Mars is approximately half the diameter of Earth and the surface area is slightly less than the total area of Earth’s dry land. Surface gravity is about 40% of that of Earth. One sol on Mars – the time it takes for Mars to rotate around itself – is about 24 1/2 hours. One Martian year is 668 sols or about 1.9 Earth years.
The main ingredient of Mars’ atmosphere is carbon dioxide. The surface pressure is less than 1% of that of Earth. Surface temperature ranges from -143° C to 35° C. The daily temperature swing is large as the heat-holding capacity of the dust that covers most of the surface is low.
The distance to the horizon is shorter than on Earth. There is no moisture, so usually there is a very high visibility. Year-round dust storms can block sunlight for weeks at a time. Mars has two moons – Phobos and Deimos. Both are much smaller than the Moon. Jupiter can be seen with the naked eye. Earth can be seen if you know where to look.
The main surface features on Mars are impact craters, lava flow plains, and volcanoes. The colors range from red-orange, golden, brown, tan and greenish, depending on the minerals present. Olympus Mons is the largest volcano in the solar system and there are still areas with volcanic activity. The Borealis basin that covers 40% of the surface was created by an impact four billion years ago. Dikes are the remains of ancient lava streams and deposit valuable minerals.
The most abundant chemical elements in the Martian crust, besides silicon and oxygen, are iron, magnesium, aluminum, calcium, and potassium. The elements titanium, chromium, manganese, sulfur, phosphorus, sodium, and chlorine are less abundant. Rarer metals are Niobium, Lanthanum, Neodymium, Europium, lead, silver, tin, bismuth, antimony, nickel, copper, platinum, palladium, and chromium. Hydrogen is present as water ice and in hydrated minerals.
The most rare thing on Mars is life.