Updated July 30, 2020
Was there once life on Mars? We'll soon find out.
On the warm sunny morning of July 30, 2020, Mike Tice watched as Cape Canaveral controllers ignited an Atlas V-541 rocket’s massive engines. Nearby buildings shook. Erupting with 379,600 lbf of thrust, the engines hurled the 1.17 million pound vehicle into space on an interplanetary voyage. If successful, the mission will confirm the one-time existence of life on Mars, and broaden our understanding of Earth and its oddly colored planetary neighbor.
Scientist believe there was life on Mars at one time, and it may not look like that which exists on Earth.
The Mars 2020 mission will explore a region where the ancient environment may have once been favorable for microbial life. Instruments aboard a newly designed roving vehicle, called Perseverance, will probe the Martian rocks and soil for signs of these lifeforms.
The mission will also collect samples for a potential return to Earth during a future mission.
Tice, a Ph.D., is an associate research scientist for geobiology and sedimentary geology at Texas A&M University. He will analyze some of the data sent back from the Mars surface to answer that age-old question about life on the distant planet.
The payload of scientific instruments will touch down in the 28-mile-wide Jezero Crater on Mars in February 2021, after its seven-month journey to the Red Planet.
It took five years to select the site, which offers geologically rich terrain with landforms as old as 3.6 billion years. Mission scientists believe the Jezero Crater was once home to an ancient river delta. The water and sediments that flowed into the crater billions of years ago may have collected and preserved ancient organic molecules and other potential signs of microbial life.
The mission could answer important questions in planetary evolution and astrobiology.
Engineers at the Jet Propulsion Laboratory in California designed the mission’s payload, the Perseverance rover. A scientific laboratory on wheels, it was built to learn more about the geology of Mars. The Perseverance will explore the geologically diverse landing site, assess ancient habitability, seek signs of ancient life, particularly in special rocks known to preserve signs of life over time, and demonstrate technology for future robotic and human exploration.
The six-wheeled vehicle carries seven instruments to analyze the Martian rock and soil, including a Raman spectrometer for chemical characterization, a UV visible spectrometer and an X-ray Fluorescence (XRF) spectrometer that uses the interaction of X-rays with materials to non-destructively determine a substance’s elemental composition.
The Perseverance will operate for at least one Mars year or “Sol”, which is equal to two Earth years, although similar vehicles used in previous missions have outperformed its life expectancies.
Hundreds of scientists, including Tice, will operate the Perseverance, its onboard lab equipment, and analyze data streamed back to earth. He is among 15 to 20 scientists with various specialties operating and analyzing data from the micro XRF spectrometer.
It’s a global effort, with team members in Pasadena, New York, Brisbane, London, Madrid and Boulder, Colorado, where Tice and his family live. The team will chose objects in the ancient lake bed, position the instrument, and interpret data that takes up to 45 minutes to transmit from Mars back to Earth.
“I'm interested in ways of detecting life that left geological signatures but aren’t around anymore,” he said of his terrestrial work. “And the more I do this here, the more it's aimed at doing the same thing on Mars.”
Part of his job with the micro XRF instrument will be to take the data that the team gets overnight, decide fairly quickly if they received what they needed, and determine what to do next. The decisions will be made in real-time.
The scientists will try to understand when the lake formed and what the environment was like at that time.
“We're always going to be asking, in this old lake, did it have the right sort of chemistry to support life,” he said. “What pH was the water, what gases were dissolved in the water, and things like that. And then we're going to be asking is there any evidence that there were organisms around taking advantage of energy sources that were available to them there.”
Previous missions used instruments that measured areas the size of about two centimeters. That was sufficient for learning the composition of rocks.
But if you're interested in traces of potential microbial life, micro XRF gives you compositional information to correlate chemical with physical structures and textures that are on the scale of millimeters at most.
The instrument, along with the rover’s other tools are mounted on an articulating arm. Customarily in a lab, researchers move the sample under the micro XRF spectrometer. But on Mars, the entire instrument will move over the stationary objects. This poses a challenge in terms of accuracy, particularly in light of the extreme thermal fluctuations on Mars and its effects on the expansion and contraction of the composite arm.
Microorganisms interact with its environment chemically in ways that alter the environment, and can leave a geologic record.
“What I really specialize in for years now in my research is using micro XRF as a technology to look for subtle traces of how a single-celled organisms chemically altered their environment,” Tice said.
“The vast majority of diversity among living things comes from how each process materials chemically, or what it eats and breaths. Where does it get the energy to survive and grow? Does it breathe oxygen, nitrate, rust, or maybe some other more exotic things? One of the first things you want to know is what it was breathing and eating.”
One of the typical ways that traces like this appear is the result of microbes which are partial to interacting with iron. Different microorganisms are able to get energy out of oxidizing or reducing iron, which it will use as energy to grow and reproduce. And when you oxidize or reduce iron, you change the minerals that it sits in.
“One of the most common things that I'll do is I'll go and look to seek evidence that the iron has been shifting around in ways that are consistent with microorganisms living in it or in sediment. And that increases the likelihood that there was a living organism there.”
Micro XRF plays a special role here.
“What’s really nice about a micro XRF is it lets you tie those signals to shapes and rocks, especially shapes and sedimentary rocks that tell you something about how water or air interacted with the sediment.”
Tice and his team hope to find chemical and physical evidence of the by-product of these processes, which if taken together, would argue for ancient life forms on Mars.
Tice’s lab at Texas A&M University in College Station features a HORIBA XGT-7000 X-ray Fluorescence Analytical Microscope, merging optical observation with elemental analysis. In fact, the XGT-7000 is a close analog to PIXL, the mapping XRF device that’s part of the scientific payload for Mars 2000.
The newest instrument in this line, the HORIBA XGT-9000, combines improved sensitivity and new imaging technology with high-speed analysis of foreign materials in one unit.
Tice believes there's a strong chance that during the time Perseverance is operating, his team will be able to confidently say whether or not there was life in the one-time lake at Jezero Crater.
“We'll tell you what kind of life there was, potentially how these organisms made their living, and what kind of scale they were,” he said. “Was there a lot of life? If it was microorganisms, were they constructing fairly large structures, or were they just sort of scattered around?”
That research may change the way we think about our neighboring Red Planet.
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