NASA’s Ames Research Center in California’s Silicon Valley, a coauthor on the new research, said in a news release. “This pair of satellites provides a dramatic illustration that moons are sometimes broken apart by comets.”
A diagram of Neptune’s inner moons, all of which (aside from Hippocamp) were discovered in 1989 during the Voyager 2 flyby. Image Credit: NASA/ESA/A.Feild (STScI)
Michael McCabe
A native of Lonedell, Missouri, Michael McCabe is a former Long Island firefighter and emergency medical technician. He is a non-active Florida EMT with 20 years of fire rescue experience. He is also a lifelong science fiction and space enthusiast. At the age of 10, he watched in his school classroom as the Space Shuttle Challenger exploded in 1986. In 2008, he moved to the Sunshine State and works as a private tour guide at Kennedy Space Center Visitor Complex for a private company based in Orlando. McCabe has been a fan of SpaceFlight Insider since our inception in 2013. He reached out to ask how he could assist our efforts to spread space flight awareness. Shortly thereafter, he was welcomed into our expanding team.
