Reading - Part 4

THE EXPLORATION OF MARS

In 1877, Giovanni Schiaparelli, an Italian astronomer, made drawings and maps of the Martian surface that suggested strange features. The images from telescopes at this time were not as sharp as today. Schiaparelli said he could see a network of lines or canali. In 1894, an American astronomer, Percival Lowell, made a series of observations of Mars from his own observatory at Flagstaff, Arizona, USA. Lowell was convinced a great network of canals had been dug to irrigate crops for the Martian race! He suggested that each canal had fertile vegetation on either side, making them noticeable from Earth. Drawings and globes he made show a network of canals and oases all over the planet.

The idea that there was intelligent life on Mars gained strength in the late 19th century. In 1898, H.G. Wells wrote a science fiction classic, The War of the Worlds about an invading force of Martians who try to conquer Earth. They use highly advanced technology (advanced for 1898) to crush human resistance in their path. In 1917, Edgar Rice Burroughs wrote the first in a series of 11 novels about Mars. Strange beings and rampaging Martian monsters gripped the public’s imagination. A radio broadcast by Orson Welles on Halloween night in 1938 of The War of the Worlds caused widespread panic across America. People ran into the streets in their pyjamas-millions believed the dramatic reports of a Martian invasion.

Probes are very important to our understanding of other planets. Much of our recent knowledge comes from these robotic missions into space. The first images sent back from Mars came from Mariner 4 in July 1965. They showed a cratered and barren landscape, more like the surface of our moon than Earth. In 1969, Mariners 6 and 7 were launched and took 200 photographs of Mars’s southern hemisphere and pole on fly-by missions. But these showed little more information. In 1971, Mariner 9’s mission was to orbit the planet every 12 hours. In 1975, The USA sent two Viking probes to the planet, each with a lander and an orbiter. The Landers had sampler arms to scoop up Martian rocks and did experiments to try and find signs of life. Although no life was found, they sent back the first colour pictures of the planet’s surface and atmosphere from pivoting cameras.

The Martian meteorite found in Earth aroused doubts to the above analysis. ALH84001 meteorite was discovered in December 1984 in Antarctica, by members of the ANSMET project; The sample was ejected from Mars about 17 million years ago and spent 11,000 years in or on the Antarctic ice sheets. Composition analysis by NASA revealed a kind of magnetite that on Earth, is only found in association with certain microorganisms. Some structures resembling the mineralized casts of terrestrial bacteria and their appendages fibrils of by-products occur in the rims of carbonate globules and pre-terrestrial aqueous alteration regions. The size and shape of the objects are consistent with Earthly fossilized nanobacteria, but the existence of nanobacteria itself is still controversial.

In 1965, the Mariner 4 probe discovered that Mars had no global magnetic field that would protect the planet from potentially life-threatening cosmic radiation and solar radiation; observations made in the late 1990s by the Mars Global Surveyor confirmed this discovery. Scientists speculate that the lack of magnetic shielding helped the solar wind blow away much of Mars’s atmosphere over the course of several billion years. After mapping cosmic radiation levels at various depths on Mars, researchers have concluded that any life within the first several meters of the planet’s surface would be killed by lethal doses of cosmic radiation. In 2007, it was calculated that DNA and RNA damage by cosmic radiation would limit life on Mars to depths greater than 7.5 metres below the planet’s surface. Therefore, the best potential locations for discovering life on Mars may be at subsurface environments that have not been studied yet. The disappearance of the magnetic field may be played a significant role in the process of Martian climate change. According to the valuation of the scientists, the climate of Mars gradually transits from warm and wet to cold and dry after magnetic field vanished.

Researchers from the Center of Astrobiology (Spain) and the Catholic University of the North in Chile have found an ‘oasis’ of microorganisms two meters below the surface of the Atacama Desert, SOLID, a detector for signs of life which could be used in environments similar to subsoil on Mars. “We have named it a ‘microbial oasis’ because we found microorganisms developing in a habitat that was rich in rock salt and other highly hygroscopic compounds that absorb water” explained Victor Parro, a researcher from the Center of Astrobiology in Spain. “If there are similar microbes on Mars or remains in similar conditions to the ones we have found in the Atacama, we could detect them with instruments like SOLID” Parro highlighted.