<P> Mercury can be easily seen from the tropics and subtropics more than from higher latitudes . Viewed from low latitudes and at the right times of year, the ecliptic intersects the horizon at a steep angle . Mercury is 10 ° above the horizon when the planet appears directly above the Sun (i.e. its orbit appears vertical) and is at maximum elongation from the Sun (28 °) and also when the Sun is 18 ° below the horizon, so the sky is just completely dark . This angle is the maximum altitude at which Mercury is visible in a completely dark sky . </P> <P> At middle latitudes, Mercury is more often and easily visible from the Southern Hemisphere than from the Northern . This is because Mercury's maximum western elongation occurs only during early autumn in the Southern Hemisphere, whereas its greatest eastern elongation happens only during late winter in the Southern Hemisphere . In both of these cases, the angle at which the planet's orbit intersects the horizon is maximized, allowing it to rise several hours before sunrise in the former instance and not set until several hours after sundown in the latter from southern mid-latitudes, such as Argentina and South Africa . </P> <P> An alternate method for viewing Mercury involves observing the planet during daylight hours when conditions are clear, ideally when it is at its greatest elongation . This allows the planet to be found easily, even when using telescopes with 8 cm (3.1 in) apertures . Care must be taken to ensure the instrument isn't pointed directly towards the Sun because of the risk for eye damage . This method bypasses the limitation of twilight observing when the ecliptic is located at a low elevation (e.g. on autumn evenings). </P> <P> Ground - based telescope observations of Mercury reveal only an illuminated partial disk with limited detail . The first of two spacecraft to visit the planet was Mariner 10, which mapped about 45% of its surface from 1974 to 1975 . The second is the MESSENGER spacecraft, which after three Mercury flybys between 2008 and 2009, attained orbit around Mercury on March 17, 2011, to study and map the rest of the planet . </P>

Where is mercury located in our solar system