Today, Oct. 23rd, most of the United States and Canada will be able to view the partial solar eclipse that will start at about 6pm EST. An eclipse, of course, is when an astronomical body is obscured, either by passing into the shadow of another body or having another body pass between it and the viewer . To mark the occasion I thought it would be interesting if we looked at some other moons in our solar system. So here are ten quick facts about all those moons that orbit the planets.
1. How many moons are there? Well, it’s hard to tell for sure. Moons are very small and hard to see and we’re still discovering new moons even to this day. Right now we know of 173 moons. This number is for the moons that orbit around actual planets in our solar system, not the satellites that orbit the dwarf planets. If we include the satellites that orbit these other dwarf planets, like Pluto and Haumea, then the number goes up to over 200 moons.
2. One-hundred and seventy-three moons is a big number, right? Where do most of these moons reside? Well, Jupiter has the most moons at 67 and Saturn is close behind that number with 62 moons. We’re even likely to find more moons the next time we send a probe past the asteroid belt again.
3. Almost all the planets in our solar system have moons. However, the larger gas giant planets have the most. Out of the eight planets orbiting our sun, six of them have moons. The gas giants all have moons in the double digits, Mars has two, and we have one. We simply call our moon “The Moon” but if you want to be fancy about it you can refer to it by its Latin name, Luna. Venus and Mercury don’t have any moons at all and if you were wondering about how many Pluto had, that would be five.
4. People think that moons are very small. Well, they are small…but not all of them. The sizes of the moons can vary greatly depending upon the size of the planet they orbit. The larger the planet, the larger the moon can be. That being said, the largest moon in our solar system is Ganymede, a moon of Jupiter. In second place is Titan, a moon of Saturn. Both of these moons are actually larger than the planet Mercury.
5. Our moon is actually the fifth largest moon in our solar system. When you compare it to the size of its primary (that would be Earth) it’s actually pretty big. When you think about it, Mars has two very small moons, Phobos and Deimos, while Venus and Mercury have no moons at all, and Pluto has one rather large moon (with four other tiny moons), which is Charon, that is no where near the size of our moon. So all things considered, Earth has quite a large moon for itself since all the other similarly sized moons orbit gas giants like Jupiter and Saturn.
6. Did you know that moons have volcanoes? Scientists know of five places in our solar system that have volcanoes: Earth, Venus, and three moons: Enceladus, Io and Triton. Out of all these, Io is the most volcanically active. So far, we’ve been able to detect over 150 active volcanoes on Io, a moon of Jupiter. Scientists estimate that it could have over 400 total.
7. Did you know that some volcanoes shoot out ice? These are called “cryovolcanoes” and its something not found on Earth. Cryovolcanoes were first seen on Triton, a moon of Saturn, and then later viewed on Enceladus. When these cryovolcanoes erupt they spit out a combination of volatiles such as water, methane, and ammonia.
9. Not all moons are round. The larger moons are round because gravity can shape them that way (that’s the short answer), but the smaller moons can sometimes take on weird shapes: Pan looks like a flying saucer from a 60’s Sci-Fi movie; the Martian moon Deimos looks like a smooth stone you’d skip across a lake; Methone of Saturn looks a lot like an egg.
10. Some moons could even have life on them. Scientists are speculating that the moons Europa and Titan could have suitable conditions to harbor simple forms of microbial life. There are even future plans to send probes to these moons to examine their surfaces for evidence of past primitive life or current microscopic lifeforms.
Remember, today is the partial solar eclipse. You can view the the solar eclipse with special eclipse glasses. NEVER look at the sun directly. These special eclipse glasses can be found in certain stores and locally at the Museum Store at LASM.