Back Again! And a look at Phoebe!

Cassini image of Phoebe in 2004. Image credit: NASA, JPL, VIMS Team, ISS Team, U. Arizona

Cassini image of Phoebe in 2004. Image credit: NASA, JPL, VIMS Team, ISS Team, U. Arizona

Hello, Earthlings! Wow, have I got some fun stuff in store for you in 2019! Apologies for the lateness in the posts, my spaceship kept breaking down near Jupiter’s magnetic field. Always seems to be Jupiter…hmm…

Anyways, let’s start the week off with a fun look at Phoebe, a tiny moon of Saturn with some mysterious water signatures!

Phoebe was discovered in 1898, but studied up-close by Cassini in 2004, one of the few tiny, irregular moons to have a wonderful close-up!

Phoebe orbits Saturn at a distance of 12,952,000 kilometers, which is almost four times the distance from Saturn than its nearest neighbor, the moon Iapetus.

Phoebe is roughly spherical and has a radius of about 106.5 kilometers, about one-sixteenth the radius of Earth's Moon. Phoebe rotates on its axis every nine hours, and it completes a full orbit around Saturn in about 18 Earth months. Phoebe's orbit is also retrograde, which means it goes around Saturn in the opposite direction than most other moons!

Unlike most major moons orbiting Saturn, Phoebe is very dark and reflects only 6% of the sunlight it receives. Its darkness and irregular, retrograde orbit suggest Phoebe is most likely a captured object. Phoebe's darkness, in particular, suggests that the small moon comes from the outer solar system, an area where there is plenty of dark material.

A recent discovery in December 2018 by the Planetary Science Institute reported that Saturn’s rings have the same water signatures as Earth’s water, except for Phoebe! Phoebe apparently shows a different isotopic ratio of the oxygen and hydrogen associated with water, making this hypothesis that Phoebe is a captured object true!

But it gets weirder…where did it come from? It may be from the Kuiper Belt arena of the Solar System, making the capture history of this tiny moon of Saturn intriguing!

Close-up of the dark-streaked craters of Phoebe as imaged by Cassini. Image Credit: NASA, JPL, VIMS Team, ISS Team, U. Arizona

Close-up of the dark-streaked craters of Phoebe as imaged by Cassini. Image Credit: NASA, JPL, VIMS Team, ISS Team, U. Arizona

Thank you for reading and come back next week for a fantastic look at the new Mars 2020 landing site!

Caitlin Ahrens