NASA’s MESSENGER spacecraft may no longer be with us, but the information it gathered is still making new discoveries possible. Researchers now have a good idea of how old Mercury’s magnetic field is.
Mercury having a magnetic field isn’t new. But, as MESSENGER orbited lower and lower, its magnetometer picked up tiny signals of magnetization in Mercury’s crust. These signals helped reveal the age of Mercury’s magnetic field – at least 3.7 billion to 3.9 billion years old.
“If we didn’t have these recent observations, we would never have known how Mercury’s magnetic field evolved over time,” said Catherine Johnson, a University of British Columbia planetary scientist and lead author on the new study. “It’s just been waiting to tell us its story.”
Mercury is a fascinating planet. Besides Earth, it’s the only planet in the inner solar system that has a magnetic field. Evidence suggests Mars also had a magnetic field, but it disappeared more than 3 billion years ago.
Our findings indicate that a global magnetic field driven by dynamo processes in the fluid outer core operated early in Mercury’s history. Ancient field strengths that range from those similar to Mercury’s present dipole field to Earth-like values are consistent with the magnetic field observations and with the low iron content of Mercury’s crust inferred from MESSENGER elemental composition data.
MESSENGER’s legacy will continue to live on. Researchers will keep sifting through data collected by the spacecraft for months. It won’t be the last we hear from MESSENGER and discoveries on Mercury.
The next visitor to Mercury
The European Space Agency and the Japan Aerospace Exploration Agency have big plans for Mercury. BepiColombo, a joint mission between the two agencies, is expected to launch on January 27, 2017.
The mission will consist of two orbiters: the Mercury Planetary Orbiter and the Mercury Magnetospheric Orbiter. Primary mission objectives center on the planet’s magnetic field, magnetosphere, interior structure, and surface.
While today’s discovery provides clues about the origins of Mercury’s magnetic field, BepiColombo will try to nail it down.
The spacecraft will conduct several flybys of Venus and Mercury before settling into an orbit on January 1, 2024.
Want to learn more about the BepiColombo mission? The ESA page dives into the technical specs of the spacecraft and mission.