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Sunday, September 26, 2021

Using big science to find tiny clues for life on Mars

For 10 days out of the month, UC Davis graduate student Amy Williams gets to wake up on Mars. Along with the several hundred other members of NASA’s Mars Science Laboratory (MSL) team, Williams synchronizes to the rhythm of the Curiosity rover’s workday as it scours the surface of Gale Crater some 140 million miles from the Jet Propulsion Laboratory’s mission control center in Pasadena, Calif.

Williams, who spends the other 20 days of the month as a doctoral candidate in UC Davis’ geology department, says that the chance for students to participate in this kind of “big science” is closer than many might think.

“I have to say that even though we’re in an economic downturn, there are still great opportunities for young scientists to participate in projects like this, especially graduate students,” Williams said. “If you find a project and say, ‘That’s really cool and I want in on that,’ the faculty, especially at Davis, are really approachable; scientists are approachable and there’s an incredible payback to your investment in that research.”

The biggest paybacks expected from Curiosity are yet to come, as its primary mission is to deliver a detailed picture of Mars’ geologic history and habitability over the course of a two-year mission. But even in its first two months, the rover has allowed the NASA team to do what Williams called “amazing science” on Mars.

Williams shared some of the early highlights, including close-up pictures of an ancient stream bed, in a slide show presentation on campus on Oct. 4. She also detailed some of the advanced instrumentation on the rover, including the ChemCam laser that can vaporize samples of rock for molecular analysis.

“It’s like we sent a ray gun to Mars,” Williams told the audience. “So we don’t have to rove all the way up to a rock to study it, we can zap it like a true Martian with a ray gun.”

The event, hosted by the UC Davis chapter of the international student organization The Triple Helix, also included an introductory talk by UC Davis professor David Osleger, who outlined key features of the Martian environment as revealed by the orbiters and rovers which have preceded Curiosity.

“Mars is very difficult to get to,” Osleger said, noting that little more than half of the attempts to reach the planet over the past 40 years have succeeded. Those that did have revealed a planet whose landscape today seems largely unforgiving, but which bears the unmistakable signs of a wet — and potentially habitable — past, and one that could yet harbor microbial organisms beneath its surface.

For Williams, the chance to study that geology up close came by way of her thesis advisor, UC Davis geobiologist Dawn Sumner, and an acid mine drainage site in Northern California, called Iron Mountain, where Williams conducts her doctoral research. Sumner is a co-investigator on the MSL camera team, a member of the mission’s Long Term Planning group and a co-chair of the mapping group. Iron Mountain harbors minerals thought to have formed in similar conditions on Mars, as well as unique, filamentous mineral formations created by bacterial communities.

“We don’t know whether or not there was life on Mars, and we don’t know what types of biosignatures might be present if life existed,” Sumner wrote in an email.  “Since we don’t know the answer, we have to go with our best guesses, based on what we know from Earth.  Amy’s work on Iron Mountain helps us ‘guess better’ because it provides insights into how bacteria on Earth influence rocks.”

New advances in imaging technology and geobiology have increased the probability that Curiosity will be able to detect mineral signatures on Mars that unambiguously originated from living organisms — if they exist.

“By quantitatively measuring the morphology of the filaments in Iron Mountain research, we’re taking it well beyond just looking at something, and saying, ‘That looks like life,’” Williams said. “The abiotic world can mimic life and vice versa, and that’s the real subtlety in the work … being able to tell the two apart. We’re at the point in our knowledge base where we’re pushing the boundaries of how you can find life based on morphology.”

As Williams settles in to her next 10-day shift in Pasadena, however, her focus will be entirely on the data streaming back from Curiosity, which has to be evaluated and incorporated into the constantly evolving mission plan for each working day on the Martian surface.

“It’s great to focus all of my energy on the Mars research, to really immerse myself in the Mars science and experience,” Williams said. “It’s a different way of doing science than I’ve done before, and it’s a really exciting way to do science. Because every day you wake up on Mars, and that’s pretty cool.”

OYANG TENG can be reached at science@theaggie.org.

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