MESSENGER Unlocks Mystery of Mercury's Ancient Magnetic Field

— -- The mysteries of Mercury, the planet closest to the sun, are continuing to be unraveled even after the probe smashed into the planet last month.

Before it ran out of fuel and made its fatal plunge into Mercury, MESSENGER flew close to the planet and used its magnometer to collect information about the levels of magnetism in Mercury's surface rocks.

That data yielded the surprising new finding that Mercury's magnetic field is at least 3.7 to 3.9 billion years old, making it much more ancient than was expected, according to a paper from the Planetary Science Institute published in the journal Science.

The discovery sheds new light on the planet's history and how it has evolved over time, including evidence of volcanic and tectonic activity billions of years ago that helped shaped the planet into what it is today.

Now a 16-meter wide crater on Mercury, MESSENGER made history during its time in space.

Launching in 2004, the probe traveled nearly 5 billion miles on a route that included 15 trips around the sun, whizzing past Earth once, Venus twice and Mercury three times.

Among MESSENGER's other discoveries about Mercury are hollows on its surface, evidence of volcanism and polar deposits of water ice.