Astronomers have carefully calculated the average distance between the Earth and other planets in the solar system based on well-known data. To do this, they abandoned the standard comparison of the radius of the orbits, the distance from the planet to the Sun. It turned out that, on average, the closest thing to the Earth is not Venus or Mars, but Mercury.
In an article for Physics Today, astronomers note that the distance between planets is often misunderstood. For example, Venus is called the planet closest to Earth because the radius of the Earth's orbit (150 million km) and the radius of Venus's orbit (108 million km) differ by 42 million km. In this case, the orbit of Mercury (ellipse 46x69 million km) is removed from the Earth's orbit by at least 80 million.
This principle - to calculate the distance between the orbits - does not really show the distance from one celestial body to another, but only the minimum possible distance. When Venus is strictly between the Earth and the Sun, it really turns out to be the closest planet to us. But if it is located on the other side of the Sun, the distance increases to 256 million km (the radius of the Earth's orbit + the radius of the orbit of Venus). It may be further not only Mercury, but also Mars - that sometimes approaches 55 million km.
When researchers consistently calculated the average distance, Mercury was closer to Venus. This was not a big surprise for professional astronomers and cosmonautics, who routinely maintain communication with robotic stations in various orbits (for example, the Parker probe flies into the orbit of Mercury). However, the misconception about Venus as the nearest planet is firmly rooted in many popular sites and in astronomy textbooks. Even the NASA website, as the authors of the calculations note, considers Venus the closest, although this, as it turned out, does not correspond to reality in the case when we are talking about the average, not the minimum possible distance.
However, in practice, the planet's availability is determined not only and not so much by the distance as by other factors. The first spacecraft entered the orbit of Mercury only in 2011 - by this time, mankind managed to land a probe on Saturn's satellite Titan, deliver several research stations (and three rovers) to Mars and take a soil sample on the asteroid. The fact is that the planet closest to the Sun has the highest orbital speed, so you must first catch up with it, gaining an extra 18 km / s. Even a flight to Pluto requires a lower speed.
This is also why, in the near future, scientists do not plan to send a research station or rover to the surface of Mercury. At the beginning of the 2000s, Russian researchers developed the Mercury-P project with an expected flight in 2019, but then this mission was actually canceled, shifting to the post-2031 mark.
Alexey Tymoshenko
