By 
December 11th, 2016
Mars true-color globe showing Terra Meridiani.
Credits: NASA/Greg Shirah
Billions of dollars later, oodles of exploration dollars have been spent on a key question: Is there life on Mars? The answer remains a head-scratcher following decades of studying Mars up-close and personal.
The perplexing nature of slam-dunking a life on Mars finding was talked about during a National Academies of Sciences’ Space Studies Board meeting on “Searching for Life Across Space and Time.”
This community workshop was held on December 5-6, 2016 at the Beckman Center in Irvine, California.
Credit: Viking Mars Missions Education & Preservation Project (VMMEPP).
False positive
It was 1976 when the dual NASA Viking landers successfully touched down on the Red Planet. Their prime directive was to hunt for evidence of life.
Both landers strong-armed Mars; each used a robotic arm to scoop up a sample of the Martian soil for study by a biology instrument to test for metabolic activity, and a gas chromatograph/mass spectrometer (GCMS) to scan the soil for organic molecules and water.
Credit: NASA/Ben Clark
One biology experiment, Labeled Release (LR), was designed to detect microbes present in the soil. The experiment did indicate metabolism. The other two biology investigations, however, did not find any evidence of biological activity. The Viking science team believed that the LR data had probably been skewed by unexpected non-biological properties of Martian soil, resulting in a false positive. That call remains controversial to this date.
Ambiguity
Viking’s box of biological experiments was a “huge engineering challenge,” recalled Ben Clark at the workshop. He developed the x-ray fluorescence soil analyzers for the Viking missions and is now with the Space Science Institute in Boulder, Colorado.
Credit: Tom Dahl
Those three life-detection experiments all had to fit into a less than a one cubic foot box, Clark said, because NASA did not allocate a Saturn V rocket to the mission, as previously expected. “It ended up being the most expensive instrument that had ever been developed for spaceflight at that time…and perhaps still rivals that.”
Regarding the LR experiment, “there was a big bottom line of uncertainty as what was actually found,” an ambiguity that remains today to some extent, Clark said.
Sample return
“The major accomplishments by Viking…first of all it was the first real search on another location for biomarkers by a robotic spacecraft system,” Clark said. Viking’s biology experiment was the first, and to date the last, search for actual metabolic activity on Mars.
Credit: Martin Marietta/Ben Clark
“My feeling is that sample return is the way we’re going to understand this…and it’s probably going to take that,” Clark said. “You could also try to do more experiments on Mars, but we can do so much more in the laboratories here on Earth.”
Noting that a proposal was advocated in 1972 to send a Viking lander to Mars outfitted with a sample return rocket, Clark said that idea did not move forward. “We have a saying in our community that Mars sample return is always 10 years away.”
Survival mode
Fast forward from Viking after more than 40 years, is there life on the Red Planet?
Data from the Viking biology experiments, which is stored on microfilm, has to be accessed using a microfilm reader. A NASA archival team worked to digitize the data to make it more accessible.
Credit: NASA/David Williams
“I’m going to take the position that we now know information that makes it more likely than perhaps we felt at the time that there is — or should be — life on Mars,” Clark said.
“Although there were two Viking spacecraft, and they landed thousands of miles apart, we learned by our measurements that they were sampling the exact same type of soil, a global unit because of the giant dust storms that periodically envelop the entire planet,” Clark later told Inside Outer Space.
“What we have learned from the rover missions is that Mars has some amazing diversity in water-lain sediments,” Clark said. “We now know that it has many great geochemical ingredients available and that the atmosphere in the past had many of the molecules that stimulate life.”
Teaser: latent life
Perhaps on Mars today, life is latent, Cark suggested. “Life on Earth is dormant many times and goes for long periods in a survival mode and it could be happening on Mars between obliquity cycles.”
Obliquity is the changing degree of tilt of Mars’ orbital axis — known to slowly increase and decrease over a 100,000-year cycle.
So what life is there today on the Red Planet may be dormant. “We may have to tease it to get it out,” Clark added. “The history of our exploration of the Red Planet is that Mars fools us most of the time.”
Clark’s bottom line: “We just need to keep going and keep looking. Mars is turning out to be extraordinarily diverse and rich.”
Smaller, cheaper rovers
Also speaking at the workshop, Caltech’s John Grotzinger, a geobiologist and former chief scientist for the Curiosity rover mission that’s now dutifully exploring Mars.
