28 September 2009
Most likely you have never seen Mercury. It’s not easy to see because it is so close to the sun. Your only chance is just before sunrise or just after sunset, and you will need to be in a really flat place or on a high mountain with a clear view of the horizon.
It’s also one of the planets we know little about. The picture above is a view taken by the Messenger spacecraft of a side of Mercury we have never seen before. NASA wanted to send a mission to Mercury but on the cheap. They did it by taking the LONG way. Messenger is using Mercury’s gravity to slow down a little as it passes by.
This is the last pass. It will slow down enough to fall into orbit the next time it comes by Mercury. That will be March 18th- 2011!
Today it will skim by at just 228km above the surface! It will allow us to see things on the surface we have never seen before. The data should start flowing back to Earth around 11pm Eastern time tomorrow (04 GMT Wednesday).
Mercury is one weird place. It rotates twice for every 3 orbits of the sun. This leads to a day lasting nearly 6 Earth months. It also has almost no tilt. Because Earth is tilted at 23.5 degrees we have seasons. On Mercury, the sun is always the same elevation above the horizon at local noon. Because of this, it’s thought that deep craters near the poles, may never see sunlight, and could be among the coldest spots in the solar system!
Recent Science points to our very own Moon as possibly being a little colder still for the same reasons. If Carl Sagan were alive he’d be on pins and needles tonight. A lot of NASA scientists certainly are! In the next few days, we will learn things we never knew before.
So teachers, do you want to get your class involved as Messenger flies by??
One of my friends on twitter is Doctor Jeff Goldstein. He is the director of the National Center for Earth Science and Space education. His blog is full of all kinds of info. Check it out, and you can follow what’s happening tomorrow as we learn new things about our home in the cosmos.
My geeky self will be there.