Mercury's magnetic field that is created through a dynamo process in the core may have existed in the planet's early days.
New findings suggest Mercury's amazing magnetic field may have been even stronger than it is today as far back as 4 billion years ago, Johns Hopkins University reported. The findings were made using NASA's MESSENGER spacecraft that crashed into Mercury last week after running out of fuel. Despite its dramatic death, the spacecraft revealed evidence of magnetization of ancient crustal rocks on our solar system's closest planet to the Sun.
"From MESSENGER and Mariner 10 observations we already knew that Mercury has had a global magnetic field today and 40 years ago," said Catherine Johnson, a senior scientist at the Planetary Science Institute and lead author of "Low-altitude Magnetic Field Measurements by MESSENGER Reveal Mercury's Ancient Crustal Field," published today in the journal Science. Johnson is also a professor of Geophysics at the University of British Columbia, Vancouver.
MESSENGER's Magnetometer instrument allowed it to first start measuring magnetic field strength and direction when orbiting Mercury at a distance of about 60 miles from the surface. The change in magnetic signal strength from about 50 to 10 miles suggested the presence of magnetized crustal rocks.
Mercury is believed to be the only planet in our solar system that has a global magnetic field caused by a dynamo in a fluid metallic outer core.
"Magnetized rocks record the history of the magnetic field of a planet, a key ingredient in understanding its evolution. We already know that around 3.7 to 3.9 billions years ago Mercury was volcanically and tectonically active. We now know that it also had a magnetic field at around that time," Johnson said. "If we didn't have the recent very low-altitude observations, we would never have been able to discover these signals. Mercury has just been waiting to tell us its story."
