The BepiColombo mission will make its first flyby of Mercury at approximately 7:34 p.m. ET on Friday and will pass within 200 kilometers of the planet’s surface. During the flight, BepiColombo will collect scientific data and images and send them back to Earth.
The mission will actually put two probes into orbit around Mercury: the planet Mercury probe led by the European Space Agency and the Mercury Magnetosphere Orbiter spacecraft led by JAXA, Mio. These orbitals will remain stacked in their current configuration with the Mercury transport unit until publication in 2025.
Once the Bepicolombo spacecraft approaches Mercury to begin its orbit, the Mercury Transfer Module portion of the spacecraft will separate and the two orbits will begin to orbit the planet.
The two probes will spend a year collecting data to help scientists better understand this mysterious little planet, for example by determining the processes that occur on its surface and its magnetic field. This information could reveal the origin and evolution of the planet closest to the Sun.
During Friday’s flight, the spacecraft’s main camera will be shielded and unable to take high-resolution images. But two of the spacecraft’s three surveillance cameras will capture images of the planet’s northern and southern hemispheres after the close approach, about 621 miles (1,000 kilometers) away.
BepiColombo will be flying over the night side of the planet, so images as you approach closer can’t show much detail.
The mission team expects that the images will show large archaeological craters scattered across the surface of Mercury, much like our moon. Researchers can use the images to map Mercury’s surface and learn more about the planet’s composition.
Some instruments will be powered from both orbits in flight so they can get their first jets of magnetic field, plasma, and Mercury particles.
The trip comes just in time to mark the 101st birth anniversary of Giuseppe “Pepe” Colombo, the Italian scientist and engineer named after the expedition. Colombo’s work helped explain Mercury’s orbit around the sun and allowed NASA’s Mariner 10 spacecraft to perform three flybys of Mercury instead of one using gravity assistance from Venus. He determined that the point at which the spacecraft flies over the planets might actually help make future passages possible.
Mariner 10 was the first spacecraft sent to study Mercury, and it successfully completed its three flybys in 1974 and 1975. Next, NASA sent its Messenger spacecraft to make three flybys of Mercury in 2008 and 2009, putting the planet in orbit from 2011 to 2015.
Now, BepiColombo will take on the task of providing scientists with the best information to unravel the planet’s mysteries as the second and most complex Mercury-orbiting mission to date.
“We are really looking forward to seeing the first results of measurements made near the surface of Mercury,” Johannes Penkoff, a scientist with the European Space Agency’s BepiColombo project, said in a statement. When I began working as a project scientist at BepiColombo in January 2008, NASA’s Messenger mission made its first flyby of Mercury. Now it’s our turn. it’s a wonderful feeling!”
Little is known about the history, surface, or atmosphere of Mercury, which is notoriously difficult to study due to its proximity to the Sun. It is the least explored of the four rocky planets in the inner solar system, including Venus, Earth, and Mars. The brightness of the Sun behind Mercury also makes it difficult to observe the small planet from Earth.
The BepiColombo will have to continually ignite xenon gas from two of the four specially designed engines in order to continuously brake against the massive gravitational force of the sun. Its distance from Earth also makes it difficult to reach – more energy is required to allow BepiColombo to “fall” on the planet than it would for missions to Pluto.
A heat shield and titanium insulation were also applied to the spacecraft to protect it from extreme heat of up to 662°F (350°C).
Orbiter instruments will study the ice in the planet’s polar craters, why it contains a magnetic field, and the nature of the “cavities” on the planet’s surface.
Mercury is full of mystery for such a small planet, barely larger than our moon. What scientists do know is that during the day, temperatures can reach as low as 800 degrees Fahrenheit (430 degrees Celsius), but the planet’s thin atmosphere means it can dip as low as 290 degrees Fahrenheit (minus 180 degrees Celsius) at night.
Although Mercury is the closest planet to the sun at about 58 million kilometers from our star on average, the hottest planet in our solar system is actually Venus because it has a dense atmosphere. But Mercury is certainly the fastest of the planets, orbiting the sun every 88 days – which is why it is named after the Roman gods’ swift and winged messenger.
If we could stand on the surface of Mercury, the Sun would appear three times larger than the Earth’s surface and the sunlight would be blinding because it is seven times brighter.
Mercury’s unusual rotation and elliptical orbit around the sun means that our star appears to rise, set and ascend rapidly over parts of the planet, and a similar phenomenon occurs at sunset.
Rob Pichita contributed to this report.
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