Orbiting 227 940 000 kilometres of 1.52 AU from the Sun, the Red Planet is the 4th planet. With a dimeter of 6 784 kilometres, it is also the second smallest. It's weight is 6.4219e23 kilograms- making it the third lightest planet. The name of the month March originates from Mars. In the last couple of decades, we've had various spacecraft visit Mars. The first was Mariner 4 in 1965, followed by Mars 2- the first spacecraft to land on Mars and the two Viking landers in 1976. The most recent is the Mars Pathfinder which successfully landed on Mars on July 4 1997.
Mars' orbit is also considerably elliptical. This has a major influence on Mars' climate which is consderably cold. The average temperature on Mars is about 218 K (-55 C, -67 F), but Martian surface temperatures range widely from as little as 140 K (-133 C, -207 F) at the winter pole to almost 300 K (27 C, 80 F) on the day side during summer. Currently, we know quite little about the interior of Mars, most of it is only by inference from data about the surface and the bulk of the planet. It is most likely to have a dense core about 1700 kilometres in radius, followed by a rock mantle which is a bit dense than the Earth's and lastly a thin crust. Data received from the Mars Global Surveyor indicates that Mars' curst is about 80 kilometre thick in the southern hemisphere but only about 35 kilometres thick in the north. It is believed that Mars' core probably contains a relatively large fraction of sulfur in addition to iron (iron and iron sulfide).
Data received from the Mars Global Surveyor has also suggested that at some time in the pat there was some sort of liquid on the surface. Liquid water is the obvious fluid, but there are also other possibilities. There may have been large lakes or even oceans; the evidence for which was strenghtened by some very nice images of layered terrain taken by Mars Global Surveyor. But it seems that this occurred only briefly and very long ago; the age of the erosion channels is estimated at about nearly 4 billion years.
Mars also has a very thin atmosphere made up mostly of the tiny amount of remaining carbon dioxide (95.3%) plus nitrogen (2.7%), argon (1.6%) and traces of oxygen (0.15%) and water (0.03%). The average pressure on the surface of Mars is only about 7 millibars (less than 1% of Earth's), but it varies greatly with altitude from almost 9 millibars to about 1 millibar.
There are also large but weak magnetic fields in various regions of Mars. The Mars Global Surveyor discovered these magnetic fields a few days after it ended Mars' orbit. Large, but not global, weak magnetic fields exist in various regions of Mars. It is known that Mars has two tiny satellites which orbit very close to the surface. They are name Phobos and Demios. Phobos is located 911 000 kilometres from the centre of Mars, while Demios is located only 236 000 kilometres from the centre. They are both considerably light, weighing 1.08e16 kilograms and 1.80e15 kilograms respectively.