moons Archives

August 21, 2022August 21, 2022 by Matt Williams

Were Phobos and Deimos Once a Single Martian Moon That Split up? Not Likely, says New Study

A composite image of Mars and its two moons, Phobos (foreground) and Deimos (background). Credit: NASA/JPL/University of Arizona

The origin of Phobos and Deimos, the two Martian moons, has been a mystery to astronomers. These two bodies are a fraction of the size and mass of the Moon, measuring just 22.7 km (14 mi) and 12.6 km (7.83 mi) in diameter. Both have a rapid orbital period, taking just 7 hours, 39 minutes, and 12 seconds (Phobos) and 30 hours, 18 minutes, and 43 seconds (Deimos) to complete an orbit around Mars. Both are also irregular in shape, leading many to speculate that they were once asteroids that got kicked out of the Main Belt and were captured by Mars’ gravity.

There’s also the theory that Phobos and Deimos were once a single moon hit by a massive object, causing it to split up (aka. the “splitting hypothesis”). In a recent paper, an international team of scientists led by the Institute of Space and Astronautical Science (ISAS) revisited this hypothesis. They determined that a single moon in a synchronous orbit would not have produced two satellites as we see there today. Instead, they argue, the two moons would have collided before long, producing a debris ring that would have created an entirely new moon system.

August 18, 2022August 18, 2022 by Laurence Tognetti

What is the Maximum Number of Moons that Earth Could Have?

In a recent study published in Earth and Planetary Astrophysics, a team of researchers from the University of Texas at Arlington, Valdosta State University, Georgia Institute of Technology, and the National Radio Astronomy Observatory estimated how many moons could theoretically orbit the Earth while maintaining present conditions such as orbital stability. This study opens the potential for better understanding planetary formation processes which could also be applied to identifying exomoons possibly orbiting Earth-like exoplanets, as well.

May 11, 2022May 11, 2022 by Evan Gough

These are the Best Places to Search for Habitable Exomoons

An artist's conception of a potentially-habitable exomoon. It seems reasonable that exoplanets have exomoons, and now we're going to look for them. Credit: NASA

Our Solar System contains eight planets and more than 200 moons. The large majority of those moons have no chance of being habitable, but some of them—Europa and Enceladus, for example—are strong candidates in the search for life.

Is it the same in other solar systems?

April 20, 2022April 20, 2022 by Nancy Atkinson

Wow! Perseverance Sees a Solar Eclipse on Mars

Screenshot from a video recorded by the Perseverance rover of Phobos eclipsing the Sun, as seen from the surface of Mars. Credit: NASA/JPL.

Imagine standing on Mars, and seeing this with your own eyes.

February 8, 2022February 8, 2022 by Evan Gough

Massive Rocky Planets Probably Don’t Have big Moons

The Earth straddling the limb of the Moon, as seen from above Compton crater on the lunar farside, taken by the Lunar Reconnaissance Orbiter spacecraft. Credit: NASA/GSFC/Arizona State University.

The Moon has orbited Earth since the Solar System’s early days. Anyone who’s ever spent time at the ocean can’t fail to notice the Moon’s effect. The Moon drives the tides even in the world’s most remote inlets and bays. And tides may be vital to life’s emergence.

But if Earth were more massive, the Moon may never have become what it is now. Instead, it would be much smaller. Tides would be much weaker, and life may not have emerged the way it did.

January 20, 2022January 20, 2022 by Evan Gough

Even Tiny Mimas Seems to Have an Internal Ocean of Liquid Water

Mimas, as imaged by NASA's Cassini spacecraft and processed by @kevinmgill

Data from the Cassini mission keeps fuelling discoveries. The latest discovery is that Saturn’s tiny moon Mimas may have an internal ocean. If it does, the moon joins a growing list of natural satellites in our Solar System that may harbour liquid water under their surfaces.