Mercury's inner core is solid and about the same size as Earth's, NASA MESSENGER data reveals

Mercury's inner core is solid and about the same size as Earth's inner core, a new study using observations from NASA's MESSENGER mission has indicated.

Mercury is the smallest planet in our solar system and the closest to the Sun. It is rocky with a solid surface that is filled with craters. Mercury takes 59 Earth days to complete one rotation on its axis and 88 Earth days to complete one revolution around the Sun.

Some earlier studies have indicated that Mercury may have a solid inner core, but there was not much data to confirm that belief.

In the current study, a team of scientists led by Antonio Genova of Sapienza University of Rome, used earlier data from NASA's MESSENGER mission to investigate the interior of Mercury and to arrive at some conclusive results about the inner core of the planet. Specifically, the team used MESSENGER observations to probe Mercury's spin and gravity.

The results obtained indicate that, for the best match of the data, Mercury must have a large, solid inner core

MESSENGER (MErcury Surface, Space ENvironment, Geochemistry and Ranging) was a robotic spacecraft, which was launched in August 2004 with an aim to study the chemical composition, magnetic field and geology of Mercury.

After completing a journey of about seven years, the spacecraft entered orbit around Mercury in March 2011. It remained in orbit for the next four years before finally crashing onto the planet's surface in 2015.

Genova's team used radio data from MESSENGER to verify Mercury's gravitational anomalies and its orientation.

This data was fed into a computer programme that enabled the research team to adjust parameters in order to match the data with the spinning rate of the planet and acceleration of MESSENGER around the Mercury.

The results obtained indicate that, for the best match of the data, Mercury must have a large, solid inner core.

The results also indicated that Mercury's solid inner core is about half the size of its entire core

The programme estimated that Mercury's solid, iron core must be about 2,000 kilometres wide (about the same size as Earth's solid core which is about 2400 kilometres wide).

The results also indicated that Mercury's solid inner core is about half the size of its entire core.

"We had to pull together information from many fields: geodesy, geochemistry, orbital mechanics and gravity to find out what Mercury's internal structure must be," said Erwan Mazarico, co-author of the new study.

Scientists hope that these new findings will help them better understand how rocky planets change over time in the solar system.

The findings of the study are published in AGU's journal Geophysical Research Letters.

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