NASA’s MESSENGER spacecraft has discovered a higher abundance of iron on Mercury’s surface. Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

NASA spacecraft flybys over Mercury have revealed interesting facts about the planet, including a higher prevalence of iron on the surface than previously believed.

The Mercury Surface, Space Environment, Geochemistry and Ranging spacecraft (MESSENGER) has completed three flybys over the smallest planet in the universe, giving scientists an almost complete view of Mercury’s surface.

According to NASA, approximately 98% of the planet closest to the Sun has now been imaged.

Sean Solomon, Principal Investigator for the mission, said: “Although the area viewed for the first time by spacecraft was less than 350 miles across at the equator, the new images reminded us that Mercury continues to hold surprises.”

The probe discovered that there are richer concentrations of iron and titanium on the planet’s surface than originally supposed. Previous observations had led scientists to believe that Mercury’s crust was generally low in iron.

David Lawrence, a participating mission scientist, said: “Now we know Mercury’s surface has an average iron and titanium abundance that is higher than most of us expected, similar to some lunar mare basalts.”

Other features of the planet discovered by the MESSENGER spacecraft was the existence of a region with a bright area surrounding an irregular depression, which NASA suspects to be volcanic, as well as a double-ring impact basin on the surface of Mercury.

MESSENGER has now completed nearly three quarters of its 4.9 billion mile journey to enter orbit around Mercury.