Earth

missions to mercury

Mercury is only ever seen near Earth's horizon, where our planet's atmosphere is turbulent. This makes it extremely difficult to study the surface. It is thanks to the Mariner 10 space probe—the only one to Mercury thus far—that we know what the planet is like in close-up. Mariner 10 flew by Mercury three times in 1974—5. Images revealed a crater-covered world reminiscent of our Moon, but little else. A second probe, Messenger, is now on its way.

Jupiter

Venus is brighter and farther from the Sun's glare than Mercury

Mercury is just visible in the light of the setting Sun messenger

Messenger will make three close flybys in 2008-9, then move into orbit in 2011. The following year it will map the entire planet. Its curved shield will protect its body and instruments from the Sun's glare.

sunshade protects. body and scientific instruments

Jupiter

Venus is brighter and farther from the Sun's glare than Mercury

Mercury is just visible in the light of the setting Sun

sunshade protects. body and scientific instruments

observing mercury

Mercury has phases like the Moon, but is difficult to see because it is never far from the Sun. It is found low in the twilight sky, before sunrise or after sunset. It is best seen at greatest elongation, when it is farthest from the Sun, six or seven times a year. Several times a century, Mercury appears to cross over the Sun's face as it passes between the Sun and Earth.

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