Because she studies ancient water on Earth, Barbara Sherwood Lollar is usually looking down, but her work is also making her look to the stars.

Sherwood Lollar, an earth sciences professor at the University of Toronto, has won the prestigious Gerhard Herzberg Canada Gold Medal for Science and Engineering for her work on ancient Earth water and for advancing the search for life on other worlds. The award is handed out each year by the Natural Sciences and Engineering Research Council of Canada (NSERC).

Humans have long wondered if we're alone in the universe. Mars has always been an appealing candidate for extraterrestrial life, but in recent years, scientists have begun to look at moons — specifically, Europa, a moon around Jupiter, and Enceladus, a moon around Saturn.

Why the change in direction? The maxim in the search for life has always been: follow the water.

While not identical, both Europa and Enceladus are similar, in that they both have icy crusts under which astronomers believe are large bodies of water. It's also believed Enceladus may have hydrothermal vents, which are areas of heated, mineral-rich water. The moon is even spewing water vapour into space.

Enceladus, a moon around Saturn, sprays water from its underground ocean into space. (NASA/JPL)

Sherwood Lollar has been studying ancient water below the Earth's surface in mines on the Canadian Shield and around the world. Determining the chemistry of that water could be used to study moons like Europa and Enceladus.

"One of the major themes of planetary science is that we use the Earth to understand processes that might be going on on other planets," Sherwood Lollar said. "And so the work we do … has direct relevance for what we do when we go out to search for processes on other planets."

Digging deep

In 2016, she and her team of scientists found what was believed to be the oldest water on Earth, estimated to be two billion years old. The discovery earned her NSERC's John C. Polanyi Award.

Probing this deep allows Sherwood Lollar and her team to find out how life could thrive in these conditions. In particular, she wants to know: "What are they living off of?"

Her interest in the subject began when she was finishing high school. Scientists were just beginning to understand the nature of life in some of the deepest parts of the oceans, including around hydrothermal vents, which she found fascinating.

This graphic illustrates how Cassini scientists think water interacts with rock at the bottom of the ocean of Saturn's icy moon Enceladus, producing hydrogen gas. (NASA/JPL-Caltech)

Scientists were surprised to discover that some life didn't need the process of photosynthesis to live; that the chemistry of water-rock reactions could provide the energy needed for microbes to survive.

While hydrothermal vents are interesting places to study chemical processes taking place that provide habitability for life, Sherwood Lollar isn't looking there. Instead, she's concentrating on cooler regions like the Canadian Shield. This ancient rock doesn't experience shifting plates that tend to generate heat around hydrothermal vents, yet there is still chemistry taking place in the water that's under the rock.

Her work could help astrobiologists and astrophysicists search for life in cooler places in the solar system, including Mars. Just last year, a team of Italian scientists published a paper that suggested there was a lake below the planet's southern polar ice cap. For many, the question this raised was whether the region was habitable.

"One way of looking at Mars is that it looks like the Canadian Shield … in the sense that it is all ancient, billion-year-old rock on the surface," Sherwood Lollar said. So her work here on Earth will likely be used in the search for life on Mars.

The European Space Agency's Mars Express has used radar signals bounced through underground layers of ice to identify a lake of liquid water buried below the planet's south pole. (ESA/NASA/JPL/ASI/Univ. Rome)

Sherwood Lollar said she's immensely honoured to receive the Herzberg Medal.

"We use the word humbling, but it really is the only word to describe [it]," she said.

She looks forward to continuing her work, and to the search for life beyond Earth. And she's happy that we're rethinking how we find that life.

"When we go to the icy planets, the ocean worlds, those places are very, very cold. But we would be wrong to think about them as geologically inactive," she said.

"Anywhere where you've got gradients, between hot and cold — even if it's between cold and colder — you still have the potential for chemistry to be taking place. And this causes us to open our thinking a bit, to think outside the box about the nature of what can sustain habitability."