Curiosity Mars rover on the prowl since landing in August 2012.
Credit: NASA/JPL/Caltech
Grotzinger said that he advocates for smaller and cheaper rovers, dispatched to varying places on Mars. “We can partner with private industry,” he said. “It’s a new paradigm.”
There’s no need for the full monty of science gear onboard robot probes to Mars, Grotzinger said, “in order to ask a very specific question of a very specific place.”
In detailing NASA’s Curiosity rover’s trek on Mars for the last four years, toward its main science destination, the foothills of Mount Sharp, Grotzinger said the robot’s investigations have been a “gold mine” to help scope out the environmental history of Mars.
Chemical reactor
Curiosity findings point to a series of long-lived streams and lakes that existed some billions of years ago, resulting in sedimentary deposits in Gale Crater. That sedimentary basin is a “chemical reactor,” Grotzinger emphasized. Primary igneous minerals are being converted under different chemical circumstances into different minerals, he said.
“We’re not sure what all this means but it’s pretty exciting for habitability,” Grotzinger added.
“Lamoose” rock on Mars.
Credit: NASA/JPL-Caltech/MSSS
Microfossil preservation
In his talk, Grotzinger singled out Curiosity imagery of “Lamoose” rock from the “Marias Pass” area of Mount Sharp – a fragment that has unusually high concentrations of silica.
Silica is a rock-forming compound containing silicon and oxygen, commonly found on Earth as quartz. High levels of silica could indicate ideal conditions for preserving ancient organic material, if present.
Lamoose could be his favorite rock, said Grotzinger…“the best rock that Curiosity could ever find that we would bring back to Earth and look for microfossils preserved in it.”
Posted in Space News
Can we drill about 10 to 20 meters deep and also do some ice drilling or core drilling on Mars please.
Europe’s ExoMars 2020 rover can drill down nearly 7 feet.
Life on Mars is about as “ambiguous” as life on Earth! The Viking LR applied a test used by municipalities all over the world, enhanced, to daily test their drinking water, and got positive results. The only reason life was not declared was presumed lack of organic material and lack of liquid water. Liquid water was confirmed many missions ago, and Curiosity has now confirmed complex organics. Had these findings been made by Viking, all would have accepted life on Mars. So why not now? Especially, since all new relative data on Mars and Earth support life, and no non-biological entity has ever been found to give a false positive in the LR – and since no finding on Mars is inimical with life!
Let’s admit life to Mars and get on with studying it!
Gil Levin,Viking Mission LR Experimenter
Just to point out that we have not, since 1997, being searching for life on Mars – we’ve been engaged in characterising the planet from the planetary to the microscopic scales, following the water (and carbon) and so on. The reason – Viking, as good as it was – was naive in its design and we’ve improved our questions and improved our approach with the outcome being the current phased approach to automated Mars exploration. The desired outcome is to uncover what Mars can tell us about origins, or possible life there – not to find life explicitly (that would be a huge bonus if found, but will be found by pot luck).
Hence the outcomes of our Mars research is to fully characterise the planet and what it might say about the origin in life. Success is not dependent on finding life there or even evidence of past life – if we fully characterise the planet and find no life, that will be equally revealing. And indeed already this quest has paid dividends – Mars is a watery planet meaning two of eight planets in our solar system are watery – we did not know that with certainty prior to Odyssey.
I feel it’s important to emphasise these points, rather than predicating success as the detection of either present life or microfossils of past life. Indeed, ExoMars is, in my opinion, a step backwards because again it’s depending in pot luck and is likely to find no evidence of life on Mars, and the public (and funding agencies) may deem that as failure. NASA’s approach over the past two decades has been the most successful engagement in space exploration because the premises and questions were sound; and I hope the likes of Grotzinger and others do not forget what the basis of successful NASA Mars exploration has been about – the systematic analytical science engagement of the planet to describe it in every improving terms that will eventually yield all of Mars’ secrets regarding habitability, prebiotic potential and even questions of life there. So the smart thing to do is to continue on the current path with a combination of every better orbiters, landers and rovers – but NOT to look for life – that will, for the foreseeable future, be always a matter of luck and likely to yield very little.
Kevin Nolan, author of Mars, A Cosmic Stepping Stone (Springer / Copernicus, NY, 2008).