Earth Day
22 April – Earth Day is an opportunity to reflect on Earth’s position in the Solar System and to compare some of its features with those of neighboring planets.
This is especially important because, in recent times, the idea of organizing conditions for human life on Mars has been mentioned increasingly often. This idea has been encouraged by rapidly accelerating global climate change and increasing pollution of the air, water and soil on our planet.
Comparisons based on just two aspects, the passage of time, meaning the length of a day and a year, and the range of temperatures on the surface of planets, will reveal some interesting facts, while also encouraging us to think about how achievable that idea really is.
The length of a day and a year on Earth is well known to everyone. However, if we compare it with the time needed for another planet in the Solar System to rotate around its axis, known as a sidereal day, or to complete one orbit around the Sun, known as a sidereal year, we discover interesting facts, such as that a sidereal day can last longer than a sidereal year, or that sunrise can happen twice in the same day.
The planets of the Solar System rotate around their axes at different speeds. Some of their orbits are shorter and some are longer than Earth’s, and they also move along them at different speeds.
Mercury, the planet closest to the Sun, rotates very slowly around its axis and needs almost 59 days to complete one rotation, while its orbit around the Sun lasts 88 days. This motion means that an observer on Mercury would experience a double sunrise.
The motion of neighboring Venus is even more unusual because it rotates around its axis even more slowly than Mercury, and its direction of rotation is opposite to that of Earth. Because of this, Venus needs 243 days to rotate around its axis and 225 days to orbit the Sun, meaning that a day on Venus is longer than a year on Venus.
A day on neighboring Mars is slightly longer than Earth’s and lasts 24 hours, 37 minutes and 23 seconds, while a Martian year lasts 687 days, almost twice as long as Earth’s.
The temperature on our planet is also familiar to us. However, the most extreme recorded temperatures would not feel pleasant at all.
According to data from the World Meteorological Organization, the highest temperature ever measured on the surface of Earth was recorded on 10 July 1913 in Death Valley, California, and was 56.7 °C, while the lowest temperature was measured at Vostok in Antarctica and was –89.2 °C.
Temperatures on the surfaces of other planets in the Solar System would not suit us at all. As a rule, planets closer to the Sun have high temperatures, while those farthest from the Sun have the lowest temperatures.
On the surface of Mercury, the temperature ranges from –180 °C to 430 °C, which is a consequence of its very slow rotation around its own axis.
Since Venus has an even more specific type of motion, the temperature on its surface reaches up to 470 °C.
The lowest temperatures are found on the surfaces of Uranus and Neptune, which are also the farthest planets from the Sun, and are approximately –200 °C.
On the surface of Mars, the temperature ranges from about –143 °C to 20 °C, while it should be emphasized that the average temperature is around –63 °C, which does not seem like a very pleasant temperature.
It should also be noted that the Martian atmosphere, which largely contains carbon dioxide, has only 0.13% oxygen, and that sandstorms are a common occurrence on Mars.
So let us protect our Earth, because the conditions for life on it are still much better than those on other planets.