Squirting guns on Mars

The scientific community is digesting the consequences of yesterday’s discovery of water sources on Mars. NASA’s Mars Exploration Program lead scientist Michael Meyer said the latest evidence appears to reveal recent water flow on the surface of the planet. Scientists examined photos sent by Global Surveyor and compared them with those taken seven years ago in the same spot. They observed water had flowed through the 20 new craters they detected recently. NASA say water may have come up from under the surface and flowed long enough to have left traces. However water would quickly freeze at the surface of the cold planet.

Mars has always excited watchers with the possibility it may contain forms of life. 19th century telescopes allowed for detailed study of the planet. Astronomers saw icecaps at the poles and light that changed colour with the seasons. Some saw the grooves in the planet and imagined they were irrigation channels of liquid water. In 1877 Italian astronomer Giovanni Schiaparelli used a new high resolution telescope to produce the first detailed map of Mars. These maps contained features he called canali. The word meant channels but was mistakenly translated into English as canals.

The American self-funded astronomer Percival Lowell was fascinated by Sciaparelli’s theories and spent much of his life studying Mars from his massive observatory at Flagstaff, Arizona. Lowell was convinced the Martian channels were irrigation canals built by a highly intelligent civilisation. His work captured the imagination of the general public and the idea of canals spread under the influence of the science-fiction of Jules Verne and H.G. Wells.

Not everyone was fooled by Lowell’s enthusiasm for the canals. In 1903, the sceptical English astronomer Edward Maunder conducted visual experiments using marked circular disks which led him to the conclusion the canals were an optical illusion. He also said the lack of temperature-equating winds and low mean temperatures meant Mars could not support Earth-like life. It took another sixty years for Maunder to be proved right.

The first flyby by a spacecraft finally dispelled the idea of canals forever. In 1965 Mariner 4 passed over the planet at an altitude of almost 10,000kms above the surface. It took almost eight months to reach its destination and carried a television camera. It returned 22 television pictures which revealed a vast, barren wasteland of craters on a rust-coloured sandy surface. There were no canals. After Mariner 4, scientists accepted the hypothesis that Mars was a dead planet.

Viking 1 was the next Earth expedition to Mars. Launched in 1975, it was planned to land on Mars to celebrate the bicentennial July 4 the following year. However the landing was delayed after the primary site was deemed too rough by NASA. It was followed by Viking 2 three months later. They scooped up samples of the soil and looked for by-products such as oxygen and carbon dioxide. But neither craft found any evidence to support life. However a seismometer aboard Viking 2 did record a marsquake.

Another 20 years would pass before the Pathfinder probe bounced onto the planet with airbags inflated to soften the landing. Aboard the Pathfinder was Mars’ first rover, the Sojourner. Sojourner contained an on-board camera which relay signals back to the base and then on to Earth. It discovered Mars has a crust, mantle, and core, with the heavier elements nearer to the centre. It also encountered evidence of wild weather in the shape of 200 kph winds which had sandblasted rocks.

Meanwhile back on Earth, scientists discovered a Martian meteorite in Antarctica. This rock with the prosaic name of Alan Hills 84001 was scooped off Mars 16 million years ago and after a long trip in space landed on Earth a mere 13,000 years ago. Of most interest were small worm-shaped structures called chondrules the scientists found on the rock. These structures formed billions of years ago when water seeped into the rock. Inside the chondrules were what appeared to be fossilised worms, organic material, and another possibly life-based compound called "magnetite." They declared this might be a form of primitive Martian bacteria, proving life exists on Mars. These findings were later disputed and most scientists now believe the rock has been “contaminated” by its recent life on Earth.

The water discoveries were made by the planet’s most recent visitor. Launched on November 7, 1996, the Mars Global Surveyor is now orbiting Mars. Between 1999 and 2001, it has mapped the entire surface of the planet. It discovered the upper half of the northern hemisphere of Mars was almost entirely flat. Scientists theorised oceans may have flattened it, as the only areas on Earth that are this flat are at the bottoms of deep oceans. In November this year NASA lost contact with the spacecraft after commanding it to adjust its solar panels. The craft’s final gift to NASA was the photos of two craters called Terra Sirenium and Centauri Montes which appear to show the presence of water on Mars within the past seven years.

These images of gullies on Mars show evidence of new flows and deposits. They seem to indicate explosive events in which some form of water burst from crater walls and ran down their slopes. Researchers are talking about a "squirting gun" theory. Mars expert Phil Christensen from Arizona State University said "there is evidence to say, yes, there is subsurface water" but it will take years to prove or disprove”. He went on to say, "ten years ago, Mars scientists were talking about water billions of years ago. Now we can honestly talk about liquid water on the surface today."