AST101H5 Lecture Notes - Lecture 12: Dayside, Escape Velocity, Permafrost
Document Summary
Mercury is hard to study from earth because. It is the planet nearest to the sun, so the sunlight makes it hard to observe. Test how strong its gravity is to find its mass. Therefore, it was not until we sent a satellite to mercury that we started to learn about it. Mercury"s radius can be measured from earth using its angular size and distance - although its small size limits the accuracy - 2440 km. Mercury"s mass cannot be measured from earth because it does not have a moon orbiting it. Finally, in 1974, our mariner 10 space probe measured mercury"s mass using the method from chapter 3 = 3. 3 x 1023 kg = 0. 055 mearth. Using the mass and radius we find mercury"s average density = 5. 43 gm/cm3, very similar to earth"s average density. Short distance from the sun, 0. 387 au, orbits in short time, 87. 97 days.
