Exploration of Mars began over 100 years ago in 1877 when an Italian astronomer called Giovanni Schiaparelli drew pictures of the surface of Mars, observing what he thought were canals (or channels), possibly built by a sophisticated civilisation. These pictures, such as the one on the left, were still being used when more advanced scientific exploration of Mars began in 1964.

Mariner 4 (USA) was the first probe to visit Mars. It was a 'Flyby' mission, simply meaning that it flew by Mars and took pictures of the planet. These were to become the first close-up pictures of the planet. These pictures (such as the one at the top of the page) disappointed scientists who discovered no canals on the surface, but thousands of craters, just like the ones seen on the Moon. Four years later, just after the first men walked on the Moon, Mariners 6 and 7 took more pictures of Mars. They were similar to the ones from Mariner 4. Scientists were again disappointed, describing the planet as being "as dead as a dodo." Mariner 9 in 1971-1972 was put into orbit around Mars to take pictures of the entire planet's surface. However, at the time, Mars was covered in a dust storm meaning the surface of the planet was not visible. Towards the end of the mission though , four peaks appeared above the clouds of dust. These peaks turned out to be volcanoes. This was the first sign of any geological life on Mars! The largest volcano seen by Mariner 9 is also the largest volcano in the entire Solar System (so far discovered). It is called Olympus Mons and is three times higher than Mount Everest, Earth's largest mountain. The picture below shows Olympus Mons from overhead. It may seem small, but that picture is actually 600km across!

Mariner 9 also discovered a huge gorge, 7 kilometres deep, which scientists believe was formed when thefour volcanoes erupted and tour up the land. This is known as Valles Marineris and can be seen sprawling across the surface of Mars in the picture on the right.

Also visible were lava plains (caused by the volcanoes), landslides and channels where water had flowed! The presence of volcanoes shows that Mars had a hot core, just like the Earth. But, does the planet still have a hot core? Can volcanoes still erupt on the planet? The Americans, in 1975, launched the Viking probes. These were probes that landed on the planet's surface to take pictures from the surface and sense rumblings under the surface which would suggest volcanic activity. Viking 1 took the very first pictures of Mars, revealing a rocky red desert, and a pink sky.

Viking 1's seismometers (sensors which detect underground rumbles - These are used on Earth to detect earthquakes) failed to work. Viking 2, which was designed to do the same thing, only succeeded in detecting wind on the planet and took more pictures. It has only been over the past few years that exploration of Mars has taken place again. Pathfinder arrived on Mars in 1997 to take more pictures and, using its Rover, the Sojourner Rover, analyse rock samples to find out what the rocks on Mars were actually made of. Below is a picture of the Sojourner Rover examining a rock named Yogi.

This mission was extremely successful, lasting much longer than scientists expected. Pathfinder also discovered that Mars must have an iron core, just like the Earth's. The Earth's outer core is still molten, which is what causes the internal heat on the planet and volcanic eruptions. There is a possibility that Mars' outer core is also still molten which is something scientists still hope to find out in the future. The Russians attempted to send a probe to Mars recently (Mars 96) to sense underground activity on the planet, but this landed in the Pacific Ocean on Earth. At the moment, the Mars Global Surveyor is orbiting Mars, looking at the planet in great detail. It has observed that there are places where boulders have recently rolled down slopes. Could this have happened because of Mars' wind, or because of underground rumblings? The Mars Global Surveyor has also sent back some other interesting pictures, a heart and a smiley face!

The Mars Polar Lander landed on Mars on 3rd December 1999, but has managed to go missing! No signals from it are being received on Earth, and the Mars Global Surveyor has been taking pictures of the surface around the area where it was meant to have landed to attempt to find it. This probe was going to penetrate the surface of Mars to see if it could sense any vibrations which could suggest volcanic activity, and look for signs of primitive life. In the near future, there are two more Landers and Rovers planned to analyse Martian rock (Mars Surveyor 2001, and Mars Surveyor 2003, both American) and, in 2005, the Mars Surveyor 2005, which plans to sample rock from Mars and bring it back to Earth. Of course, the best way to discover Mars' secrets is by sending a man to Mars. It is expected that a manned mission to Mars will take place in the next fifteen years!