#### To know what are the times to reach Mars it is necessary to calculate the distance between the Earth and Mars: here are the methods carried out to know it.

If it is true that the colonization of Mars is one of the great future challenges of humanity, it is useful to know the distance between the Earth and Mars. In fact, the red planet is considered a life no longer so distant for humanity, especially considering that space missions to this planet in recent years have multiplied, as well as the study of the same. In short, the exploration of Mars using human crews is a very coveted goal of the major world powers.

#### The distance between Earth and Mars

When talking about the red planet there are many questions, how long it takes to reach Mars is one of them. There is an average distance between Earth and Mars, which is 254 million kilometers. We talk about average distance because in reality it is not a fixed value, as this parameter also varies very significantly.

Simply think that these two planets are in motion, and follow elliptical orbits around the sun. This means that between the maximum and minimum distance there are about 345 million kilometers of difference. In particular, the minimum distance is 55.7 million kilometers, while the maximum reaches even 401 million km.

#### The study of the distance between Earth and Mars

In fact, the question "How long does it take to get to Mars" nags human beings for quite some time. But it was only in the second half of the seventeenth century that someone managed to find a method to scientifically calculate the distance between the Earth and Mars. It was the astronomer Giovanni Domenico Cassini, who used nothing less than a method dating back to ancient Greece, called the parallax method. He first focused on the distance between the Earth and the Moon, and then tried to calculate the distance that separates us from the great red planet.

#### The method of parallax

In short, it is an ancient system, but exploited by Cassini with new parameters, thanks to the data that science and astronomy were in possession at that time. It is based on Kepler's third law, which establishes the proportionality between the cube of the average distances of the planets from the Sun and the square of their orbital periods.

Considering now that measuring the orbital period of the planets is quite simple, it will be sufficient to calculate the average distance Earth-Sun by measuring it in two different points, in order to obtain a constant of proportionality. From both observatories it was possible to see Mars with the naked eye, so they calculated its exact position with respect to the stars. Calculating then the angular difference, and knowing the orbit of Mars, it is enough a trigonometric calculation to be able, from Mars, to know the distance from the Earth.

#### The evolution of the calculation to measure the distance between Earth and Mars

For a couple of centuries there were no other methods, while in the second half of 1900 to measure the distance between Earth and Mars became much more accurate, thanks to the use of radar astronomy. This system is based in the use of micro waves that are put from the Earth, directed towards the red planet. When these waves bounce back, their echo is recorded of the Earth. It is precisely the intensity of the Lecco that allows you to derive the distance between Mars and Earth.

#### Mars at the shortest distance from Earth

It happens very rarely indeed that the distance between Earth and Mars is minimal, that is, 56.6 million kilometers. Such an event occurred a few years ago, in 2018, the date of July 31. That evening, the red planet, which was 57.5 million kilometers from Earth, was seen very close and bright, as had not happened for about 15 years.

#### But how long does it take to go to Mars?

So if the distance is so variable, how long does it take to go to Mars? Obviously, even the timing is very variable, as it depends precisely on the distance in which the two planets are at that time. Currently, in any case, with the technologies available to the world powers, using a space vehicle of the most modern, it is possible to arrive on Mars in a time that varies from 6 to 9 months.