Searching for Life on Mars Through a New Lens –“Ancient Life Organized Around Oasis”




NASA scientists are in agreement that ancient Mars was habitable at one point in history. According to Nathalie Cabrol, a senior research scientist and director of the Carl Sagan Center, our current level of observation and astrobiological the focus of our search for life on Mars is geared towards broad questions of potential habitability rather than searching for actual habitats.

In a lecture at the American Geophysical Union in San Francisco yesterday, Cabrol explained how we need to take a more subtle approach to the way Mars has changed over time, rather than just lumping them into the Noachian, Hesperian, and Amazonian periods. “It’s a gross caricature of what happened,” Cabrol said. “You don’t understand how one went to the next.”

Cabrol has been a principal investigator at the SETI Institute since 1998. She leads projects in planetary science and astrobiology, develops science exploration strategies for Mars, Titan, and the Outer Solar System icy moons, and designs robotic field experiments.

In place of a manned expedition to Mars, she explores high altitude lakes in the Andes where environmental conditions are analogous to early Mars. With her team, she documents life’s adaptation to extreme environments, the effect of rapid climate change on lake ecosystems and habitats, its geobiological signatures, and relevance to planetary exploration. Since January 2015, she leads the SETI Institute NASA Astrobiology Institute team that seeks to understand the impact of rapid environmental change on habitability and biosignature potential on Mars.

Cabrol observed that early life on Mars would have been under “incredible environmental stress” as the environment is historically less stable than Earth’s. Microbial life most likely existed in heated lakes created by impact craters and warmed by volcanic activity. NASA's current Mars' Curiosity Rover for example is probing the anicent Gale Crater –an impact crater that once formed a potentially habitable lake.



“The life will have to organize around oasis where they have resources,” she said.

The NASA image above is an artist’s concept as to where water may have once flowed in ancient Gale Crater lake (NASA/JPL). A lake with these conditions could provide an ideal environment for simple microbial life.  The researchers think that a lake like this could have provided perfect conditions for simple bacterial life such as chemolithoautotrophs, which are rock-eating microbes that live on and derive their energy from mineral compounds.

Cabrol says that looking at Earth can be helpful, so long as we don’t get too much of our terrestrial norms. “We’re seeking guidance, not truth,” she said. Different areas in and around the Andes mountains, including the Atacama desert and Altiplano, can be used as decent stand-ins for Mars over time, a technique Cabrol called “space for time substitution.” By observing how lakes deal with high levels of radiation, evaporation, and geological change, it colors how scientists need to look for Martian habitats on the micro level.


“We need to think about habitat fragmentation when we are looking for life on Mars,” she explained, noting that all these lakes likely divided into basins as they dried up over the ages. For the best chance of finding signs of life, scientists need to find “the last oasis that will last the longest.”

“We are just seeing tipping points, we are not seeing what happens on the subtle transitional level,” she said.

Cabrol continued, saying that we need to work on creating a “critical intermediate detection threshold” — a sort of middle stage between physical, surface level studies and the broad evaluations we’re doing now. She highlights mineralogy and composition data, as well as a greater understanding of climatic cycles and events that would actually affect the planet on a habitat level.

“We need to adopt the tool to the exploration, not the exploration to the tools,” she said, adding that explorers need to have specific places of interest identified years in advance before they land for a more thorough examination. Otherwise, she declared, “we’re wasting time.”

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