On Thursday, March 18th the Messenger unmanned spacecraft entered Mercury’s orbit. The last time a spacecraft sent to Mercury was Mariner 10 in 1974 and at that time Mariner 10 was only able to photograph 75% of Mercury’s surface. Messenger will orbit Mercury for one year and will map the entire surface including color photographs. On April 4th, the science portion of the mission will begin as NASA scientists and engineers will begin getting data to interpret from Mercury’s surface. Over the next few months we should be getting some never before seen images of Mercury. NASA has a website dedicated Messenger webpage with updates on the mission and photographs.
Weather on Mercury today: very hot (again)
Mercury is a strange, small planet. Mercury is a bit smaller than Earth’s moon. Mercury takes 88 Earth days to circle the sun – this is the length of its year. Oddly, one day on Mercury is equal to 59 days on Earth. It takes Mercury 1,407 hours to rotate 360o. Mercury does not have an atmosphere to retain heat so its temperatures range from 800 oF in the day to -279 oF at night. Mercury is a dense planet and its core is 65% iron in a form that is not normally seen on Earth. This composition is unexpected in such a small planet. Some scientists theorize that Mercury could have been a larger planet at one time and some sort of massive collision caused it to lose its outer layers. The elemental composition of Mercury is one of the topics that is being studied in the Messenger mission. You can learn more about Mercury on NASA’s Mercury page.