By Dr Irengbam Mohendra Singh
On the enduring human question, where we came from, NASA puts it in this way:
“Knowing where we come from means understanding how the great chain of events unleashed after the Big Bang culminated in us and in everything we observe today.”
“It is the story of our cosmic roots, told in terms of all that precedes us: the origin and developments of our galaxies, stars, planets, and the chemical conditions necessary to support life.”
On November 26, Saturday at 15.02 GMT, NASA has launched a 900 kg robot (Curiosity) from Cape Canaveral, Florida, to find if life has ever been on this planet, carrying a six-wheeled vehicle. It will take eight and half months to reach Mars.
The robot, the size of a mini car (3 m long) will land on a chosen site around the foot of a three mile high mountain. Its soil is known to contain exposed layers of sediment rich in clays and minerals that must have formed in water.
NASA has been looking for Earth-like planets to test the presence of life forms similar to those living on Earth, with the presence of large amounts of oxygen in the atmosphere.
The inability of NASA’s Viking 1 and Viking 2 interplanetary spacecraft in the 1970s, to detect life, based on Carbon dioxide chemistry on Mars in the past, may simply mean that there was no life on Mars or it may simply mean the experiments were not designed correctly.
In September 1965, a team of French astronomers, using a powerful telescope, studied the infrared spectrum of the atmosphere of Mars, and found that it is almost entirely carbon dioxide. The implication was that there was no life on Mars.
Encouraged by the recent discovery of extrasolar planets in the 1990s, both NASA and ESA (European space agencies) invested in very expensive telescopes. The American version was called the Terrestrial Planet Finder (TPF) and the European version, Darwin.
That was followed by attempts to find terrestrial planets ie planets more or less the size of Earth, Venus and Mars, in orbits more or less like those of Earth, Mars and Venus.
The astronomers were confident that within 20 years they would know for sure if there were other life-bearing planets within 50 light years of Earth. After finding life, the quest will continue to find if there is intelligent life out there.
Now, let us see what the scientists think of the beginning of life on earth. There is serious research going on to find the origin of life, distinct from the evolution of life.
Two scientists, Oparin and Haldane postulated that the early Earth were conducive to the formation of organic compounds from inorganic elements. This would have made it possible to form many chemicals common to all forms of life as they exist today. This scientific discipline is called prebiotic chemistry. They are making progress but not quite.
Another alternative theory is called Panspermia. This postulates that the first elements of life may have formed on another planet with more favourable conditions and they have been carried to Earth by a variety of means.
Recently, in October 2011, scientists found that the Cosmic dust (tiny particles of solid material floating around in space between the stars) that permeates the universe contains organic matter that could be created naturally and rapidly by stars.
Further, scientists suggested that these compounds may have been related to the development of life on earth, and said that “if this is the case, life on Earth may have had an easier time getting started as these organics can serve as basic ingredients for life.” The quest goes on.
The sort of life NASA is looking for on Mars is a kind of microbial life though there is no atmosphere to support life today.
Mars is chosen out of all the planets. As the moon has no atmosphere (air) to support life, scientists have turned their search to Mars, because of the proximity and similarity to Earth.
Mars is known as the Red planet because it is covered with rust – the compound of iron-oxide.
As early as the 17th century Mars’ polar icecaps were observed. By the 19th century astronomers knew that Mars has a similar axial tilt similar to earth, which means it experienced seasons as earth does.
However, in 1894 a US astronomer William Campbell showed, by spectroscopic examination that neither water nor oxygen was present in the Martian atmosphere.
Many other observations and studies were made by many scientists to speculate the possibility of life on Mars. This has stimulated H G Wells to write The War of the Worlds in 1897. Some of us have seen the film and read the book.
As liquid water is necessary for known life and metabolism the search on the surface of Mars is primarily for water in any form and anywhere deep down. If water is present on Mars, the chance of its having supported life may have been determinant.
In 1965 Mariner Probe 4 performed the first successful ‘flyby’ of the planet Mars, returning from there first pictures of the Martian surface. The photographs showed the surface of Mars without rivers, oceans or any sign of life, and that it was covered in craters, indicating a lack of plate tectonics and weathering of any kind in the last 4 billion years.
The Viking Orbiters performed in the 1970s found evidence of possible river valleys and erosion and branched streams in many areas in the southern hemisphere.
Encouragingly and satisfyingly, NASA’s Phoenix Lander Spacecraft that touched down on Mars on May 25 2008 (died there later), has found for the first time and returned data from either of the poles that water in a sample of soil collected from the planet’s surface “has been touched and tested for the first time.”
The evidence so far shows that water was once widespread on Mars. This raised the prospect of finding water on Mars. Where there is water there is life. And so NASA launched Curiosity in the hope that the Red planet could have supported life, at least as microbes.
While talking about life on the planets, some scientists used to argue that life can only exist in regions where the temperatures are between 0degreesC and 100degreesC where liquid water can exist ie it is neither cold that water freezes, nor so hot that water boils. This is known as Stellar (or Solar) Habitable Zone (SHZ), which covers the region around a star.
The argument has been disputed by the fact that complex life forms like ourselves and others on Earth cannot survive at temperatures above 50OC. However, recent discoveries (late 1970s) by scientists who study the deep ocean floor have discovered the existence of “hydrothermal vents”.
These are vents that are thousands of meters below the surface of the sea with hot water where no sunlight ever reaches but teeming with life including the eyeless shrimps (Pompeii worms) that live where the water temperature exceeds 80OC. All they need, it seems, a supply of liquid water.
The planet Earth is in the middle of SHZ, while Venus, the next planet, nearer the Sun is too hot for liquid water to exist. Mars, the next planet away from the Sun is too cold. But Mars has possibilities for colonisation by the human race on earth, which is overcrowded with more than six billion people.
Mars has been chosen by NASA, among many other findings, because the recent NASA probes have hints to a warmer past on Mars, one in which water may have flowed and life might have existed. There is now evidence of water that may be frozen at the polar icecaps, the existence of carbon and oxygen in the form of carbon dioxide, and nitrogen.
To scientists, there are many similarities between the Martian atmosphere that exists today and the atmosphere that existed on Earth billions of years ago, such as the complete absence of oxygen but full of carbon dioxide and nitrogen. It was not until photosynthetic bacteria developed on earth, which produced enough oxygen that allowed the development of animals, which eventually evolved into humans.
Scientists have envisaged that the human race could one day make Mars habitable by altering the current climate and atmosphere to more closely resemble that of the Earth’s. This process is called “terraforming”.
That is the reason why a serious search for life on Mars has begun
PS. The good news is that an article in the Daily Telegraph, December 6 2011, announced that NASA has found a planet (Kepler 22B), very similar to our Earth, and has been identified as a potential future home for mankind. It contains both land and an average temperature of around 72 OF (22 OC). It is however 600 light years from earth (compare with 0.0000007 light years to Mars). It is expected to be in the SHZ.
The writer is based in the UK
Email: imsingh (at) onetel.com
Website: www.drimsingh.co.uk