Curiosity Rover's discovery of the redox stratification on Gale crater's lake allowed scientists to find evidence that Mars was once habitable — at least in the human sense — for a long time.
In fact, scientists have now concluded from the evidence in Gale crater that Mars once had a very Earth-like environment for about 700 million years sometime between 3.1 and 3.8 billion years ago. So what exactly does this mean for Martian life?
The most exciting answer is that Martian life could really have existed and thrived, but things are not always so simple.
Mapping Mars' Geological History
Scientists studied the rock samples Curiosity collected over the course of its first three and a half years exploring the Red Planet, especially the samples collected on the varying depths of the dried-up lake in Gale crater, and they found that the lake was rich in minerals that could have supported life.
"This type of oxidant stratification is a common feature of lakes on Earth ... The diversity of environments in this Martian lake would have provided multiple opportunities for different types of microbes to survive," lead author and Stony Brook University scientist Joel Hurowitz said.
Life-Supporting Climate
Using the data Curiosity collected, the team of scientists mapped out the planet's past climate and discovered that Mars experienced a climate change much like Earth's, though it happened when Earth was still in its earlier stages.
The researchers remind that they are not as familiar with mineral and rock components in Mars so much of their findings were based on comparing the data they have with what have been observed and confirmed on Earth.
"If we were looking at the same rock chemistry on Earth .... We can say it's colder and warmer, but exactly what the climate condition was is a little more difficult," Hurowitz explained.
What If Mars Supported Life?
The researchers found that Mars experienced a climate change before it lost its atmosphere and became its current condition. According to the study, Mars was first really cold before warming enough to have stable Earth-like conditions before it dried up. The pattern seems eerily familiar.
"But we have to remember that at the time of Gale Lake, life on our planet had not yet adapted to using oxygen — photosynthesis had not yet been invented. Instead, the oxidation state of certain elements like manganese or iron may have been more important for life, if it ever existed on Mars," study coauthor Roger Wiens said. Wiens is a planetary scientist at the Los Alamos National Laboratory.
So if life ever existed in Mars, we could probably expect the life-forms to differ from what we have on Earth — at least until further exploration and studies are done to determine whether Mars steadily became an oxygen-rich planet like ours.
If that is not the case, however, everyone will just have to wait until 2020, when the ExoMars rover begins to dig for more evidence under Martian soil.
