Mercury has set many planetary records, but humans have only visited it twice. Is it all the Sun's fault?

Mercury is the closest planet to the sun in the solar system, about 57.9 million kilometers away from the sun, which is only one-third of the distance between the sun and the earth. Because of its proximity to the sun and the strong gravitational pull of the sun, Mercury has the fastest orbital speed among the eight planets in the solar system. It takes Mercury only 88 days to orbit the sun. Its year is even shorter than a quarter of the earth.

Mercury is the smallest of the eight planets, even smaller than some satellites in the solar system, with a radius of only 2,440 kilometers, equivalent to running from Beijing to Shanghai and back. Although Mercury is small in size, its density is very high, about 5.427g/cm³, second only to the Earth among the planets in the solar system.

The dense Mercury is also a giant iron mine. It is estimated that Mercury contains about 200 billion tons of iron. Based on the current consumption of steel by humans, Mercury is enough for us to mine for 240 billion years. The temperature difference between day and night on Mercury reaches 600 degrees Celsius, which sets another record among the planets in the solar system.

Mercury is a very strange planet. Our Earth is not very far away from it, but so far, humans have visited this neighbor no more than three times. You should know that humans have sent nearly 50 probes to Mars, and in the next decade, humans are likely to land on this red planet themselves.

The Earth and Mars are about 56 million kilometers apart at their closest point. The Earth and Mercury are only 77 million kilometers apart at their closest point. The gap between the two is not that far apart, so why do humans value "fire" so much and despise "water"?

In addition to the harsh environment of Mercury itself, the main reason is the huge gravitational force of the sun, which makes it very difficult to detect Mercury.

Mercury was first discovered by the Semites, a nomadic people originating from the Arabian Peninsula, in 3000 BC. Due to its small size and close proximity to the sun, Mercury is often submerged in the dazzling sunlight, and the only time it can be observed on Earth is at sunrise or sunset.

After humans entered the space age, we didn't expect that what would hinder our exploration of Mercury was still the sun and its huge, omnipresent gravity.

The Earth is outside of Mercury. Wouldn't it be more helpful for us to explore Mercury by using the huge gravity of the Sun to pull the probe toward Mercury? In fact, this is the difficulty. Acceleration is easy, but braking is difficult. Behind Mercury is the Sun, which is 330,000 times heavier than the Earth and concentrates more than 99% of the mass of the solar system. Its control range can even reach the Oort Cloud light years away.

It is not easy to resist its gravity and brake accurately. Although Voyager 1 and Voyager 2 have both flown out of the (narrow sense) solar system a few years ago, only two probes have visited Mercury so far.

On November 3, 1973, NASA's Mariner 10 probe was successfully launched. The probe weighed about half a ton and was equipped with scientific instruments such as an ultraviolet spectrometer, a magnetometer, and a television camera.

On March 29 of the following year, Mariner 10 flew over Mercury at an altitude of 700 kilometers above the surface of Mercury, marking the first close observation of Mercury by humans. After orbiting the sun for half a year, on September 21, Mercury 10 encountered Mercury again and conducted a second flyby exploration.

On March 6, 1975, Mariner 10 passed over Mercury for the third time, conducting a "close" detection of the planet at a distance of only 330 kilometers. This flight observation lasted for a week. After that, Mariner 10 ran out of fuel and drifted forever in the vast space.

During these short three flybys, Mariner 10 not only achieved humanity's first feat of exploring water, but also obtained valuable scientific data, taking tens of thousands of close-up photos of Mercury alone.

Mariner 10 discovered that Mercury has an extremely thin atmosphere composed mainly of helium. Mercury has an iron core and a magnetic field. Mariner 10 explored about 45% of Mercury's surface, which is very similar to the surface of the Moon. There is likely water ice at Mercury's poles...

The Mariner 10 probe's exploration of Mercury was only a glimpse, and the scientific information obtained was extremely limited, and many important questions remained unanswered. If you want to understand Mercury more fully, you must conduct orbital exploration of Mercury.

Humans want to launch a probe that is captured by the gravity of Mercury and becomes an artificial satellite orbiting Mercury. However, it has to overcome the terrifying gravity of the sun and accurately enter orbit. This is a major test of human wisdom and technological level.

Time has passed, and humans have entered the 21st century. The MESSENGER Mercury exploration mission came into being. After more than 30 years of dormancy, NASA finally took action on Mercury again.

We’ll talk next time.

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