The presence of water, oxygen and other ingredients key to the existence of life have been found on the surface of Mars -- the first definitive evidence that the planet was once habitable.

NASA scientists announced the findings Tuesday after analyzing powder drilled from Mars’ surface by the Curiosity rover -- the first successful drill sample ever taken on the Red Planet.

"This is the only definitively habitable environment that we've described and reported. There would be places we would suggest would be habitable, but we haven't measured them," said David Blake, a principal investigator for Curiosity's Chemistry and Mineralogy investigation.

Blake and other NASA scientists said the rock dust analyzed by Curiosity contains clay minerals that formed in a wet environment that may have been be favourable for simple microscopic organisms.

Curiosity filtered the dust sample through various on-board instruments that included an oven for heating, and a spectrometer to analyze the gas that was released. A hydrocarbon trap was also used to seach for signs of organic compounds.

The instruments picked up evidence of the following:

Water, which appeared at high temperatures, seen as evidence the sample likely contained clay compounds.

Oxygen, which is likely a result of the decomposition of a perchlorate.

Carbon dioxide, which was likely produced from oxyden reacting with carbon in the sample, or from the decomposition of a carbonate.

Oxidized and reduced forms of sulphur, sulphur dioxide and hydrogen sulphide.

John Grotzinger, Curiosity project scientist, said the new data suggests Mars was once "an environment that a microbe could have lived in and maybe even prospered in."

“With a really good habitability now in the bag, we can search for a brighter carbon signal. The search for an organic carbon is a focus of this mission,” Grotzinger said.