Mars has been taunting researchers for decades as to whether or not the Red Planet has ever been — or is today — an abode for life.
Next year, multiple nations are launching spacecraft to Mars (China, Europe, United States, the United Arab Emirates) drawn once again to help unravel the complexities of that world and tease out clues as to whether or not it could be an extraterrestrial habitat for life.
NASA has called for a set of Mars exploration concepts in addition to, or after, robotically returning Martian specimens to Earth. A Mars Architecture Strategy Working Group is charting a wide range of new missions, covering a decade and a half in terms of time period.
There is active interest in continuing the search for “extant” — currently existing — life on Mars. But that pursuit demands new scientific concepts and understandings keyed to where to explore and what to measure.
To address those questions, a group of experts took part in a Nov. 5-8 “Mars Extant Life: What’s Next?” conference, held at the National Cave and Karst Research Institute in Carlsbad, New Mexico.
One upshot from the gathering is that fresh advances, including enhanced information of Mars’ geologic diversity and history, terrestrial life in extreme environments, and measurement methods, would improve search strategies. Furthermore, if “biosignatures,” telltale indicators of biological processes, can be found in relatively young rocks — even up to 100 million years old — this would be viewed as proof that extant life still exists, somewhere, on the distant world.
“What has happened is that we’ve gone through decades of study, not only opening our eyes about what is happening on Earth in terms of life in extreme environments, but also we’ve had a tremendous amount of exploration on Mars that has been very positive,” Michael Meyer, lead scientist for the space agency’s Mars Exploration Program at NASA Headquarters, told SpaceNews.
A co-convener of the workshop, Meyer says it’s still a very credible question to ask whether or not life ever got started on Mars. “We need to revisit that question every once in a while to see what new ideas there are. Mars is diverse. It’s not just a big, red rusted ball. There are lots of things going on. Is it a potential habitat for life? Our exploration has shown us that’s a good question. We haven’t hit the jackpot yet, but you’ve got to keep on trying.”
During the four-day meeting, there was consensus by conference participants that four candidate geologic environments on Mars are viewed the best in which to look for extant life, specifically in the deep subsurface of the planet, within caves, and in salt deposits and ice. However, the conference group did not reach harmony in prioritizing options. Getting these prioritized may best be done by a future competition, “and that’s always a healthy thing,” said David Beaty, chief scientist of the Mars Directive at the Jet Propulsion Laboratory in Pasadena, California. “We don’t know what the actual state of affairs at Mars is … if it has life or doesn’t have life. So that’s an open question.”
Beaty says that scientists building life detection experiments that cleanly yield a yes or no answer, and do not produce ambiguous results, is vital. “If they can’t design the experiment correctly, then it shouldn’t be flown. Dealing with ambiguous results just muddies the water and makes a mess of everything.”
Mars is quite the toxic place for life as we know it, says Roger Wiens of the Space & Planetary Exploration Team at Los Alamos National Laboratory in New Mexico. He is the project leader for both the Chemistry and Camera instrument aboard the Mars Curiosity rover now on duty, and also principal Investigator for the SuperCam instrument, to be carried by NASA’s Mars 2020 rover. It will inspect rocks and soils with a camera, laser and spectrometers to seek organic compounds that could be related to past life on Mars.
Wiens notes that Mars requires scientists to broaden their outlook and ways of carrying out research on the Red Planet. What life might be on Mars is not very accessible, not on the surface for instance. “We have discovered a lot of interesting things about Mars that we had no clue about earlier. If you are going for the biggest question about life, it’s going to take a long time to really understand the planet,” he says.
Life does one of two things, Wiens told SpaceNews. It either goes where conditions are better or it adapts. If life is still on Mars’ surface, he said, how did it adapt … and likely that it’s dormant at various times and can only come back to reanimate when conditions on the surface are favorable. The other avenue is life went to a better climate and that might be underground. “Those are the two possibilities. Studying the building blocks of life on Mars is challenging and painstaking business,” he said.
The right tools to better characterize the prospect of life on Mars are available today said Vlada Stamenković, a research scientist at the Jet Propulsion Laboratory. As an example, he detailed two prospective Mars lander missions. One is VALKYRIE, short for Volatiles And Life: Key Reconnaissance & In-situ Exploration. The other is Transmissive H2O Reconnaissance, or TH20R, a small impact-lander platform to remotely sense and study liquid subsurface groundwater via low-frequency electromagnetic waves. Such groundwater might be the only habitat for extant life on Mars if it still exists today.
“I think we should now go deeper and really explore the territory where life is most likely to be found. We have clear analogues on our Earth. A large fraction of our planet’s biomass is in deep subsurface environments,” Stamenković said. “One of the most habitable environments of Mars today, and maybe always, has been the subsurface. We have some data, but not sufficient data to make this claim.”
Over the past 10-20 years, there has been a lack of discussion of Mars extant life. NASA’s dual Viking Mars landers of the 1970s were the first and only attempts to robotically detect extant life by way of on-the-spot measurements on a planetary body.
“I think there was a lot of disappointment with the results of Viking being at worse negative, at best inconclusive. And that was frustrating for a lot of people,” said Brandi Carrier, a planetary scientist and systems engineer in JPL’s Mars Program Office.
Perhaps fear of reproducing those results led to NASA taking smaller incremental goals of identifying water on Mars and finding that the planet does indeed have habitable environments, Carrier said. “But I think we are getting to the point where, if there is life on Mars, we are closer to knowing how to find it and interpret our answers. Slowly but surely, hopefully, we can get an answer to this question.”
This article originally appeared in the Dec. 23, 2019 issue of SpaceNews magazine.