Opportunity, the rover which explores Mars, found evidence that the Red Planet has supported microbial life 4 billion years ago.
The rover has landed on Mars' surface in January 25, 2003 so it is now celebrating its 10th anniversary. During its exploration, it has found evidence that nearly neutral pH water flowed on Mars surface at least 4 billion years ago.
Opportunity's discovery was announced on Jan.23 and it backs up the initial discovery of Curiosity, the most recent rover sent to Mars, which indicated that 3.7 billion years ago, Mars once had a groundwater system and a habitable lake.
"These [benign] water conditions existed over a long period of time," said Ray Arvidson, Opportunity deputy principal investigator and lead author of the study, to SPACE.com.
This evidence of water found on Mars supports the theory that the planet could have had microbial life. "That wouldn't be a surprise. Maybe not globally; [habitable environments] could have occurred here and there regionally. And it may not have been for the whole time continuously. We don't know," Arvidon added.
As soon as Opportunity landed on Mars, the rover has been sending data about the rocks that it found on the planet's surface. Researchers have studied rocks from the planet's Noachian era, which was 4.5 billion years ago, characterized by dried up river valleys and delta features. Scientists believe that the climate on this era was warmer and more humid than the succeeding eras. These rocks, which are rich in clay, consisted of BB-size "spherules" and have numerous fractures, which indicate that water flowed on these rocks millions of years ago.
At present day Mars, water in its liquid state cannot exist because the planet's atmosphere is only one percent as thick as Earth. Arvidson theorizes that Mars' atmosphere may have been thicker before, if groundwater systems and lakes have existed.
The results of the study were further discussed in the Jan. 23 issue of Science.
