Planet Mercury's Most Important Noticeable Features


I'm Eric Loberg, director of the Taylor Planetarium here at the Museum of the Rockies. I'm going to discuss observational interests of Mercury. It's touch to observe Mercury first of all if we're going to look at it observationally, Mercury is hard to find. Mercury never gets more than 28 degrees from the sun. Which means it's not very far from the sun, it's not very far off from your horizon. If you hold one hand out in a kind of a Y, the other hand is a fist, you can put those together. Mercury never gets that much farther off your horizon. And so a lot of people just never see Mercury. If you're near a mountain if you're in a city and you have lots of city lights on your horizon, Mercury can never get higher than that 28 degrees. Either off your evening horizon or your morning horizon. And so Mercury can be difficult to find first of all. That makes it very difficult for those big telescopes to find as well. Those big telescopes like Hubble have a hard time shooting a Mercury because it never gets very far from the sun, it goes around the sun once every 88 days so about half that about 45 you'll get it in your evening sky, over here and then you'll have it in your morning sky over here and Mercury will make phases. If you have a small telescope you can look out at both Mercury and Venus and you'll see it makes phases as it goes around the sun and that's because of how we see it here on Earth. We're Earth, farther away, that sunlight is going to bounce off parts of Mercury so highlighting the whole half of Mercury in space but that orbit depending on where it's at, we'll see different portions of it lit up farther behind Mercury would be just about full. So if we really want to see Mercury we're going to have to go our to Mercury with our spacecraft. Mariner 10 went out to Mercury in 1976 and shot some images of it. We only saw about half of Mercury lit up at that time. And that's all we learned for a long time. We've only been to Mercury two times. Once with Mariner 10 and more recently with the Messenger spacecraft. The Messenger spacecraft was launched in 2008 and arrived in 2010. It took a long time to get to Mercury and that's because Mercury is a small little round planet and we're shooting off towards the sun and so Messenger had to this very long elliptical orbit and slow down over a couple of years. As it did this, it took more and more images of Mercury and so we got in 2010 a little bit more pictures of Mercury but until it reached the circular orbit in 2012 we had never mapped all of Mercury. Just recently in 2012 did we get all of Mercury finally all revealed. And now we know a lot more about Mercury and we can learn that Mercury has lots of craters because it doesn't have volcanoes, it's not getting covered up with lava flows, it doesn't have any moving liquid water. Although there is ice in the north part of Mercury. We think that Mercury is zero degrees from the sun so we think that the Mercury goes around the sun stays tilted up all the time and on the north and on the southern hemispheres there's probably ice remaining in those craters. We saw that with radar we confirmed that with Messenger and ice stays in those craters all the time on Mercury. Perhaps life can even live there which is difficult to believe because the sun side of Mercury stays sunny for almost two months and is over 400 degrees and the cold side is under 100 degrees below zero so it's very cold on the far side and very warm on the hot side of Mercury. We've also seen that Mercury is actually a little bit like a dried up orange. It's so close to the sun that the sun actually shrunk it and there's some cracks in Mercury where that whole planet has start to shrink down a little bit as the sun has cracked it and made it smaller over time because it's so close to the sun. We've also seen that Mercury travels at different speeds when it gets close to the sun it travels a little faster. When it gets farther away it travels a little slower. All the planets do this but Mercury has the longest centric orbit. It's not in a perfect circle. It's a little bit at an ellipse all the planets are but this one has the most elliptical of the orbits and so it's traveling around the sun kind kind of at an odd speed. And we figured that out by looking at it through telescopes as well. I'm Eric Loberg with the Taylor Planetarium.

J. Eric Loberg is the manager, lecturer, and program planner at the Taylor Planetarium at the World, a renowned museum of the Rockies in Bozeman, Montana.