Spacecraft reaches innermost planet of solar system – Mercury

By Satyen Mohapatra

About a week ago, the BepiColombo spacecraft took its closest look at Mercury, the least explored planet of our solar system. Black and white photos of the pock marked surface of Mercury are being streamed back to earth.

It was a joint mission of the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) to make studies regarding several mysteries of the celestial body like of issues such as why such a small planet has a magnetic field, the ice in the polar craters of the hot planet, the nature of the hollows, and mysterious dents on the planet’s surface. These dents are not seen on any other planet in the solar system which is believed perhaps to be caused by evaporation of volatile  material from inside Mercury. BepiColombo’s flyby was a virtual touch and go because it came almost  within 200 KMs of the planet.

The flybys are  gravity-assist maneuvers that use the gravity of one planet to accelerate or change a spacecraft’s trajectory.

There are to be four more flybys of BepiColombo before the spacecraft is in the correct position to finally enter the planet’s orbit, which is set to happen in 2025. This was the closest the spacecraft would come to the planet, it used the planet’s gravity to slow itself down.The eventual  target scientific orbit around the planet in 2025 will keep the spacecraft at a distance of 480 to 1,500 KMs.

According to the Japanese Aerospace Exploration Agency, the mission was inspired by the late Italian astrophysicist Dr. Giuseppe “Bepi” Colombo, who suggested that a spacecraft could get close to Mercury several times by using a gravity-assist swing-by of Venus.

Hence, the name of the project, BepiColombo.

NASA’s Mariner 10 had revealed the presence of a magnetic field and magnetospheric activities in Mercury. BepiColombo will conduct comprehensive observations of Mercury’s magnetic field, magnetosphere, and studies of its surface and interior.

That will help determine how much it has in common with other planets and what elements are unique to Mercury as well as the origin and evolution of terrestrial planets.

The spacecraft consists of two orbiters, ESA’s Mercury Planetary Orbiter (MPO) and JAXA’s Mercury Magnetospheric Orbiter, that will eventually circle the planet separately.

The €650 million ($750 million) BepiColombo mission which took off in 2018, will take measurements of the environment around the planet and images of Mercury’s surface. BepiColombo’s next flyby at Mercury will take place in June 2023.

The National Aeronautics and Space Administration (NASA) of USA’s Mariner 10 spacecraft launched in 1973 was the first to reach near Mercury and was the first to use gravity of one planet (Venus) to reach another planet Mercury.

NASA’s robotic space probe MESSENGER “Mercury Surface, Space Environment, Geochemistry, and Ranging” became the first spacecraft to orbit Mercury between 2011 and 2015, studying Mercury’s chemical composition, geology, and magnetic field.  Eventually, completing its mission it crashed into the planet in 2015.

Mercury is the closest planet to the Sun and is a small planet with its radius just about 2,440 kilometers located inside the solar system.

Even today we do not know much about Mercury one of the reasons clearly being its observation from earth with ground-based telescopes is not very easy because it is very close to the Sun’s bright light.

Not many spacecrafts have been sent close enough to Mercury to study it because of sun’s intense radiation and heat.

Mercury is the smallest planet but fastest planet (moving through space at nearly 47 kilometers per second) in our solar system and closest to the Sun completing its one orbit around the sun or one year in 88 days.

On Mercury, the sun would be three times larger than on earth and seven times brighter. It is, however, not the hottest planet of solar system even though the sun is just about 36 million miles away from it, the hottest planet is Venus because of a denser atmosphere.

There is a vast difference between the day temperature of 430 degrees Celsius and the night temperature of minus 180 degree Celsius in Mercury.

With no moons circling it, it is rocky and slightly larger than the moon. It is exosphere is made up of gases like oxygen, sodium, hydrogen, helium, and potassium. Scientists believe that life as we know it would not survive on it due to solar radiation and extreme temperatures.