Week of Moons: Triton

Today we have a guest post by Laura Arnold about Neptune's moon Triton!

The largest moon of Neptune, and the 7th largest moon in the solar system, has a peculiar orbit. It orbits opposite the rotation of Neptune. Moons are theorized to form in the same way solar systems are, from a rotating flattened disk of gas and dust. And the fact that all of the planets orbit the Sun in the same direction as the sun rotates supports this theory. Scientists think that Triton's backward orbit indicates that it once orbited the Sun and was captured by Neptune when they came close to each other. In order for a massive body to enter into orbit around Neptune and not just whizz right by it would have to lose a lot orbital energy, or angular momentum. One theory states, that if Triton had a moon itself or was in a planetary binary system, Triton could be captured if the excess orbital energy had been carried off by its satellite which with all this energy would be ejected from orbit around Triton and Neptune

 

 Voyager 2 returned pictures of Triton in 1989, revealing an icy surface with very few impact craters. The surface of Triton smooth in some places and crinkled, like the skin of a cantaloupe, in other places. Because of the lack of cratering, it is thought that Triton's got a face-lift around 10-100 million years ago. This resurfacing could be done if ice in Triton's interior was heated due to tidal interactions with Neptune or heat from radioactive decay. This would provide for a liquid ocean under the icy surface of Triton, similar to Jupiter's moon Europa and Saturn's moon Enceladus. If pressure built up enough, ice volcanoes (cryovolcanism) could form spewing liquid, likely water mixed with ammonia and methane, onto Triton's dreadfully cold surface (colder than -382 F) which would then freeze. Voyager 2 saw two active geysers on Triton which spewed nitrogen gas as high as 8 km into the air. The energy powering these geysers is thought to come from sunlight, as these arose around the point on Triton which receives the most sunlight (though this is still about 1 thousandth of what Earth receives.)

 Image credit: NASA/JPL/USGS

Week of Moons: Did Man Really Land On The Moon?

Believe it or not, this  is a very controversial question: Did man really step foot on the moon? I'm sure many of you that were alive to  see Buzz Aldrin and Neil Armstrong set foot on the moon in 1969 would go "of course we did!" But there are still a lot of skeptics out their that think this was all a big hoax. Well I wasn't around back then to see it, but I really think we did land on the moon! Here's some proof....

One way to prove that we landed on the moon is to take a picture of the landing site. Above is an image taken by the Lunar Reconnaissance Orbiter, a satellite that's orbiting the moon and taking pictures, of the Apollo 11 landing site and astronaut foot prints. It sure looks like we landed and walked there! The Astronauts also left a reflector on the moon, much like one that you have on your bicycle. With a very high powered laser you can actually bounce the laser beam off this reflector, and trust me astronomers have tried this out and succeeded. I mean seriously, who would pass up the  opportunity to play with a high powered laser? (See episode 63 of The Big Bang Theory. Point proven.) The reflectors are also used to accurately measure the distance between Earth and the moon and do tests of Einstein's theory of general relativity.

Now you may ask why haven't we gone  back? And my short answer to that is money and ethics. Sure it's cool to send astronauts into space, but If we can do better science with cheaper robotic equipment and don't have to put lives in danger, then why would we send man to the moon again? Don't get me wrong, I'm very much for manned space missions, but in our society we tend to do things the cheapest and safest way we can. And that means, sadly, no more manned missions to the moon.

Want to see more proof that the moon landing was real? Check out Mythbusters episode #104

Image credit: NASA/LRO

Week of Moons: Moon Facts

Today I thought I'd give some interesting facts about our beloved moon.

 

The moon...

• Spins at a rate of ~10mph
• orbits earth in about 27.3 days
• Is not made of cheese (as apparently 13% of the population still believed in a survey conducted in 1988). It's actually made of heavy metals, mostly iron and silica. The surface is covered in a dusty glass like material called silicon dioxide.
• Has a core which is partially molten.
• Surface consists of dust that smells like burnt gunpowder
• Is tidally locked to Earth which means the same side of the moon is always facing Earth viewers
• Is covered in craters because it has no atmosphere to destroy objects before they crash into the surface
• Is about 1/4 the size of earth and has a surface area of about 9.4 billion acres
• Is the only other astronomical body that humans have set foot on.
• Has small amounts of water ice near its surface
• Causes tides here on Earth

Image Credit: Luc Viatour  www.lucnix.be

Week of Moons: An Overview

This coming weekend I'm helping with a moon activity for ASRAS' Young Astronomers Program, so I thought I'd talk a bit about moons in our solar system this week.

We've all looked up at night and seen our big, bright, shiny moon glaring back at us. The moon actually doesn't shine at all. It only looks bright because it's reflecting light from the Sun! Earth is not the only planet with a moon. Most of the  other planets in our solar system have moons, and some even have multiple moons! A moon (or natural satellite as astronomers often call the moons of other planets) is loosely defined as an object that is  gravitationally bound to and orbiting a planet. Below is a list of each planet and the number of moons it has.

Mercury: 0

Venus: 0

Earth: 1

Mars: 2

Jupiter: 63

Saturn: 47

Uranus: 27

Neptune: 13

Moons come in all shapes and sizes, and most don't look anything like our moon! They don't have to be round white objects made of sand and rock. Some moons are made of metal while others some sort of liquid. Jupiter's moon Io even has erupting volcanoes on it! The picture below shows some of the more popular and well known moons in our solar system to scale so you can see how other planets moons size up to ours!

(Phobos, Dactyl and Deimos are there, they are just very tiny in comparison!)

Image credit: NASA