Scientists have long known that Earth and Mercury have metallic properties.
nuclei. Like the Earth, the outer core of Mercury is composed of liquid metal, but
there was only evidence that the innermost core of Mercury is solid. Now,
in a new study, scientists report evidence that the inner core of Mercury is
in fact solid and almost the same size as the Earth's solid
Some scientists compare Mercury to a cannonball because its metal
The nucleus fills almost 85% of the planet's volume. This big
nucleus – huge compared to the other rocky planets of our solar system –
has been one of the most intriguing mysteries about Mercury.
Scientists also wondered whether Mercury would have a solid interior
The discoveries of Mercury's solid inner core, published in the AGU newspaper Geophysical research charts,
scientists to better understand Mercury, but also to
how the solar system formed and how the rocky planets change over time.
"The interior of the Mercury is still active due to the molten core
feeds the weak magnetic field of the planet, relative to that of Earth, "he said.
Antonio Genova, assistant professor at the Sapienza University in Rome
who led the research, while at NASA's Goddard Space Flight Center in
Greenbelt, Maryland. "The interior of Mercury has cooled more rapidly than
of our planet. Mercury can help us predict how the Earth's magnetic field
will change when the core cools. "
To find out what the Mercury core is made of, Genova and its
the colleagues had to stay, more figuratively, closer. The team used several
observations from the NASA MESSENGER mission to investigate the Mercury interior.
The researchers analyzed, more importantly, the rotation of the planet and
The MESSENGER spacecraft entered orbit around Mercury in March 2011
and spent four years observing this planet closest to our Sun until
was deliberately brought to the surface of the planet in April 2015.
The scientists used MESSENGER radio observations to determine
Mercury gravitational anomalies (areas of local increases or decreases)
in mass) and the location of their rotational pole, which allowed them
understand the orientation of the planet.
Each planet rotates on an axis, also known as a pole. Mercury rounds
much slower than the Earth, with its day lasting about 58 Earth days.
Scientists often use slight variations in the way an object rotates to
reveal clues about its internal structure. In 2007, radar observations
made of the Earth revealed small changes in the rotation of Mercury, called
which proved that part of the planet's nucleus must be liquid
metal. But the observations of the rotation rate alone were not enough to
give a clear measure of what the inner core was like. There could be
a solid core lurking underneath, the scientists wondered?
Gravity can help answer that question. "Gravity is a powerful tool
look at the deep interior of a planet because it depends on the
density structure of the planet, "said Sander Goossens, a NASA researcher.
Goddard and co-author of the new study.
While MESSENGER orbited Mercury throughout its mission and received
increasingly close to the surface, scientists have recorded how the spacecraft
accelerated under the influence of the planet's gravity. The density
the structure of a planet can create subtle changes in the orbit of a spacecraft.
In the later parts of the mission, MESSENGER flew about 120 miles up
the surface, and less than 65 miles during its last year. Final
low-altitude orbits from the best data yet and allowed Genova
and your team to make the most accurate measurements on the internal
structure of Mercury still taken.
Genoa and its team put the data of MESSENGER in a sophisticated
computer program that allowed them to adjust parameters and
what the inner composition of Mercury should be like combining the path
and the way the spacecraft sped around it. The results
showed that for the best game, Mercury must have a large, solid interior
a testimony. They estimated that the solid iron core is about 1,260 miles
(2,000 kilometers) wide and makes up about half of the entire Mercury core
(about 2,440 miles, or nearly 4,000 miles wide). In contrast,
The solid core of the Earth is about 2,400 kilometers in diameter
occupying a little more than a third of the entire nucleus of this planet.
"We had to gather information from many fields: geodesy,
geochemistry, orbital mechanics and gravity to find out what Mercury
internal structure should be, "said Erwan Mazarico, a planetary scientist
at NASA Goddard and co-author of the new study.
The fact that scientists needed to approach Mercury to discover
more about its interior highlights the power to send spacecraft to
other worlds, according to the researchers. Such precise measurements
of rotation and gravity of Mercury simply could not be done
Earth. New discoveries about Mercury are practically guaranteed
waiting in the archives of MESSENGER, with each discovery about our
planetary neighborhood giving us a better understanding of what is
"Every new information about our solar system helps us understand the larger universe," said Genova.
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