Mercury: What's special about the smallest planets? | Cosmic vacuum

Imagine a planet without seasons, where two years pass in three days and light never reaches the poles. Every three (terrestrial) months, temperatures at the surface alternately rise so high that they can melt lead and fall so low that they freeze methane. But above all, think about what it would be like to gaze from that farthest place at a sunset in which the star dips below the horizon and then comes back a moment later, as if someone had pressed the rewind button, and after a day or two it usually disappears at the western sunset. .

This strange planet is right here in the neighborhood and we've named it Mercury. The star that serves as the protagonist in this impressive sunset is our own, and the planet travels around the sun faster than any other body in the solar system, completing a full orbit every 88 days. Mercury is very bright in the sky. But due to its proximity to the sun, it is very difficult to study it, and for this reason we do not know it well.

It moves quickly in the sky and is small in size, which is why in ancient Greece the planet was associated with the role of a messenger who puts one god in touch with another (before they had no communication satellites). Mercury takes its name from the Roman god of shopkeepers, merchants, thieves, and crooks. It is associated with the Egyptian god Thoth and the Scandinavians Odin, and as a celestial being it also held a prominent place in Maya culture. All this mythological significance in different cultures reveals something very simple: it is a prominent object in the night sky.

The planet rotates very slowly, which is why its days are very long. One day on Mercury is equivalent to 58.6 Earth days. Its year, which is 88 Earth days, is very short, which is why it is the closest planet to the Sun. It does not have a period of rotation that is simultaneous with its orbital period, as is the case with the Moon, but both periods are close together. Similar to what we know as conjunction 3:2. This means that for each revolution around the Sun (orbital period) Mercury rotates one and a half times on its axis and that in two complete orbits around the Sun the planet rotates three times on its axis, so it does not always have one side of the planet facing the Sun and the other in total darkness. Of course, the alternating periods between dark and light are very long.

Mercury moves in a rather long orbit at an average distance of 57.9 million km around the Sun, and in such an elliptical orbit, according to Kepler's second law, the speed of the planet changes dramatically at its extreme points. So, when Mercury is at perihelion, the closest point in its orbit to the Sun, it is moving at 59 kilometers per second. By comparison, Earth is moving at 30 kilometers per second. Remember, it was specifically a measurement of Mercury's perihelion advance that was explained in terms of the curvature of spacetime, one of the key pieces to proving the theory of general relativity.

On the surface of Mercury, it rises in the east and sets in the west, as is the case on Earth. But once a year, when it passes through perihelion, the orbital motion exceeds the planet's slow rotation and on that day the Sun's evolution in its sky is interrupted. At that point in its orbit, you can contemplate these strange sunsets. The star stops completely in the sky of Mercury and moves backward to return to its normal path, as the planet's speed decreases as it moves through its orbit.

Because Mercury is closer to the sun, the light that reaches its surface is seven times stronger than the light that reaches Earth. This light has about three months to warm its surface. The planet rotates very slowly, and as a result, temperatures on its surface are high enough, at least 420 degrees, that they can melt lead (now I recommend taking a short walk to your kitchen to determine what temperature your oven can reach). . Likewise, the time from sunset until it rises again is about three Earth months. Three months in complete darkness cool the planet's surface to nighttime temperatures below -170 degrees, where methane and carbon dioxide freeze.

Furthermore, Mercury has no seasons because it rotates on its axis almost perpendicular to its orbit, which also means that in the polar regions the interiors of large craters are permanently in shadow. One of the big mysteries that the probe will try to solve Baby Colombo It is to determine whether these craters contain sulfur or ice.

The small planet has a magnetic field similar to ours, at only 1% of its strength, and it is unique among the rocky planets in our solar system because, like Earth, it has a self-sufficient magnetic field. Why Earth or Mercury maintain a magnetic field while Venus, Mars, or the Moon do not is something we still do not understand. Mercury still hides many of the questions posed by the joint mission European Space Agency (ESA) The Japan Aerospace Exploration Agency (JAXA) Baby Colombo On the way to decoding. She has only been visited twice with the tentacles Mariner 10 And messenger.

Baby Colombo This will be the third probe launched to a unique, small, mysterious and difficult-to-explore planet, but it is the probe that helped us lay the foundations of current physics and will certainly give us essential clues to understanding the evolutionary history of our solar system and planet. Earth formation.

Cosmic vacuum It is a section in which our knowledge about the universe is presented in a qualitative and quantitative manner. It aims to explain the importance of understanding the universe not only from a scientific point of view but also from a philosophical, social and economic point of view. The name “cosmic vacuum” refers to the fact that the universe is, for the most part, empty, with less than one atom per cubic meter, although in our environment, paradoxically, there are quintillions of atoms per meter. A cube, which invites us to contemplate our existence and the existence of life in the universe. The section is composed Pablo G. Perez Gonzalezresearcher at the Center for Astrobiology, and Eva VillaferDirector of the Space and Society Office of the Spanish Space Agency, and Research Professor at the Institute of Astrophysics of the Canary Islands.

You can follow Theme in Facebook, s And Instagramor sign up here to receive Our weekly newsletter.