NASA’s Curiosity rover is shedding new light on Mars’ ancient climate. The rover is exploring Gale Crater, an area where there are signs liquid water may have once existed. This discovery points to a time when Mars may have been more habitable to life.
However, as conditions on the planet changed, its surface became too harsh for life as we know it to survive. These findings help researchers understand how Mars went from a possibly habitable planet to one that is cold and bleak today.
Carbonates as clues to Mars’ past
Scientists focus on carbon-rich minerals, called carbonates, in Gale Crater. These minerals are crucial because they preserve details about the environment in which they formed.
By studying them, researchers can learn about the water’s temperature, acidity, and makeup of Mars’ atmosphere at the time. NASA’s Curiosity rover has been key in uncovering these clues, providing new insights into how Mars’ climate evolved.
Extreme evaporation on ancient Mars
David Burtt, a researcher at NASA’s Goddard Space Flight Center, explains that the carbonates found in Gale Crater show signs of extreme evaporation. This suggests that liquid water was present but only for short periods of time.
The high levels of heavy carbon and oxygen isotopes in these carbonates indicate Mars experienced significant evaporation unlike anything witnessed on Earth. While this doesn’t completely rule out the possibility of life, it suggests that any surface life on Mars would have been short-lived or limited to underground environments.
Isotopes and their role in understanding Mars
Isotopes are different forms of an element, with varying weights. When water evaporates, lighter isotopes of carbon and oxygen escape into the atmosphere, leaving the heavier ones behind. Over time, these heavier isotopes accumulate in minerals such as carbonates.
The carbonates found on Mars contain unusually high levels of heavy carbon and oxygen isotopes, much higher than those found on Earth.
According to Burtt, these extreme values point to an intense process of evaporation. The heavy isotopes remained, while any lighter ones were minimal. This suggests that evaporation on Mars was far more extreme than anything we see on Earth, preserving these high levels of heavy isotopes.
Two possible climate scenarios
Researchers have proposed two possible ways the carbonates in Gale Crater may have formed. The first scenario involves repeated cycles of wet and dry conditions.
In this process, water would occasionally fill the crater, evaporate, and leave behind carbonates. The second scenario suggests the carbonates formed in very salty water under cold, ice-forming conditions.
Jennifer Stern, a co-author from NASA Goddard, explains that these two processes point to different climates on ancient Mars. A wet-dry cycle would indicate that Mars had periods during which life could potentially exist, alternating with less habitable times.
On the other hand, the cold, salty conditions would suggest a less favorable environment for life, where most water was locked in ice, making it difficult for life to thrive.
Supporting isotopic evidence
While these climate scenarios have been discussed before, this study is the first to add isotopic evidence from actual rock samples. Previous ideas were based on mineral evidence and large-scale models, but the isotopic data from Curiosity’s samples provides more concrete support.
The high levels of heavy isotopes align with the idea that Mars went through periods of extreme evaporation, whether during cycles of wet and dry conditions or in cold, icy environments.