NASA Scientists have announced that Jupiter, the largest planet in our solar system, has ninety-two moons, thanks to the discovery of a dozen new ones.

Ancient astronomers, like the Mayans and the Chaldeans, knew of Jupiter with naked-eye astronomy. It was not until 1610 that Terran astronomers learned that Jupiter had moons. In 1610, both Italian astronomer Galileo Galilei and German astronomer Simon Marius independently discovered Ganymede, Jupiter’s largest satellite. Galileo discovered three other of Jupiter’s moons the same year. Ganymede is larger than Mercury, with a diameter of a diameter of about 5,270 km (3,275 miles). Robert A. Heinlein and other science fiction writers predicted Ganymede and the other Jovian moons would someday be used for human colonization.

Jupiter has, of course had ninety-two moons for aeons. It did not just suddenly pop out a dozen new ones. Human technology has improved enough that scientists have discovered moons they had not previously been able to observe. Twelve previously unobserved moons have been discovered, bringing Jupiter up to a grand total of ninety-two confirmed moons.

Dr. Scott Sheppard of the Carnegie Institute of Science said, “the Jupiter moons were added recently to a list kept by the International Astronomical Union’s Minor Planet Center.” Jupiter’s newly discovered moons have yet to be named. Dr. Sheppard said only half of them are big enough — at least 1 mile or so — to warrant a name. These newly discovered moons range in size from 0.6 miles to 2 miles (1 kilometer to 3 kilometers).

Of Jupiter’s nearly one hundred moons, only twenty-two are named. The four largest are Ganymede, Callisto, Io, and Europa. Five of the twelve “new” moons have been named.

  • Pandia (was S/2017 J4)
  • Ersa (was S/2018 J1)
  • Eirene (was S/2003 J5)
  • Philophrosyne (was S/2003 J15)
  • Eupheme (was S/2003 J3)

Dr Sheppard said more moons were probably waiting to be found around Saturn, but that astronomers would need larger telescopes – such as those set to come online in coming decades — to discover these smaller satellites of around 1km in size.

Moons – Which Planets Have Them, and How Many?

Ganymede, Jupiter’s largest moon

Here is the list of which planets have how many moons (that we know about so far):

  • Mercury: no moons
  • Venus: no moons
  • Earth: one moon (technically two, if you count its trojan moon Cruithne, a three mile wide chunk of rock that takes 770 years to complete one orbit).
  • Mars: two moons, Deimos and Phobos
  • Jupiter: 92
  • Saturn: 83 moons
  • Uranus: 27 moons
  • Neptune: 14 moons
  • Pluto: 5 moons, Caron, Styx, Nix, Kerberos, and Hydra

Dr. Sheppard explained “Jupiter and Saturn are loaded with small moons, believed to be fragments of once bigger moons that collided with one another or with comets or asteroids.”

In April, the European Space Agency (ESA) is sending a spacecraft to Jupiter to study the planet and some of its biggest, icy moons. In 2024, NASA will launch the Europa Clipper to explore the Jovian moon Europa. Scientists suspect Europa may hide an ocean beneath its frozen surface. If so, that would be a boon to future colonists.

Who is Dr. Sheppard?

Dr. Scott Sheppard {image via the Carnegie Institute of Science

Dr. Scott Sheppard is an American astronomer who studies  “studies the dynamical and physical properties of small bodies, such as asteroids, comets, moons, trans-neptunian objects (bodies that orbit beyond Neptune), and free floating substellar objects. These small bodies in our Solar System have a fossilized imprint from the formation and migration of the major planets in our Solar System.”

The universe is a wondrous place and the more we study it the more we learn. Stick with SciFi.Radio for more updates as science catches up with science fiction.


Susan Macdonald
Susan Macdonald

Susan Macdonald is the author of the children’s book “R is for Renaissance Faire”, as well as 26 short stories, mostly fantasy in “Alternative Truths”, “Swords and Sorceress ”, Swords &Sorceries Vols. 1, 2, & 5, “Cat Tails” “Under Western Stars”, and “Knee-High Drummond and the Durango Kid”. Her articles have appeared on’s web site, in The Inquisitr, and in The Millington Star. She enjoys Renaissance Faires (see book above), science fiction conventions,  Highland Games, and Native American pow-wows.