“You don’t drown by falling in the water; you drown by staying there.” -Edwin Louis Cole
Our Solar System is — at least from our perspective — the most well-studied system of planets, moons, asteroids and comets in the entire Universe.
Image credit: Olaf Frohn, from earlier in 2012.
And in this system, the closest planet to our Sun, Mercury, was also one of the most poorly understood planets until very recently. Because Mercury is so close to the Sun, it’s very difficult to view it under good conditions with a telescope; the risk of ruining your optics by exposing them to direct sunlight is tremendous! (Hubble has never imaged Mercury for exactly this reason.) You have to wait until after sunset, and even then, Mercury is so small and distant that ground-based telescopes can barely resolve features on it.
Image credit: Boston University / Baumgardner et al., 2000 (Astronomical Journal).
It was only in the early 1970s that we got our first good picture of the planet Mercury, thanks to the Mariner 10 spacecraft, which was the first NASA mission to visit the innermost world in our Solar System.
Image credit: NASA / JPL / Ted Stryk, 1974.