Section 1 Missions to Mars

**3**

to winter [2].

**Chapter 1**

Long

**1. Introduction**

**1.1 Exploration aims**

interest in Mars exploration?"

future.

Introductory Chapter: Mars

*Giuseppe Pezzella and Antonio Viviani*

Exploration - A Story Fifty Years

Mars has been a goal of exploration programs of the most important space agencies all over the world for decades. It is, in fact, the most investigated celestial body of the Solar System. Mars robotic exploration began in the 1960s of the twentieth century by means of several space probes sent by the United States (US) and the Soviet Union (USSR). In the recent past, also European, Japanese, and Indian spacecrafts reached Mars; while other countries, such as China and the United Arab Emirates, aim to send spacecraft toward the red planet in the next

The high number of mission explorations to Mars clearly points out the impor-

The interest in Mars is due to several practical, scientific, and strategic reasons. In the practical sense, Mars is the most accessible planet in the Solar System [1]. It is the second closest planet to Earth, besides Venus, averaging about 360 million kilometers apart between the furthest and closest points in its orbit. Earth and Mars feature great similarities. For instance, both planets rotate on an axis with quite the same rotation velocity and tilt angle. The length of a day on Earth is 24 h, while slightly longer on Mars at 24 h and 37 min. The tilt of Earth axis is 23.5 deg, and Mars tilts slightly more at 25.2 deg [2]. Further, Earth and Mars revolve around the Sun with about the same revolution velocity. The former orbits at 30 km/s and the latter at 24 km/s. A year is 365 days on Earth and almost double that at 687 Earth Days on Mars [2]. Both Earth and Mars have four seasons each. Severe dust storms occur during the summer in the Mars' southern hemisphere. They are so strong that block most of the surface from view by satellites. During the fall, in the Mars' polar regions, crystals of carbon dioxide (CO2) form and so much of the atmosphere gets absorbed that atmospheric pressure drops up to 30% as seasons transition from fall

From the scientific point of view, it is worth noting that exploring Mars provides the opportunity to possibly answer origin and evolution of life questions and could someday be a destination for survival of humankind. In fact, the red planet is a stony body with atmosphere, like Earth, with the same age, yet with only half the diameter of Earth, and with similar geological structures, as cold and desert-like

tance of Mars within the Solar System. Thus, the question is: "Why this great
