Bethany Ehlmann

Planetary Geologist

Emerging Explorer

An illustration of the Curiosity rover.

Illustration courtesy Caltech/NASA

Picture of Bethany Ehlmann

Photograph by Lance Hayashida/Caltech

Bethany Ehlmann is a participating scientist on the NASA Mars Rover Curiosity mission, a research scientist at the Jet Propulsion Laboratory, and assistant professor of planetary science at Caltech. She explores our solar system, seeking to understand its history over billions of years of geologic time and searching for habitable environments for life.

At 9:45 each Mars morning, a car-size rover loaded with scientific instruments wakes up, looks toward Earth, and asks, “What do I do today?” Bethany Ehlmann is one of the scientists who answers that question. As a geologist on the NASA Mars Rover Curiosity mission, she helps direct the rover and analyzes the minerals and geochemistry of Martian rocks for clues about the planet’s environment over billions of years.

The history of Mars is written on rocks. Particularly the history of water—the most crucial clue of all in the search for past life. “We know liquid water shaped Mars’s surface,” Ehlmann explains. “Lakes, rivers, and hot springs were widespread enough to form minerals on Mars three billion to four billion years ago.” Today, Ehlmann analyzes those ancient minerals by zapping Martian rocks with the ChemCam laser spectrometer aboard the rover. The laser vaporizes a tiny amount of rock, producing a glowing cloud of plasma. Light from the plasma creates a “fingerprint” of emission lines, revealing particular chemical elements that compose the rock, allowing Ehlmann and the team to determine the chemistries of waters that formed it. “The grand slam home run of the mission would be detecting preserved organic matter relating to biology in some of the sediments,” she says. “Another huge finding will be evidence for what sort of environment with water existed, and how climate allowed liquid water on Mars.”

“Advances in robotics let us be virtual explorers,” Ehlmann notes. “Rovers are a proxy for us, taking samples and measurements on the surface of another planet. This technology has only been available in the last decade, and it’s very exciting to be on the forefront of using it.”

Ehlmann says Mars and Earth have valuable news for each other. The rock record of life’s origins on Earth is very limited; less than one percent remains from our beginnings 3.5 billion years ago, due to recycling of rocks by plate tectonics. In contrast, about 50 percent of Mars’s surface dates from those ancient days. “This gives us insight into the early history of our solar system at a time when meteorites bombarded terrestrial planets and more active volcanoes belched out gases to the atmosphere,” Ehlmann says. “Studying the first billion years of Mars’s history helps answer questions about how Earth evolved to sustain and maintain environments good for life.”

In turn, exploring remote corners on Earth can help inform how to best tackle exploration on Mars. “The places we are likely to find life on other planets are far colder, dryer, hotter, or more acidic than anyplace on Earth,” Ehlmann points out. “So I travel to some extreme spots to find geologic features and environmental conditions that most closely resemble the surfaces of distant planets.” Scientific quests have taken her from the deserts of California to Oman. Iceland and Hawaii are both particularly fertile proving grounds for testing techniques and instruments destined for Mars. Both places are basaltic lava flows, not the dominant continental crust on Earth, but exactly what composes most of the surface of Mars. “We start by running experiments with typical geological lab instruments and then try performing the same tasks with technology designed to fly on orbiters or attach to rovers,” she says. “For example, we thought one of the instruments orbiting Mars showed evidence of water reacting at high temperatures with basalt to form clay minerals in a hydrothermal environment. So we took a backpack-size version of that instrument into the field in Iceland, measured data on basaltic areas there, and brought rocks back to the lab to see if our conclusions were correct. Testing instruments this way really pushes technology ahead before we move outward to other planets.”

While Curiosity sleeps, mission scientists and engineers work through the Mars night to review and analyze the daily downlink of photographs and data and plan where the rover should drive, dig, zap, and sniff the next day. The painstaking work involves multiple daily meetings of scientists and engineers; rapid integration and data processing of spectra, images, and thermal data; and precise computer codes. But then, there are transcendent moments. “Something will snap me back and remind me of the big picture. A perfect photo taken during Martian sunset. A neat rock that looks just like one I saw on Earth. An amazing color palette of infrared channels that’s not only scientifically interesting but just beautiful,” Ehlmann explains. “I step back, pause, and say this is a really great endeavor to be part of, understanding the generation of life-sustaining environments and extending our human knowledge and presence to other worlds.”


In Their Words

Rocks hold the secret to life’s origins and history here on Earth and may do the same on remote planets like Mars.

—Bethany Ehlmann


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