Mars – the neighbor of Earth – is always questioned whether life existed on its surface. There are certain similarities like same seasons due to the tilt of axis, and presence of polar caps which suggest existence of water, between Earth and Mars which pushes us to this very question.
Earlier it was believed that Mars would have life forms similar to human beings on Earth. After series of mishaps by USSR and USA, Mariner 4 by US was successful and it returned 21 photos. All those thoughts of human like beings on Mars were shattered when Mariner 4 returned pictures of dry and dusty environment of Mars. Thus the search for intelligent life forms on Mars was deserted and search for basic life organisms began.
Clue for existence of basic life is given through water “the elixir of life”, the first evidence of water was found through the photos by Mariner 9, the craft which orbited the planet in 1971. The photographs showed river beds that have dried and it was concluded that water once existed on Mars. This was followed by Viking whose images proved Mariner 9 images.
Viking 1 mission (first man made vehicle on Mars) was combined an orbiter and a lander. While the orbiter took images of mars and transmitted it, the lander conducted experiments for existence of life. Though all experiments gave negative result, one experiment ended positive suggesting that life existed on Martian surface. It was earlier dismissed that the metabolic reactions detected could be due to non-living organisms, but later studies have suggested that building blocks of life may have really been present on the dirt that Viking experimented.
This was followed by a rover mission Mars Pathfinder by US. Named Sojourner it landed somewhat west (chosen by scientists) to where Viking 1 lander landed, where the surface was rocky and contained various varieties of rocks. The rover on landing conducted various experiments. The images of the sky enabled the scientists to determine size of particles, the color of soil was taken as support to the theory that Mars in past had warm and wet climate. These were certain results of Pathfinder, though direct evidence for water or life on Mars couldn’t be established by Pathfinder.Before the launch of Pathfinder a meteorite was found in Antarctica. The discovered meteorite contained magnetite, a mineral associated with presence of microorganisms.
NASA Mission of twin rovers Spirit and Opportunity in 2003 was successful in finding evidence of water and certain chemicals found were suggested as evidence for salt sea water. Mars Reconnaissance Orbiter in 2006 found water frost on a crater firm. Phoenix lander launched in 2008 measured the isotopes of carbon and oxygen present in the carbon dioxide of Martian atmosphere and suggested that liquid water existed at freezing temperature.
The latest mission to Mars is Curiosity Rover by US launched in 2012. Slated for two years lifetime, its main objective is to find out whether Mars is or was habitable to life. Recently NASA revealed that Curiosity has discovered signs that lead us to think that Mars had elements necessary for supporting life. A rock sample contained sulfur, nitrogen, hydrogen, oxygen, phosphorous and carbon. These are considered to be building blocks of living organisms. Also a streambed has been analyzed which contained minerals that can be formed only in presence of fresh water. A leading scientist in NASA has answered YES to the question whether Mars could have supported a habitable environment.
The picture shows an ancient stream bed found by Curiosity 100-millimeter Mastcam telephoto lens.This is an evidence for flowing stream in Mars in ancient times.
Again taken by the same camera of Curiosity, the picture shows us veins that could be formed when water circulates depositing minerals. The white lines in the picture are none but calcium sulphate deposited in the veins.
Finally India is gearing up with its first mission to mars named as Mars Orbiter Mission to be launched in October. This 450 crore mission aims at exploring the atmosphere of Mars for signs of methane, as life produces methane. We have to wait and watch what the results of this mission would be.
Until now evidence for water has been established through various missions by different organizations, and that Mars had a habitable environment. As for the title question, it is yet to be proven that life really existed on Mars.