Messenger took these images of Earth during its travels towards Mercury
It's been almost 40 years since the last (and only) time human beings have gotten a glimpse of the solar system's first sibling. Mercury, an airless, rocky world dwells in fearful proximity to the Sun. Living at just a third of the Earth-Sun distance, Mercury takes just 88 days to complete an orbit. That terrible intimacy with a star has left planet Mercury with daytime temperatures hovering around 800 F (though near the poles airless Mercury may be so cold that water ice might hide in the shadows of crater walls).
In the 1970s Mariner 10 flew by Mercury twice and beamed back images of a world that appeared to be a larger version of the Earth's Moon. Now, 35 years later the MESSENGER space probe has just entered into an elliptical orbit around Mercury in preparation for extended stay.
This was not an easy task for mission planners (as if any of the missions are easy). The gravitational influence of the Sun is enormous at these distances and it took some tricky astronautics to insert Messenger into its required orbit.
hide captionThe surface of Mercury is seen in a picture taken by NASA's Messenger spacecraft as it approached the planet during a fly-by on January 14, 2008. The image was taken about 11,000 miles from the planet and shows a region 300 miles across.
The surface of Mercury is seen in a picture taken by NASA's Messenger spacecraft as it approached the planet during a fly-by on January 14, 2008. The image was taken about 11,000 miles from the planet and shows a region 300 miles across.
While Mercury may not look very exciting compared to a sexy planet like Mars, it holds keys to understanding how the rocky planets in our solar system formed. Living so close to the Sun, Mercury coalesced at the inner edge of a gaseous disk that birthed all the Sun's planets 5 billion or so years ago. Learning more about Mercury's history can tell us a lot about the generic process of planet assembly and is, therefore, relevant to all those 50 billion or so worlds we now believe are whirling around the galaxy's many alien Suns.
So congratulations to all those folks at NASA and elsewhere for bringing delivering MESSENGER to its new home.